Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session G00: Poster Session I (2pm- 5pm CST)Poster Undergrad Friendly
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Room: McCormick Place Exhibit Hall F1 |
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G00.00001: UNDERGRADUATE RESEARCH
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G00.00002: Chaotic Dynamic Through Its Invariance That Does Not Depend On Initial State Quoc A Nguyen, Gemunu H Gunaratne Chaos is everywhere in nature, from the formation of the snowflake or the trajectory of planets in the universe. All these chaotic behaviors, although random and unpredictable, form their attractor that is independent of the initial condition. Studying invariances of the attractor is the most reliable way to describe and learn about the chaotic dynamic. In this project, we study Henon, Lozi, and Lorenz attractors through invariance including Lyapunov exponent and fractal dimension. |
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G00.00003: Cost-effective solar cells with earth abundant transparent materials Dongheon Ha, Dontae J Milner Traditional antireflection coating (ARCs) are used to reduce the reflectivity and improve the efficiency of solar cells. However, traditional ARCs have limitations of being wavelength- and angle-dependent. It is also required to employ expensive, complicated fabrication processes. In an effort to realize cost-effective solar cells, we will show how inexpensive transparent materials, such as PET, can improve optical and electrical characteristics of Si solar cells. We created an incoherent light propagation model to see the effect of the transparent material atop Si solar cells. It is found that we can reduce the reflectivity by more than 20 % with the material having a refractive index of 1.5 to 2.5. With the improved optical characteristics, we also found that the current generation can be improved by 24 % when the material of a refractive index of 2.0 is applied. In this presentation, we will also discuss the method to further improve the optical and electrical characteristics. |
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G00.00004: Analysis of the Length Distribution of Microtubules with Different Structural Compositions Stephany Salazar, James Heid, Dr. Mitra Feizabadi Microtubules are one of the cellular filaments that are structured from alpha tubulin and beta tubulin. These biofilaments are dynamic and randomly switch between growing and shrinking phases while they polymerize. The four major parameters that define the polymerization specifications of microtubules are growing velocity, shrinking velocity, frequency of catastrophe, and frequency of rescue. Experimental evidence and theoretical analysis indicate that the length distribution of microtubules depends on these polymerization parameters. In this study, we will analyze the length distribution of different types of microtubules that have structurally distinct compositions from one another. Both the theoretical and experimental results will be compared and analyzed. |
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G00.00005: Nonlinear dynamics of trapped Leidenfrost drop Tianrui Wu, Jenny Magnes, Harold M Hastings We present our experimental investigation of the dynamics of trapped ultra-mobile Leidenfrost water drop in heated spherical dishes. We use Leidenfrost drops to investigate non-linear motion of underdamped macroscopic objects in a two-dimensional Hookean field under thermal forces. We use high-speed video to image and locate the oscillating drops with different initial conditions. The motion of drops is examined with frequency spectra analysis and recurrence methods. We also evaluate quantitative markers of non-linear dynamics of Leidenfrost drops. |
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G00.00006: Electro-spun poly(lactic acid)/poly(triarylamine) composite nanofibers: Making a biocompatible polymer electroactive Nicholas J Pinto, Alejandro J Cruz-Arzon, William Serrano, Rolando Oyola Composite poly(lactic acid)-(PLA)/poly(triarylamine)-(PTAA) nanofibers were fabricated via electrospinning for the first time. The objective was to make PLA electroactive via the addition of a p-doped conducting polymer (PTAA). Using CHCl3 as the common solvent, several composite solutions of PLA and PTAA were prepared. No phase separation or polymer precipitation was observed in the composite solutions prior to electrospinning. At 1wt% and 3wt% PTAA concentrations, the electro-spun fibers were short, and a large amount of polymer beads filled the target substrate. Above 5wt% the fibers were long and uniform with no bead formation. The fiber diameters increased with increasing PTAA concentration. UV/Vis spectra of the blend solutions show a characteristic peak at 390nm and was similar to the spectra of pure PTAA. Using nanofibers electro-spun from the 5wt% solution we fabricated a p-n diode with a turn-on voltage of 0.63V, and an on/off ratio of 800. In addition, the diode was successfully used to rectify a low frequency ac signal with a rectifier efficiency of 15%. Electrospinning is therefore presented as a facile technique of fabricating electroactive polymer nanofibers that are biocompatible and can be used in devices and sensors. |
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G00.00007: Conformal Invariance in Mechanical Models Siddharth Tiwary The problem of a single bead on a rotating hoop has been studied extensively in the past, and serves as a mechanical model for the Landau theory of phase transitions. We consider a situation with infinitely many beads on a rotating hoop, with each bead coupled to its nearest neighbours with springs. The system approximately obeys the Landau-Ginzburg Hamiltonian, and shows features characteristic of ferromagnetism, such as domain formation and long-range correlations at criticality. This is confirmed using numerical simulations. Moreover, solitons hosted by the system map directly to instanton solutions in the single-bead-on-a-hoop problem. |
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G00.00008: Mechanically Transduced Immunoassay (METRIS) Apparatus Ethan Hall, Brian Winchester Here we present a novel apparatus to work in concernt with the METRIS technique. We propose to develop a Helmholtz-Coil apparatus to drive the motion of magentic probes. Additionally, this structure will be supported with aluminum T-slots and will utilize an inverted light microscope. A slide holder will be manufactured to work with any number of well plate configurations to improve the throughput of this assay and in the future mutliple CMOS cameras will be integrated for simulationaneous visualization and data collection. |
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G00.00009: Electrical characterization of a carbon nanotube network based ferroelectric field effect transistor at different gate voltage scan rates Nicholas J Pinto, Karina Reyes-Olmeda, Kelotchi S Figueroa Nieves, Zhang Qicheng, Christopher Kehayais, Suh Yeonjoon, A T Charlie Johnson A ferroelectric field effect transistor (FE-FET) was fabricated using single walled carbon nanotube networks as the active semiconducting layer, and the copolymer poly (vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) as the ferroelectric gate insulator. The device was electrically characterized at different gate voltage (VG) scan rates in the range 4mV/s < dVG/dt < 1V/s. Gate voltage scan rates play an important role in device operation since it controls the polarization of the gate material. This in turn affects the device on/off ratio, charge mobility, memory window width and other important device parameters. During device operation VG was scanned as follows: -30V → +30V → -30V and resulted in the copolymer dipole switching its orientation between two polarized states (↑↓). The resulting device transconductance curves showed p-type behavior and exhibited a hysteresis due to the FE properties of the gate insulator. At high dVG/dt the hysteresis effect was weak due to the inability of the dipoles to switch orientation, leading to linear operation. As dVG/dt was lowered, the device on/off ratio and charge mobility increased, while the memory window width and sub-threshold swing decreased. Our results show that the volatile and non-volatile modes of operation can be accessed by this device by controlling the gate voltage scan rate. |
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G00.00010: Addition of ZnTe in ITO/CdS/CdTe, ITO/CdS/Si/CdTe, and ITO/CdS/SiGe/CdTe thin films using WxAMPS and Pulsed Laser Deposition Venise Jan Castillon, Matthew Herington, Iain Morton, Sarah Tuttle, Matthew J Melfi, Mehmet A Sahiner Semiconductor materials consisting of a wide band gap such as cadmium sulfide (CdS) show promising potential applications in the area of electronics, specifically photovoltaics. Extensive research has been carried out to maximize its efficiency through the embedding of different nanoparticles to CdS/CdTe thin films such as Ag, Au, and Si. However, recombination loss at the back contact of CdS/CdTe solar cells may occur due to the cell’s high absorption property. Thus, Zinc Telluride (ZnTe) having a wide band gap of 2.26 eV would impede the loss at the back contact, potentially resulting to a higher energy conversion. In this research, the addition of ZnTe layer, impeding the loss at the back contact will be observed. The addition of ZnTe in ITO/CdS/CdTe, ITO/CdS/Si/CdTe, and ITO/CdS/SiGe/CdTe thin films will be implemented both using Widget Provided Analysis of Microelectronic and Photonic Structure (WxAMPS) Simulation and Pulsed Laser Deposition experimentally. In the simulations, the thickness range for ZnTe is kept between 0.1 and 0.35 micrometers and the PLD conditions of the experimental solar cells are optimized according to the photovoltaic conversion parameters from the simulation. |
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G00.00011: Computer simulations of plasma with the one-dimensional electrostatic PIC method: A tutorial description of the method and the development of a desktop application Sara Gómez, Jaime H Hoyos The particle-in-cell (PIC) method constitutes one of the most useful kinetic plasma models being able to simulate different plasma phenomena. The basic assumption of the electrostatic PIC model on which we focus considers that positions and velocities of charged particles take continuous values at the phase space, while spatial macroscopic quantities such as charge density and the associated electric field caused by particle dynamics are calculated at discrete spatial points. We explain the physical details of the PIC which can be obscure for the novel reader and also explain in detail the numerical implementation of the PIC method trying to clarify all the algorithm steps and through the implementation of the numerical code we simulate different electrostatic phenomena in order to gain insight of the plasma physics behind. Also, we develop an application called PlasmAPP which will allow the user to simulate plasma phenomena by varying its parameters trough the use of a friendly graphical user interface. The user will be able to choose the numerical method for solving the equations of motion (Leapgfrog, Euler's Method, Runge-Kutta 4th order) and the Poisson´s equation (Fast Fourier transform, Finite Difference Method) with the aim to compare the functionality and the velocity of the methods. In addition, the application will allow the user to select which diagnostics he wants to see. To show the functionality of the application, we simulate different examples such as the two-stream instability, cold plasma oscillations, ion acoustic waves, and Buneman Instability. |
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G00.00012: Effect of Interfacial Defects on Deflection-Penetration Criteria within PMMA Composites Suraj M Reddy, Zubaer Hossain Looking into the microscale of composites, there is still much more we must understand on what exactly governs the toughness of composite materials. It is important to understand that different regions and properties in composites can influence fracture toughness and how a crack forms. In particular, crack deflection is a mechanism in which a propagating crack tip follows a near parallel line about the interface before penetration of the interface. The criteria for the deflection mechanism to occur play a major role in governing the fracture toughness of a composite material. On the other hand, crack penetration is a critical failure that can cause the crack to completely break through the interfacial region, which will cause a critical failure of the composite material. The relation between deflection and penetration is key to understanding toughness; as the longer a crack experiences deflection, the longer it takes for the crack to penetrate. At the microscale of a composite, the interface will be imperfect, meaning that defects will be very common within the interfacial region. Since it is near impossible to control these defects at the manufacturing phase, we must understand how these defects influence composite toughness. For our choice of composite, we have chosen a Polymethyl Methacrylate (PMMA) composite, which is a synthetic resin that is strong and lightweight. In this work, we have investigated the effect of defect density on the criteria for the penetration of a deflecting crack in a Polymethyl Methacrylate (PMMA) composite, which has yielded useful information that is applicable to the engineering and manufacturing world. After the study was completed, we have concluded that defect density plays an important role in changing the criteria for the crack deflection mechanism. |
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G00.00013: Mechanical Anisotropy and Phase Transition in Black Phosphorus Nathan Zhao Black phosphorus (BP), a puckered 2D allotrope of phosphorus, has shown high carrier mobility and surface area to mass/volume ratio in recent research. Because of this, BP has seen much interest from industries such as electronics, photonics, biomedical applications, linear polarizers, and plasmonics. Due to its unique orthorhombic lattice structure, BP has also shown incredible in-plane anisotropy in thermal, electrical, optical, and phonon properties. Additionally, BP presents novel properties such as a tunable bandgap and thickness-dependent charge-carrier mobility. Using Density Functional Theory (DFT) simulations, we investigate the mechanistic basis of BP's anisotropic properties under different loading conditions spanning both linear and nonlinear regimes of mechanical deformation. Our results suggest a unique anisotropic behavior of BP, where a phase transition occurs when strain is applied in the zigzag direction at Ɛ = 24.79%. Apart from this, analyzing the mechanical properties of the layer and its changed electronic characteristics with increasing strain, we obtain the fundamental insights that govern the unique behavior of BP. Thus, we discuss possible applications of BP in electronics and optics. |
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G00.00014: From superconductor to Anderson Insulator: harnessing disorder in quantum materials DaVonte R Lewis, Hanna Terletska, Wasim R Mondal, Anirudha Mirmira, Sudeshna Sen, Vidhyadhiraja N Sudhindra Superconductors are 21st-century quantum materials that promise fascinating technological and societal benefits once properly harnessed. One of the hurdles we face towards that end is that of disorder: the inherent impurities and imperfections that exist in all real materials. Recently, there has been significant progress in the development of numerical tools capable of treating different ranges of disorder, allowing for a more robust investigation into its effects on the spectral and conducting properties of materials. In this work, using the in-house typical-medium theory of the single-site attractive Hubbard model on a Bethe lattice, we aim to explore the effects of strong disorder on superconductive properties. In particular, our focus is the study of disorder-induced Anderson localization and the associated superconductor-insulator transition (SIT). We construct a phase diagram in the disorder and electron-electron interaction parameter space and demonstrate how sufficiently strong disorder can destroy superconductivity in materials. |
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G00.00015: Sub-10 nm Iron-Oxide Nanospheres and Nanocubes for Hyperthermia Therapy Thomas Hulse, Supun B Attanayake, Amit Chanda, Hariharan Srikanth Magnetic hyperthermia offers promising potential for supplementary cancer therapy. By applying an alternating magnetic field, magnetic nanoparticles generate heat that can raise the temperature of target cells to a point at which they begin to break down. In this research, nanospheres and nanocubes less than 10 nm in size were synthesized and characterized for use in hyperthermia treatment. It was found that these two shapes of superparamagnetic particles exhibit distinct properties below their blocking temperature—namely, the nanocubes display strong exchange bias not present in the nanospheres. This exchange bias, paired with an increase in shape anisotropy, resulted in a higher Specific Absorption Rate (SAR) for nanocubes compared to nanospheres. Finally, measurements on SAR in different mediums were carried out, showing that synthesized nanocubes are superior in hyperthermia treatments compared to nanospheres. |
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G00.00016: Violin Base Glitch Joshua K Katsuren
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G00.00017: Effects on stimulated forward Raman scattering in magnetized density rippled plasma channel K S Senthil Kumaran, Oriza Kamboj, Niti Kant, Jyoti Rajput A plasma wave and two electromagnetic sideband waves are produced by stimulated forward Raman scattering(SFRS) of an intense laser beam propagating in a static, density rippled plasma channel in the presence of a static magnetic field. Langmuir wave along with two electromagnetic sideband waves are produced. The density ripple interacts with the main Langmuir wave created by the SFRS process, resulting in a high Landau damping on the electrons. The electromagnetic waves are localized within a width ≈ (ca/ωpo), where ‘a’ is the channel radius, ‘ωpo' is the plasma frequency on the channel’s axis and ‘c’ is the speed of light. The plasma wave’s localization is determined by the SFRS growth rate. The electron response to eigenmodes is modified by the non-local impact caused by the static magnetic field, which lowers the region of non-local interaction and hence the growth rate. With increasing pump wave amplitude, the growth rate slows down. A theoretical formalism is thus developed to observe the growth rate of SFRS due to the localization of sideband electromagnetic waves. The interaction region and the growth rate are reduced due to localization effects. |
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G00.00018: Effects of Annealing on Thermoelectric Transport in Polycrystalline NbP Katherine A Schlaak, Eleanor F Scott, Chenguang Fu, Satya N Guin, Safa Khodabakhsh, Ashley E Paz e Puente, Claudia Felser, Sarah J Watzman The topological band structure of Weyl semimetals results in highly-mobile two-carrier systems which produce interesting transport properties. The Nernst effect is a thermoelectric phenomenon which occurs upon the application of a temperature gradient and a perpendicular magnetic field, resulting in a mutually orthogonal output voltage. Here, thermoelectric transport properties including the Seebeck effect, magneto-Seebeck effect, Nernst effect, thermal conductivity, and electrical resistivity, are presented for two polycrystalline samples of NbP. We find a significantly pronounced magneto-Seebeck effect, comparable in magnitude to the Nernst effect, which was not present when previously measured isothermally in single crystalline NbP [1]. This magneto-Seebeck effect is linear in magnetic field as theoretically predicted by Skinner and Fu [2]. Due to the similar scale of thermopower contributions from both Seebeck and Nernst effects in a magnetic field, we suggest a device in which the transverse and longitudinal thermopowers are connected electrically in series so that they may be added for even greater conversion between thermal and electrical energy. |
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G00.00019: Connecting Atomic and Electronic Structure in Monolayer FeSe on SrTiO3 Hunter Sims, Alexander Kellerhouse, Tom Berlijn Monolayer FeSe deposited on SrTiO3 exhibits a superconducting TC of 40 – 80 K compared to 8 K in bulk FeSe. We have investigated how the electronic structure of FeSe depends on changes in the atomic structure of the substrate. To do this, we used density function theory (DFT) to simulate the atomic structure of FeSe on top of STO. We see that oxygen vacancies and the alignment of Se above the substate both affect the interlayer distance. With the altering of the interlayer distance doping of the compound is also affected. We also found that Ti impurities placed on the double-TiO layer further affected the bond lengths between FeSe and the surface below. The exact atomic structure of the FeSe/SrTiO3 interface is difficult to determine from experimental data alone, and furthermore the real interface will inevitably be imperfect. We account for both this uncertainty and the likelihood of defects by implementing a Wannier-orbital-based approach that allows us to project the electronic structure, isolate the effect of impurities, and generate structures with arbitrary impurity concentrations. The resulting unfolded band structures are comparable to experimental ARPES spectra and may provide insight into how to isolate and replicate this enhances superconductivity in other materials. |
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G00.00020: Resistivity of doped filled skutterudite compounds: Ce1-xPrxOs4Sb12 (x=0.1, 0.2) Xingyu Zhao, Leticia M Ramos, Zachary C Carrender, Pei-Chun Ho, Tatsuya Yanagisawa, M Brian Maple Through previous experiments, it has been proven that the compound CeOs4Sb12 exhibits properties of Kondo insulating behavior as well antiferromagnetism below 1 K. This compound has a unique temperature-magnetic field (T-H) phase diagram, indicating valence transitions between Ce3+ and Ce4+ are involved [1,2]. Based on these findings, we are planning on observing the effects of hole doping on valence transitions by the Pr substitution of Ce atoms. In this report we will present the preliminary data of T dependence of normal-state resistivity at various magnetic fields of Ce1-xPrxOs4Sb12, where x = 0.1 and 0.2 to monitor the change of phase boundary of valence transitions. Refs: [1] K. Götze et. al, PRB 101, 075102 (2020). [2] P.-C. Ho et. al, PRB 94, 205140 (2016). |
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G00.00021: Experimental study of the effects of interactions on Henkel and △M plots Sauviz Alaei, E. Dan Dahlberg The magnetic field-dependent remanent magnetization and demagnetization of an isoparaffin-based ferrofluid1 have been measured as a function of magnetic interaction strength. Samples of this ferrofluid were prepared with varying magnetite concentrations to alter the average particle separation and thus the magnetic interactions. The ferrofluid samples were demagnetized thermally and frozen prior to measurement of the magnetization and demagnetization remanences. The measured magnetization and demagnetization remanences were plotted parametrically in magnetic field magnitude to produce Henkel and △M plots. The Henkel plots for more concentrated ferrofluid samples deviated from the predictions of the Wohlfarth model for non-interacting particles, and were consistent with demagnetizing interactions in the system. The magnitude of this deviation decreased with decreasing magnetite concentration, and the Henkel plot for the most dilute sample agreed with the Wohlfarth model’s predictions. Furthermore, a quantitative model that accounts for deviations from the Wohlfarth model is presented and may be applied to other systems. |
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G00.00022: Determining the Rotational Period of a Minor Planet via Differential Photometry Jacob P Willis, Jaxon J Porter, Ramsey R Rouabhia We describe the method used to calibrate the West Point Observatory's telescope for the determination of asteroid rotational periods by the analysis of their light curves through differential CCD photometry. The techniques employed are illustrated using observations of the asteroid Eleonora 354 from August 2021 to October 2021 from the US Military Academy, located at West Point, NY. The calibration run was followed by the analysis of photometric data acquired from November 2021 to February 2022 for an asteroid with unknown rotational period. We also present progress made in automating the observatory using software running a script that allows image data collection throughout the night without the need of a person having to be physically present in the observatory. With weather sensors connected, this automation software shuts down the observatory in case of inclement weather unexpectedly rolling in during an imaging session. |
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G00.00023: Influence of the fill height of the fluid on cavitation due to sudden acceleration Hans-Peter Wagner, Andrew Roden, Ian VandeVelde, Peter smith, Heidrun Schmitzer Cavitation is a phenomenon in fluid dynamics that causes a liquid such as water to evaporate during an instant of low pressure and form so-called cavitation bubbles. This instant of low pressure can be caused by a sudden acceleration or pressure wave. We use the sudden downward acceleration from a piston below a cylindrical column of water to cause cavitation. This apparatus was constructed specifically for this experiment to ensure consistent results. Our goal was to investigate how increasing the fill height of the water column would change the amount of cavitation. Therefore we varied the water column fill heights from 0.5 cm to 74 cm. When the piston suddenly accelerates downward, the adhesion between the piston head and the water is broken and a void is created. We found that for a larger fill height of water a bigger void is formed. This void leads to a force of suction against the downward motion of the piston, thus slowing down the piston. However, we did not achieve reliable results to determine whether the number of cavitation bubbles, which form outside the void, relate to the fill height. Further studies are in progress. |
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G00.00024: Investigating the dielectric functions of molecular beam epitaxy-grown PtSe2 films via in-situ spectroscopic ellipsometry Maria Hilse, Roman Engel-Herbert, Dickson Boahen PtSe2 has the distinct advantage high-tunability in its band gap, mainly due to quantum confinement and strong interlayer coupling produced between individual PtSe2 sheets. For this study, we have used a series of PtSe2 films, grown either by directly selenizing ultrathin metal Pt films or by co-depositing Pt and Se on Al2O3 (0001) substrates using molecular beam epitaxy. In-situ spectroscopic ellipsometry were performed on all samples while they were grown inside the MBE chamber. Modeling the ellipsometry spectra, we determined the thickness and the dielectric function of a series of PtSe2. To obtain reliable fits for the experimental spectra, the dielectric function of PtSe2 was represented as a collection of six oscillators, each representing an electronic transition in the Brillouin zone. The first oscillator, representing the fundamental band gap of PtSe2 was located around 1.22 eV, which is consistent with previous published results. |
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G00.00025: Determining the Origins of Helix Glitches in LIGO's H1 Detector Kara G Shepard Because the LIGO detectors are so sensitive, they are highly susceptible to short duration bursts of noise (glitches) from various sources that can disrupt gravitational wave signals. Thus it is important to reduce or eliminate these glitches in the detectors, and in order to do this, the cause of the glitches must be found. |
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G00.00026: Determining Characteristics of Interferometer Glitches Lisa L Johnston Since 2015, interferometers have been able to measure gravitational waves from galactic events. However, these interferometers are necessarily sensitive, and several glitches can occur in the data gathered. Mostly these glitches are caused by environmental factors near or on the interferometers, such as heavy delivery trucks, or recent installations of equipment. I will investigate a certain glitch, named "tealight" due to its appearance on data graphs. It was first noticed by one of many volunteers who sift through significant portions of interferometer data on an open, volunteer-based website, Zooniverse. I will collect data on the tealight glitch, such as the frequency, times the glitch occurred, and which interferometer(s) measured it. With this data, I will compare it with similar data in the large database hosted by Zooniverse, as well as records kept on occurrences at the interferometer. I hope to understand what caused the tealight glitch, with the goal of determining whether such a disturbance was a single event, or something that can be fixed. |
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G00.00027: Atomistic Simulations of Defects in Silicon Carbide Ananya Chakravarti, Elizabeth M Lee, Juan De Pablo Spin defects in silicon carbide (SiC) are desirable platforms to create quantum technologies, such as quantum sensing, communication, and metrology. Notable spin defects are divacancies, which are formed when a silicon and carbon atom adjacent to one another are removed, generating a vacancy complex. Despite their importance, divacancies have been challenging to controllably synthesize experimentally. Here, we provide computational investigations into defect migration phenomena in 4H-SiC, a common polytype that is used experimentally but has not been studied theoretically. We employ classical and ab initio approaches to study the dependence of defect migration and formation on crystal structure, temperature, and defect concentration. We find that the choice of classical force field affects the melting behavior of 4H-SiC. We also find that vacancy migration occurs at an increased frequency for higher defect concentrations. Finally, we show how the crystal symmetry impacts the defect migration behavior across a range of temperatures, using both classical force fields and density functional theory (DFT) calculations. |
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G00.00028: Using a Numerical Model to Investigate the Analytical Limits of Thermal Diffusion Jamie Woodworth, Matthew C. Sullivan Our project explores the thermodynamics of heat transport through a thin metal rod, which is governed by the one-dimensional thermal diffusion equation. This equation has an analytical solution only when you assume a thin metal rod of infinite length where heat is applied instantaneously to an infinitesimal segment of the rod. We created a numerical model of the diffusion equation in order to investigate the situations where the analytical solution breaks down. Our model agrees with the analytical solution under the analytical conditions and can be extended to conditions that violate analytical assumptions, including: finite rod lengths, long heat pulses, and heat-sunk and free-floating rods. In addition, the numerical model can investigate situations that are difficult to replicate experimentally, such as testing various heater sizes. We compared our numerical model to experimental data in systems with both high and low heat loss (in air and in vacuum). Our results show that, when compared to the analytical solution, the numerical simulation more accurately models thermal diffusion in metal rods. |
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G00.00029: Annealing and Characterization of Zinc Doped Niobium Oxide for Neuromorphic Computing Applications Emma G Sargent, Alexander Mesiti, Carl A Ventrice, Karsten Beckmann, Nathaniel Cady, Matthew C. Sullivan, Timothy N Walter, Hans Cho, Alexander C Kozen Deposition of niobium dioxide on silicon wafers is a potential post-transistor application for memristors as part of a neuromorphic computing architecture. Since pure niobium dioxide (NbO2) has a crystallization and insulator to metal transition (IMT) temperature that exceeds the thermal budget of current semiconductor processing techniques, doping NbO2 to reduce both crystallization and IMT temperatures is essential for it to become usable. Through numerous tube furnace anneals with systematically varied temperatures and times, we show that a 10 percent zinc doped sample lowered the NbO2 crystallization temperature by an average of 75°C, lowering the temperature range in which crystallization is observed from 825-900°C to 750-825°C, along with a decrease in requisite annealing time. The crystallization patterns were first observed through optical microscope imaging, and confirmed with XPS and Raman Spectroscopy. Preliminary optical reflectivity measurements performed in an ultra-high vacuum system in an effort to measure the IMT will be discussed. |
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G00.00030: Resonant Coupling of Nonradiating Anapole States to Quantum Emitters Brighton X Coe, Uttam Manna, Michal Szczerba Resonant excitation and manipulation of high-index dielectric nanostructures (such as Silicon, Germanium) provide great opportunities for engineering novel optical phenomena and applications. Here, we report the results of resonant coupling of nonradiating anapole states in silicon nanospheres to quantum emitters in the form of J-aggregates under excitation with radially polarized cylindrical vector beams. The results show that the resonance coupling is accompanied by a scattering peak around the exciton transition frequency, and the anapole mode splits into a pair of eigenmodes. Resonant coupling of the anapole states and heterostructures could be a promising platform for future nanophotonic applications such as in information processing and sensing. |
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G00.00031: Synthesis and photoluminescence studies of colloidal CdSe quantum dots Jordan Natchez-Carroll, Biplob Barman Cadmium Selenide quantum dots (QD) have been widely studied for their photovoltaic properties. CdSe QDs doped with copper have been reported to have a high degree of quantum yield.1This work focuses on a one pot synthesis of CdSe QDs in an ambient atmosphere with varied reaction times, which results in QD emission at different wavelengths. The colloidal QDs were spin coated onto silicon substrates for subsequent reflectance and photoluminescence (PL) measurements. While the former is achieved using a stabilized Tungsten Halogen light source operating in the 360 - 2600 nm range, PL is measured using the 405 nm excitation of a CW laser. All the measurements were performed with the samples placed inside a variable temperature optical cryostat spanning the 10 K - 290 K temperature range. |
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G00.00032: Development of a high sensitivity magneto-optical Kerr effect apparatus for study of spin crossover molecules Alexander Q Phillips, Jonathan Yang, Jared Phillips, Ruihua Cheng Molecular based electronic devices demonstrate promising applications in material science research. Spin crossover molecules exhibit binary stability between high spin and low spin states and the transition between two states can be controlled using different stimuli such as temperature, pressure and light. Recently the electric field manipulation of spin states in spin cross over molecules has attracted much interest in molecular spintronics. The magneto optical Kerr effect (MOKE) shows the interaction of light with magnetic materials and that the photon polarization rotation is proportional to the magnetic moment of the sample. The study of spin crossover molecules using a MOKE apparatus is advantageous due to the surface sensitivity. We have developed a homebuilt MOKE device in order to study the magnetic field effect on spin crossover transition temperature. During the development, computation skill were used to optimize our design. Both the instrumentation development and experimental data on spin crossover molecules will be presented. |
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G00.00033: Gravitational Time Dilation and Chip Scale Atomic Clocks George S Zhang, Sean K Huh, Aaron C Flowers, Timothy J Godsil, Henry B Duggins, Chelsea P Grogan Einstein's theory of general relativity stipulates that clocks in a stronger gravitational field run more slowly than clocks in a weaker gravitational field. This time dilation is difficult to measure when two clocks are at locations separated by small differences in gravitational potential. We explore theoretical aspects of this gravitational time dilation and we attempt to verify them by collecting experimental data using Chip Scale Atomic Clocks (CSACs). We investigate the possibility of detecting gravitational time dilation during balloon satellite flights with CSACs that we will precisely synchronize and characterize for time error. Currently, we are working on identifying and reducing the effect of environmental factors that may influence the accuracy and precision of our CSACs in laboratory conditions and in-flight up to a maximum altitude of approximately 30,000 meters. We expect that this data will be useful for CSACs operating in high-altitude environments as well as future balloon satellite flights. |
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G00.00034: Mobile observations of methane to constrain agricultural greenhouse gas emissions Muhtasim T Hossain, Eric Leibensperger, Jacob Cooney, Jennifer Bockhahn, Lauren Ray, Peter Wright Methane is a potent greenhouse gas that also degrades air quality over decadal time scales. Increases in anthropogenic sources of methane have contributed about a quarter of observed global warming since the preindustrial era. New York State is actively pursuing climate action goals that include the reduction of greenhouse gas emissions, including methane. Thus, locating, quantifying, and monitoring methane sources is critical to set realistic goals and ensure accountability. Here we present mobile observations conducted in central New York to better understand regional methane sources. Using high precision gas sensors mounted on a mobile platform, we performed 6 campaigns to measure concentrations within and around two farms located within the Finger Lakes Region. Methane observations and meteorological measurements were combined to create mass balance estimates of methane emission fluxes from various areas of the farm (barns, waste storage). From our observations within barns, we estimate emission rates of 5-24 kg per barn per day from enteric fermentation. Observations near manure storage indicate emission rates of comparable magnitude, 12-17 kg per day. Our results show that emissions from both the cow and its waste are important considerations for greenhouse gas accounting. |
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G00.00035: Measuring dn/dc for Polysaccharide Microgels of Varying Crosslinking Density Patrick Herron, Andrew L Scherer, Samantha C Tietjen, Kiril A Streletzky Crosslinking chains of amphiphilic polymer suspended in solution yields microgel particles. Due to the properties of the parent polymer, microgels undergo reversible temperature dependent de-swelling. Our microgels were synthesized from a polysaccharide, hydroxypropylcellulose. Static light scattering (SLS) was used to determine the molecular weight, Mw, the radius of gyration, Rg, and the second virial coefficient, A2, of synthesized microgels at varying cross-linker density. However, proper SLS measurements require determination of the specific refractive index increment (dn/dc) for the samples studied. This project is focused on dn/dc measurements for microgel samples of varying crosslinking concentrations. The dn/dc values were found to have a temperature dependence as well as a crosslinker concentration dependence at higher crosslinker concentrations. Here we present how dn/dc results affect the obtained Mw, Rg, and A2 of the microgels and show the importance of direct dn/dc measurements for the samples studied by SLS. |
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G00.00036: Characterizing correlated and topologically driven dynamics of prime knots Hyo Jung Park, Lakshminarayanan Mahadevan, Anna Lappala Knots, as entangled objects, provide a natural platform for studying the link between the dynamics and structure of complex systems. Across the scales, knots have been used in modeling the magnetic flux loop of the sun and vortex formation in fluids. In polymers, knots are known to alter the properties of the polymer bulk such as relaxation time, fragility, and viscosity. In this work, we present a detailed examination of the dynamics of prime knots modelled as polymer chains. We disentangle their complex dynamics into three basis motions— orthogonal, aligned, and mixed— and identify their contributions to the overall dynamics that give rise to a unique set of motions for each knot topology. We also investigate dynamics that emerge purely as a result of topology, focusing on dynamical arrest— the suppression of motions as knot complexity increases. |
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G00.00037: Study of Aeolian Dominated Landscapes in Jezero Crater, Mars Nitika Sachdeva The surface of Mars is dynamically active and is currently being influenced by the high speed winds, dry granular flows and by the sublimation of the seasonal ice deposits. To conduct in situ studies focused on understanding the past geological history and biosignature preservation potential on Mars, a 6 wheeled scientist named Perseverance rover is sent to Jezero crater (~45 km diameter; 18.4°N, 77.7°E). Perseverance rover touched down inside the Jezero crater on 18 February 2021. Jezero crater landing site is surrounded by aeolian landforms of various types that includes sand dunes, transverse aeolian ridges (TARs), slope streaks, dust devil etc. The Perseverance rover on its way to scientifically important sites is very likely to encounter these aeolian landforms, in particular the TARs, as these features dominate the area surrounding the spot where Perseverance landed inside the Jezero crater. So it will be imperative to determine the morphometric characteristics of the TARs within the crater, which is to get a pre-traverse idea of the length, width, and height of the TARs for reducing any traversability risk to the rover. Our study is focused on determining the morphometric details of the TARs located in the vicinity of the Perseverance landing spot. We found that the height of most of the TARs range from 50 meters to 90 meters. Not many TARs with extreme values of height are observed. 66% of all the TARs lie in the 'Intermediate Range'. The study provides new insights into the scale of TARs within the Jezero crater and thus giving the mission team an idea of the terrain complexities that the rover is expected to encounter on its way to the scientific sites for detailed in-situ investigation. |
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G00.00038: Particle Dynamics Through the Earth: A Study of Non-Zero Tunnel Diameters Walker T Hayes A standard problem in undergraduate mechanics derives the trajectory of a particle that has been dropped through a gravity tunnel passing through the center of the Earth as simple harmonic oscillation, assuming constant earth density and negligible tunnel diameter. We show that when the more accurate PREM density profile and non-negligible tunnel diameters are taken into consideration, significant deviations from harmonic oscillations are observed along with reduced particle speeds. Furthermore, we report that a particle traveling perpendicular to the axis of the gravity tunnel is unable to reach the center of the earth beyond a critical tunnel diameter of 71.36% of the earth's diameter under a constant density, or 72.36% of the diameter under the PREM density model. When the rotation of the earth is incorporated, the particle trajectories occasionally extend beyond the surface of the earth at large tunnel diameters, owing to tunnel-induced non-uniformity of the earth's potential energy surface. In addition, we numerically calculate the brachistochrones connecting two points on the surface for various tunnel diameters using the PREM density profile. Our results highlight the effect of non-negligible tunnel diameters on the overall potential energy surface and particle dynamics. |
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G00.00039: First-principles computational prediction of new topological compound Jack Howard, Alexander Rodriguez, Neel Haldolaarachchige, Kalani Hettiarachchi Recent attempts at topological materials have revealed a large class of materials that show gapless surface states protected by time-reversal symmetry and crystal symmetries. Among them, topological insulating states protected by crystal symmetries, instead of time-reversal symmetry are classified as topological crystalline insulators. We computationally predict new 3-dimensional topological crystalline insulating compounds of space group 139(I/4mmm). We perform volume optimization by allowing to rearrange atomic positions and lattice parameters in performing the first principle density functional calculation with a generalized gradient approximation. Multiple Dirac crossings near X and P points on the Brillouin-zone near Fermi energy are identified by imposing spin-orbit coupling. Additionally, we performed formation energy, elastic properties, and phonon modes calculations to verify the structural, mechanical, and dynamic stability of the compound. Therefore, we suggest the compound for further investigation and experimental realization. |
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G00.00040: On the Spectral Cubes and Moment Maps from the Galaxy Datacubes Outputed by SÍGAME Jay Motka Simulator of Galaxy Millimeter/submillimeter Emission (SÍGAME) is a framework that derives far-infrared (FIR) line emissions for particle-based cosmological hydrodynamics simulations galaxies using a postprocessing step that applies radiative transfer and other physics. Using the outputs from SÍGAME, we present a method to create spectral cubes, moment maps, and line profiles of these galaxies. The output galaxy data cubes from SÍGAME contain spatial information, cell sizes, and cell luminosities, which were combined to attain the surface brightness of each pixel, creating moment0 maps of these galaxies by weighing each cell by its volume filling factor in the column covered by each pixel. This algorithm was further extended to integrate the velocity profiles of each cell to create spectral cubes, which were used to generate moment1 maps and line profiles. We also present the use of these moment maps and line profiles to understand the physics of the interstellar medium (ISM) of these galaxies as the same algorithm can also be used to derive the maps of other properties, including surface mass density, star formation rate, and hydrogen density. |
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G00.00041: Patterning of concave wells using monodisperse bubbles for the creation of spheroids. Gilda Castellanos-Von Borstel, Dr. Carlos Luna Lopez Multicellular organisms consist of three-dimensional organized environments. 3D cell culturing shows better in vivo cellular behavior than 2D culture, offering better cellular communication and signaling pathways. Concave wells provide high production of spheroids with reproducible sizes by culturing inside uniform wells. This work is an innovative way to create concave wells by using mono-dispersed bubbles as a patterning force. First, we designed a 3D-printed millifluidic coflow device for the production of homogeneous bubbles. This allows the fabrication of the concave wells to be cost-effective and widely available. Agarose gel was formed inside a 35-mm dish, and bubbles were deposited on top of the agarose. When hardened, concave wells were left behind. By controlling the flow rate, we changed the bubble size and thus the size of the wells. |
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G00.00042: Nanophotonics Research Involving Undergraduates at Illinois State University Dylan D Qualls, Chris Achammer, Minani Alexix, Robert Sevik, Mahua Biswas, Uttam Manna Resonant excitation and manipulation of dielectric nanostructures (such as Silicon, Germanium) provide great opportunities for engineering novel optical phenomena and applications. At Illinois State University (ISU), Manna Lab is involved in investigating various aspects of optical properties of dielectric nanostructures involving undergraduate students. Here, we will present our recent efforts on selective excitation and enhancement of multipolar resonances, and excitation non-radiating anapoles in dielectric nanostructures. |
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G00.00043: First Principles Study of Amorphous Al2O3 Coating in Li-S Battery Electrode Design Jake A Klorman, Kah Chun Lau, Qing Guo The lithium-sulfur (Li-S) battery is exceptionally appealing as an alternative candidate in beyond lithium-ion (Li-ion) battery technology due to its promising high specific energy capacity. However, several obstacles (e.g. polysulfides dissolution, shuttle effect, high volume expansion of the cathode, etc.) remain and thus hinder the commercialization of Li-S batteries. To overcome these challenges, a fundamental study based on atomistic simulation can be very useful. In this work, a comprehensive investigation of the interaction of electrolyte (solvent and salt) molecules, lithium sulfide, and polysulfide molecules with an amorphous Al2O3 surface was performed based on first principles density functional theory (DFT) calculations. The results based on the DFT calculations suggest that the amorphous Al2O3 can be used as a likely coating material in Li-S battery electrode design to tackle these problems. |
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G00.00044: Simulation Studies on CdTe/CdS Solar Cells with Polymer Back Contact Brooke E Richards Cadmium Telluride/Cadmium sulfide (CdTe/CdS) solar cells are one of most studied thin film solar cells, and their efficiencies have reached up to 22.1%. In order to improve the efficiency, a good ohmic back-contact on p-type CdTe is needed. However, CdTe has a high electron affinity (about 4.5 eV), making it hard for a metal to form a good ohmic contact with CdTe. Conducting polymers, with their high work function and conductivity, can be a good alternative for metal back-contact of CdTe solar cells. In our previous studies, we have showed that PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate) can be used as the back-contact of CdTe solar cells, and the results are very promising. |
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G00.00045: Experimental Studies of Applied Magnetic Field Induced Chain Formation in a Magnetorheological Fluid Kayla A Lehtola, E. Dan Dahlberg The physical properties of magnetorheological (MR) fluids change upon application of a magnetic field. One such change is the formation of chains of the magnetic particles. Although chain formation is well known, and there have been some theoretical models of chain formation [1,2,3] this effect has not been studied in detail. Reported here is an investigation in chain formation of a magnetorheological fluid consisting of relatively large magnetic particles, from 150 μm to 850 μm, suspended in either corn syrup or vegetable oil. The length and width of chains was measured as a function of applied magnetic field (5 Gauss to 150 Gauss) and volume fraction of magnetic particles (0.1% to 0.5%). A discussion of the results of the chain formation will be presented. |
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G00.00046: Anisotropic Optical Properties of FePS3 Akarys Yegizbay We have investigated the anisotropic dielectric functions of an antiferromagnetic semiconductor, FePS3. Using a commercially available bulk sample, we performed Mueller matrix-based ellipsometry at multiple angles of incidence, and between 200 nm and 1700 nm. The isotropic model was used as a starting point to analyze each element of the Mueller matrix. In order to develop an anisotropic model, we also performed Mueller matrix-based ellipsometry measurements at several azimuthal angles. Initially, an isotropic model was developed for spectra obtained by conventional ellipsometry. Multiple measurements were performed to improve the signal, and the resulting spectra of each of the Mueller Matrix elements were modeled as a collection of oscillators associated with electronic transitions of FePS3. This analysis shows that the dielectric functions of FePS3 are biaxial, commensurate with its monoclinic crystal structure. The talk will also discuss how the dielectric functions change with temperature. |
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G00.00047: Temperature Dependence of Current Density-Voltage Characteristics of CdTe Solar Cells Eryka Kairo, Weining Wang CdTe solar cells are among the most-studied thin-film solar cells and yet, the efficiency of CdTe solar cells has only reached 22.1%, which is below the theoretical limit. One of the factors limiting the efficiency of the solar cell is the Schottky barrier formed at the back contact. To improve the efficiency of CdTe solar cells, a better understanding of this back contact barrier is needed. |
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G00.00048: Synthesis of Colloidal Silicon Nanosphere Involving Undergraduate Students at Illinois State University Marcos A Perez, Amelia Korveziroska, Uttam Manna, Mahua Biswas High Refractive Index dielectric (HRI) nanoparticles have arisen as an alternative in nanophotonics research for their low loss compared to plasmonic (gold and silver) particles, and the possibility to generate Mie resonances of both electric and magnetic character, which can yield highly directional light scattering. Among several HRI materials, silicon (Si) has attracted significant attention as the lowest order Mie resonances, i.e., the electric and magnetic dipole resonances, of a few hundred nanometer Si sphere appear in the optical regime. In Applied Nanomaterials Lab at Illinois State University, we are using a high-temperature fabrication method to obtain perfectly spherical and monodisperse Si nanoparticles with diameter ~ 150-200 nm dimension for various nanophotonic applications. The fabrication process begins with the high temperature (1500 oC) annealing of silicon monoxide (SiO) to obtain Si nanoparticles embedded in SiO2 matrix. At the end, the Si nanoparticles are liberated from SiO2 using hydrofluoric acid (HF) acid. We have imaged the particles using scanning electron microscopy, and UV-VIS spectroscopy and single particles spectroscopy were performed to characterize the scattering of the particles. |
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G00.00049: Monitoring the structural transformation of polymers via spectroscopic ellipsometry Huijun Mao We have used spectroscopic ellipsometry to map the dielectric function of Poly(Disperse Red 1 methacrylate, PDRM), a thermo-responsive polymer, during its structural transformation. The polymer films were fabricated by dissolving PDRM in tetrahydrofuran, and were spin coated on silicon substrates. Series of films, with varying concentration and thickness were fabricated and analyzed using ellipsometry; spectra were obtained at multiple angles of incidence, and between 200 nm and 1700 nm. The ellipsometry spectra were modelled to obtain the dielectric function and thickness of each film. Subsequently, we coupled a heating stage into the ellipsometer, and obtained temperature-dependent spectra. Analyzing the dielectric function and mapping the corresponding oscillators that represent the dielectric function of PDRM with temperature, allow us to gather information on how the electronic transitions effect the structural transformation. |
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G00.00050: Calculating the Electronic Stopping Power of Perovskites Berkley Delmonico, Rosty B Martinez Duque, Brian C Leininger, Charith R DeSilva, Mario F Borunda Radiation-hard photovoltaic materials are needed to make satellites for deep space powered by solar cells that run effectively while being hit with radiation. We study FAPbI_3 perovskites, which are among the higher-performing materials for solar cells to date. One aspect of curiosity is the electronic stopping power. The electronic stopping power of these perovskites describes the energy transfer rate to electrons in the material during ion irradiation. We calculate in triple-cation perovskites (formamidinium, methylammonium, and cesium) with the inclusion of several intrinsic defects using the SRIM software (Stopping and Range of Ions in Matter), and time-dependent density functional theory (TD-DFT) methodologies. From simulations, we estimate the effects of defects on the stopping process of ions in these systems and their implications in the development of photovoltaic devices for space missions. |
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G00.00051: Source Mass Development for the Axion Resonant InterAction DetectioN Experiment (ARIADNE) Emma R Hogan, Joshua C Long The axion, a light pseudoscalar particle postulated as a solution to the strong CP problem of quantum chromodynamics, has emerged as a leading dark matter candidate. It is also predicted to mediate weak forces between fermions. The Axion Resonant InterAction DetectioN Experiment (ARIADNE) uses Nuclear Magnetic Resonance techniques to probe axion-mediated forces between nucleons with unprecedented sensitivity. A dense, non-magnetic, rotating sprocket is brought into close proximity with a cell of polarized 3He atoms, which are in turn monitored for an induced transverse magnetization with a SQUID sensor. Matching the source rotation to the frequency of the 3He precession is critical to reaching the desired sensitivity. This poster describes the techniques used to develop the source mass, including a periodic, reflective pattern on it for tracking the angular velocity with a laser. Thin film deposition is used to create metallic patterns on a silicon wafer, which is then attached to the sprocket. This process has demonstrated good pattern adhesion and conductivity. The projected sensitivity of the experiment is also discussed. |
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G00.00052: Synthesizing iron oxide nanoparticles for water purification Kristen S Repa, Ryan J O'Connor, Samuel Lotemple Clean water is a basic human right. Many current methods of water purification involve chemicals that are harmful to humans. Processes exist to decrease these chemicals to a safe drinking level, however, they're not gone entirely. Functionalized iron oxide nanoparticles, which are biocompatible, offer a solution in that they can aid in the removal of impurities from drinking water and can be easily removed with external magnets, eliminating the need for harmful chemicals. In this study, we compare three separate synthesis procedures to create the particles: thermal decomposition with oleate coating, chemical co-precipitation with polyethylene glycol coating, and electrolysis with no coating. Each method was examined in terms of yield, efficiency and ease of reaction, and the respective size- shape- and crystallinity-controlling capabilities when producing nanoparticles. Each method successfully synthesized the iron oxide with chemical co-precipitation producing the highest yield. Particles were characterized to confirm appropriate size, shape, and crystallinity. |
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G00.00053: The effect of composition on the dynamics and properties of deep eutectic solvents William D Brackett Deep eutectic solvents (DESs) are an emerging class of materials attracting immense attention for their ideal properties and easy synthesis from bio-friendly components. A fundamental understanding of these materials is still needed, especially how operating at the eutectic composition affects the overall physicochemical properties. To elucidate this, various techniques including differential scanning calorimetry and broadband dielectric spectroscopy were used to examine various DESs above and below their eutectic compositions to observe how the dynamics and properties evolve. Generally, it was observed that the solvents exhibited the fastest dynamics and highest DC ionic conductivity at the eutectic composition corresponding to the lowest melting temperature. |
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G00.00054: Mapping out Teleportation Space for Usage within a Quantum Network Aidan M Gillam Since the seminal paper on quantum teleportation by Bennet et al. PRL 70, 1895 (1993), a large set of new teleportation schemes have been proposed. They involve varying numbers of qubits to be teleported, entanglement resources to enable the teleportation, and quantum circuitry design. I organize these results to achieve two goals: to create a map of the current state of teleportation research and to search for additional teleportation schemes with particular emphasis on networking within quantum computers. |
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G00.00055: Ising model simulation of the effect of nearest neighbors on critical transition temperatures in spin crossover molecular system Sajal Malhotra, Ashley Dale, Ruihua Cheng
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G00.00056: High-Resolution Nonlinear Imaging Mateo Murillo, Zahin Ritee, Sean J Bentley An interferometric optical system for writing arbitrary 2-D patterns on nonlinearly absorbing substrates at a resolution better than normally allowed by the Rayleigh criterion is studied. The manipulation of these patterns can be used to create arbitrary 1-D and even 2-D images at a resolution better than the Rayleigh limit, due to the nonlinear nature of our interference. Both computer simulations and experimental verifications are performed. Computer simulations of this process will account for experimental limitations, such as difraction. Details of the system along with preliminary results will be presented. |
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G00.00057: Nanolithography using Sequential Infiltration Synthesis Involving Undergraduate Students at Illinois State University Amelia M Korveziroska, Marcos A Perez, Devon Mann, Mahua Biswas With the rise in emerging technologies in the field of microelectronics, optoelectronics, sensing, and bioengineering exploring different patterning processes for inorganic nanomaterial patterns became imperative. Sequential infiltration synthesis (SIS) a vapor phase inorganic material deposition method has been established recently to make inorganic nanopatterns using a polymer as a template. SIS enables the control of localized inorganic material growth in the targeted domains of polymers (such as in block copolymers). The effectiveness of the SIS process for advanced nanopatterning has been demonstrated for oxide materials such as aluminum and titanium oxides. In this work, we have fabricated aluminum oxide (Al2O3) nanoparticles using SIS in two different polymers and removed the polymers with oxygen plasma etching (referred to as nanolithography). We have used nanoparticles of polymethylmethacrylate (PMMA) and polycaprolactone (PCL) polymers, which contain active functional groups carbonyl (C=O) to interact with SIS metallic precursor trimethylaluminum (TMA). We have previously shown using in-situ Fourier Transform Infrared Spectroscopy (FTIR) that PCL thin film has strong interaction with TMA and far more compared to PMMA thin film. In this work, we have performed a comparative study on the amount of infiltration in nanoparticles of these polymers and studied the effect on nanoparticles size after nanolithography using scanning electron microscopy. |
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G00.00058: Beam Chopping Control using Digital Pulse Generators Arian G Dovald, Timothy Suzuki, Vola M Andrianarijaona, Charles C Havener In experimental measurements of statistical nature, signal must be extracted from background noise. This applies to the previous absolute cross section measurements of charge transfer [1] with the merged beams technique at the Oak Ridge National Laboratory Multicharged Ion Research Facility. Improvements to the chopping scheme is required to prepare for new high-resolution X-ray measurements from charge transfer between H and highly charged ions using merged beams. This is accomplished by chopping the two beams with pulses from a pair of digital pulse generators. Signal is measured with beam pulses in phase and merged while the background is measured with beam pulses out of phase and de-merged. Once the pulse generators are programmed, electronic counters are used to ensure there are an equal amount of merged and de-merged pulses. |
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G00.00059: Maintaining Ultra High Vacuum Integrity Through Leak Chasing Timothy Suzuki At the Multicharged Ion Research Facility at Oak Ridge National Laboratory, the measurement of charge transfer induced soft X-Rays [1] in a new merged-beams configuration requires ultra-high vacuum to reduce backgrounds. A systematic, reproducible approach to finding and eliminating leaks is vital. Major leaks due to improperly sealed flanges were found by spraying ethyl alcohol on the sealing surfaces and observing fluctuations in pressure using a Pirani gauge. Then, at a vacuum at 10-5 Torr and below, we sprayed helium gas outside the beam lines and observed vacuum fluctuations in the helium levels using a residual gas analyzer (RGA). Ultimate pressures inside a tube held at 1.8 K temperatures where H and ion beams will be merged is expected to be around 10-13 Torr. |
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G00.00060: First Passage of Active Self Propelled System in the Presence of Obstacles Leon Armbruster, Moumita Dasgupta The motility phases of active matter systems depend sensitively on the structural features of their environment. In this study, we investigate the first passage properties of an active self-propelled system - a robotic bug - as it navigates through a heterogeneous environment characterised by spatially patterned densities of obstacles. We show, using extensive experiments and simulations, that different spatial patterning - as characterized by the nature of the obstacles, their number, and physical properties - can give rise to non-trivial first passage properties. We discuss how these results can theoretically be interpreted by simple physical arguments that highlight the interplay between energy and entropy in these systems. |
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G00.00061: Discovery of Novel Thermoelectric Zintl Materials Sarah Longworth, Tiglet Besara This project is aimed at discovering new intermetallic thermoelectric compounds based on Zintl phases. Thermoelectric materials are materials that can convert thermal energy directly into electrical energy via the Seebeck effect, which utilizes a thermal gradient to generate an electric current. Thermoelectric materials are potentially useful in terms of green energy, as they can harness waste heat and therefore make other energy sources and electronic devices more efficient; however, the efficiency of materials needs to be improved before they can be realistically applied to any technology. The discovery of new thermoelectric materials is necessary in order to find more efficient materials. Zintl phases, characterized by wide electronegativity differences that lead to ionic interactions within the crystal, have been shown to have high thermoelectric figure of merits, making them promising candidates in the search for novel thermoelectric materials. Crystals are grown using the flux method in high-temperature furnaces. |
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G00.00062: Title: Quantum Optical Magnetic Field Sensor Amanta A Promi, Sean J Bentley, Shalauni Patel We plan to use the properties of quantum-entangled photons with Faraday's effect to develop a magnetic field sensor with enhanced properties as compared to existing sensors. The Faraday effect is the rotation of polarized light passing through certain materials in the presence of a magnetic field. Light polarization will rotate based on the length of the material, the magnetic field strength and the property of the material known as Verdet constant. In the lab we used two different crystals, Cd0.57Mn0.43Te and Cd0.86Mn0.14Te. For the initial calibration portion of the experiment, we use a laser, a polarizing beam splitter, the Faraday crystal, a linear polarizer, and a power meter. We recorded the power of the beam using the power meter as a function of polarization angle. We are performing the measurement at various distances of the crystal from the magnet to compare the measured field to the theoretical field distribution from the magnet. Currently, we are completing alignment checks of the very sensitive quantum entanglement system as it needs to be optimized before being incorporated into the magnetic field sensor. We will be using entangled photons as a source that will provide unique properties to the Faraday effect sensor. |
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G00.00063: Electrical, thermal, and thermomagnetic transport properties of the chalcopyrite compound CdSnAs2 Eva Laney, Chad Dutra, Wilarachchige D Gunatilleke, Dean Hobbis, George S Nolas, Matt K Beekman In the ongoing effort to identify new semiconducting materials with improved thermoelectric performance, compounds having the chalcopyrite structure with general formula II-IV-V2 are recently receiving significant attention. In the present work, we report the results of a study of the galvanomagnetic, thermomagnetic, and thermal transport properties of CdSnAs2 with the chalcopyrite structure. Temperature dependent transport measurements on nominally undoped polycrystalline CdSnAs2 indicate n-type semiconducting behavior with a relatively high thermoelectric power factor. This is correlated with a very high Hall mobility greater than 1700 cm2 V-1 s-1 at 300 K that increases with temperature, in contrast to the behavior for typical semiconductors. Using the “method of four coefficients,” in which the electrical resistivity, Seebeck coefficient, Hall coefficient, and Nernst coefficient are measured on a single sample, we glean insights into the underlying mechanisms for this behavior and its relationship to the effective mass and dominant charge carrier scattering mechanism in this material. This work contributes to the fundamental understanding of chalcopyrite-based materials, providing guidance for investigations into altering/improving their properties for thermoelectric applications. |
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G00.00064: Influence of voltage offsets on measurement of the Seebeck coefficient Christian K Posadas, Matt K Beekman, Ben C Clark Thermoelectric materials enable conversion of heat to electrical energy with no moving parts. The Seebeck coefficient, defined as the ratio of the thermoelectric voltage generated to the applied temperature difference, S = - dV/dT, is an important material property commonly measured in the characterization of new thermoelectric materials, and directly influences energy conversion efficiency. As such, accurate measurement of S is critical to the design and development of new thermoelectric materials. In this work, we have used simulations to evaluate the influence of voltage offsets on the accuracy of Seebeck measurements performed using common protocols. We discuss how the polarity and magnitude of possible voltage offsets can impact the accuracy of the resulting Seebeck values, including the maximum offsets that can be tolerated under various conditions. The results will be of use to the thermoelectric materials research community, particularly for those wishing to characterize and improve experimental measurement of the Seebeck coefficient. |
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G00.00065: Modeling Ca2+-mediated spontaneous ATP release by neurons Ethan H Fleming, Temitope Adeoye, Angelo Demuro, Ghanim Ullah Stochastic fluctuations in cytosolic Ca2+ play a crucial role in the spontaneous release of ATP and other neurotransmitters by neurons. Here we ask how Ca2+ fluctuations quantitatively relate to various statistics involving the release of ATP. We hypothesized that an increase in Ca2+ concentration in a neuron increases the rate at which ATP is released and decreases the time it takes for ATP to reach its peak release rate. To test this hypothesis, we use a kinetic scheme where the transition rates between different states of the vesicle encapsulating ATP depend on Ca2+ concentration. The model also includes a simple formalism for Ca2+ fluctuations in a neuron. The model agrees well with experimental results and shows that when Ca2+ concentration is increased, peak ATP release rate increases and the time to peak ATP release rate decreases. Since the model is specifically fit to experimental data for the release of ATP, these results may not be generalizable to the release of other neurotransmitters. Additionally, since a simple formalism for Ca2+ dynamics was used, we expect that using a more nuanced model for Ca2+ dynamics will improve the model fit to the experimental data. Finally, we believe that our work sets the stage for investigating the effects of impairments in neuronal Ca2+ homeostasis on ATP release during different neurological diseases. |
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G00.00066: Theoretical and Experimental Investigation of Surface Resistivity of Yttrium Stabilized Zirconium as a Thin Film Vincent De Castro, Matthew P Herington Solid Oxide Fuel Cells are devices that use electrochemical reactions to convert chemical energy from fuel to electricity. In comparison with coal power plants, a SOFC produces a higher electrical conversion efficiency. However, at higher temperatures (1000°C) it creates a lower ionic conductivity, which limit the SOFC. When lowering the temperature, the ohmic resistance increases. In our research, a YSZ layer will be produced from a fine dimple grain structure allowing high flow of oxygen mobility. This mobility increases ionic conductivity and decrease ohmic loss. The goal of our research is first using computational methods to determine the surface resistivity for the simulated YSZ structures and then use these theoretical results to optimize the experimental film deposition parameters that will lead to minimum surface resistivity in these films YSZ thin film synthesis using pulsed laser deposition leads to minimize ohmic resistance of the films at optimum film thickness. We will use Zirconium, Sapphire and Silicon substrates for the YSZ films, and compare the properties of the YSZ layer. The thin films will be characterized through electrical measurements such as 4-point probe resistivity measurements as well as SEM, SIMS, and XPS for the structural and compositional characterization. |
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G00.00067: Construction of Detection Electronics to Measure Superconducting-to-Normal Switching Events in a Josephson Junction Dan A Fauni, Gianna Calligy, Keeran O Ramanathan, Roberto C Ramos Wide interest in superconductor-based quantum computing motivates our investigation of one of the mechanisms driving the readout of the quantum state of a Josephson junction. Escape of a Josephson phase particle from the zero-voltage state of a current-biased, hysteretic Josephson junction has been studied experimentally, in agreement with Kramers theory for the escape of a Brownian particle from a potential well. The effect has been investigated in devices made from single-gap superconductors such as Al and Nb, high-Tc superconductors, and multi-gap superconductors such as MgB2[1]. We report on progress in building electronics that allows physics undergraduates to perform similar experiments using a 2 Kelvin cryocooler, potentially on multi-gap superconductors. The electronics consist of current ramp bias circuit and a Schmidt trigger detection circuit that amplifies and measures the switching of voltage of a Josephson junction, and a universal time interval counter to measure switching statistics. This work is being performed by a team of undergraduates. |
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G00.00068: Temperature dependence conductivity of r-GO in the presence of UV irradiation Idalia Ramos, Jose L Perez-Gordillo, Nayelie M Morales Colón, Anamaris Melendez, Nicholas J Pinto Graphene oxide (GO) was synthesized by the thermal decomposition of sucrose and was reduced by thermal annealing under a nitrogen atmosphere. We report on the conductivity of reduced graphene oxide (r-GO) thin films in the temperature range 20K < T < 300K. The conductivity measurements were performed in vacuum under dark conditions and in the presence of UV irradiation of two different wavelengths (365nm and 254nm). Our results confirm that UV irradiation increases the conductivity, with the short wavelength radiation showing a larger conductivity increase. During the cooling run, the conductivity showed a metallic response at high temperatures, while at low temperatures there was a switch to semiconducting behavior. Short wavelength UV irradiation extended this metallic behavior to lower temperatures compared to that measured under dark conditions. During the heating run however, the conductivity response was semiconducting indicating that the metallic response could have shifted to higher temperatures beyond 300K. Preliminary results indicate that the response to UV irradiation is slow, taking several minutes or even hours to reach saturation. We shall present our analysis on possible conduction mechanisms in r-GO and the response/recovery times to UV irradiation. |
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G00.00069: Repump Laser Light for a Magneto Optical Trap from a Laser Locked to a Frequency-modulated Sideband. Paul Russell, Mara Klebonas, Brendan Silva We have worked on rebuilding a magneto optical trap previously used by our lab group. We have set up an additional injection-locked laser for the repump frequency which is locked to a frequency modulated sideband on our trap laser which is generated by phase modulation at 6.66 GHz. This apparatus will be used to study controlling ultracold collisions with frequency-chirped light. |
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G00.00070: Characterizing the Role of Potential Fluctuations on the Reactivity of a Solvated Electrolyte Pair Alyssa M Spencer, Dylan Suvlu, Adam P Willard Molecular dynamics and free energy pertubarion simulations are performed on a solvated NaCl ion pair in order to determine the contribution of the madelung potential to the vertical energy gap in an electron transfer reaction. This will be acheived by computing the mutual information betweeen the madelung potential around the ions in an aqueous solution and the vertical energy gap using LAMMPs. The bulk water results will then be compared to energy gap calculations at an electrode surface to characterize the solvent effects on the electron transfer reaction. |
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G00.00071: EARLY CAREER
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G00.00072: Correlating Local Structure and Dynamics in Li-salt Liquid Electrolytes using Dielectric Relaxation Spectroscopy Benjamin A Paren, Benjamin D Burke, Jeffrey Lopez, Graham A Leverick, Yang Shao-Horn Understanding the interplay between local structure and dynamics is critical for developing design rules for the next generation of safer, high-performing liquid electrolytes. We present an overview of a set of Li-salt liquid electrolytes at a variety of concentration, studied using dielectric relaxation spectroscopy (DRS). The electrolytes investigated include lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in varying solvents, as well as varying Li-salts with tetraethylene glycol dimethyl ether (tetraglyme) as a solvent. While the conductivity and other physical properties of many of these electrolytes have been previously reported, in this study, DRS is used, in combination with other experimental techniques, to identify relaxation processes associated with the solvent and different ion-solvent coordinating structures. This is accomplished by examining correlations between several electrolyte properties, including conductivity, relaxation time and strength, ionicity, and viscosity. The systematic analysis of the wide range of Li-salts and solvents in this single study provides valuable insight into the different local structures and dynamic processes that contribute to bulk conductivity, laying a foundation for the development of new liquid electrolyte systems. |
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G00.00073: Non-equilibrium statistical physics of complex materials - a story on cement, bacteria and catheters. (Edmond) Tingtao Zhou Many biological and artificial materials and devices operate under non-equilibrium conditions. To optimize their design for manufacturing, performance, and durability, it is critical to understand the fundamental underlying physical principles governing their functionality and performance. In this talk, I will present findings from my research that reveals mechanisms and design principles that apply to complex systems such as bacteria colonies, cement paste, and catheters devices. Specifically, I will talk about the connection of bacteria motion with fractional-order calculus in bounded domains due to power-law statistics and the generalized Central Limit Theory. Then I switch to a new theory ⏤ nanofluidic salt trapping ⏤ proposed for the cement free-thaw damage problem, based on electrokinetics and cement amorphous pore network structure. These two topics are then integrated into a newly proposed manufacturing protocol to exploit activity-assisted assembly to control pore size distribution and network connectivity. Finally, I will discuss geometric design principles of medical catheters, based on our investigations of bacteria upstream swimming inside a channel and physics-informed deep learning approach. |
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G00.00074: Machine Learning Discovery of Multi-Functional Polyimides Lei Tao, Jinlong He, Vikas Varshney, Wei Chen, Ying Li Polyimides have been widely used in modern industries but it takes decades of experimental efforts to develop a successful product. Aiming to discover high-performance polyimides, we utilize computational methods of machine learning (ML) techniques and molecular dynamics (MD) simulations. We first build a dataset of more than 8 million hypothetical polyimides based on the polycondensation of existing dianhydride and diamine/diisocyanate molecules. Then we establish multiple ML models for thermal and mechanical properties of polyimides based on their experimentally reported values. The obtained ML models demonstrate excellent predictive performance and identify the key chemical substructures influencing the thermal and mechanical properties of polyimides. Applying the well-trained ML models, we obtain property predictions of the 8 million hypothetical polyimides. In such way, we explore the whole hypothetical dataset and identify 3 novel polyimides that have better combined properties than existing ones through Pareto frontier analysis. Furthermore, we validate the ML predictions through all-atom MD simulations and examine their experimental synthesizability. This study discovers novel polyimides and guides the further experimental synthesis of innovative polyimides. |
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G00.00075: Investigating parameters in the multi-angle approximate optimization algorithm Rebekah Herrman The multi-angle ansatz for QAOA (ma-QAOA) is a modification of the quantum approximate optimization algorithm (QAOA), which is used to approximately solve combinatorial optimization problems. This modification can improve the approximation ratio by increasing the number of classical parameters from two per iteration to n+m for MaxCut on a graph. Here, n is the number of vertices of the graph and m is the number of edges. A large proportion of the parameters for ma-QAOA receive a value of zero when solving MaxCut on a collection of eight-vertex, fifty-vertex, and one-hundred vertex graphs, so their associated gates can be removed from the circuit implementation which decreases the circuit depth. In this poster, we investigate the relationship between parameters that receive a value of zero and properties of the associated edges and vertices.This work was supported by DARPA ONISQ program under award W911NF-20-2-0051. |
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G00.00076: Constructing large period discrete time crystals with quantum repetition codes Raditya W Bomantara Discrete time crystals (DTCs) represent a class of time-periodic systems characterized by robust observable dynamics that displays n times longer periodicity than the driving period. At present, successful experimental studies are limited to the realization of period-doubling or period-tripling DTCs. My work establishes a connection between the physics of DTCs and the mechanism of quantum repetition codes. This in turn allows the systematic and realistic construction of virtually any large period DTCs, achieved by utilizing a series of spin-1/2 chains and devising a time-periodic Hamiltonian that simulates appropriate quantum gates in a fault-tolerant manner. As a very important feature, explicit numerical studies demonstrate that the proposed DTCs can be directly observed in existing trapped ions and superconducting circuit platforms under the accessible number of particles used in previous successful DTC experiments. This work thus opens an exciting opportunity to bring a new family of DTCs into reality and potentially explore their technological applications in the immediate future. |
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G00.00077: Investigating the Role of Phonons in the Phase Stability of Uranium based Laves phases Erik Nykwest, Zachary Brubaker, Ashley Shields, Andrew Miskowiec, Jennifer Niedziela Laves phases are intermetallic alloys which form in one of three specific structural arrangements, denoted C14 (P63/mmc), C15 (Fd-3mS), and C36 (P63/mmc), and comprise interconnected tetrahedra that facilitate high electrical and thermal conductivity. The factors governing the formation of a Laves phase into one structure over another remains an open question. In particular, the role of phonons, which may provide information about phase transition mechanisms, transition temperatures, and vibrational contributions to entropy, has been widely overlooked. |
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G00.00078: Photoluminescence quenching in mixed-dimensional heterostructures from non-covalent functionalization of monolayer WSe2via aryl diazonium chemistry Iqbal B Utama, Hongfei Zeng, Anushka Dasgupta, Tumpa Sadhukhan, S. Carin Gavin, Dmitry Lebedev, Wei Wang, Jia-Shiang Chen, Kenji Watanabe, Takashi Taniguchi, Tobin J Marks, Xuedan Ma, George C Schatz, Nathaniel P Stern, Mark C Hersam Monolayer WSe2 is an important member of the 2D layered materials family due to its valley physics and excitonic properties with potential applications in quantum optoelectronics. Chemical functionalization of monolayer WSe2 has been performed with nitrobenzenediazonium (4-NBD), resulting in surface functionalization with nitrophenyl oligomers that induces hole doping of the monolayer. Here, we discuss the optical properties of 4-NBD-treated WSe2 at the limit of full coverage of the nitrophenyl oligomers. In ambient conditions, we observe strong photoluminescence (PL) quenching and redshifting. Moreover, the PL at low temperature shows a nearly complete quenching of the exciton fine structures beyond the neutral exciton. This quenching effect is reversible upon oligomer removal and can be attributed to processes beyond hole doping. X-ray photoelectron spectroscopy reveals that the functionalization is non-covalent, and further elucidates the mixed-dimensional heterojunction formation that contributes to PL quenching in a manner consistent with first-principles calculations. Overall, these results demonstrate that diazonium functionalization is an effective pathway for modifying the optical properties of monolayer WSe2. |
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G00.00079: An efficient multiparticle collision dynamics approach to immiscible binary fluids: Hydrodynamics and application to membrane protein diffusion Zihan Tan, Vania Calandrini, Jan Dhont, Roland G Winkler, Gerhard Nägele We present a multiparticle collision dynamics (MPC) implementation of layered immiscible fluids A and B of different shear viscosities separated by planar interfaces[1]. The simulated shear flow profile, and the time-dependent shear stress functions, are in excellent agreement with our continuum hydrodynamics results for the composite fluid. The wave-vector dependent transverse velocity auto-correlation functions in the bulk-fluid regions of the layers decay exponentially, and agree with those of single-phase isotropic MPC fluids. In addition, we determine the hydrodynamic mobilities of an embedded colloidal sphere moving steadily parallel or perpendicular to a fluid-fluid interface, as functions of the distance from the interface. The obtained mobilities are in good agreement with hydrodynamic force multipoles calculations for a no-slip sphere moving under creeping flow conditions near a clean, ideally flat interface. Moreover, we discuss our preliminary simulation results for a simple model of G protein-coupled receptors diffusing alongside a coarse-grained membrane based on a layered binary fluid model. The results show that this model is computationally efficient and feasible to study the diffusion of interacting membrane proteins over extended time and length scales[2]. |
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G00.00080: Magnetic Control of Soft Chiral Phonons in PbTe Andrey Baydin, Felix Hernandez, Martin A Rodriguez-vega, Anderson Okazaki, Fuyang Tay, Gary T Noe, Ikufumi Katayama, Jun Takeda, Hiroyuki Nojiri, Paulo Rappl, Eduardo Abramof, Gregory A Fiete, Junichiro Kono PbTe crystals have a soft transverse optical phonon mode in the terahertz frequency range, which is known to efficiently decay into heat-carrying acoustic phonons, resulting in anomalously low thermal conductivity. Here, we studied this phonon via polarization-dependent terahertz spectroscopy. We observed softening of this mode with decreasing temperature, indicative of incipient ferroelectricity, which we explain through a model including strong anharmonicity with a quartic displacement term. In magnetic fields up to 25T, the phonon mode splits into two modes with opposite handedness, exhibiting circular dichroism. Their frequencies display Zeeman splitting together with an overall diamagnetic shift with increasing magnetic field. Using a group-theoretical approach, we demonstrate that these observations are the result of magnetic field-induced morphic changes in the crystal symmetries through the Lorentz force exerted on the lattice ions. Our study thus reveals a novel process of controlling phonon properties in a soft ionic lattice by a strong magnetic field. |
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G00.00081: On the hunt for new Weyl physics in double-symmetry-breaking Weyl semimetals Hung-Yu Yang Weyl semimetals can exhibit interesting phenomena, such as giant anomalous Hall effect and chiral anomaly, due to their topological properties. However, these reported phenomena may not be unique to Weyl semimetals, or may be hindered by other classical effects, and the search for new Weyl physics - new phenomena that result from the topological Weyl nodes - remains an exciting challenge. Recently, we have been working on a new class of Weyl semimetals RAlSi (R = rare-earths) that break both inversion and time-reversal symmetry, and found evidence of new Weyl physics. In CeAlSi, we observed an unconventional Hall effect, termed “loop Hall effect”, that only appears when the Fermi level is tuned to be in the proximity of the Weyl nodes. In NdAlSi, thanks to the breaking of two symmetries, Weyl-mediated Dzyaloshinskii–Moriya interactions are found to drive collective magnetism and unusual chiral components. Our results show that double-symmetry-breaking Weyl semimetals are promising platforms for finding new Weyl physics. |
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G00.00082: Kinetics of block copolymer micelle fragmentation in mixed ionic liquids Supriya Gupta, Timothy P Lodge Block copolymers self-organize into a myriad of micellar nanostructures when placed in selective solvents, offering great potential as drug delivery carriers and nanoreactors. A comprehensive understanding of the dynamics of micelle formation and equilibration can be very useful to optimize structure-property relationships. Micelle fusion, fragmentation, and chain exchange present the likely relaxation mechanisms leading to micellar equilibration. The present study examines the kinetics of fragmentation of 1,2-polybutadiene-b-poly(ethylene oxide) block copolymer micelles in ionic liquids after a temperature jump. Micelles are characterized using in-situ characterization techniques such as dynamic light scattering, small-angle X-ray scattering, and transmission electron microscopy to obtain the tie evolution of average micelle size, aggregation number, and size distribution, respectively. The role of the driving force for fragmentation on the kinetics is investigated by altering the solvent quality after micelle preparation. Dilution of a selective solvent with a less selective solvent is found to influence the kinetics of fragmentation. |
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G00.00083: The nonequilibrium dynamics of a temporally responsive, single-molecule automaton Zhongmin Zhang, Zhiyue Lu Molecules with multiple meta-stable configurations on rough energy landscapes could demonstrate complex hysteresis responses to various temporally changing environments. We argue that such nonequilibrium hysteresis responses could allow a molecule to recognize, memorize, and respond specifically to temporal patterns of a changing environment. Moreover, such molecules could be steered into far-from-equilibrium configurations if the environment is programmed to change according to specific protocols. We demonstrate both behaviors in a simple solvable model of a linear polymer chain with a temporally controlled end-to-end distance λ(t). A polymer consisting of N foldable segments is modeled by a novel dual-rate master equation over the 2N possible configurations. With an asymmetric energy landscape for folding/unfolding, we designed a polymer that can function as a molecular timer and temporal pattern recorder. Moreover, we discovered that the evolution of the dominant configuration of the molecule acts like an automaton, which allows us to design driving protocols to steer the molecule into nonequilibrium distributions dominated by any desired configuration. |
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G00.00084: Observation of spontaneous valley polarization in a two-dimensional electron system Md. Shafayat Hossain, Meng K Ma, Kevin A Villegas Rosales, Edwin Y Chung, Kenneth W West, Kirk Baldwin, Loren N Pfeiffer, Mansour Shayegan Memory or transistor devices based on electron's spin rather than its charge degree of freedom offer certain advantages and comprise a cornerstone of spintronics. Recent years have witnessed the emergence of a new field, valleytronics, which seeks to exploit electron's valley index rather than its spin. An important component in this quest is the ability to control the valley index in a convenient fashion. Here we show that the valley polarization can be switched from zero to 1 by a small reduction in density, simply tuned by a gate bias, in a 2D electron system. This phenomenon, which is akin to Bloch spin ferromagnetism, arises fundamentally due to electron-electron interaction in an itinerant, dilute electron system. Essentially, the kinetic energy favors an equal distribution of electrons over the available valleys, whereas the interaction between electrons prefers single-valley occupancy below a critical density. The gate-bias-tuned transition we observe is accompanied by a sudden, two-fold change in sample resistance, making the phenomenon of interest for potential valleytronic transistor device applications. Our observation constitutes a quintessential demonstration of valleytronics in a simple experiment. Ref: Md. S. Hossain et al., Phys. Rev. Lett. 127, 116601 (2021). |
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G00.00085: Using analogical reasoning to build transferable models Cody L Petrie, Christian N Anderson, Casie Maekawa, Travis Maekawa, Mark K Transtrum Humans use analogical reasoning to connect understanding of one system to another. Can machines use similar abstractions to transfer their learning from training data to other regimes? The Manifold Boundary Approximation Method constructs simple, reduced models of target phenomena in a data-driven way. We consider the set of all such reduced models and use the topological relationships among them to reason about model selection for new, unobserved phenomena. Given minimal models for several target behaviors, we introduce the supremum principle as a criterion for selecting a new, transferable model. The supremum principle shares connections with the theory of analogical reasoning in cognitive psychology. Having unified the relevant mechanisms, the supremal model, i.e., the least upper bound, is the simplest model that reduces to each of the target behaviors. Describing multiple behavioral regimes, the supremal model provides a controller to move between various states of interest, e.g., sick and healthy cells in systems biology. Additionally, the supremal model transfers to domains outside of the training data, allowing it to describe new, emergent behaviors. We present a general algorithm for constructing a supremal model and demonstrate with examples from various disciplines. |
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G00.00086: Structural Bayesian Optimization for Active Physical Learning: Applications in Ferroelectrics and Magnetic Systems Ayana Ghosh, Sergei V Kalinin, Maxim Ziatdinov A typical modern-day scientific study includes learnings from both theoretical and experimental components. Even though such methods are different by the nature of their operations, both rely on explorations over parameter spaces. Classical Bayesian Optimization (BO) provides a smart way to explore broad parameter spaces, well suitable for solving data-driven scenarios where inclusion of physical knowledge is not necessarily important. To incorporate physical knowledge in the form of priors, we combine unstructured (non-parametric) and structured (semi-parametric and parametric) BO approaches in this work. This approach seeks to guide exploration of parameter space while refining physical laws to describe functional behavior over this space. It also uses combined aleatoric, estimated epistemic uncertainty to guide the exploration. This routine is demonstrated for modeling magnetization using Ising model, simulating excitation energies for two dimensional magnetic systems and energy wells for ferroelectrics. It is aimed to be extended towards performing automated experiment in the context of automated materials synthesis and microscopies. |
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G00.00087: Investigation on the stress-free two-way shape memory effect of semicrystalline networks towards reversible shape-shifting hinges and metamaterial structures Nicoletta Inverardi, Giulia Scalet, Maurizio Toselli, Massimo Messori, Ferdinando Auricchio, Stefano Pandini Soft materials capable of autonomously changing their shape with an on-demand and reversible response are considered very interesting in the fields of soft robotics and bioengineering, for the development of artificial muscles, smart grippers and active hinges. To this aim, the use of two-way shape memory polymers results promising. These materials are capable of switching between two shapes when exposed to cooling/heating cycles across their crystallization and melting regions both under stress-driven and stress-free conditions. Here, we characterized semicrystalline networks based on poly(ε-caprolactone) crosslinked by a sol-gel approach or by photocrosslinking. All the materials displayed an excellent two-way shape memory effect under the application of an external load. Interestingly, after the set-up of a proper thermo-mechanical protocol as a training step, it was possible to achieve a stress-free reversible deformation under tensile and bending conditions. The effect of the macromolecular architecture and the employed thermo-mechanical parameters (actuation temperature and applied pre-strain) was investigated to identify optimal conditions for the development of responsive hinges and of an auxetic unit cell capable of repeatedly self-expanding and shrinking. |
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G00.00088: Symmetry-Enforced Topology of Chiral Band Crossings Wan Yee Yau, Kirill Alpin, Niclas Heinsdorf, Moritz M Hirschmann, Andreas P Schnyder Chiral band crossings, like Weyl points, are points where two or more energy bands become degenerate. They are of interest since they emit Berry flux, which is in turn related to the Chern number as a topological invariant. The latter characterizes the surface states and the anomalous responses to external perturbations. In this work we use the relation between screw rotation symmetries and the chiralities to obtain constraints on the total number of chiral crossings. By utilizing the fermion doubling theorem it becomes possible to predict the existence of a non-zero number of topological crossings independently of the specific system. Our discussion explains how this amplifies 2D band crossings, nodal planes, with a nontrivial topology and it yields an overlooked type of double Weyl point. To show the validity of the method, we study the band topology of general tight-binding models and propose example materials. |
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G00.00089: Joint Parity-Time (PT) and Anti-Parity-Time (APT) Symmetric Qubits Julia Cen, Avadh B Saxena One of the greatest obstacles to building large-scale quantum computers is the sensitivity of qubits to noise from their environment. This can shorten quantum computers' computational lifetime and lead to high error rates. A common way to mitigate this is by using quantum error correction, but this can be expensive in terms of qubit count. We suggest another approach, which is through incorporating non-Hermiticity with PT and APT symmetries into our qubits. We consider a PT and APT-symmetric two-level system coupled to a bosonic bath and present how to compute the dynamics and properties for these models by utilizing a time-dependent Dyson map for density matrices. We observe improved properties of decoherence, von Neumann entanglement entropy, and quantum Fisher information. This suggests that non-Hermitian PT and APT-symmetric qubits may be better suited for quantum computing and quantum information processing than conventional Hermitian qubits. |
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G00.00090: The Interplay of Fermi liquid theory and Luttinger's theorem in strongly correlated materials Joshuah T Heath Fermi liquid theory and Luttinger's theorem are two fundamental results in condensed matter physics which connect the degrees of freedom in the interacting system to those of the free Fermi gas. In the case of a Landau-Fermi liquid, the many-body physics and thermodynamics are described with the assistance of renormalized quasiparticles, while for systems where Luttinger's theorem is applicable the Fermi volume remains invariant with respect to interaction strength. While these two theorems are normally thought to go hand-in-hand, the underlying microscopic requirements for both are highly non-trivial, and require careful consideration. In this poster, I will explore and categorize both "Luttinger's theorem violating Fermi liquids" and "Luttinger's theorem preserving non-Fermi liquids", in addition to briefly discussing recent work on when both Luttinger's theorem and Fermi liquid theory remain applicable near an unconventional quantum critical point. |
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G00.00091: The conservation and nonlinear conversion of spatiotemporal topological charges of light Chen-Ting Liao, Guan Gui, Nathan Brooks, Henry C Kapteyn, Margaret M Murnane The orbital angular momentum (OAM) of light is a type of angular momentum (longitudinal OAM), associated with wavefront or phase vortices in the electromagnetic field and it has been demonstrated very useful in applications such as optical tweezer, super-resolution microscopy, telecommunication, scatterometry, and quantum information. On the other hand, light carrying spatiotemporal orbital angular momentum (ST-OAM) is a recently discovered type of structured and localized electromagnetic field. This field carries characteristic space-time spiral phase structure and transverse intrinsic OAM. ST-OAM of light was theoretically proposed 15 years ago and finally realized experimentally over the past 5 years. In this work, we present the generation and characterization of the second-harmonic of ST-OAM pulses. We uncovered the conservation of transverse OAM in a second-harmonic generation process for the first time. We found that the space-time topological charge of the fundamental field is doubled along with the optical frequency. Our experiment thus suggests a general ST-OAM nonlinear scaling rule— analogous to that in conventional OAM of light. Furthermore, we observe that the topology of a second-harmonic ST-OAM pulse can be modified by complex spatiotemporal astigmatism when using a thick nonlinear crystal. After analyzing canonical momentum density and energy density flux of fundamental and second-harmonic ST-OAM pulses, we identified the causes of spatiotemporal astigmatism in a dispersive medium that gives rise to multiple phase singularities separated in space and time. Our study opens a new route for nonlinear conversion and scaling of light carrying ST-OAM with the potential for driving other secondary ST-OAM sources from electromagnetic waves, mechanical or acoustic waves, to matter waves such as electrons and neutrons. |
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G00.00092: Defect mediated morphogenesis Livio Nicola Carenza, Ludwig A Hoffmann, Julia Eckert, Luca Giomi It has been a long-standing mystery how complex biological structures emerge during embryonic development from such seemingly uncoordinated building blocks as cells and tissues without guidance. Recent experiments suggested that misalignment in the collective structure –so called topological defects– could play a fundamental guiding role in morphogenesis. Here, we provide a theoretical study explaining how active defects interact with geometry and how this could play a crucial role in morphogenetic processes. Using a combination of computational fluid dynamics and analytics we study the instabilities of a cell monolayer in the framework of the active gel theory. We consider an active polar liquid crystals coupled to an elastic deformable surface. We find that the cooperative interaction of active disclinations and geometry drives the buckling instability of the active membrane. This eventually results in the formation of long protrusions with a tentacle shape or even the nucleation of a vescicle. This work clarifies the interaction of active defects and geometry and provides potentially new insight into the physics beyond processes such as the metastatic cascade in cancer development or embryogenesis. |
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G00.00093: Structural transformation determination in Sodium Chloride during shock compression and release Vinay Rastogi, Raymond F Smith, Damian C Swift, Richard Briggs, Martin G Gorman, Amy L Coleman, Dayne E Fratanduono, Jon H Eggert, Cynthia A Bolme, Federica Coppari, Arianna Gleason, Hae Ja Lee, Phil Heimann, Thomas S Duffy, June K Wicks
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G00.00094: Highly non-linear interlayer exciton-polaritons in bilayer MoS2 Biswajit Datta, Mandeep Khatoniar, Prathmesh Deshmukh, Rezlind Bushati, Simone D Liberato, Stephane K Cohen, Vinod M Menon Realizing nonlinear optical response in the low photon density limit in solid state systems has been a long-standing challenge. Semiconductor microcavities in the strong coupling regime hosting light-matter quasiparticles called exciton-polaritons have emerged as an attractive candidate in this context. However, the weak interaction between these quasiparticles has been a hurdle in this quest. Two-dimensional transition metal dichalcogenides (TMDCs) owing to their inherently large oscillator strength present an opportunity to address this challenge. A prime candidate is the interlayer excitons that form in heterostructures of TMDCs. Due to the spatial separation of the electron and holes in different layers, they have a permanent dipole moment making them interact stronger. This advantage is often diminished by their poor oscillator strength making them unsuitable for realizing polaritons. The recent discovery of interlayer excitons in naturally occurring homobilayer MoS2 alleviates this issue owing to their hybrid characteristics arising from the interlayer charge transfer state and intralayer B exciton. Here we demonstrate the strong coupling of interlayer excitons in bilayer MoS2 with cavity photons resulting in unprecedented nonlinear interaction strengths. A ten-fold increase in nonlinearity is observed for the interlayer excitons compared to the conventional A excitons which have been used extensively for strong coupling studies. The measured interaction strength in the weak pump limit is ~100 µeV µm2. The formation of the interlayer exciton-polaritons in naturally occurring homobilayers of TMDCs makes them very attractive for scalability. |
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G00.00095: Stabilizing fluctuating high-temperature ferromagnetism in YTiO3 by optically driving the lattice Ankit S Disa In complex oxides, the coupling between spin, orbital, and lattice degrees of freedom leads to competing ground states and, often, large fluctuations of the order parameter up to high temperatures. The Mott insulating rare-earth titanates provide a prime example of such physics, where structural distortions dictate the t2g orbital order and the low-temperature magnetism. Here, we explore the effect of selective optical phonon excitation in ferromagnetic YTiO3 which is known to exhibit magnetic fluctuations well in excess of Tc (= 27 K). We discover an ultrafast, phonon-dependent magnetization change below Tc induced by the pump and a corresponding modified ferromagnetic onset temperature. The strongest effect is found when driving the 9 THz B2u mode, for which the enhanced magnetization at low temperatures saturates at the ideal spin-½ limit and non-equilibrium ferromagnetism persists up to ~100 K, more than 3 equilibrium Tc. Our findings are explained with a coupled spin-orbital model, in which the optically driven lattice vibrations modify the occupied t2g orbital states and reduce competing antiferromagnetic fluctuations. These results highlight the ability to optically engineer crystal structures to realize non-equilibrium functional properties in complex oxides. |
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G00.00096: Enabling Electrically Controllable Nanophotonic Structures Using 2D Materials Safura Sharifi, Yaser Banadaki, Georgios Veronis The rapid development and unique properties of two-dimensional (2D) materials enable them to become intriguing candidates for future photonic applications. We propose new aperiodic multilayer structures based on 2D materials to enable fully electrically controllable switchability. The structure is composed of alternating layers of graphene and hexagonal Boron Nitride (hBN) sandwiched between two layers of Tungsten Disulfide (WS2). This aperiodic multilayer structure provides spectra-altering properties similar to those of more complex and harder to fabricate two- or three-dimensional structures, demonstrating a proof of concept to design and implement more complex structures. We use a hybrid optimization method, consisting of a micro-genetic global optimization algorithm coupled to a local optimization algorithm, to find the optimum thicknesses of the layers in the aperiodic multilayer structure in order to maximize the absorptance to the excellent value of unity at a prespecified wavelength, under zero bias condition. By changing the chemical potential, we can manipulate the refractive index of Graphene and thus have control over absorption. The structure is promising for various applications, such as spacecraft thermal control systems (TCS). |
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G00.00097: Thermoelectric properties of inversion symmetry broken Weyl semimetal-Superconductor (WSM-SC) junction Ruchi Saxena, Nirnoy Basak, Pritam Chatterjee, Sumathi Rao, Arijit Saha We theoretically study the thermoelectric properties following the work by of an inversion symmetry broken Weyl semimetal and proximitized superconductor (WSM-SC) junction employing Landauer-Büttiker formalism to noninteracting systems. The study unfolds interesting features of various relevant physical quantities such as thermal conductance, thermoelectric coefficient and figure of merit. Further, we compute the ratio of thermal to electrical conductance in different temperature ranges and found that the Wiedemann-Franz law violates for small temperatures near the Weyl point while saturates to the Lorentz number for metals away from it at all temperatures. Contrasting with other Dirac material hetrostructures, we provide a detailed analysis of the thermal transport in the WSM-SC hetrostructure that would help fabricating mesoscopic thermoelectric devices based on thermoelectric effects. |
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G00.00098: Polarized Resonant Soft X-ray scattering reveals interfacial molecular orientation in amorphous regions of multi-phase organic films. Camille Bishop, Thomas Ferron, Marie E Fiori, Eliot H Gann, Mark D Ediger, Dean M DeLongchamp Molecular orientation at interfaces in multi-component and semi-crystalline films can significantly affect the material's function, but it can be difficult to quantify. The interaction between oriented chemical bonds and polarized resonant soft X-rays results in scattering (p-RSoXS) that is sensitive to interfacial molecular orientation, in addition to chemical composition. We use p-RSoXS to measure both a two-component, phase separated vapor-deposited glass, and a semi-crystalline polymer. For both systems, we use a forward-scattering GPU-accelerated simulation based on high-quality real space imaging to identify a real-space model that produces a combination of compositional, orientational, and vacuum scattering contrast that is consistent with experiment. This approach allows us to measure the direction, spatial extent, and magnitude of orientation in molecules at amorphous-amorphous and amorphous-crystalline interfaces. These results provide insight into the effect of processing conditions on the structure and properties of non-equilibrium materials. |
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G00.00099: Accelerated importance sampling of energy landscapes with discrete symmetries and barriers Matthew J Grasinger When the energy landscape of a thermodynamic system consists of multiple wells separated by large barriers, the convergence rate of the standard Metropolis Markov chain Monte Carlo (MCMC) method can suffer from slow convergence. Here we show that in many cases, energy barriers are a consequence of discrete (approximate) symmetries in the Hamiltonian and develop a group-theoretic based sampling algorithm which uses knowledge of these symmetries to accelerate convergence of MCMC. We show that this group theoretic sampling approach is a generalization of the well-known and highly successful clustering algorithms. Importantly, this method does not rely on the symmetries being exact, but merely approximate, so that the approach is more broadly applicable and can consider the effects of symmetry breaking. We present results from Hamiltonians with discrete reflection, rotational, and translational approximate symmetries for which the proposed method convergences much more rapidly than either standard or umbrella sampling. We conclude by outlining how the proposed method is well-suited for studying polymers subject to electromagnetic fields with potential phase transitions, which has far reaching applications in energy harvesting, soft bio-inspired robotics and biomedical devices. |
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G00.00100: Ultra-fast and low-noise homemade cryogenic transimpedance amplifier for spin-qubit read-out Heorhii Bohuslavskyi, Masayuki Hashisaka, Takase Shimizu, Takafumi Akiho, Koji Muraki, Norio Kumada While radio-frequency reflectometry and circuit-quantum-electrodynamics spin-qubit read-out techniques are promising for large qubit arrays [1], they are challenging to implement for quickly benchmarking new qubit materials and geometries. Cryogenic current amplifiers for fast charge sensing reported in 2007 [2] have a measurement bandwidth similar to the current reflectometry setups. Here we report on home-made GaAs HEMT-based, low-noise cryogenic transimpedance amplifiers with low power consumption of 2mW. |
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G00.00101: Self-consistent Schrödinger-Poisson simulation of Quantum Point Contacts with varying top gate shapes Eleni Chatzikyriakou, Junliang Wang, Maria Cecilia da Silva Figueira, Thomas Grange, Antonio Lacerda Santos Neto, Christopher Bäuerle, Xavier Waintal Quantum Point Contacts (QPC) are essential components in many quantum nanoelectronics, due to the control they provide in quantum channels.1 Their operation has only been examined before using a combination of numerical and analytical techniques, or using only a single device. We present herein the results of three-dimensional self-consistent Schrödinger-Poisson simulations for different designs of the surface gates that define the shape of the electron density distribution in the 2DEG under a GaAs/AlGaAs heterostructure. Each design is also examined at varying dimensions. The parameters used for the simulations were extracted from experiments. The method used to extract the simulated voltage at which the last conductance channel in the experimental QPC is expected to turn-off (pinch-off voltage) is also presented. A very good agreement between the two was achieved with the parameters used throughout our work. |
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G00.00102: Tunable, ferroelectricity-inducing, spin-spiral magnetic ordering in monolayer FeOCl Deliang Bao, Andrew O'Hara, Shixuan Du, Sokrates T Pantelides Spin spirals (SS) are a special case of non-collinear magnetic ordering, where the magnetic-moment direction rotates along an axis. The presence of SS ordering reduces the symmetry of the electron density and induces a spontaneous electrical polarization (ferroelectricity, FE) without atomic displacements. Materials with such features have potential applications in spintronics and information technology. The SS have been observed on multilayers/interfaces and artificial metal-atom films/chains, but so far not on monolayer (ML) two-dimensional (2D) materials. Here, we report density-functional-theory calculations and demonstrate that SS form in ML FeOCl, which was recently synthesized. The propagation wavelength and energetic stability of the SS can be tuned by electronic doping and uniaxial strain. Relative to the ferromagnetic state, the spin-spiral state's bandgap increases in both bulk and ML FeOCl by ~0.6 eV, enabling bandgap engineering through magnetism manipulation. A SS-induced out-of-plane FE in ML FeOCl is predicted, whereby the SS chirality can be switched by an electric field. Finally, forming a heterostructure, e.g., with graphene or boron nitride, SS are sustained, thus providing another way of modulation and the potential for magnetoelectric devices. |
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G00.00103: Emergence of memory manifolds Kamesh Krishnamurthy, Tankut U Can The ability to store continuous variables in the state of a biological system (e.g. a neural network) is critical for many behaviours. Most models for implementing such a memory manifold require hand-crafted symmetries in the interactions or precise fine-tuning of parameters. We present a general principle that we refer to as frozen stabilisation, which allows a family of neural networks to self-organise to a critical state exhibiting memory manifolds without parameter fine-tuning or symmetries. The principle works by momentarily freezing/slowing the dynamics of a subpopulation, thereby creating a static background input which serves to stabilise the remaining population. These memory manifolds exhibit a true continuum of memory states and can be used as general purpose integrators for inputs aligned with the manifold. Perturbations off the manifold relax back to equilibrium with a heavy-tailed distribution of timescales. The response to inputs over a wide range of timescales is an essentially collective property of the system. Moreover, frozen stabilisation allows robust memory manifolds in small networks, which is relevant to the puzzle of implementing continuous attractors with a small number of neurons in light of recent experimental discoveries. |
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G00.00104: Strong correlation in atomically thin 1T-TaSe2 Siqi Wang, Yi Chen, Peiyao Zhang, Sui Yang, Takashi Taniguchi, Kenji Watanabe, Kai Rossnagel, Michael F Crommie, Xiang Zhang Charge density wave (CDW) alters the electronic structure of its host material by periodically distorting the lattice. As a result, electronic states drastically different from the host may emerge after the reconstruction, sometimes exhibiting surprising properties. In 1T-phase tantalum dichalcogenides, a unique star-of-David shape CDW forms at low temperatures, where 12 tantalum atoms aggregate towards the central one. While band structure calculations have shown the reconstruction results in a flat band of 5d character around the Fermi level, subject to a Mott transition into a correlated insulator, controversial experimental evidence of metallic and insulating phases coexists, possibly due to complicated vertical stacking of the CDW pattern. Fortunately, recent advances in van der Waals materials provides the access to individual layer properties with unprecedented control and therefore make the “bottom-up” study of these complicated systems possible. With state-of-the-art two-dimensional material preparation and characterization techniques, we successfully prepared 1T-TaSe2 devices down to bilayer thickness and discovered the emergence of a correlated insulating phase at the atomic limit with transport and tunneling measurements. Density functional theory calculation revealed the charge transfer insulator nature and demonstrated a suppression of this phase in the bulk due to the hybridization between the central tantalum 5dz2 orbital and nearby selenium 4pz orbitals. An 1T/1H heterostructures was further prepared via thermally induced polymorph transition to examine the magnetic ground state in monolayer 1T-TaSe2. Both transport and scanning tunneling spectroscopy measurements confirmed the existence of localized magnetic moments and established the system as a quantum spin liquid candidate. Our results have provided a promising and versatile platform for the investigation of strongly correlated physics in atomically thin 1T-TaSe2. |
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G00.00105: Deep high resolution 4D ultrafast ultrasound imaging with 2D matrix arrays Hanna Bendjador, Josquin Foiret, Robert Wodnicki, Katherine W Ferrara As a non-invasive, non-irradiant and accessible modality, ultrafast ultrasound is more and more favored. Particularly, its role in cancer diagnosis is crucial since a cheap and highly effective imaging modality will allow early and wide screening of patients and considerably enhance the survival rates. In this work, we propose a novel probe design to provide unprecedented spatial resolution in ultrasound imaging, from three spatial dimensions up to 4D (x,y,z,t) when imaging media on ultrafast time scales. |
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G00.00106: Strongly enhanced quantum emitter fluorescence from a single nano-de-focusing waveguide Nicholas A Gusken, Ming Fu, Maximilian Zapf, Michael Nielsen, Paul Dichtl, Robert Roeder, Stefan A Maier, Carsten Ronning, Rupert F Oulton Enhancing quantum emitter fluorescence by tailoring its electromagnetic environment on the nanoscale is key for realizing brighter light sources with associated control over their modal coupling behaviour. In this context, the Purcell effect [1] constitutes an important mechanism allowing to greatly enhance fluorescence rate of emitters when coupled to electromagnetic cavity modes. However, highly resonant structures such as dielectric cavities are inherently bandwidth limited, strongly restricting their use to one specific transition or optical state. Meanwhile, metallic structures can provide extremely high enhancement factors over a wide frequency range due to small modal volumes provided by plasmonic sub-wavelength confinement, even off-resonance. One important feature, which has remained elusive in this context, is the efficient coupling and guided extraction of enhanced quantum emission on and from the nanoscale. |
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G00.00107: Molecular view of the plasticization process of poly(vinyl) alcohol. Ernesto Carlos Cortes Morales, Jonathan K Whitmer, Vikramjit S Rathee, Ahmad Ghobadi The use of atomistic simulations is currently being used in addressing questions of mechanism in many materials, such as self-assembly phenomena in polymers, or host-guest binding applied for drug design, among others. When combining simulations with advance sampling methods that are able to bias the potential energy surface based on preset slow collective variables the simulation improves its efficiency, and this opens the possibility to treat more realistic complex systems. In this work, we will follow the analysis of the free energies governing the interactions of complex systems by employing the Artificial Neural Network sampling method developed by Hythem and Whitmer (JCP 2018). The discussion will highlight the configurational sampling using atomistic simulations of a polymer chain model, and its interaction with different small-weight molecules, representing with their interaction the plasticization process. In particular, we focus on conformational and hydrogen bond-structure changes induced in globules of a polymer chain by the plasticizer molecules, with the hypothesis that hydrogen bonding plays a role in the incorporation into polymer materials, and thus in the observed mechanical properties. The findings derived from this system showcase physical features relevant to the design of tailored materials, and the methods developed are intended to be part of a robust framework applicable to an assortment of experimental works useful for industrial proposes. |
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G00.00108: PHYSICS EDUCATION
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G00.00109: Two Content Pathways in Presenting Electromagnetism in Introductory Algebra-Based Physics Textbooks Liang Zeng, Yi Zeng, Guang Zeng Vector cross products play a fundamental role in determining the directions of electromagnetism in introductory physics courses. After examining thirteen introductory algebra-based physics textbooks, we found authors adopt the following two content pathways in presenting the electromagnetic phenomena: Over 90% of the textbooks follow pathway one which presents only algebraic formulas and mnemonic techniques for right- and left-hand rules. Scarcely few follow pathway two, which presents vector cross products as a mathematical model and reinforces this model by presenting the specific cross product formula for each electromagnetic phenomenon. Physics instructors teaching college physics courses similarly present electromagnetism using these two content pathways. In light of Bloom’s taxonomy of educational objectives and constructivist learning theory, we recommend the second pathway. |
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G00.00110: Demonstration of phase transitions using a 1D longitudinal mechanical topological insulator Parker A Fairfield, Luke Thatcher, Juan M Merlo-Ramirez We constructed a mechanical model of a metallic spring to demonstrate the properties of a one-dimensional Su-Schrieffer-Heeger (SSH) model of topological insulators. In our model, the spring propagates longitudinal waves and was shown to demonstrate phase transitions between the insulator, conductor, and topological insulator phases of the SSH model. The former was done by changing the spring constant between atoms within sites. A clear edge state was also shown in the topological insulator phase. In addition, these findings are supported by a mathematical model derived from the mechanics of harmonic oscillators. Our device is simple to construct and easy to understand. It is a great tool to demonstrate an important aspect of condensed-matter physics research to undergraduate students. |
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G00.00111: Teaching graduate quantum mechanics in the 21st century John S Faulkner The choices of topics and emphasis in the new textbook "Modern Quantum Mechanics and Quantum Information" by J. S. Faulkner stem from the demonstrated interests of the physics community. Those interests are best illustrated by the list of the divisions of the American Physical Society (APS) that represent physicists who use quantum mechanics. The divisions established between 1943 and 1950 cover the fields of atomic physics, condensed matter physics, and chemical physics. The interest in applying the developments in those fields to the understanding of commercially interesting materials instigated the establishment of the Division of Materials Physics in 1984 and the Division of Computational Physics in 1986. In 2017, the rapidly growing applications of quantum mechanics into such new areas as quantum computing and quantum cryptography led to the establishment of the Division of Quantum Information. Topics in "Modern Quantum Mechanics and Quantum Information" that do not appear in older texts are the following. A mathematically sound treatment of delta functions and the rigged Hilbert space. A large chapter on relativistic Dirac theory. The explanation of chemical bonds and energy band theory. A separate chapter on group theory including Lie groups. A chapter on exotic quantum phenomena such as the Berry phase and quantum erasure. A chapter on interpretations of quantum theory. Two chapters on quantum computers and quantum cryptography that prepare the student to read and understand Shor's fundamental paper. Many-body theory including density functional theory and Feynman diagrams. |
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G00.00112: Lesson learned from remote and HyFlex teaching and learning Mahendra B Thapa In the initial phase of COVID-19, teaching and learning were performed remotely using a combination of available resources such as email, zoom, and skype. In fact, heavy adaptation of those technologies was necessary to cope with the unexpected situation. Both students and instructors were frequently overwhelmed. To support sick and quarantined students in this situation, many instructors also ran remote or hybrid flexible (HyFlex) classrooms. In this presentation, I will share students' responses on questions such as (i) What worked for you and what didn't during remote/HyFlex class, and (ii) Share your perceptions about remote/HyFlex class in comparison to in-person class. Student responses were collected via survey throughout the semester. I will focus my discussion on (a) how students' feedback correlates with their grade, and (b) how the active learning and flipped classwork went. The feedback and data were collected from students from a teaching focused, four-year university and a community college. All students were taking either of following courses: general algebra-based physics, calculus-based physics, and introductory astronomy. Initial data shows that the digital-divide has also been playing an important role for the successful remote or HyFlex class and self-motivated hardworking students are among the least affected when transitioned to the remote and HyFlex classroom. |
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G00.00113: Adding hands-on activities one week at a time: a sustainable approach to enrich undergraduate physics curricula using minilabs Laura Clarke, Neelam Sheoran, Erin Crites, Dana Thomas, Joy Gayles Most physics undergraduate curricula have relatively few class-based, hands-on experiences. At NC State, aside from one electronics course, majors have no labs for two years. This scheme negatively impacts students inclined towards experimental work and those intending bachelor's degree careers. Since 2012, we have developed a minilab program which enables labless physics courses to add an experimental component (a single lab innately associated with the course content) which students perform on research-grade equipment in a shared user facility. Other minilabs help develop confidence and connect with real-world applications for freshman students. Each experiment (and associated analysis) replaces a traditional homework assignment for one week of the course; minilabs are mostly unchanged from year to year and are taught by a single TA. This scheme provides an enriched undergraduate experience with minimal financial or faculty time cost. Examples are measuring the mechanical properties of salt-water taffy, observation of chaotic motion, and carbon dating of Brazil nuts. We discuss student perceptions (what they learn, what they like) and recent preliminary results that assess these activities in the context of physics ability beliefs, belonging, and persistence. |
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G00.00114: Writing-to-Learn in Introductory Materials Science and Engineering Hongling Lu, Leah Marks, Timothy Chambers, Solaire Finkenstaedt-Quinn, Rachel S Goldman Writing to Learn (WTL) enables students to apply content knowledge to "real-world" situations via writing, which promotes deeper thinking and compels students to explain concepts in their own words. The subsequent peer review and revision processes provide additional learning opportunities as the students give and receive feedback and critically assess their work. In this poster, we describe the impact of writing‐to‐learn (WTL) on promoting conceptual understanding of introductory materials science and engineering, including crystal structures, stress‐strain behavior, phase diagrams, and corrosion. Using pre/post assessments and analysis of writing products, we examine student gains in conceptual understanding and critical reasoning. Our research suggests that WTL assignment was effective in promoting understanding of microscopic properties to macroscopic behavior. For all draft submissions (following the peer review stage), writing fellows provide rigorous written feedback to the students. This additional intervention provides a scaffolded review process in which students receive directed feedback and reinforcement on how to better align with assignment expectations and goals. We also investigate the effects of this additional intervention on student learning. |
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G00.00115: Development a prototype of a didactic tool for the development of laboratory practices (HeDiLab) John E Ordoñez, Carlos W Sanchez, Victor Viera The didactic tool for the development of laboratory practices - HeDiLab, aims to improve the learning of the students of Catholic Universitary Foundation "Lumen Gentium" in the study of chemical and thermodynamic phenomena, tracing as an application route the articulation of concepts and theories with phenomenology, experiments and mathematical models. Internally, it is composed of a Raspberry Pi 4 microcomputer, Arduino Mega 2560 development boards, and externally with different modules with sensors for voltage, current, light intensity, temperature, among others. As it is made from free access hardware and software elements, it allows improving the teacher / phenomenon / student interaction, through a series of experimental practices or teacher-oriented experiences in the selected subjects. To facilitate its implementation, it has a software that allows the user to interact with the tool and its different modules, as well as a learning material that through laboratory guides of chemical and thermodynamic phenomena will allow the student an improvement in apprehension of knowledge. Also, it is intended to encourage the use of free access programs, such as LibreOffice, which has characteristics very similar to the office package for commercial use. Finally, some laboratory practices that could be developed by users (student, laboratory worker and teacher) with the help of a tool are described. |
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G00.00116: Graduate Physics Programs During COVID-19: Admissions, Resilience and Diversity Christopher D Porter, Geoff Potvin, Galen Pickett The sudden COVID-19 outbreak introduced unexpected barriers and uncertainty for prospective graduate students and physics departments. Chief among concerns are the safety and health of students, recruitment, economic shortfalls resulting from reduced enrollment, and effects on the diversity of incoming graduate cohorts. More recently, programs have attempted to return to “normalcy”, while still ensuring the safety of students and employees. Our group is conducting surveys of students and physics departments, augmented by follow-up interviews with both groups, between fall 2020 and spring 2022. We will report on how COVID-19 has impacted the processes, pressures, and demographics of physics graduate programs, and also on the primary concerns that emerged among first-year graduate students. We will also discuss the process of returning to pre-pandemic operations, and the resilience of various programs. We will present practices implemented by departments, with special attention paid to those that have been successful in maintaining the size, diversity, and preparedness of the 2020 and 2021 graduate cohorts. We will compare and contrast findings from the first “pandemic academic year” (2020-21) with the current academic year (2021-22). |
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G00.00117: OUTREACH AND ENGAGING THE PUBLIC
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G00.00118: │Hop> - A board game for quantum many-body physicists João S Ferreira |Hop> is a new competitive strategic board game aimed at quantum researchers and students alike. Players compete in a lattice structure to cause a short-circuit and win the game. To do so, they must apply important concepts of quantum many-body physics such as Pauli's principle, spin flips, vortices, etc. |
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G00.00119: Soft matter physics in art: Engaging art students and enriching their practice Baudouin Saintyves I will share my physicist experience teaching at the School of the Art Institute of Chicago (SAIC) as their scientist-in-residence. The reciprocal influence of art and science is obvious when noticing the many relationships between scientific discoveries, new inventions, and art movements. Soft matter physics is of special interest, as it deals with materials, scales, properties, and “visuals” that are relevant to a broad range of artistic disciplines. Painters work with suspensions, emulsions, polymers, flows and drying processes. Fashion designers play with knitted patterns and wrinkling instabilities. Printmakers deal with capillary action and fluid transport in paper. Architects think about force networks, modular assemblies, or the links between collective behaviors and spatial boundaries. My course, which I have entitled “The Physics of Shapes, from nature to the hand”, introduces state-of-the-art concepts of soft matter physics from the perspective of pattern formation, both in nature and in human creations. With examples from my students' final projects, I will show how hands-on soft matter physics expend their art practices, an opportunity for more personal engagement in a public that is often “physics anxious”. I will also share my experience in an online setting giving lectures, kitchen home labs, and bringing together artists and researchers as an invited curator of SAIC’s Conversation on Art and Science speaker series. |
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G00.00120: A Virtual Physics Camp for Middle School Girls during COVID Kayla Dickert, Dan A Fauni, Gianna Calligy, Keeran O Ramanathan, Roberto C Ramos How does a virtual physics camp for middle school girls during the COVID pandemic look like? We will present our experience in organizing and executing the Virtual Physics Wonder Girls Summer Camp in 2021. The theme of this year's free, week-long physics camp revolves around renewable energies and quantum physics. On its ninth year, the camp provides immersion experiences to cohorts of middle school girls selected from a pool of high-performing students in the Philadelphia-New Jersey area. Campers come from diverse communities and are introduced to renewable energy and the basics of solar cells, and experience project-building by building and testing solar cars, and solar boats, and do hands-on optics experiments. Campers receives a free kit of materials for projects and experiments. Campers interact with physics majors who serve as crew, women physicists and engineers, experience virtual tours of plants and manufacturing facilities, and give capstone presentations. |
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G00.00121: PUBLIC POLICY
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G00.00122: Research Integrity, the Responsible Conduct of Research, and Plagiarism Cases Analysis Aaron Manka Among its duties, the National Science Foundation (NSF) Office of Inspector General (OIG) is responsible for helping ensure the integrity of research programs at NSF. We investigate allegations of research misconduct (plagiarism, falsification, and fabrication) in NSF proposals and awards. We handle allegations conflict of interests and violations of the confidentiality of NSF’s merit review to ensure the integrity of that process. We also investigate allegations of retaliation against whistleblowers. |
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G00.00123: Prevention of accidental nuclear war by developing a dual-code launching system Donald C Chang In the past several decades, mankind have been living under the threat of nuclear war. Under the current system, a leader of any country with nuclear arms can start a nuclear attack unilaterally. There is no check and balance from the international community. Once a country uses nuclear weapons to attack another country, it can trigger an all-out nuclear war. It could be the end of human civilization! |
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G00.00124: ENERGY RESEARCH AND APPLICATIONS
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G00.00125: The effects of polarization on the rotational diffusion of ions in Organic Ionic Plastic Crystals SeoWoo Park, Bong June Sung The organic ionic plastic crystals (OIPCs) have been regarded as a great solid-state electrolyte due to their high stability and conductivity. Conventional solid electrolytes have high viscosity such that it is hard to achieve high electrical conductivity. However, ions in OIPCs maintain a long-range ordered crystalline lattice structure but may rotate simultaneously. The rotational motions facilitate the diffusion of dopant ions, which also enhances the conductivity. Therefore, it is important to investigate the rotational diffusion in OIPCs at a molecular level, where molecular simulations can be a great tool. But polarization effects have not been taken into account because of high computational costs and lacks of proper models. In this work, we investigate how the polarization affects the rotational diffusion of OIPCs. We perform atomistic molecular dynamics simulations of 1-methyl-3-methylimidazolium hexafluorophosphate ([MMIM][PF6]) at temperatures from 75 to 500K under NPT conditions with and without electronic polarization. Polarization increases the density of [MMIM][PF6] slightly. However, we find polarization induces a faster rotational relaxation, which will certainly enhance the diffusion and the conductivity of dopants in OIPCs. |
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G00.00126: Spectroscopic and computational analysis of the dimeric chlorophyll acceptor in the M688HPsaA genetic variant of Photosystem I Elijah M Gruszecki, Michael J Gorka, Philip Charles, Vidmantas Kalendra, John H Golbeck, K.V. Lakshmi Studies of the photosynthetic reaction center, Photosystem I (PSI), have shown that its polypeptide core contains highly coupled chlorophyll molecules that serve as the primary electron donor and acceptor. Notably, a recent study found that the primary acceptor, A0, is a dimer of chlorophyll a molecules, Chl2 and Chl3, where the electron spin density on the reduced acceptor, A0-, is distributed on both molecules.1 Previous biochemical studies have shown that the replacement of the soft base sulfur axial ligand of Chl3A from a methionine residue to a hard base nitrogen ligand of a histidine in the M688HPsaA variant of PSI severely impacts forward electron transfer from the A0A cofactor.2 In this study, we determine the electronic structure of the A0- state of M688HPsaA PSI using a combination of experimental hyperfine sublevel correlation (HYSCORE) spectroscopy and computational analysis including molecular dynamics and density functional theory (DFT).3 Understanding the electronic structure of the dimeric A0 acceptor in the wild- type and M688HPsaA variant of PSI has widespread implications ranging from the evolution of naturally occurring reaction centers to the development of a new generation of highly efficient artificial photosynthetic systems. |
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G00.00127: The role of cation disorder in the low conversion efficiency of Cu2ZnSnS4 kesterite solar absorber Wei Chen, Diana Dahliah, Gian-Marco Rignanese, Geoffroy Hautier The power conversion efficiency of kesterite solar cells remains at a low level compared to other thin-film technologies despite years of optimization. The low efficiency is often associated with the extensive cation disorder, but recent experiments show that a higher degree of ordering does not necessarily improve the open-circuit voltage, thereby questioning the actual role of cation disorder. Through a statistical treatment of disorder in the Cu2ZnSnS4 (CZTS) absorber, we show that extensive Cu--Zn disorder alone cannot be responsible for the large Urbach tails observed in many CZTS solar cells. While cation disorder reduces the band gap as a result of the Gaussian tails formed near the valence-band edge due to Cu clustering, band-gap fluctuations contribute only marginally to the open-circuit voltage deficit, excluding Cu--Zn disorder as the primary source of the low efficiency of CZTS devices. On the other hand, the extensive disorder stabilizes the formation of Sn on Zn antisite and its defect complexes, which as nonradiative recombination centers account for the large open-circuit voltage loss in CZTS. Our analysis suggests that a further improvement of the conversion efficiency for CZTS devices is challenging given the persistent presence of catio disorder. |
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G00.00128: Thermionic Cooling and Energy Coversion with Functionalized Carbon Nanotubes Thin Flim Feng Jin, Ansibert Miruko, Ethan Carman Strong thermionic emission is a key to thermionic cooling and thermionic energy conversion. Thermionic cooling and energy conversion using functionalized carbon nanotubes with a thin layer of low-work function barium strontium oxide thin film is presented. Surface temperature reduction as much as 81 oC has been obtained, and the and the thermionic cooling efficiency, defined as thermionic cooling power as a percentage of total input heating power to the surface, is reported as well. The large thermionic cooling effect observed is a result of strong thermionic emission that ejects a large amount of hot electrons from the surface. Details of the fabrication of the surface coating, as well the measurement of the thermionic cooling effect, and thermionic cooling efficiency are also provided. |
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G00.00129: Computational studies of defect mediated ion transport mechanisms in organic ionic plastic crystals Hyungshick Park, Bong June Sung Organic ionic plastic crystals (OIPCs) have drawn attention as one of excellent solid electrolytes due to its high ionic conductivities and plastic-like mechanical properties. Due to its crystalline nature, defects mediated ion transport mechanisms were suggested. Experiments showed the relationship between ion conductivities and the defect volumes. Also, grain boundary diffusion mechanisms were suggested from NMR data. However, the length and lifetime scales of defects were so short that it was challenging to investigate the transport mechanism at a molecular level via experimental techniques. In this study, we conduct atomistic molecular dynamics simulations to understand the effect of defects on the dynamics of ions in OIPCs. Two types of defects are considered: 1) point vacancies and 2) grain boundaries (GBs). With point vacancies, the mobilities of all species are facilitated. In addition, matrix ions show enhanced dynamic heterogeneities in the presence of point vacancies. In the case of GBs, disordered structures at boundaries are observed. We find that Li+ diffuses along the boundaries and coordinates with more anions than Li+ in bulk crystals without any vacancies. In the future study, correlated motions between Li+ and anions will be investigated. |
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G00.00130: Electron-phonon Interaction and Fröhlich Polaron Diffusion of Ferroelectric Perovskite Materials Koichi Yamashita, Masanori Kaneko In 2009, methylammonium lead perovskite was introduced as a light-absorbing material for solar cells, and solar cells based on this material achieved an astonishing conversion efficiency improvement of 25% in 2020. It has been pointed out that the diffusion distance of photogenerated carriers (electrons and holes) is extremely long compared to that of conventional semiconductor inorganic materials as a factor for the high efficiency, but the mechanism of carrier recombination suppression remains unclear. In this study, based on first-principles calculations of carrier-phonon interactions in ferroelectric perovskite materials, we discuss the mechanism of carrier recombination suppression in terms of Fröhlich polaron formation due to the interaction between photogenerated carriers and longitudinal optical phonons. |
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G00.00131: Exploring Exciton and Polaron Dominated Photophysical Phenomena in Ruddlesden-Popper Phases of Ban+1ZrnS3n+1 (n=1-3) from Many Body Perturbation Theory Deepika Gill, Saswata Bhattachara Ruddlesden-Popper (RP) phases of Ban+1ZrnS3n+1 are an evolving class of chalcogenide perovskites in the field of optoelectronics, especially in solar cells. However, detailed studies regarding its optical, excitonic, polaronic, and transport properties are hitherto unknown. Here, we have explored the excitonic and polaronic effect using several first-principles based methodologies under the framework of Many Body Perturbation Theory. Unlike its bulk counterpart, the optical and excitonic anisotropy are observed in Ban+1ZrnS3n+1 (n = 1-3) RP phases. As per the Wannier-Mott approach, the ionic contribution to the dielectric constant is important, but it gets decreased on increasing n in Ban+1ZrnS3n+1. The exciton binding energy is found to be dependent on the presence of large electron-phonon coupling. We further observed maximum charge carrier mobility in the Ba2ZrS4 phase. As per our analysis, the optical phonon modes are observed to dominate the acoustic phonon modes, leading to a decrease in polaron mobility on increasing n in Ban+1ZrnS3n+1 (n = 1-3). |
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G00.00132: Exploring Lead-Free Perovskite Solar Cells by Machine Learning Suzune Omori, Hinako Hatanaka, Masanori Kaneko, Koichi Yamashita, Azusa Muraoka Perovskite solar cells have high energy conversion efficiency and are one of the promising next generation solar cells that are expected to generate renewable resources and solve the global energy problems. The remarkable performance includes a large absorption coefficient in the UV-visible absorption spectra, high carrier conductivity, long electron and hole diffusion lengths, and direct band gap properties. Perovskite solar cells can be easily synthesized at low cost, but the toxicity of typical candidate compound materials due to the presence of lead is a problem. Recently, Nakajima et al. performed DFT calculations on 11025 new candidate materials in a high-throughput study using the supercomputer "K" [1]. Based on the obtained data sets, we used statistical and machine learning methods to explore the suitable candidate compounds for solar cell materials. As a result, we were able to identify the important physical properties for the features we focused on and evaluate the scatter plot to analyze the compounds suitable for solar cell materials. |
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G00.00133: Theoretical study of the charge separation process in NTz-based fluorinated non-fullerene type organic thin-film solar cells Sumire Ikeyama, Nozomi Ohta, Reina Tachibana, Koichi Yamashita, Azusa Muraoka In order to further improve the light conversion efficiency of organic thin-film solar cells (OSCs), it is important to search for high-performance donor (D)/acceptor (A) materials based on the elucidation of exciton dynamics and photoelectric conversion mechanism at the D/A laminated structure interface. Recently, it has been reported that the bulk heterojunction OSCs, which contain fluorinated naphtho [1,2-c:5,6-c'] bis [1,2,5] thiadiazole-based non-fullerene acceptors has a better photovoltaic performance [1]. In this study, we calculated absorption spectra, excitation energy transfer (EET), the amount of transferred charge and the charge transferred distance with the non-fullerene complex PCPD-TBT (D)/NTz-Teh–FA (A) and the fluorinated PCPD-TBT (D)/FNTz-Teh-FA (A). We performed DFT calculations with ωB97XD/6-31G(d) using Gaussian16. Comparing fluorination with non-fluorination, since the charge transfer distance is long, it is considered that there is a strong tendency for a 'hot process' that does not involve the charge transfer state between the exciton generation and the charge separation state. In addition, it is considered that the charge separation efficiency is increased from EET. |
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G00.00134: Investigation of MgV2O4 as a Cathode Material for Multivalent Ion Batteries Using Atomic Resolution Electron Microscopy Francisco J Lagunas Vargas, Grant C. B Alexander, Christian Moscosa, Linhua Hu, Jordi Cabana-Jimenez, Robert F Klie Nanocrystal spinel vanadium oxides are promising candidate materials for post lithium rechargeable batteries. Recent reports demonstrate that, despite the presence of complex structural defects, V2O4 nanocrystals are capable of cycling Mg2+ at capacities greater than Cr and Mn spinel counterparts [1]. In this contribution, we will present a characterization of spinel MgV2O4 using atomic resolution scanning transmission electron microscopy (STEM) techniques, such as nanoscale electron energy loss measurements (EELS) and x-ray energy dispersive spectroscopy (XEDS) elemental determination. As part of our analysis, we will explore the effects that crystal size and structural defects have on electrochemical cycling performance. We will demonstrate that nanocrystalline particles (~5nm in diameter) react entirely upon electrochemical cycling, while activity in larger crystals is typically confined to a thin surface layer. Using nanoscale EELS measurements, we will measure variability in electrochemical activity between individual particles as well as locally within larger single crystals. |
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G00.00135: Understanding the role of Li in strongly correlated cathode material LiMnO2: Density functional and dynamical mean-field theory calculations Vijay R Singh, Tomas Rojas, Hyowon Park, Anh T Ngo Layered lithium intercalating transition metal (TM) oxides are promising cathode materials for Li-ion batteries. LiNiO2 doped with Co, LiNi1-xCoxO2, are widely used as cathode materials for rechargeable lithium-ion batteries. However, the high cost and the potential toxicity of Co make it imperative to search for alternative cathode materials. In this regard, LiMnO2, equivalent in a chemical formula to LiCoO2, has drawn much attention because of the lower cost and the more environmentally benign nature of Mn as opposed to Co. In this talk, combining density functional theory with dynamical mean-field theory (DFT+DMFT), we will discuss the electronic structure properties of strongly correlated LiMnO2 at different delithiation levels, specifically in their paramagnetic state. Interestingly, an insulating solution with an energy gap value was obtained in agreement with experimental data. We will also discuss the role of Li-2s in understanding the hidden correlation effects in these materials. In order to understand the role of Li to apprehend the strong correlation in LiMnO2, we apply the crystal orbital Hamilton population method where chemical bond analysis dissects the effects of Li in LiMnO2. Coupling between Mn-3d and Li-2s orbital hybridization will also be discussed. |
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G00.00136: Hybrid Supercapacitor Electrodes Made of Carbon Nanotubes, Zeolitic Imidazole Framework and Molybdenum Disulfide Jong Hyun Choi, Jaehoon Ji, Duncan Houpt Supercapacitors are electrochemical energy storage devices that are developed to bridge the gap between batteries and capacitors. Despite the progress over the years, the energy densities of supercapacitors are not yet comparable to those of lithium-ion batteries. This work introduces a hierarchical framework composed of hetero-materials for synergetic effects. We prepared an electrode with a highly conductive network of carbon nanotubes (CNT) encapsulated by zeolitic imidazole framework (ZIF) allowing a fast ion diffusion and molybdenum disulfide (MoS2) offering a large ion capacity. The hybrid electrode shows exceptional performances, with a specific capacitance over 262 F/g and an energy density of ~52 Wh/kg at 20 mV/s while maintaining a high-power density. Our analysis suggests that the ternary network behaves as a hybrid supercapacitor through both double-layer capacitive and faradaic reactive mechanisms. We monitored the outstanding durability with 95 % of the capacitance retention over 30,000 cycles. The findings from this study could help develop highly efficient energy devices. |
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G00.00137: Characterizing the Back-Contact Interface of Poly-Crystalline Cd(Se)Te Devices Using Transmission Electron Microscopy John Farrell, Robert F Klie, Michael Heben, Adam B Phillps, Manoj Jamarkattel Poly-crystalline Cd(Se)Te based thin film solar cells have shown to be competitive in terms of efficiency and cost of electricity production. Yet, the presence of hetero-interfaces in Cd(Se)Te structure and low minority carrier lifetime have limited the thin film devices from reaching their maximum theoretical efficiency of approximately 30 percent.[1] The back-contact of CdSeTe devices is a significant limitation to increased device performance since no metal has been identified that has a sufficiently high work function for Ohmic contact with the CdTe absorber at the back-surface of the film stack. Thin layers of different materials are tried for band-engineering to achieve passivation and hole-selectivity.[2] Here, we will explore novel back-contact film layers in an effort to overcome this energy band mismatch. Atomic-resolution imaging in a scanning transmission electron microscope (STEM) combined with electron energy-loss spectroscopy (EELS) and energy-dispersive X-ray spectroscopy (XEDS) are used to characterize these devices and to inform the production process. The goal is to identify the ideal atomic and electronic structures, as well as any interfacial diffusion of elements. |
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G00.00138: Adding Barium Thiocyanate to CsPbBr3 Perovskite Nanocrystals for Better WLEDs Saroj Thapa, Gopi C Adhikari, Yang Yue, Hongyang Zhu, Peifen Zhu The potential of all-inorganic cesium lead bromide (CsPbBr3) perovskites as promising emitters has gained significant attention in the development of solid-state lightings and displays technology. Engineering the composition of ions in perovskite structure controls the characteristics of the material, including bandgap, morphology, and electronic properties. However, few reports have dealt with the effect of simultaneous doping at the Pb2+ and Br− lattice sites. This report summarizes the impact of Ba(SCN)2 (with Ba2+ and SCN− as a substituent to Pb2+ and Br−, respectively) on the optoelectronic performance of CsPbBr3 nanocrystals (NCs). The experimental results demonstrated that the combined effect of Ba2+ and SCN− enhances the optical performance of materials, primarily the photoluminescence quantum yield (~98%) and long-term stability towards air and moisture, due to the mitigation of non-radiative radiative centers. Implications of color-tunable NCs over a novel 3D-printed multiplex design result in white light-emitting diodes with a characteristic correlated color temperature of 6764 K and a color rendering index of 87. |
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G00.00139: Relation of site disorder, band gap and localization in ZnGeN2 Jacob Cordell, Moira K Miller, M. Brooks Tellekamp, Garritt Tucker, Adele Tamboli, Stephan Lany In ZnGeN2, site disorder is studied to manipulate the band gap to align with current technological deficiencies at green/amber emission wavelengths in light emitting diodes known as the “green gap,” while maintaining low lattice mismatch with GaN. We present cluster-based Monte Carlo simulations to evaluate site disorder in ZnGeN2 at short- and long-range. Converged configurations are relaxed in volume and lattice parameters through Density Functional Theory. Band gap-corrected hybrid calculations are used to obtain the electronic structure of the 1,024 atom supercells and structural and electronic parameters are then used in device modeling to study the effects of site disorder on quantum well design for light emitting diodes. We calculate nitrogen coordination and Bragg-Williams short- and long-range order parameters, respectively, to relate order and electronic structure and analyze state localization as a means of differentiating defect states from band gaps which remain ill-defined in disordered systems. In ZnGeN2, the non-isovalent character of the disordered species (Zn2+ and Ge4+) subjects the cation ordering to strong short-range order effects which influence band structure by decreasing the band gap relative to ordered ZnGeN2 across a wide range. |
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G00.00140: Lithium doped nickel ferrite for enhanced performance in hydroelectric cell SANDEEP SAINI, K. L. Yadav, Jyoti Shah, R. K. Kotnala Hydroelectric cell (HEC) is one of the emerging devices in green energy production that produce electricity by splitting water molecules on the sites of unsaturated cations, oxygen vacancies or surface defects. Oxygen vacancies and surface defects are the active sites for the water adsorption/dissociation on the surface of metal oxides. To increase these defects in the nickel ferrite, we synthesized lithium substituted nickel ferrite and pure nickel ferrite via the Ball milling method. Lithium substitution at the Ni2+ and Fe3+ sites imbalance the charge neutrality in the material and leads to defect formation and lattice strain, which enhances the hydroelectric cell’s performance. X-ray diffraction and Raman analysis confirm the cubic spinel structure in both materials. The average grain size has been estimated from the FESEM micrographs and found to be in the range of ~100-200 nm. A higher output current is observed in the Li substituted Nickel ferrite-based HEC than nickel ferrite-based HEC. |
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G00.00141: Additive Assisted Growth of Pb-Sn Mixed Low-bandgap Absorber for Efficient Perovskite Solar cells Nabin P Ghimire, Md Ashiqur Rahman Laskar, Quinn Qiao, Yue Zhou Pb-Sn mixed low-bandgap perovskites suffer from the quick formation of surface defects and charge traps within the perovskite surface during film formation. Furthermore, the facile oxidation of Sn+2 into more stable Sn+4 introduces Sn vacancies and point defects, introducing non-radiative recombination pathways. This would compromise the PV parameters of the final solar device. This work accurately tries to suppress the formation of perovskite surface defects and traps via additive-assisted growth of highly crystalline perovskite film by using a controlled amount of Phenethylammonium Hydrochloride (PEACl), i.e., (C8H12ClN) to the Pb-Sn mixed perovskite solution. As a result, passivated FA0.85 MA0.1 Cs0.05 Pb0.5Sn0.5I3 films possess lower electronic disorder, as evidenced with Urbach energy calculation. Moreover, PEACl passivated perovskite films exhibit improved crystallinity, film morphology, and lower trap densities, as evidenced with XRD, SEM, and space charge limited current experiments. In addition, PEACl performs Sn-N coordination bonding with Sn2+ and reduces the Sn vacancies on the perovskite surface, which helps to improve the device performance. Consequently, the power conversion efficiency boosts from 14.11% to 17.21% through the simultaneous improvement of open-circuit voltage (VOC) and fill factor (FF). |
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G00.00142: Importance of the Ion-Pair Lifetime in Polymer Electrolytes: From all-atom MD simulations Harish Gudla, Yunqi Shao, Daniel Brandell, Chao Zhang Ion pairing is commonly considered as a culprit for the reduced ionic conductivity in polymer electrolyte systems. However, this simple thermodynamic picture should not be taken literally, as ion-pairing is a dynamical phenomenon. Here we construct model poly(ethylene oxide)−bis(trifluoromethane)sulfonimide lithium salt systems with different degrees of ion-pairing by tuning the solvent polarity and examining the relationship between the cation−anion distinct conductivity σ+−d and the lifetime of ion pairs τ+− using molecular dynamics simulations. It is found that there exist two distinct regimes where σ+− d scales with 1/τ+− and τ+−, respectively, and the latter is a signature of longer-lived ion pairs that contribute negatively to the total ionic conductivity. This suggests that ion pairs are kinetically different depending on the solvent polarity, which renders the ion-pair lifetime highly important when discussing its effect on ion transport in polymer electrolyte systems. |
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G00.00143: Structural Dynamics and Transport in Deep Eutectic Solvents Stephanie Spittle, Benworth B Hansen, William D Brackett, Kaylie Glynn, Joshua Sangoro Deep eutectic solvents (DESs) have shown potential in many areas of electrochemical technology like solar cells and redox flow batteries. Their cheap and easy synthesis present a large design space and therefore make them a desirable alternative to toxic and/or expensive solvents currently being used commercially. However, to rationally approach the vast library of possible DESs, structure-property relationships should be developed so that properties of DESs can be predicted simply based off of the molecular structure. To elucidate this, a wide range of techniques were employed, including broadband dielectric spectroscopy, dynamic mechanical spectroscopy, differential scanning calorimetry on a series of carefully selected prototypical DESs and their derivatives. It was observed that slight changes in molecular structure of the components can have large impacts on the dynamics and physicochemical properties. For example, in choline-based DESs, changing the counteranion from chloride to bromide to iodide shifts the eutectic composition to lower ChX composition, slows down the dynamics, and decreases the dc ionic conductivity at each respective eutectic composition. |
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G00.00144: Platinum loaded molybdenum thin film: An advanced electrocatalyst for the hydrogen evolution reaction Baleeswaraiah Muchharla, Praveen Malali, Wei Cao, Hani E. Elsayed-Ali, Adetayo Adedeji, Abdennaceur Karoui, Kishor Kumar Sadasivuni, Bijandra Kumar In this work, we report the performance of a novel transition metal based electrocatalyst thin film for the hydrogen evolution reaction (HER). A DC magnetron sputter-deposited molybdenum (Mo) thin film with traceable amount of Pt i.e., Pt loaded Mo (Mo-Pt) as an electrocatalyst for the HER in both alkali and acidic media. The Mo-Pt electrocatalyst presents high catalytic activity with low overpotentials of 100 mV and 250 mV to achieve current densities 10 mA cm-2 and 45 mA cm-2, respectively. Differential electrochemical mass spectrometry (DEMS) results show that the Mo-Pt electrocatalyst produced hydrogen at a rate comparable with that of a pristine Pt sample. The Mo-Pt sample was also found to be stable after 1000 cycles of continuous operation, thus, making it durable. Overall, the Mo-Pt electrocatalyst exhibited high catalytic activity and stability towards HER. |
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G00.00145: Unveiling Structural Evolution and Charge Transport Mechanisms of Energy Storage Materials via Multi-Modal Operando Techniques Mikaela R Dunkin, Lei Wang, Jason Kuang, Kenneth J Takeuchi, Esther S Takeuchi, Amy C Marschilok Global energy storage use is predicted to grow more than 10-fold by 2040, however current battery technologies face rising concerns about their scale up costs, societal and environmental impact, and safety, motivating research into alternative battery chemistries. Understanding how these unique battery chemistries work is crucial to their implementation, with innovation driven by our understanding of material properties. Advanced characterization techniques, such as operando X-ray diffraction (XRD), energy dispersive X-ray diffraction (EDXRD), and X-ray absorption spectroscopy (XAS), provide a synergistic investigation of nanostructured materials, which in turn allows for a unique perspective into their chemical and physical properties. We conducted multi-modal operando studies to determine the storage and degradation mechanism(s) in various battery chemistries, including lithium ion, lithium-sulfur, and aqueous rechargeable zinc-ion with water-in-salt electrolytes. Understanding how battery materials change during cycling and their intrinsic limitations, will enable scientists to design more efficient, high-performance materials for battery systems. |
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G00.00146: Two-Dimensional WS2 Nanosheet Embedded PVDF Nanocomposites for Photosensitive Flexible Piezoelectric Nanogenerators with a Colossal Energy Conversion Efficiency ~ 25.6% Didhiti Bhattacharya, Sayan Bayan, Rajib K Mitra, Samit K Ray Here we have demonstrated record efficiency self-poled photosensitive flexible piezoelectric nanogenerators (PENG) using polyvinylidene fluoride (PVDF) polymer and chemically exfoliated tungsten disulfide (WS2) nanosheets. The two-dimensional (2D) WS2 nanosheets in PVDF matrix play dual role to enhance the nucleation of electroactive b-phase as well as induces a strong photosensitivity in the nanocomposite. The PVDF-WS2 composed flexible device is able to produce an enormously high output voltage~116 V (for impact ~ 105 kPa) and a piezoelectric energy conversion efficiency ~25.6%, which is the highest among the reported values on PVDF-2D materials based piezoelectric nanogenerators and also able to harvest energy from biomechanical and natural resources. This self-poled piezophototronic device exhibits strain-dependent photocurrent with photoresponsivity 6.98 mA/W (0.75% strain) under 410 nm at zero bias with higher piezo power harvesting under visible light. These results open up a new horizon in piezophototronics through the fabrication of photosensitive multifunctional highly stable PENGs, which can be scaled up for fabricating compact, high performance, portable and self-powered wearable electronic devices for smart sensor applications. |
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G00.00147: INSTRUMENTATION AND MEASUREMENT SCIENCE
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G00.00148: MPSoC Configuration of Tunable Waveform Generator and Mixer for NEMS Excitation and Detection Ben Rogers, Oleksiy Svitelskiy Our goal is to design a cost-effective instrument to enable NEMS research in colleges with limited resources. For this purpose, we implement a design of a waveform generator and mixer with the Artix-7 FPGA on the Basys 3 Development Board and the Xilinx Zynq 7010 MPSoC on the RedPitaya DAQ Board. Our design is able to output sine waves in the range of 100 kHz to 100 MHz with a tuning accuracy of about 0.5 Hz. The design utilizes the RedPitaya's two 14 bit 125 Msps RF Analog to Digital Converters to mix waveforms and two 14 bit 125 Msps RF Digital to Analog Converters to generate waveforms. Waveforms can be tuned using IO on the RedPitaya. The speed and accuracy of our waveform generator and mixer is demonstrated. Our proposed design may be useful for other projects. |
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G00.00149: Imaging Atomic-Scale Chemistry from Fused Multi-Modal Electron Microscopy Jonathan Schwartz, Zichao Wendy Di, Yi Jiang, Alyssa Fielitz, Don-Hyung Ha, Sanjaya D Perera, Ismail Baggari, Jeffery A Fessler, Colin L Ophus, Steve Rozeveld, Robert Hovden The chemical composition of specimens is revealed by spectroscopic techniques produced by inelastic interactions in the form of energy dispersive X-rays (EDX) or electron energy loss of the transmitted electrons (EELS). Unfortunately, the dose requirements for high-resolution chemical-spectroscopy often far exceed the dose limits of a specimen—chemical maps are noisy or missing entirely. More reliable interpretation of material structure is to be made in combination with elastically scattered electrons that can measure structure, but not chemistry, at high signal-to-noise ratios (SNR). The deluge of inelastic and elastic signals (i.e. modalities) are typically analyzed separately. |
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G00.00150: Measuring Magnetoelectric effects in matter with Tunnel diode oscillators. Marc L Lewkowitz, Ali Sirusi, Johnny L Adams, Neil S Sullivan Magnetoelectric materials present many novel applications for future technologies. These couplings in matter have been mostly studied by using magnetic fields to change electric properties. Recently, using electric fields to change magnetic properties has been of increased interest. We present a novel system for studying electrically driven changes of the magnetic properties of matter. This was done by using a tunnel diode to drive an LC circuit, with a sample placed inside the coil. An electric field can be applied to the sample perpendicular to the magnetic field. This setup can detect changes in the magnetic susceptibility of around 100 ppb. Our experimental setup can operate between 1.6 K and 100 K and can apply electric fields of around 100 kV/m. Results from this experiment on preliminary samples, demonstrate the capability of this experiment to search for magnetoelectric couplings. |
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G00.00151: Pulsed Infrared Thermography with Unsupervised Machine Learning for Imaging of Microscopic Subsurface Defects in Metals Alexander Heifetz, Xin Zhang, Jafar Saniie, Sasan Bakhtiari We have developed a Pulsed Infrared Thermography (PIT) system with Spatial Temporal Denoised Thermal Source Separation (STDTSS) unsupervised machine learning (ML) algorithm for processing of thermal images. The PIT imaging technique is based on recording material surface temperature transients with infrared (IR) camera following thermal pulse delivered on material surface with a white light flash light. Information in surface temperature transients can reveal presence of internal defects, such as voids with lower thermal conductivity than the host material, because thermal resistance of defects results in relatively slower local decay of material surface temperature. PIT imaging has a number of potential advantages in detection of subsurface pores in metals produced with laser powder bed fusion additive manufacturing method. However, limited imaging resolution of existing systems must be increased substantially. The challenge of detection of microscopic material defects in PIT images involves indentifying weak thermal signals with intensity comparable to IR camera noise level. STDTSS algorithm developed for processing of thermograms involves wavelet transform preprocessing, followed by principal component and analysis (PCA) and independent comonent analysis (ICA). We show that STDTSS recovers microscopic defects which are not visible in recorded PIT images. In this study, stainless steel 316 (SS316) and Inconel 718 (IN718) specimens were developed with a pattern of subsurface calibrated flat bottom hole (FBH) defects with diameters created with EDM (electron discharge machininig) drill. Selecting appropriate IR camera magnification lenses and imaging frame rate, and processing PIT data with STDTSS algorithm, we show that defects as small as 200µm are dtected in SS316 and IN718 specimens. |
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G00.00152: Polarization selectivity of aloof-beam electron energy-loss spectroscopy in one-dimensional ZnO nanorods Yao-Wen Yeh, Sobhit Singh, David Vanderbilt, Philip E Batson Orientation dependent electronic properties of wurtzite zinc oxide nanorods are characterized by aloof beam electron energy-loss spectroscopy (EELS) carried out in a scanning transmission electron microscope (STEM). The two key crystal orientation differentiating transitions specific to the in-plane (13.0 eV) and out-of-plane (11.2 eV) directions with respect to the wurtzite structure are examined by first principles density-functional theory calculations. We note some degree of orientation dependence at the onset of direct band gap transition near 3.4 eV. We demonstrate that good polarization selectivity can be achieved by placing the electron probe at different locations around the specimen with increasing impact parameter while keeping the beam-specimen orientation fixed. The observed results are qualitatively elucidated in terms of the perpendicular electric fields generated by the fast electron (60 kV) used in the microscope. The fact that good polarization selectivity can be achieved by aloof beam EELS without the requirement of sample reorientation is an attractive aspect from the characterization method point of view in the STEM-EELS community. |
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G00.00153: SquidLab - a user-friendly program for background subtraction and fitting of magnetization data Matthew J Coak, Cheng Liu, David M Jarvis, Seunghyun Park, Matthew J Cliffe, Paul A Goddard We present an open-source program with full user-friendly graphical interface for performing flexible and robust background subtraction and dipole fitting on magnetization data. For magnetic samples with small moment sizes or sample environments with large or asymmetric magnetic backgrounds, it can become necessary to separate background and sample contributions to each measured raw voltage measurement before fitting the dipole signal to extract magnetic moments. |
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G00.00154: Measuring dielectric changes at the solid-liquid interface of Parylene films with microwave microfluidic spectroscopy Jacob T Pawlik, Nikolas D Barrera, Eugene J Yoon, Angela C Stelson, Ellis Meng Implantable MEMS-based devices enable wireless RF sensing and power transmission within the body. These devices often incorporate a polymer interface, such as Parylene-C, to serve as a substrate or coating for electronics. However, the solid-liquid interface is poorly understood, and the dielectric response is largely unknown at RF frequencies. Moreover, recent research suggests that Parylene-C can delaminate over time, compromising lifetime. Understanding the solid-liquid interface of Parylene-C layers will be essential for ensuring device performance and longevity. We have developed a microwave spectroscopy technique that captures the dielectric response of liquid media over a broad frequency range (100 kHz – 110 GHz). In this work, we use microwave microfluidic spectroscopy to analyze the interface between Parylene-C films and aqueous salt solutions. Our initial results suggest that water can permeate into Parylene-C within hours of soaking, changing the film’s electrical properties. Here we present the time-dependent electrical properties of Parylene devices as they are exposed to aqueous environments. More broadly, we will demonstrate the utility of microwave microfluidics for characterizing dielectric changes at solid-liquid interfaces over time. |
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G00.00155: Real-time 3D single particle tracking in noisy environment using lifetime-gated two-photon emission Tian Zhao, Haw Yang, Joseph S Beckwith, M. Junaid Amin The real-time 3D single-particle tracking technique offers great potentials to reveal the behaviors of the single units in different environments. However, intrinsic background photons and excitation-induced scatterings from the complex environments render observation of the behaviors of the probes difficult. A microscopy platform that leverages the arrival time of individual photons to enable 3D single-particle tracking of fast-moving (translational diffusion coefficient of ≃ 3.3 μm2/s) particles in high-background environments is presented here. It combines a hardware-based time-gating module, which enables the rate of photon processing to be as high as 100 MHz, with a two-photon excited 3D single-particle tracking confocal microscope to enable high sample penetration depth. Proof-of-principle experiments, where single giant quantum dots (gQDs) were tracked in solutions containing dye-stained cellulose with a ~100-fold improvement in signal-to-background ratio using the hardware-based time-gating module, are shown here. Compared with previous works, a 33-fold improvement was achieved in terms of the mobility of the particles that can be tracked. This implementation of a time-gated real-time 3D single-particle tracking capacity, which should in the future be able to be coupled to other imaging and control modalities, can be expected to broaden the scope of experimentally accessible systems. Such a microscope design is anticipated to be of use to a variety of communities who wish to track single-particles in cellular environments, which commonly have high fluorescence and a scattering background. |
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G00.00156: Versatile Monochromatic X-ray sources with Energy Tunability for Nuclear Security and Medical Applications Stylianos Chatzidakis, Junghyun Bae One of the most important components in any X-ray imaging and computed tomography system intended as a probe for detection and characterization of nuclear materials is the X-ray source. The source affects several important imaging parameters such as spatial and temporal coherence, emission energy, and photon flux. However, existing mobile or transportable X-ray sources in the form of X-ray tubes induce bremsstrahlung radiation that offers little to zero energy tunability or directionality capabilities. These limitations motivate research into new materials with the potential to create monochromatic X-ray sources with energy and angular tunability. Recent advances in van der Waals layered superlattice crystalline materials have been used to demonstrate new X-ray generation mechanisms such as parametric X-ray radiation and coherent bremsstrahlung that have the advantages of being tunable relative to existing sources. In this paper, we explore a wide range of superlattices and their characteristics to precisely tailor the X-ray spectrum and angular distribution. We show that by using inverse design techniques and material customization at the atomic level we can optimize the output radiation characteristics for different imaging scenarios. |
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G00.00157: Development of a low temperature STM cryogenics equipped with a fast-ramping vector magnet Yeonjin Jung, Lei Fang, Hong T Bui, Sangwon Yoon, Soo-hyon Phark, Andreas J Heinrich, Denis Krylov Molecular spins on surface are feasible systems to realize on-surface integrated nanoscale qubit devices in terms of the scalability. As a promising candidate, single molecule magnets often require a high-speed variable magnetic field to control their quantum states [1]. Here, we report a development of home-built cryogenic system for low temperature scanning tunneling microscopy (STM) in a fast-ramping magnetic field. It is equipped with a vector magnet of 1 T (in axial) and 0.25 T (in lateral) at a ramping rate up to 0.5 T/sec and 0.1 T/sec, respectively, and designed to minimize the generation of eddy current from such a fast-ramping of the field by careful selection of materials for STM head assembly. The cryostat is cooled down by the Joule-Thomson (JT) principle. Our special design of heat exchange mechanism allowed us to precool the JT stage from 100 to 5 K only in 4 hours. Using 4He cryogen gas, we reached at a base temperature (Tbase) of 1.50 ± 0.025 K at JT stage in a continuous circulation mode. In one-shot mode, we obtained Tbase = 1 K, stable for 8 hours. In addition, the cryostat is equipped with RF signal cables for electron spin resonance STM on atomic spins on surface [2]. [1] S. Thiele et al. Science (2014); [2] S. Baumann et al. Science (2015) |
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G00.00158: Extracting Affinity and Kinetics of Protein-Ligand Interactions using Rigorous Theory and High-Performance Electronic Measurements Seulki Cho, Ryan M Evans, Anthony J Kearsley, Arvind Balijepalli Biochemical measurements that determine both the affinity and kinetics of protein-ligand interactions using field-effect transistors (FETs) are demonstrated. The measurements were performed in two configurations – a droplet measurement where the diffusion of concentrated protein was observed as a function of time and with a microfluidic injection where the fluid cell was filled with a protein with the desired final concentration. We chose the high-affinity Biotin–Streptavidin pair as a model system, where thiol modified biotin was conjugated to a gold surface to form a self-assembled monolayer. Streptavidin was then introduced at different concentrations to measure its interaction with Biotin. Each method was rigorously modeled by describing the diffusion-limited kinetics of the interactions and by establishing error bounds on the spatio-temporal accuracy of the numerical solutions [1,2]. The model included a novel denoising kernel to drastically improve the signal-to-noise ratio of the measurements. This modeling effort, in turn allowed the extraction of kinetic constants of the reaction from a single real-time time-series measurement. The results were found to be consistent across three orders of magnitude change in the Streptavidin concentration from 100 pM to 100 nM and the kinetic constants were found to be invariant and in agreement with literature values. The results our approach can be readily used to quantify numerous protein and antibody systems for impact in biophysics and biotechnology. |
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G00.00159: Accelerated development of a general purpose active-pixel CMOS sensor Aled V Cuda Accelerated development of a general purpose active-pixel CMOS sensor: We developed an active pixel CMOS sensor and pixel array readout circuitry suitable for high energy particle detection, direct topmetal charge collection, and potential other applications. We targeted the recently open sourced Skywater 130nm process and exclusively used open source tooling which means our design is unencumbered by NDAs and licensing restrictions. During development we produced several tools to help expedite the analog design process, and scripted a large portion of the system integration. The reduction in complexity brought by the simplified flow allowed the design to be completed by only 2 people in a span of around 3 months. |
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G00.00160: Development of a Highly Sensitive Remote Controlled Vibrating Sample Magnetometer Jared Phillips, Saeed Yazdani, Wyatt Highland, Ruihua Cheng This work details the construction and optimization of a fully automated remote controlled vibrating sample magnetometer (VSM) for application in spintronic research and teaching. In our development, four pick-up coils were connected in a Mallinson configuration to minimize the noise level. The apparatus was carefully calibrated using a standard Ni disc, and hysteresis loop measurements of magnetic thin film samples acquired by the constructed VSM were also compared to Superconducting Quantum Interference Device (SQUID) data taken for the same samples. In plane and out of plane measurements of 25nm Fe thin films are also presented. The fabricated VSM is currently able to achieve a sensitivity near 1x10−5emu. Further alterations to the design that could improve beyond this limit are also discussed. |
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G00.00161: On-body seismology for continuous monitoring of tissue mechanics Xiaoyue Ni, Changsheng Wu, Chenhang Li, Heling Wang, Mengdi Han, Ziwu Song, Jiahong Li, Lin Shu, Haixu Shen, Tzu-Li Liu, Wenbo Ding, Yonggang Huang, John A Rogers Recent progress in wearable devices provides new opportunities for precise, non-invasive, long-term recording of body mechanics. The soft device incorporating a single MEMS accelerometer captures subtle vibration of the skin with a resolution of 1×10-4 g/√Hz in the frequency range from 0 to 800 Hz. In this study, we introduce an on-body mechano-acoustic sensing technology based on a skin-mounted accelerometer array to assess the mechanical profiles of subdermal tissues in-vivo, similar to seismology. A system-level wearable device construction, optimized for a comfortable skin interface and high precision, incorporates a broadband dual-accelerometer sensor, an audio actuator, and a Bluetooth System-on-Chip and enables a wireless, automated operation. An automated algorithm, leveraging the spectral analysis of surface waves (SASW) methods, computes the depth-sensitive, elastic modulus information of the propagation media from the mechanical dispersion relationship. Comprehensive theoretical and experimental investigation verifies that the device, together with the automated data-processing platform, provides a robust, calibration-free, and non-invasive evaluation of the elasticity with a resolution of ~5 kPa and depth information in the range of ~2-140 mm of various phantom materials (Young’s modulus E= ~10-1500 kPa). The device also identifies the softening of pork tissues with increasing injected water content and the changes of modulus of muscle under different levels of tension. The results are in agreement with the in-parallel Ultrasound Elastography measurements. Quantitative access to the stiffness profile of the rectus femoris muscle during leg-press exercise demonstrates the continuous monitoring capability in an ambulant environment that can support long-term clinical assessment of different tissues and disease states in a large population. |
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G00.00162: Study of Au and graphite thin films by MeV ultrafast electron diffraction for use as a beam diagnostic tool Mariana A Fazio, Salvador Sosa Guitron, Destry Monk, Junjie Li, Marcus Babzien, Mikhail Fedurin, Hisato Yamaguchi, Nathan A Moody, Mark A Palmer, Sandra G Biedron MeV ultrafast electron diffraction (MUED) is a pump-probe structural characterization technique to investigate material dynamics in the ultrashort range. It utilizes a Ti:Sapph ultrashort laser and an ultrashort relativistic electron beam to study the dynamic response of the material structure. Electron beam instabilities currently limit the applicability and accuracy of MUED, hindering the use of single shot measurements. |
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G00.00163: Modeling Positronium induced background in the time-of-flight (TOF) spectra of positron induced secondary electrons using Monte Carlo methods. Varghese A Chirayath, Sima Lotfimarangloo, Alexander Fairchild, Randall Gladen, Jack Driscoll, Ali R Koymen, Alex H Weiss The energy spectra of positron induced secondary electrons (PIE) can be determined from the electron time of flight as determined from the difference between the signal produced by the positron annihilation gamma in a scintillator and the signal produced by the secondary electron impacting a channel plate. Measuring the energy of PIE using a TOF spectrometer has the advantage of the parallel collection of electrons with a wide range of energies greatly reducing the data collection time. However delayed annihilations produced by long lived ortho-positronium (o-Ps), an electron-positron bound state, can result in an unwanted background to the PIE signal corresponding to unphysically short electron flight times. Here, we have developed a Monte Carlo based method to model the spectral contribution of o-Ps annihilations to the TOF spectra of PIE. Our modelling extracts the true electron TOF spectra associated with prompt gamma, provides the fraction of positrons which forms o-Ps as a function of positron beam energy and gives an estimate of the energy spectrum of the o-Ps. We report and discuss the results obtained by the application of the method to PIE spectra from pure copper. |
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G00.00164: Electronic Structure Mapping via Correlative Scanning Photocurrent and Electron Beam Induced Current Microscopies Christopher J Hawley, Annemarie L Exarhos, Terrence McGuckin, Amelia J Reilly We demonstrate a correlative microscopy technique relating electron beam induced current (EBIC) and scanning photocurrent measurements to map out the electronic structure of active regions of semiconductor junctions and device structures, including boundary and edge effects. Comparisons between the two microscopies provide a clearer picture of the electronic properties of samples than either individual technique allows. Varying electron beam and laser energy in these complementary techniques enables electronic level mapping above and below the band gap as well as at various penetration depths. |
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G00.00165: Improving the energy resolution of a time-of-flight (TOF) spectrometer used to measure the energy of positron induced electrons Varghese A Chirayath, Jack Driscoll, Randall Gladen, Alexander Fairchild, Sima Lotfimarangloo, Ali R Koymen, Alex H Weiss The energy resolution of a TOF spectrometer used to measure the energy of electrons varies nonlinearly with the energy of the electron. This resolution degrades for large kinetic energies as the difference in flight times among high energy electrons becomes comparable to the inherent timing resolution of the spectrometer. This is often solved by extending the flight paths of the electrons or by applying a negative DC potential, thus slowing down the electrons and spreading the flight times. Increasing the length of the flight path may not be feasible in all cases due to experimental constraints, whereas a constant negative bias precludes the detection of electrons with energies less than the potential applied. Here, we investigate, using SIMION®, the feasibility of increasing the energy resolution of a TOF spectrometer by applying a time varying negative potential aimed at increasing the time interval between the flight times of the electrons without stopping any electrons from reaching the electron detector. We model a TOF spectrometer used to measure the energy of positron-induced electrons and show that, through the application of an appropriate time varying potential, we are able improve the energy resolution without causing spectral modification. |
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G00.00166: Extracting elemental composition of topmost-atomic layers using Doppler Broadening Spectroscopy (DBS) Varghese A Chirayath, Philip A Sterne, Sima Lotfimarangloo, Jack Driscoll, Randall Gladen, Alexander Fairchild, Ali R Koymen, Alex H Weiss Our recent results have shown that the Doppler broadened gamma spectra originating from the annihilation of surface trapped positrons can provide elemental information of the topmost atomic layer even with the enhanced annihilation of positrons with valence electrons and the presence of positronium annihilation induced gamma. Here, we show that it is possible not only to identify but also to obtain quantitative chemical composition of the top surface through the analysis of Doppler Broadened annihilation gamma line shape. We have simulated Doppler broadened annihilation gamma spectra as measured by a high purity germanium detector representing annihilations from the surface of various elements (Cu, Si, C, Au, Ag, O). The simulated experimental spectra include statistical uncertainties, white noise, and background due to the inelastic scattering of the annihilation gamma. We show that it is possible to obtain the concentration of the trace element (<10% on surface) through the analysis of Doppler spectra. Our results open pathway for a positron-based technique that can provide quantitative chemical composition of inaccessible surfaces as the annihilation gamma can escape from inner surfaces of the sample without any loss of information. |
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G00.00167: MEDICAL PHYSICS
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G00.00168: Creating Patient-Specific Vein Models for Hemodynamic Characterization in Hemodialysis Population Andres Moya Rodriguez, Bingqing Xie, Maren Klineberg, Cameron Bernstein, Mary Hammes, Anindita Basu Up to 70% of End-Stage Renal Disease hemodialysis patients receiving treatment by means of an arteriovenous fistula (AVF) suffer from AVF thrombosis, primarily in the cephalic vein arch. This greatly contributes to morbidity and mortality in an already vulnerable population. Understanding the exact mechanism of thrombosis in these patients has proved challenging due to the complex interplay between contributing factors: abnormal hemodynamics, patient-specific vein geometry and biochemical factors that lead to coagulation. We present personalized 3D fluidic models of the cephalic arch of dialysis patients at 3 and 12 months after surgical creation of the AVF. Computational 3D models are created from patient-specific Intravascular Ultrasound and venogram imaging data. These models are then explored using Computational Fluid Dynamics simulations and fabricating fluidic devices to simulate physiologic flow. Fluorescent beads added to a blood-mimicking fluid allow us to calculate Reynolds number and local Wall Shear Stress across the cephalic arch. Comparative analysis of these parameters will allow us to elucidate the interplay between vein geometry and flow. Elucidating the parameters of thrombogenesis in these patients will enable more efficient and personalized treatments to maintain AVF access and prevent complications during hemodialysis. |
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G00.00169: Understanding the Effects of Metal Implants in Proton Therapy Corbin G Maciel When treating cancer with high energy particles, patients having metal implants near the tumor can create a difficult situation. When particles interact with the metal it can cause scattering within the patient. This creates difficulty because scattering makes it harder to predict the dose distribution in the planning process, thus making it difficult to accurately prescribe a treatment plan. A study was performed to better understand the effects metal implants can have on proton therapy treatments targeting tumors near the spine, and in so doing take steps toward making the treatment planning process less difficult and more accurate. The preliminary results, which show both underdosing and overdosing to the gross tumor volume and clinical target volume, will be discussed here as well as what will be done to confirm these results and resolve any discrepancies. |
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G00.00170: Automatic Flow Property Quantification on Time Series Images from PDMS Fabricated Veins Andres Moya Rodriguez, Bingqing Xie, Maren Klineberg, Mary Hammes, Anindita Basu Accurate quantification of the fluid flow is crucial for studying the physiology of blood flow and associated pathologies like thrombosis. Here we generate 3D models of blood vessels in patients undergoing dialysis and fabricate fluidic devices (using PDMS) to perform flow experiments in vitro, using flow parameters measured in the same patients. We perform Particle Imaging Velocimetry on fluorescent tracer beads suspended in a fluid that matches the viscosity and density of blood. Videos of multiple regions of interest (ROI) of the fluidic model are used to characterize flow in vein regions that are likely to thrombose. Each bead moving along with the fluid displays a streamline highlighting the path along which it travels during a short exposure time. We obtain 25-30 images and hundreds of streamlines per ROI. Videos of multiple ROIs under different physiologic flow conditions are generated. We developed an automatic pipeline to extract the streamlines using computer vision algorithms. The streamlines are annotated with their length in pixels, angle orientation, and their distance from the vein wall from which we calculate wall shear stress (WSS), a critical predictor of thrombosis. For each ROI, we estimate WSS sampling rate for statistics. We apply the pipeline to 3D models of different geometry and flow conditions and obtain > 95% coverage on the vein wall boundary on average, for each ROI. |
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G00.00171: Computational Modeling of Multi-drug Therapy in Parkinson's Disease Olivia Williams, Davon W Ferrara Parkinson’s Disease (PD) is the second most common neurodegenerative disorder in the world after Alzheimer’s. The hallmark symptoms of PD are tremor and rigidity, which are caused by the death of dopaminergic neurons in the basal ganglia. These symptoms are often treated by levodopa (L-DOPA), MAO-B inhibitors, and other pharmaceuticals with the goal of increasing dopamine in the brain. To better understand the underlying mechanics of L-DOPA and its clinical effects on patients, various computational models have been developed. One model, by Véronneau-Veilleux et. al (Chaos 30, 093146, 2020), integrates L-DOPA pharmacokinetics, dopamine dynamics, and a neurocomputational model of the basal ganglia to predict the impact of L-DOPA regimens on a patient's motor function. In this study, we extended the model to investigate the interactions of L-DOPA with other pro-dopamine drugs and dosing regimens to provide a framework for improving treatment strategies. |
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G00.00172: Mechanical and Geometrical Changes in Human Aorta with Age Karen Yuan, Kameel Khabaz, Dina Khabaz, David Jiang, Nicole Pierce, Seth Sankary, David Hampton, Luka Pocivavsek The aorta carries blood throughout the human body. With age, there is a notable increase in aortic diameter and decrease in aortic distensibility. The aorta also becomes more stiff and anisotropic. Identification of these age-related geometric changes can help inform treatment strategies and timing for intervention for older adults with aortic diseases. Two of the most common diseases involving the aorta are dissections, a tear in the inner layer of the aorta, and aneurysms, an abnormal enlargement of the aortic wall. Our research investigates the fragile nature of the aorta by characterizing the geometry and mechanics for different patients using mathematical and image-based analysis algorithms. We hypothesize that aortic surface curvature is influenced by each patient's unique physiological state. By assessing aortic geometry under different physiologic stresses, we can better understand how the surface curvature changes in relation to those stresses. We will investigate the effect of aging on wall stresses and hemodynamics in healthy aortas to better inform treatment protocol in older patients. |
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G00.00173: QUANTUM INFORMATION
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G00.00174: Knowledge in Positive Measurements in Quantum Mechanics Douglas M Snyder
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G00.00175: Majorana approach for driven quantum systems. Polina Kofman, Oleh Ivakhnenko, Sergey Shevchenko, Franco Nori The description of driven two-level quantum systems is important for the development of quantum technologies. Different ways of solving such non-trivial problems provide a versatile understanding of how to work with these systems. We study the evolution of a two-level system with a linear perturbation, known as the Landau-Zener-Stückelberg-Majorana transition. This provides the basis for the so-called adiabatic-impulse model, ubiquitously used for describing diverse quantum systems. The evolution of driven quantum two-level systems usually follows the solution by C. Zener. Less known is the approach by E. Majorana. In our work, we apply Majorana’s approach to obtain not only the final excitation probability but also the time evolution and the phase of the wave function. We analyze the regions where this asymptotic result correctly describes the evolution by comparing the analytical solution with the numerical one. Therefore, we can classify the problems where this approach could be effective. |
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G00.00176: Theory of reflection spectroscopy for superconducting quantum parametrons Shumpei Masuda, Aiko Yamaguchi, Tomohiro Yamaji, Tsuyoshi Yamamoto, Toyofumi Ishikawa, Yuichiro Matsuzaki, Shiro Kawabata Superconducting parametrons in the single-photon Kerr regime, also called KPOs, have been attracting increasing attention in terms of their applications to quantum computations. Theory of spectroscopy of prametrons is needed for obtaining information such as energy level structure and coupling strength between the energy levels from experiments. In this talk, we report the results of our theoretical study on the reflection spectroscopy of superconducting parametrons. We show formulae of the reflection coefficient, the nominal external and internal decay rates. We present that the difference of the populations of energy levels manifests itself as a dip or peak in the amplitude of the reflection coefficient, and one can directly extract the coupling strength between the energy levels by measuring the nominal decay rates when the pump field is sufficiently large. |
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G00.00177: Full View of the Generalized Newton's Laws and Monodromy Data Zhi an Luan I present and clarify important monodromy data on freedoms, ambiguities and mutual transition in Unitary Space-Time: |
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G00.00178: Fu-Xi Constant Ψ = 1/√3 - A Real Universe Constant Different From Classical Λ Zhi an Luan This study presents an important mathematical- physical constant called as the Fu-Xi Constant |
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G00.00179: Voltage staircase in a current-biased quantum-dot Josephson junction Dmytro Oriekhov, Yevheniia Cheipesh, Carlo W Beenakker We calculate the current-voltage (I-V) characteristic of a Josephson junction containing a resonant level in the weakly coupled regime (resonance width small compared to the superconducting gap). The phase φ across the junction becomes time dependent in response to a DC current bias. Rabi oscillations in the Andreev levels produce a staircase I-V characteristic. The number of voltage steps counts the number of Rabi oscillations per 2π increment of φ, providing a way to probe the coherence of the qubit in the absence of any external AC driving. The phenomenology is the same as the ''Majorana-induced DC Shapiro steps in topological Josephson junctions'' of Phys. Rev. B 102, 140501(R) (2020) --- but now for a non-topological Andreev qubit. |
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G00.00180: Ultimate limit of quantum pulse-compression ranging: hypothesis testing and parameter estimation Quntao Zhuang, Jeffrey H Shapiro It is well known that entanglement can benefit quantum information processing tasks. Quantum illumination (QI), when first proposed, was surprising as the entanglement’s benefit survived entanglement-breaking noise. Since then, many efforts have been devoted to quantum sensing in noisy scenarios. Such schemes, however, have been limited to binary quantum hypothesis testing for target detection, while classical radars are capable of more advanced sensing tasks. For example, radars use time-of-flight measurement to infer the range to a distant target from its return's roundtrip range delay. They typically transmit a high time-bandwidth product waveform and use pulse-compression reception to simultaneously achieve satisfactory range resolution and range accuracy under a peak transmitted-power constraint. Despite the many proposals for quantum radar, none have delineated the ultimate quantum limit on ranging accuracy. |
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G00.00181: Fast suppression of classification error in variational quantum circuits Bingzhi Zhang, Quntao Zhuang Variational quantum circuits (VQCs) have shown great potential in near-term applications. However, the discriminative power of a VQC, in connection to its circuit architecture and depth, is not understood. To unleash the genuine discriminative power of a VQC, we propose a VQC system with the optimal classical post-processing—maximum-likelihood estimation on measuring all VQC output qubits. Via extensive numerical simulations, we find that the error of VQC quantum data classification typically decays exponentially with the circuit depth, when the VQC architecture is extensive—the number of gates does not shrink with the circuit depth. This fast error suppression ends at the saturation towards the ultimate Helstrom limit of quantum state discrimination. On the other hand, non-extensive VQCs such as quantum convolutional neural networks are sub-optimal and fail to achieve the Helstrom limit. To achieve the best performance for a given VQC, the optimal classical post-processing is crucial even for a binary classification problem. To simplify VQCs for near-term implementations, we find that utilizing the symmetry of the input properly can improve the performance, while oversimplification can lead to degradation. |
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G00.00182: Nonclassical Behaviors of Two-Sender Multiple Access Channels Brian Doolittle, Eric A Chitambar, Felix Leditzky We take a device-independent approach to comparing the input-output correlations generated by quantum and classical multiple access channels (MACs). Classically, each sender transmits one bit to the receiver while an unlimited amount of shared randomness is held between devices. We derive a set of linear inequalities bounding the probability distributions accessible to classical MACs and use these inequalities to witness nonclassical behaviors. We consider two types of quantum MACs. In the first, each sender transmits one qubit to the receiver, while in the second, the senders each transmit one classical bit and are assisted with shared entanglement. Using variational quantum optimization, we find maximally nonclassical behaviors for both types of quantum MAC. Both models are shown to violate the linear inequalities bounding classical MACs while entanglement-assisted MACs yield larger violations. Additionally, we identify fingerprinting as a task that shows no advantage when quantum communication is used, however, entanglement-assisted MACs demonstrate an advantage. Ultimately our results provide new insight into the role that distributed quantum resources can play in multi-party communication. Work funded by NSF award DMR-1747426 |
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G00.00183: Simple Experiment Testing Gravity and Quantum Mechanics Louise Riofrio A novel experiment tests Planck masses and a quantized gravity. This research began with cosmology, an expanding Universe of scale R = ct, where c is speed of light and t is age of Universe. Gravity would then cause expansion to slow over time. The prediction of the speed of light varying by 0.72 cm/sec/yr has been verified by data from our Lunar Laser Ranging Experiment, and may be further tested by the Atomic Clock Ensemble in Space aboard ISS. In Planck units two equations combine as M = R = t, suggesting that these tiny units are fundamental. The Planck mass is an observable quantity similar to a flea's egg. We place two spherical masses on a level low-friction surface, grounded within a vacuum chamber, and observe for gravitational attraction. A negative result indicates that gravitational mass is quantized at the Planck scale. Quantum mechanics has applications for astrobiology and living cells, explaining why most cells are limited by the Planck mass. A further development of the experiment may be performed in Earth orbit. This continuing research connects cosmology of the large Universe with the microscopic world. |
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G00.00184: Variational Quantum Optimization of Nonlocality in Noisy Quantum Networks Brian Doolittle, Eric A Chitambar, Thomas Bromley, Nathan Killoran We consider the nonlocal correlations accessible to noisy quantum communication networks. We focus on chain and star topologies with entanglement linking adjacent nodes. To find maximally nonlocal correlations, we apply variational quantum optimization across a wide range of network configurations, resources, and noise models. In this procedure, parameterized quantum circuits efficiently simulate noisy quantum networks on a quantum computer. Nonlocality is quantified using known Bell inequalities. Gradient ascent is used to maximize the nonlocality while gradients are computed using numerical techniques compatible with quantum hardware. Using our optimization framework, we investigate the effect of different noise models on the nonlocal correlations of quantum networks with fewer than 20 qubits. We analyze our numerical results to evaluate the noise robustness of network nonlocality. Our work helps inform the development of near-term quantum communication protocols and networks. Furthermore, as larger quantum computers become available, our optimization technique shows promise in scaling beyond the limits of classical computing . |
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G00.00185: Making a triangular spectrum of zero-point energy Peter H Ceperley
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G00.00186: Photonic Honeycomb Lattice with circuit QED system by Triple-Leg Stripline Resonator Kyungsun Moon, Dongmin Kim A circuit quantum electrodynamic (QED) system which is used superconducting resonator has |
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G00.00187: Bright Squeezed Light from Dissipative Optomechanical Light Squeezer Daniel B Soh, Matt Eichenfield Squeezed light has become extremely useful for various quantum optical metrology applications as it provides measurements of optical processes that are less contaminated by quantum noise in a desired light quadrature. Additionally, the measurement error decreases as the light amplitude increases. Bright squeezed light delivers the desired drastic reduction of measurement error beyond what classical light can accomplish with the same intensity. A typical way to generate bright squeezed light is to create squeezed vacuum via optical parametric amplification and then mix it with bright coherent light. Alternatively, one would inject an optical parametric amplifier with a non-zero amplitude coherent signal, which produces a displaced squeezed light at the output. We show that these two methods mix the squeezed quantum noise with non-squeezed noise from the bright coherent state, resulting in less squeezed noise in the combined, brighter output. Recently, a new method for optical noise squeezing has been developed—dissipative optomechanical light squeezing. We will present on theory showing this new method can produce bright squeezed light without compromising noise-squeezing at any amplitude, unlike existing methods. |
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G00.00188: Atom interferometry improved by neural networks Alireza Seif, Changhun Oh, Tao Hong, Liang Jiang For applications in metrology, it is important to both estimate the parameters of interest from data and characterize the error in those estimates. Here, we present a machine learning-based method for model-free inference of physical parameters from an interferometer data. We consider estimating quantities such as acceleration and rotations from interference patterns generated by an atom interferometer without the need for an exact mathematical model of the device and the error processes affecting it. Imperfections in the model, systematic errors, and noise severely limit the performance. Our method, based on neural network, learns to simultaneously estimate the quantities of interest and the error in those estimates from noisy input images. It extends the applicability of the interferometer when the resolution is limited, and noise and imperfections are present. |
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G00.00189: Single Flux Quantum-Based Superconducting Qubit Control and Quasiparticle Mitigation Chuanhong Liu, Alexander M Opremcak, Chris D Wilen, Owen Rafferty, Andrew L Ballard, Vito M Iaia, Tianna A McBroom, Yebin Liu, Kenneth R Dodge, Jaseung Ku, David Olaya, John P Biesecker, Adam J Sirois, Dan Schmidt, Joel N Ullom, Samuel P Benz, Peter Hopkins, Jonathan L DuBois, Britton L Plourde, Robert McDermott The Single Flux Quantum (SFQ) digital logic family has been proposed as a scalable approach for the control of next-generation multiqubit arrays. In an initial implementation, the fidelity of SFQ-based qubit gates was limited by quasiparticle (QP) poisoning induced by the dissipative SFQ driver. Here we introduce a multi-chip module (MCM) architecture to suppress phonon-mitigated QP poisoning, where the SFQ unit and the qubit unit are fabricated on two chips separated by Indium bump bonds. Additionally, we use superconducting bandgap engineering to mitigate QP poisoning in this system. We further characterize the SFQ-based gates fidelity in the MCM structure with randomized benchmarking. |
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G00.00190: Nanoscale Vector AC Magnetometry with a Single Nitrogen-Vacancy Center in Diamond GUOQING WANG, Yi-Xiang Liu, Yuan Zhu, Paola Cappellaro The nanoscale detection of vector AC magnetic fields is desirable in applications ranging from fundamental physics, such as detecting dynamic properties of spins and charges in quantum materials, to engineering, such as microwave (MW) device characterization and optimization. Isolated quantum spin defects, such as the nitrogen-vacancy center in diamond, can achieve the desired spatial resolution with high sensitivity. Still, vector AC magnetometry currently relies on using different orientations of an ensemble of sensors, with degraded spatial resolution, and a protocol based on a single NV is lacking. Here we propose and experimentally demonstrate a protocol that exploits a single NV to reconstruct the vectorial components of an AC magnetic field by tuning a continuous driving to distinct resonance conditions. We map the spatial distribution of an AC field generated by a copper wire on the surface of the diamond. The proposed protocol combines high sensitivity, broad dynamic range, and sensitivity to both coherent and stochastic signals, with broad applications in condensed matter physics, such as probing spin fluctuations. |
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G00.00191: Open Quantum Dynamics with Singularities: Master Equations and Degree of Non-Markovianity Abhaya S Hegde Master equations describing open quantum dynamics are typically first order differential equations. When such dynamics brings the trajectories in state space of more than one initial state to the same point at finite instants in time, the generator of the corresponding master equation becomes singular. The first order, time-local, homogeneous master equations then fail to describe the dynamics beyond the singular point. Retaining time-locality in the master equation necessitates a reformulation in terms of higher order differential equations. We formulate a method to eliminate the divergent behavior of the generator by using a combination of higher order derivatives of the generator with suitable weights and illustrate it with several examples. We also present a detailed study of the central spin model and we propose the average rate of information inflow in non-Markovian processes as a quantity that captures a different aspect of non-Markovian dynamics left unexplored previously. |
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G00.00192: Topological superconducting circuit optomechanical lattices Amir Youssefi, Andrea Bancora, Shingo Kono, Mahdi Chegnizadeh, Tatiana Vovk, Jiahe Pan, Tobias J Kippenberg Over the past decades, optomechanics has allowed major progress in the quantum control of engineered mechanical systems. Yet, nearly all prior schemes have employed single- or few mode optomechanical systems. In contrast, novel dynamics and applications are expected when utilizing optomechanical arrays and lattices. |
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G00.00193: Beware of entropy phase transition! How to make quantum denoising successful? Joséphine Pazem, Mohammad H Ansari Quantum autoencoders can help to generate denoised entanglement on a noisy neural network. However noise outweighs the process if it gets too strong. [1] |
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G00.00194: Quantum imaginary time evolution steered by reinforcement learning Chenfeng Cao, Zheng An, Shi-Yao Hou, Duanlu Zhou, Bei Zeng Quantum imaginary time evolution is a powerful algorithm to prepare ground states and thermal states on near-term quantum devices. However, algorithmic errors induced by Trotterization and local approximation severely hinder its performance. Here we propose a deep-reinforcement-learning-based method to steer the evolution and mitigate these errors. In our scheme, the well-trained agent can find the subtle evolution path where most algorithmic errors cancel out, enhancing the recovering fidelity significantly. We verified the validity of the method with the transverse-field Ising model and graph maximum cut problem. Numerical calculations and experiments on a nuclear magnetic resonance quantum computer illustrated the efficacy. The philosophy of our method, eliminating errors with errors, sheds new light on error reduction on near-term quantum devices. |
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G00.00195: Measurement-Device-Independent Verification of a Quantum Memory Yong Yu, Peng-Fei Sun, Yu-Zhe Zhang, Bing Bai, Yu-Qiang Fang, Xi-Yu Luo, Zi-Ye An, Jun Li, Jun Zhang, Feihu Xu, Xiao-Hui Bao, Jian-Wei Pan We report an experiment that verifies an atomic-ensemble quantum memory via a measurement-device-independent scheme. A single photon generated via Rydberg blockade in one atomic ensemble is stored in another atomic ensemble via electromagnetically induced transparency. After storage for a long duration, this photon is retrieved and interfered with a second photon to perform a joint Bell-state measurement (BSM). The quantum state for each photon is chosen based on a quantum random number generator, respectively, in each run. By evaluating correlations between the random states and BSM results, we certify that our memory is genuinely entanglement preserving. |
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G00.00196: Multiqubit gates for generating entangled states Yun-Pil Shim, Miguel Rodriguez, Edward Takyi The standard approach for building quantum circuits is to use a universal gate set that contains single-qubit gates and at least one entangling two-qubit gate. This typically leads to a long sequence of gate operations, putting severe restrictions on the fidelity of the quantum circuit. Using generically multiqubit gates may offer an efficient alternative. We study the effectiveness of two types of multiqubit gates with auxiliary single-qubit gates in generating highly entangled multiqubit states: (i) Simultaneous exchange couplings between many spin qubits with tunable exchange interaction, (ii) multiqubit gate from a quantum data bus architecture where many qubits can be connected to a common data bus. We find that multiqubit gates can significantly reduce the depth of the required quantum circuits for entangled states. |
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G00.00197: Effect of matrix sparsity and quantum noise on error of quantum random walk in linear solvers Benjamin Wu, Hrushikesh Patil, Predrag Krstic We study a hybrid quantum-classical solver for systems of linear equations using quantum random walk, applied to stoquastic Hamiltonian matrices [1]. In the absence of quantum noise, sparse matrices are expected to achieve solution vectors with lower error than dense matrices. We find that quantum noise reverses this effect, with error increasing as sparsity increases. This is a consequence of a corresponding increase in the number of invalid quantum random walks. We propose an improved algorithm that mitigates invalid quantum random walks. |
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G00.00198: Classical Optical Analogue of Quantum Discord Jacob Leamer We present a method for simulating the quantum discord in two qubit Bell states using classical light that takes advantage of the analogy between the state of two two level qubits and the modes of a Laguerre-Gauss beam. We demonstrate the validity of this approach by comparing the beam profiles of theoretical simulations to experimental results for different values of discord. |
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G00.00199: Hidden variable models and non-abelian anyons Qian Peng The recent progress of the Majorana experiments paves a way for the future tests of non-abelian braiding statistics and topologically-protected quantum information processing. However, a deficient design in those tests could be very dangerous and reach false-positive conclusions. A careful theoretical analysis is necessary in order to develop loophole-free tests. We introduce a series of classical hidden variable models to capture certain key properties of Majorana system: non-locality, topologically non-triviality, and quantum interference. Those models could help us to classify the Majorana properties and to set up the boundaries and limitations of Majorana non-abelian tests: fusion tests, braiding tests and test set with joint measurements. We find a hierarchy among those Majorana tests with increasing experimental complexity. |
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G00.00200: ZZ freedom in two-qubit gates Xuexin Xu, Mohammad H Ansari This poster describes the overall picture of the two-qubit ZZ interaction no matter the circuit is driven or not. |
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G00.00201: Learning via Many-Body Localized Hidden Born Machine Weishun Zhong, Xun Gao, Susanne F Yelin, Khadijeh Najafi Born Machines are novel generative models that leverage the probabilistic nature of the quantum states. While Born Machines based on tensor networks has shown great success learning both classical and quantum data, here, we use many-body localized states as a novel resource for learning. We present rigorous proof of expressibility of the MBL-Born Machine and show our numerical results that the driven quantum state via MBL dynamic is able to learn both MNIST data set and data from the quantum many-body state. At this end, we demonstrate that adding hidden unit boost the learnability power of the Born Machine . We further investigate the connection between disorder and the learnability power of the MBL phase by calculating various local quantities. |
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G00.00202: Maximum entanglement of formation for a two-mode Gaussian state over passive operations Spyros Tserkis, Jayne Thompson, Austin P Lund, Timothy C Ralph, Ping Koy Lam, Mile Gu, Syed M Assad We quantify the maximum amount of entanglement of formation (EoF) that can be achieved by continuous- variable states under passive operations, which we refer to as the EoF potential. Focusing, in particular, on two-mode Gaussian states we derive analytical expressions for the EoF potential for specific classes of states. For more general states, we demonstrate that this quantity can be upper bounded by the minimum amount of squeezing needed to synthesize the Gaussian modes, a quantity called squeezing of formation. Our work, thus, provides a link between nonclassicality of quantum states and the nonclassicality of correlations. |
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G00.00203: Biocompatible Surface Functionalization Architecture for a Diamond Quantum Sensor Xiaofei Yu, Mouzhe Xie, Lila Rodgers, Daohong Xu, Ignacio Chi Durán, Adrien Toros, Niels Quack, Nathalie P de Leon, Peter Maurer Diamond-based quantum metrology has enabled a new class of biophysical sensors and diagnostic devices that are being investigated as a platform for cancer screening and ultra-sensitive immunoassays. However, a broader application in the life sciences based on nanoscale nuclear magnetic resonance spectroscopy has been hampered by the need to interface highly sensitive quantum bit sensors with their biological targets. Here, we demonstrate a new approach that combines quantum engineering with single-molecule biophysics to immobilize individual proteins and DNA molecules on the surface of a bulk diamond crystal that hosts coherent nitrogen-vacancy qubit sensors. Our thin (sub-5 nm) functionalization architecture provides precise control over protein adsorption density and results in near-surface qubit coherence approaching 100 μs. The architecture remains chemically stable under physiological conditions for over five days, making our technique compatible with most biophysical and biomedical applications. This method should facilitate the realization of NV-based single-molecule electron paramagnetic resonance (EPR) or nuclear magnetic resonance (NMR) experiments on a variety of biomolecules to deepen our understanding of their biological functions. |
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G00.00204: Preparation of Metrological State in Dipolar Interacting Spin Systems Anran Li, Jude Rosen, Sisi Zhou, Martin Koppenhoefer, Ziqi Ma, Fred Chong, Aashish Clerk, Liang Jiang, Peter Maurer The creation and control of highly entangled states lies at the heart of quantum metrology and promises sensing beyond the Standard Quantum Limit. Dipolar interacting spins in atomic and solid-state systems have recently emerged as an attractive candidate for engineering such states. This work discusses a novel variational method that efficiently generates metrologically relevant entangled states in small dipolar interacting spin ensembles using only limited qubit control and no knowledge of the actual spin configuration. Our results show that the generated entangled states provide sensitivity approaching the Heisenberg Limit. Depending on the depth of the variational ansatz the resulting metrological states resemble Greenberger–Horne–Zeilinger (GHZ) or Squeezed Spin states. We further show that these results hold in the presence of experimental imperfections, such as finite initialization/readout fidelity and coherence. The developed black-box variational optimization techniques provide a deeper understanding of the connections between spin arrangement (random vs regular arrays), entanglement, and obtainable sensitivity. Our results are directly applicable to systems in which the number of spins is limited, such as diamond-based nanoscale sensing. |
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G00.00205: Central Spin Induced Spin Bath Relaxation Dynamics Probed via Hyperpolarization Injection William Beatrez, Otto Janes, Arjun Pillai, Dieter Suter, Ashok Ajoy We report on experiments that quantify the role of a central electronic spin as a relaxation source for nuclear spins in a nanoscale environment. Our strategy exploits hyperpolarization injection from the central spin as a means to controllably probe an increasing number of nuclear spins in the bath, and subsequently interrogate them with high fidelity. We use an ensemble central spin model system in diamond consisting of a nitrogen-vacancy (NV) center surrounded by ∼104 13C nuclear spins. We observe that the NV center relaxes 13C nuclei to a considerable degree within a ∼2nm radius; consequently, distant 13C nuclei are measured to have extended transverse state spin lifetimes T2'>65.5s, extended by close to an order of magnitude in comparison to 13C nuclei in close proximity to the NV center. These experiments demonstrate a means to isolate nuclear spins in a nanoscale environment of a central electronic spin, with relevance to quantum memories and sensors constructed out of hyperpolarized nuclei. They also presage interesting new means to measure the extent of spin injection in dynamic nuclear polarization (DNP) experiments. |
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G00.00206: Characterization of CPW resonators on InAs-Al heterostructures Aminatou K Dabokemp, William M Strickland, Bassel H Elfeky, Joseph Yuan, Javad Shabani Superconducting microwave coplanar waveguide (CPW) resonators are essential for many quantum devices. From applications in quantum information to sensing CPW, resonators are used as an integral part of superconducting circuits. In the pursuit of gatemon microwave devices on III/V and Si, we characterize resonators on these substrates under fabrication conditions for qubit processors. We study the internal and external Q factors from the complex transmission signal. Furthermore, we also investigate the influence of environmental terms to find the limitations for microwave circuits on InP and Si platforms. |
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G00.00207: Measurement-induced entanglement phase transitions in variational quantum circuits Roeland C Wiersema, Juan Carrasquilla, Yong Baek Kim, Cunlu Zhou Recent studies on measurement-induced entanglement phase transitions in random quantum circuits hint at universal critical behavior. Currently, it is largely unknown if similar phase transitions occur in more structured circuits, e.g., circuits performing Hamiltonian dynamics, since it is difficult to simulate large circuits efficiently and extract the relevant critical behavior. Moreover, the practical applications of these ideas are still largely unexplored. In this work, we show that measurement-induced entanglement phase transitions take place in two prototypical variational quantum circuits, the Hamiltonian variational ansatz (HVA) for the XXZ model and the Hardware efficient ansatz (HEA). We find that the measurement-induced entanglement transition in these systems belongs to the same universality class as found in previous work. In addition, we show that the measurement-induced entanglement transition coincides with a ``landscape transition'' where we observe mild/no barren plateaus in the area law phase of the model. In producing these results, we derived a parameter shift rule for calculating quantum gradients on circuits with intermediate projective measurements, which might be of independent interest. |
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G00.00208: Relationship between the quantum approximate optimization algorithmand diabatic time evolution for ground-state preparation Zekun He, James K Freericks The quantum approximate optimization algorithm (QAOA) has emerged as an accurate and efficient way to solve many optimization problems including ground-state preparation. In this work, we examine the transverse field Ising model and compare the QAOA procedure to prepare the ground state to a diabatic state preparation via time evolution. In the QAOA, the Ising piece is the problem Hamiltonian, while the magnetic field is the mixing Hamiltonian. We find that the ratio of the amplitudes used in a QAOA track closely to the local adiabatic magnetic field used in diabatic time evolution. But, the optimal QAOA profile has an additional oscillatory behavior for both the problem and the mixing amplitudes. By introducing an overall time-dependent amplitude to the Hamiltonian of a diabatic state preparation, we mimic this behavior as well. Using adiabatic perturbation theory we can understand why the amplitude of the oscillations must be large to optimize the fidelity of the final approximate ground state. |
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G00.00209: Quantum field thermal machines Marek Gluza, João Sabino, Nelly H Ng, Giuseppe Vitagliano, Marco Pezzutto, Yasser Omar, Igor Mazets, Marcus Huber, Joerg Schmiedmayer, Jens Eisert Recent years have enjoyed an overwhelming interest in quantum thermodynamics, a field of research aimed at understanding thermodynamic tasks performed in the quantum regime. Further progress, however, seems to be obstructed by the lack of experimental implementations of thermal machines in which quantum effects play a decisive role. In this work, we introduce a blueprint of quantum field machines, which - once experimentally realized - would fill this gap. The concept of the quantum field machine presented here is very general and can be implemented in various many-body quantum systems described by a quantum field theory. We provide here a detailed proposal how to realize a quantum machine in one-dimensional ultra-cold atomic gases, which consists of a set of modular operations giving rise to a piston. It can then be coupled sequentially to thermal baths, with the innovation that a quantum field takes up the role of the working fluid. In particular, we propose models for compression on the system to use it as a piston, and coupling to a bath that gives rise to a valve controlling heat flow. These models are derived within Bogoliubov theory, which allows us to study the operational primitives numerically in an efficient way. By composing the numerically modelled operational primitives we design complete quantum thermodynamic cycles that are shown to enable cooling and hence giving rise to a quantum field refrigerator. The active cooling achieved in this way can operate in regimes where existing cooling methods become ineffective. We describe the consequences of operating the machine at the quantum level and give an outlook of how this work serves as a road map to explore open questions in quantum information, quantum thermodynamic and the study of non-Markovian quantum dynamics. |
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G00.00210: Benchmarking optimizers and parametrizations for variational quantum optimization with Rydberg atoms Xiuzhe Luo, Mao Lin, Jin-Guo Liu, Alexander Keesling, Sheng-Tao Wang Hybrid quantum-classical algorithms have been a promising class of algorithms in exploring potential quantum advantages using near-term quantum hardware. Selecting an optimizer and a corresponding parameterization of the model is a central step in the algorithm. Different choices of optimization procedures and the parameter space may result in very different performances. However, there is still a lack of systematic benchmarks of different choices of model parameterizations and optimizers. In this work, we benchmark various popular optimizers with hyperparameters search and different model parametrizations including QAOA and quasi-adiabatic algorithms, using the Rydberg Hamiltonian to solve the maximum independent set problem as an example. This benchmark result can be used as heuristics for selecting optimizers and parameterizations for other problems and experimental platforms. Our benchmarks can also be used as the baseline for developing new variational algorithms and optimization procedures. |
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G00.00211: Optimal Quantum Transfer from Input Flying Qubit to Lossy Memory Eric Chatterjee, Daniel B Soh, Matt Eichenfield A key challenge in a quantum network is to transfer a propagating input qubit to a stationary memory mode. For an uncontrolled transfer, the input qubit faces significant reflection from the memory resonator. A solution can be provided by a resonator with a dynamically tunable rate for coupling internal and external fields. For a given input temporal profile, the coupling rate can be tuned such that the raw resonator output continuously destructively interferes with the immediately reflected input signal, making the overall output field a vacuum state, and thus ensuring that the input is fully absorbed into the resonator. Here, we derive the resonator's optimal output coupling rate profile in the presence of intrinsic loss, employing the scattering-Lindbladian-Hamiltonian (SLH) formalism to model the open quantum system. It is imperative to provide a "seed" internal population, using the initial edge of the input field, in order to subsequently cancel out the reflected input via destructive interference. We derive the time required for this initial stage, showing that the loss due to reflection is small enough that the fidelity remains close to unity. We demonstrate that a net transfer fidelity of 99.9% can be reached given practical input and resonator parameters. |
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G00.00212: Non-adiabatic geometric quantum gate of spins in quantum dots Yuefeng Lin, Yu He, Peihao Huang High-fidelity quantum gates, including single-qubit and two-qubit gates, are keys to realize universal quantum computing. Quantum computation based on non-adiabatic geometric phases is an important method to realize high-fidelity quantum gates, due to the merits of both geometric robustness against control errors and high-speed evolution. Here, we propose a scheme to implement universal non-adiabatic geometric quantum gates in silicon-based spin qubits and suppress effectively the off-resonance noise and systematic noise by composite-pulse. Furthermore, we achieve CNOT gate directly and quickly via electric-dipole induced spin resonance (EDSR) techniques and symmetric operation, rather than obtaining by combining single-qubit gates and iSWAP gate in previous schemes. |
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G00.00213: Continuous Bloch sphere mapping of nuclear states via weak measurement Ozgur Sahin, William Beatrez, Otto Janes, Erica de Leon Sanchez, Amala Akkiraju, Ashok Ajoy We report on a strategy for the continuous mapping of nuclear spin states on a Bloch sphere for minute long periods. Our approach exploits nuclear spins initialized in Floquet prethermal transverse states on a Bloch sphere via spin-lock quantum control, and their non-destructive interrogation spins via homodyned weak measurement. Signal-to-noise gains are provided by hyperpolarizing the nuclear spins via coupling to optically pumped electrons. We demonstrate the technique for hyperpolarized 13C nuclear spins in diamond, and show the Bloch-sphere mapping of quantum states for up to 50s. We apply it to the continuous ``tracking’’ of magnetic fields with Floquet prethermal 13C quantum sensors. Overall this work opens intriguing possibilities for continuously interrogated quantum sensors and in mapping phase diagrams of driven out-of-equilibrium phases of quantum matter. |
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G00.00214: Principles of Phase Coherence in Multi-Channel Quantum Control Architectures Yonatan Cohen, Ramon Szmuk, Lior Ella, Oded Wertheim, Nissim Ofek Executing multi-qubit quantum circuits with high fidelity requires maintaining a high level of phase coherence between all qubit drive channels. In this talk, we show how fluctuations in the relative phase of drive channels affect two-qubit gate fidelities and then discuss how to measure and quantify relative phase coherence. Finally, we consider the relative phase coherence of different signal generation architectures that are used in practice. |
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G00.00215: Proposal for a modified Afshar Experiment with Superconducting Nanowire detector array Shahriar Afshar, Aaron J Miller, Timothy Rambo, Stephanie Norwood The Afshar experiment is a quantum optics experiment that demonstrated the presence of simultaneous complementary wave and particle behaviors of single photons in the same experiment in apparent contridiction to Bohr's Principle of Complementarity. It employed passive elements i.e. thin Nitinol® wires placed at the minima of the interference pattern in order to indirectly confirm existence of interference by observing the lack of reduction in total flux downstream of the interference pattern where both beams were well-separated. We propose to use superconducting nanowire single-photon detectors at the minima of the interference pattern. By replacing the passive wires in the original Afshar experiment we will directly measure the photon flux at the minima and obtain the visibility of the interference pattern. The advent of new thin-profile semi-transparent detectors allows us to further refine the results of the original experiment and gain a better understanding of the nature of wavefunction evolution in spacetime. We will present the general setup of the experiment and share any results if available. The theoretical analysis of the experiment and implications of the experiment will also be discussed. |
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G00.00216: Long-Distance End-to-End Quantum State Transfer in a Transmon Qubit Network Connected Via Optical Photons Eric Chatterjee, Daniel B Soh, Rupert M Lewis, William F Kindel, Lisa Hackett, Jeffrey C Taylor, Matt Eichenfield An essential aspect of a quantum internet is the transfer of qubits between different physical modes. Transmon qubits excel in computation, long-decoherence-time phonons are suitable for storing qubits, and optical photons are efficient for long-distance communication. Therefore, an ideal quantum network will be based on hybrid physical platforms. We present an efficient protocol for quantum state transfer between two transmon qubits at the end nodes, connected by an optical channel, piezoelectric RF-photon/phonon qubit converters, and optomechanical phonon/photon transducers. Starting with a qubit initially encoded in a transmon, we theoretically study the sequential transduction of the qubit to transient microwave photon, microwave phonon, and optical photon modes, followed by the inverse of those processes to convert the qubit back to transmon encoding in the other end node. We derive the optimal time profiles for the system's tunable parameters in the presence of intrinsic losses, using the scattering-Lindbladian-Hamiltonian (SLH) formalism to model the open quantum subsystems. For a practical system, a fidelity of 92.2 to 92.7% in the limit of a lossless optical fiber is attainable. |
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G00.00217: SU(2) gadgets for counterpropagating polarization states Teodor Strömberg, Robert Peterson, Philip Walther It is well known that gadgets consisting of simple combinations of fixed linear retarders can be used to generate any SU(2) transformation of a polarization state. However, photons propagating through such a gadget in reverse will in general undergo a completely different transformation. We discuss how to engineer the relation between the transformations in the two different propagation directions, and show how they can be made to be identical, the adjoint or transpose of each other, or in the most general case two completely independent, arbitrary transformations. This is made possible through the use of fixed Faraday rotators, which allow for selective engineering of the symmetry properties of a gadget under change of propagation direction. Our work opens up new possibilities for controlling the polarization of light inside Sagnac interferometers and in other common-path geometries. In particular it can greatly simplify optical implementations of the quantum SWITCH and enable the realisation of new processes such as the recently proposed quantum time flip. |
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G00.00218: Pinpointing sweat spots for the Kerr-Cat Qubit Arne Schlabes, Arne Schlabes, Mohammad H Ansari Introducing a detuning and a single photon drive to the Kerr-Cat Qubit alters its eigenstates to be not coherent states. |
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G00.00219: Risk aggregation by quantum generative modeling of copulas Daiwei Zhu, Sonika Johri, Annarita Giani, Saikat R Majumder, Weiwei Shen The copula is a type of multivariate distribution with uniform marginals, which has been widely used in various fields to study the dependence between random variables. A recent study [1] demonstrated a technique that leverages the expressive power of quantum computers to model copulas for two variables. In particular, the structure of a copula is naturally mapped to a variational ansatz that creates a multipartite maximally entangled state. Here we extend the technique to model the joint distribution of three variables using IonQ quantum computers, specifically, The Dow Jones Total Stock Market Index, The Market Volatility Index, and the Japan Nikkei Market Index. We present numerical and experimental results comparing our approach to state-of-the-art classical methods. We also present and characterize methods that improve the initialization and training of the variational ansatz. Such improvements address vanishing gradients (barren plateaus), which are crucial for real applications which may involve several variables. |
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G00.00220: A Quantum Algorithm for the Collisional Linearized Vlasov Equation Abtin Ameri, Paola Cappellaro, Hari K Krovi, Nuno F Loureiro Simulating plasma dynamics is notoriously challenging. It is natural to seek alternative computational platforms that may speed up such simulations. Quantum computers are an attractive option, as they can solve certain problems exponentially or polynomially faster than classical computers (Grover 1996, Shor 1999). This project aims to investigate whether quantum algorithms can speed up plasma simulations. As a first step, we consider a quintessential plasma problem: Landau damping. Using a Fourier expansion in real space and a Hermite expansion in velocity space, we obtain, from the linearized Vlasov equation, a system of differential equations (Kanekar et al. 2014) which can be mapped to Schrodinger’s equation. In the collisionless limit, we attain unitary time evolution from a Hermitian Hamiltonian, which can be implemented on a quantum computer using Hamiltonian simulation techniques (e.g., Berry et al. 2015). Our algorithm is more flexible than previous ones (Engel et al. 2019) in that it allows for different target problems and it can be naturally extended to the collisional case. In this more realistic scenario, while unitarity is lost, Trotterization can be used to simulate the system by splitting the classical Hamiltonian into a Hermitian and a non-Hermitian matrix. |
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G00.00221: Progress towards atom array programmable quantum circuits using nuclear spins Brett N Merriman, Will Huie, Lintao Li, Neville Chen, Mingkun Zhao, Ian Vetter, Nathan Zachar, Jacob Covey Neutral atom arrays with Rydberg-mediated interactions have become promising platforms for quantum science applications. Alkaline earth atom (AEA) arrays have expanded the neutral atom toolbox by offering new techniques for the control of Rydberg states and opportunities for metrology. However, most of the work with AEA arrays uses zero nuclear spin isotopes. This poster will present our analysis of the nuclear spin degree of freedom in Yb-171 (I=1/2) for Rydberg-based quantum circuits and remote entanglement generation. We then will discuss our experimental progress towards utilizing the nuclear spin for applications in quantum computation and networking. |
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G00.00222: Schmidt and Other Multipartite Entanglement Measures of Graph States Louis Schatzki, Linjian Ma, Yuchen Pang, Eric A Chitambar, Edgar Solomonik Graph states play an important role in quantum information theory through their connection to measurement-based computing, error correcting codes, secret sharing, and stabilizer computation. While much effort has gone into the entanglement properties of such states, primarily bicolorable graphs have been characterized. In this work we prove various multipartite entanglement properties for odd cycle graphs. We first start by tightening the bounds on Schmidt the measure of such states to (n, n+log3]. This improves previous bounds on the entanglement cost for creating odd-cycle graph states using local operations and classical communication (LOCC) with shared entanglement. Next, we prove that several multipartite extensions of bipartite entanglement measures are dichotomous for graph states: either 0 or near maximal based solely on if the graph is connected. Lastly, we show that the n-tangle, which is related to stochastic LOCC invariance, can be computed in a graph theoretic manner: it is one if all vertices have odd degree, and zero otherwise. These dichotomous results indicate that other entanglement measures may be more insightful for graph states. |
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G00.00223: Acceptor qubit in silicon with tunable strain Shihang Zhang, Peihao Huang, Yu He Spin qubits in semiconductor are a potential platform for quantum computers. Hole spin qubit is widely studied recently. However, hole spin of acceptor dopant atom is less discussed compared with that in quantum dot. Here, we introduce model and all-electrical manipulation of boron acceptor spin qubit near Si interface with tunable strain. In our model, strain plays an important role. After utilization of strain, there will be two sweet spots, where decoherence from electrical noise is weak. And the two sweet spots are getting closer with higher asymmetric strain. They may form a 'sweet region' having strong immunity to electrical noise with proper condition. And interaction with stain can mix different hole and spin states, which can realize manipulation of spin qubit. Moreover, Strain can tune the splitting between heavy hole and light hole. The larger LH-HH splitting brings longer relaxation time without changing much the gate time. |
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G00.00224: Certainty of a Quantum Measurement System Donald R LaCoy An improved theory of quantum measurement is presented which relates a polarizer experiment to an Einstein-Podolsky-Rosen-Bohm [1] experiment via clean mathematics and a clear narrative. Many classical measurement systems are comprised of an object and an apparatus. These classical measurement systems are not perfect and have < 100% certainty. This measurement certainty generally is a f(object, apparatus). The outcomes of these classical measurements are often expressed as a value with a certainty interval. |
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G00.00225: Psitrum and Universal Simulation of Quantum Computers Mohammed Alghadeer, Eid Aldawsari, Khaled Alutaibi, Fahhad H Alharbi Quantum computing is a radical new paradigm for a technology that is capable to revolutionize information processing. Computation based on quantum algorithms have proved to be more efficient in processing information and solving wide range of complex problems. Quantum computer simulators are important for understanding the basic principles and operations of the current noisy intermediate-scale quantum (NISQ) processors, and for building in future universal fault-tolerant quantum computers. A universal simulator of quantum computers can be implemented based on David Deutsch model for a Quantum Turing Machine (QTM). Thus, any quantum algorithm can be expressed formally as a particular QTM. The practical equivalent model is a quantum circuit defined as a quantum algorithm implemented on a gate-model based quantum computer with special logic gates and variety of introduced noise modules. In this work, we show simulation of universal quantum computers by introducing Psitrum - a universal gate-model quantum computer simulator implemented on classical hardware. The simulator allows to emulate and debug quantum algorithms in form of quantum circuits for many applications with the choice of adding variety of noise modules that limit coherence of quantum circuits. In addition, Psitrum allows to keep track of quantum operations and provides variety of visualization tools. The simulator allows to trace out all possible quantum states at each stage M of an N-qubit implemented quantum circuit. |
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G00.00226: Informationally complete POVM-based shadow tomography Atithi Acharya Recently introduced shadow tomography protocols use `classical shadows' of quantum states to predict many target functions of an unknown quantum state. Unlike full quantum state tomography, shadow tomography does not insist on accurate recovery of the density matrix for high-rank mixed states. Yet, such a protocol makes multiple accurate predictions with high confidence, based on a moderate number of quantum measurements. One particular influential algorithm, proposed by Huang, Kueng, and Preskill, requires additional circuits for performing certain random unitary transformations. In this paper, we avoid these transformations but employ an arbitrary informationally complete POVM and show that such a procedure can compute k-bit correlation functions for quantum states reliably. We also show that, for this application, we do not need the median of means procedure of Huang {}. Finally, we discuss the contrast between the computation of correlation functions and the fidelity of reconstruction of low-rank density matrices. |
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G00.00227: Benchmarking quantum annealing dynamics: the Spin-Vector Langevin model Fernando J Gomez-Ruiz, David A Subires, Antonia Ruiz-Garcia, Daniel Alonso, Adolfo del Campo The classical Spin-Vector Monte Carlo model (SVMC) is a reference benchmark for the performance of a quantum annealer. As a Monte Carlo method is unsuited for an accurate description of the annealing dynamics in real-time. We introduce the Spin Vector Langevin (SVL) model as a benchmark in which the time evolution is described by Langevin dynamics. |
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G00.00228: Ordering the processes with indefinite causal order Stanislav Filatov, Marcis Auzinsh We show a method of describing processes with indefinite causal order (ICO) by a definite causal order. We do so by relabeling the processes that take place in the circuit in accordance with the basis of measurement of control qubit. Causal nonseparability is alleviated at a cost of nonlocality of the acting processes. This result highlights the key role of superposition in creating the paradox of ICO. We also draw attention to the issue of growing incompatibility of language in its current form (especially the logical structures it embodies) with the quantum logic. |
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G00.00229: Purcell-enhanced emission of erbium ions in nanocrystals using a tunable Fabry-Perot resonator Zach M Brown, Jacob R Slocum, Malsha Udayakantha, Rachel Davidson, Hira Farooq, Ayrton Bernussi, Sarbajit Banerjee, Myoung-Hwan Kim
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G00.00230: Getting Rid of Crosstalk Between Superconducting Qubits Xuexin Xu, Mohammad H Ansari A major roadblock in using superconducting qubits to make large scale fault-tolerant quantum computers are their imperfect gate fidelities. The main source of these imperfections can be traced to the fundamental parasitic interactions between coupled qubits. The parasitic interactions bend the computational and non-computational levels of the qubits thus creating a parasitic ZZ interaction. In this poster, we provide a detailed overview of such parasitic interactions in a multi-qubit system and some techniques to suppress them. |
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G00.00231: Quantum-Assisted Support Vector Regression for Detecting Facial Landmarks Archismita Dalal, Mohsen Bagherimehrab, Barry C Sanders The classical machine-learning model for support vector regression (SVR) is widely used for regression tasks, including weather prediction, stock-market and real-estate pricing. However, a practically realizable quantum version for SVR remains to be formulated. We devise annealing-based algorithms, namely simulated and quantum-classical hybrid, for training two SVR models, and compare their empirical performances against the SVR implementation of Python's scikit-learn package and the SVR-based state-of-the-art algorithm for the facial-landmark-detection (FLD) problem. Our method is to derive a quadratic-unconstrained-binary formulation for the optimisation problem used for training a SVR model and solve this problem using annealing. Using D-Wave’s Hybrid Solver, we construct a quantum-assisted SVR model, thereby demonstrating a slight advantage over classical models regarding landmark-detection accuracy. Furthermore, we observe that annealing-based SVR models predict landmarks with lower variances compared to the SVR models trained by greedy optimisation procedures. Our work is a proof-of-concept example for applying quantum-assisted SVR to a supervised learning task with a small training dataset. |
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G00.00232: High power measurement and non-linearity of cavity JeaKyung Choi, Hyeok Hwang, Eunseong Kim We studied nonlinear bistability of a strongly driven cavity in a dispersive regime. Cavity, a high quality photon resonator, is one of the most important components in realizing Jaynes Cummings interaction, dispersive measurement of a qubit, and bosonic quantum information memory. Low power and slow measurement are necessary to minimize the number of photons in a cavity and, therefore, to stay in a linear regime. Non-linearity of a cavity with many photon state is obtained at high power and fast measurement, which can be understood by the generalized Jaynes Cummings Hamiltonian. [1] The Fock state of a cavity photon can carry qubit information and, accordingly, the non-linearity of the photon states is major limitation to expand the Hilbert space for bosonic information. We will present a preliminary study to correct such non-linearity. |
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G00.00233: Electric-dipole induced nuclear electrical resonance in a phosphorus donor in silicon Jiyuan Su, Peihao Huang, Yu He The nuclear spin of phosphorus atom in silicon is considered as a good information carrier for solid-state qubits because of its good coherence. The coherent control of nuclear spin is generally done using a nuclear magnetic resonance (NMR) that has slow Rabi frequency. Here, we theoretically propose that with the help of hyperfine interactions and magnetic field gradients, we can achieve fast electric-dipole induced nuclear electrical resonance (EDNER) through a Raman-like process. The hybridization of electrons, nuclear and charge in this scheme leads to stronger dipole transitions compared with NMR. By choosing specific manipulation points, the nuclear spin resonance frequency is less sensitive to electrical noise, resulting in longer coherence time and high-fidelity quantum gate operation. Fast electrical control of donor nuclear spin qubit in silicon may have potential applications in silicon-based quantum computing. |
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G00.00234: Quantum Semi-Supervised Learning with Quantum Supremacy Shangnan Zhou Quantum machine learning promises to efficiently solve important problems. There are two persistent challenges in classical machine learning: the lack of labeled data, and the limit of computational power. We propose a novel framework that resolves both issues: quantum semi-supervised learning. Moreover, we provide a protocol in systematically designing quantum machine learning algorithms with quantum supremacy, which can be extended beyond quantum semi-supervised learning. In the meantime, we show that naive quantum matrix product estimation algorithm outperforms the best known classical matrix multiplication algorithm. We showcase two concrete quantum semi-supervised learning algorithms: a quantum self-training algorithm named the propagating nearest-neighbor classifier, and the quantum semi-supervised K-means clustering algorithm. By doing time complexity analysis, we conclude that they indeed possess quantum supremacy. |
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G00.00235: Quantum Mechanical Models for the Szilard Engine Sergio Diaz, Jean-Francois S Van Huele The Szilard engine combines concepts from thermodynamics, computation, and information theory to probe the validity of the second law of thermodynamics. By considering a single-molecule gas in a box with a movable partition, Szilard constructs a machine that extracts work from information at a single temperature. Quantum models have been proposed to generalize Szilard’s classical treatment to the quantum realm by considering a particle in a quantum box. Zurek1 proposed a rigid box with a step barrier, and Davies2 proposed a harmonic box with a delta function barrier. We probe the quantum model using an infinite rigid box with a delta function barrier. We slowly increase the strength of the barrier. We analyze the dependence of the solutions on the parameters of the box. We compute the thermodynamic quantities, including the entropy balance, throughout the Szilard cycle. We compare our results across the different box models. These results point us towards the development of quantum circuitry. |
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G00.00236: Robust optimal control of interacting multi-qubit systems for quantum sensing Nguyen H Le, Max Cykiert, Eran Ginossar Realising high fidelity entangled states in controlled quantum many-body systems is challenging due to experimental uncertainty in a large number of physical quantities. We develop a robust optimal control method for achieving this goal in finite-size multi-qubit systems despite significant uncertainty in multiple parameters. We demonstrate its effectiveness in the generation of the Greenberger-Horne-Zeilinger state on a star graph of capacitively coupled transmons, and discuss its crucial role for achieving the Heisenberg limit of precision in quantum sensing. |
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G00.00237: Superconducting circuits may make and interesting addition to the Circuit as originally put forward by Oliver Heaviside RICHARD M KRISKE There is a 3 volume set of books that Oliver Heaviside wrote, in which he explains circuits in this way. He proposed, that it was the circulation of the Magnetic Field in a loop that set the electrons in motion and this loop or circle is the "circuit." He then went on to show that Faraday's and Ampere's law formed a linking of circular fields called light. Einstein also claimed this was how light worked. The Tensor in this case was not Faraday's Law, nor Ampere's law by itself, but rather the totality of the two. Quantum circuits, throw a monkey wrench into this idea in that when there is spin, one of the parties can fashion a state with one spin, unknown to the other party. The Tensor is the combination of known and unknown information about the spin. It may be that there are other fields that are also part of the Tensor in Maxwell's Equations, that are not strictly Electromagnetic. The full Tensor in the Quantum Circuit would then have to include the other fields, so it may be that there is more "unknown" information, or it may be that all the information can be known. |
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G00.00238: Sensing electric currents using a quantum diamond microscope Pralekh Dubey, Jayita Saha, Shashank Kumar, Phani K Peddibhotla Nitrogen-vacancy (NV) defects in diamond have demonstrated unique capabilities in sensing the magnetic, electric, and stress fields. These capabilities are vested to the NV center by its atomic size, long spin coherence time, and diamond's robust environment. Previous studies have shown the applicability of NV ensembles to wide-field magnetic imaging of a wide range of physical and biological samples under ambient conditions. In this work, we employ the ensemble of NVs in a widefield setup to map the vector magnetic fields generated by the electric currents. The end goal of this work is to implement the non-invasive imaging of magnetic fields generated by the electric currents in electronic devices. Here we present the underlying theory, our approach, preliminary experimental results, and our future work. |
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G00.00239: Stochastic Schrödinger equation derivation ofnon-Markovian two-time correlation functions Rafael Carballeira We derive the evolution equations for two-time correlation functions of a generalized non-Markovian open quantum system |
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G00.00240: Dynamical quantum phase transitions in the spin-boson model David Dolgitzer We study dynamical quantum phase transitions in a 2-qubit system interacting with a transverse field and a quantized bosonic environment in the context of open quantum systems. By applying the stochastic Schrödinger equation approach, the model with a spin-boson type of coupling can be solved numerically. It is observed that the dynamics of the rate function of the Loschmidt echo in a 2-qubit system within a finite size of Hilbert space exhibit nonanalyticity when the direction of the transverse field coupled to the system is under a sudden quench. Moreover, we demonstrate that the memory time of the environment and the coupling strength between the system and the transverse field can jointly impact the dynamics of the rate function. We also supply a semi-classical explanation to bridge the dynamical quantum phase transitions in many-body systems and the non-Markovian dynamics of open quantum systems. |
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G00.00241: Global quantum clock synchronization network using a constellation of satellites - A precursor to the Quantum Internet Stav Haldar, Ivan Agullo We propose the near-term implementation of a hybrid quantum network of satellite and ground based clocks with the ability to implement a quantum clock synchronization (QCS) protocol to the picosecond level. We simulate the sync outcomes for cities across the globe using a minimalistic constellation of satellites, low-cost entanglement sources, portable atomic clocks, and avalanche detectors. Such a QCS network will form the basis of future quantum networks like the Quantum Internet, distributed quantum sensing and Quantum GPS. In contrast to classical techniques, QCS does not require an apriori knowledge of time of travel between two parties, instead both time of travel and clock offset can be extracted independently. It utilizes the tight time-correlations between entangled photons and the information transfer efficiency gains offered by optical communication using single photon detection over radio frequency (RF) based classical communication. Using the polarization correlations, the QCS protocol also has quantum security. Picosecond level sync outcomes can be achieved with < 100 exchanged photons making the protocol ideal for Deep Space Quantum Links (DSQLs). The use of free space optical communication and fast-moving LEO satellites increases the network size considerably. |
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G00.00242: Concentration for Trotter error Chi-Fang Chen, Fernando Brandao Quantum simulation is one promising application of quantum computers. Product formulas, or Trotterization, is the oldest and still today one of the most studied methods for quantum simulations, due to their relatively simple implementation without ancillae. For an accurate approximation in the spectral norm, the gate complexity of the state-of-the-art product formulas depends on the number of terms in the Hamiltonian and a certain 1-norm of its local term coefficients. |
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G00.00243: Arbitrary response measurements via Quantum Signal Processing Sina Zeytinoglu, Sho Sugiura The experimental platforms for quantum information conventionally offer only projective measurements on single qubits. Hence the realization of generalized measurements require the interaction between the system and an ancilla. Although a complete theoretical framework for such generalized measurements is in place, an explicit experimental protocol that allows the design of arbitrary measurement operators has so far been elusive. In this work, we show that combining Quantum Signal Processing (QSP) with many-body interferometry yields a vast library of protocols for measuring high-order space-,time-, and frequency-dependent response functions. We provide a detailed analysis of the implementation of our protocol in the Rydberg atom platform. Our work demonstrates the close relation between QSP and generalized measurements, and naturally yields a novel way of block-encoding arbitrary functions of Hamiltonians realized in Rydberg atom systems. |
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G00.00244: Fast Quantum State Tomography Implemented by Measurement Axis Adjustment Hyeok Hwang, JeaKyung Choi, Eunseong Kim We developed a fast quantum state tomography method by choosing three independent measurement axes based on the initial statistical sampling of qubit state measurements. The measurement standard deviation (SD) is inversely proportional to the square roots of N, the number of readout, and proportional to the square roots of p(1-p) where p is a probability that state readout results in 0 (or 1). Accordingly, a straightforward way of reducing SD is to increase N which requires a large number of state-readout. An alternative way is to adjust measurement axes and, thus, modify the probability p of state readout. After the adjustment, we were able to obtain the equal error bound of SD with only 2/3 of N required previously. This method is independent of the 0/1 state resolution of the system. Therefore, the worse the system resolution, the more the required number of readout decrease. |
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G00.00245: Performance Optimization of Cascaded Subband Degeneracy Cryogenic Refrigerator Thomas Douglas, Chulin Wang, Matthew Grayson The design for a cascaded solid-state refrigerator is introduced as an alternative to dilution refrigerators for eventual use in cryogenic cooling of quantum computers. The design achieves cooling through adiabatic subband degeneracy expansion in a closed-cycle electron heat-pump controlled by electrostatic gates – a cooling mechanism whose single-shot principle was first outlined by Rego and Kirceznow (1999). Whereas a single stage reduces temperature by at most the ratio of the degeneracies g1 and g2 of the “compressed” and “expanded” quantum well states, here a multi-stage, cascaded design is shown to reach lower temperatures. The optimal ratio of areas between successive hot and cold stages is equal to the square root of g2/g1. In a 1 K heat bath, a 1 cm2, double degeneracy two-stage device can reach a base temperature of 0.68 K. Multi-stage refrigerators have base temperatures below 0.10 K, where electrons and phonons thermally decouple. Modeling the Joule heating and thermal conduction through gate wires, as well as electron-phonon coupling, the parasitic heat load at low temperatures can be determined. The thermodynamic coefficients of performance for this device are also derived. |
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G00.00246: Aharonov-Bohm effect as a material phenomenon V. Rubaev1, L. Fedichkin2 1. NIX, Zvezdny blvd. 19, Moscow, Russia, vladislav@nix.ru 2. Valiev Institute of Physics and Technology, Russian Academy of Sciences, Moscow, Russia, leonid@phystech.edu Vladislav Rubaev We provide the consideration of Aharonov-Bohm effect by investigating at quantum microscopic level the whole system comprising not only our particle but also the solenoid generating electromagnetic potential. We show that the action on particle phase is physical natural phenomenon rather than spooky action at a distance as it may seem when solenoid is considered classically. Dipoles are considered to be initially in quantum state which may be even entangled with environment. By properly taking path integral over particle trajectories accounting for force action between dipole and particle we arrive at expressions which are just the same as Aharonov‑Bohm result. In contrast to previous attempts to explain Aharonov-Bohm effect as an action of charged particle magnetic field upon the source of magnetic vector potential our results are general and rigorous. We hope that our reverse approach to consideration of this effect paves the way for better understanding of physical processes behind Aharonov-Bohm effect and our alternative technique of calculations may occur to be useful for investigation of electronic transport in nanosystems. In particular, we predict that perfect superconducting shield of solenoid must eliminate the influence of solenoid on particle phase. |
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G00.00247: Concepts and conditions for error suppression through randomized compiling Adam Winick, Joel Wallman, Dar Dahlen, Ian Hincks, Egor Ospadov, Joseph V Emerson Randomized compiling reduces the effects of errors on quantum computers by tailoring arbitrary Markovian errors into stochastic Pauli noise. During this talk, we prove that randomized compiling also tailors non-Markovian errors into local stochastic Pauli noise and investigate the technique's limitations. We show through analysis and numerical results that randomized compiling alters errors in three distinct helpful ways. First, it prevents the coherent accumulation of errors (including hard to remove crosstalk effects) across gate cycles by destroying intercycle coherent correlations. Second, it converts individual gate cycle errors into Pauli noise. Finally, randomized compiling reduces the variability inherent to noisy devices. We confirm these theoretical predictions with the IBM Quantum platform and describe experimental data that illustrates a drastic performance improvement across public devices. These results cement the importance of randomized compiling in near- and long-term quantum information processing. |
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G00.00248: Fast-fowarding quantum dynamics with quantum Krylov subspace algorithms Cristian L Cortes, Stephen K Gray In this talk, I will present a new method for fast-forwarding quantum dynamics simulations using quantum Krylov subspace algorithms. Our approach consists of a hybrid quantum classical algorithm that constructs a projected Schrodinger equation in a Krylov subspace, where the matrix elements are computed using the quantum computer and the Krylov-based fast-forwarding is performed on a classical computer. We show that this method is highly competitive to other quantum variational fast-forwarding techniques, requiring less resources overall for a wide variety of Hamiltonians relevant to nuclear physics, condensed matter physics, and quantum chemistry. We validate our approach through numerical experiments of various molecular systems, showing excellent recovery of ideal quantum dynamics beyond the coherence time of near-term quantum computers. |
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G00.00249: Is Quantum Money a Waste of Time? Noah Lindsell, Christian Querrey The idea of a universal currency realized by quantum states was first proposed by Weisner in 1983 [1]. Weisner’s proposal was quickly dismissed as little more than a novel, albeit practically useless idea, because of its lack of realizability. Since then, the idea of Quantum Money has received little attention, compared to far more popular areas of research such as quantum computation and quantum communication. However, new advancements and research in digital currencies, quantum communication, and quantum cryptography present attractive avenues which warrant revisiting the idea Quantum Money. Current cryptographic currencies solve the double-spending problem often by integrating a blockchain which is backed by hard-to-solve cryptographic hash functions. This ensures that each “coin” is unique, and also maintains the value of the underlying asset via the difficulty of “mining” such coins through the hash-solving process. The study of Quantum Information presents many concepts such as quantum teleportation, quantum digital signatures, and quantum secret sharing which make its application to such problems extremely attractive and a rich source of scientific research. In this study, we ask ourselves the question, "Is Quantum Money a waste of time?". We begin by discussing the vulnerabilities and inefficiencies of present digital currency schemes. We then proceed to a thorough literature review and categorization of research regarding quantum money since Weisner’s proposal, discussing the improvements each scheme proposes, and classifying the methods used to do so. Finally, we motivate our own proposals to incorporate quantum technology into cryptocurrency. |
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G00.00250: Ab initio characterization of defect centers in silicon Jacopo Simoni, Vsevolod M Ivanov, Liang Tan, Arun Persaud, Thomas Schenkel, Yeonghun Lee In this work we report a theoretical study of color center defects in silicon. Color centers with photon emission in the telecommunication bands are promising candidates for the implementation of a quantum network between several computing nodes, this however requires long spin coherence times and a narrow linewidth for the qubit energy levels. Here we employ ab initio density functional theory to characterize W and G centers by extracting energy levels, photoluminescence spectra, zero field splitting and decoherence properties like dephasing times and fluctuations of the defect energy levels. The calculation of these properties requires, in addition to a deep understanding of the energetic structure, also a detailed knowledge of the vibronic excitations close to the defect center. We also discuss the effect of disorder on these properties and the potential applicability of these systems for quantum information applications. |
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G00.00251: Enabling Quantum Cryptography using IBM QX Yaser Banadaki, Hasmika Kesineni Quantum computation is gaining popularity as a practical application of quantum physics, which is based on quantum superposition, entanglements, and the no-cloning theorem. Because the security of electronic transactions is vital, various cryptographic protocols based on distributed keys between the intended participants have been created. Complex mathematical models and lengthy keys determine the security of these protocols. These keys, on the other hand, are readily broken. The security of information has undergone a paradigm shift as a result of quantum technologies. The quantum circuits in this thesis were constructed utilising the IBM quantum experience platform with the goal of realising safe quantum key distribution (BB84 algorithm). With increasing the number of runs, the possibility of these circuits being realised on a practical quantum computer accessed through the IBM QX online platform increased. Furthermore, there is a significant likelihood of identifying the presence of a third party. The probability of identifying a third-party stealing information increases as the number of qubits increases. |
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G00.00252: Coherent microwave-to-optical conversion of a frequency qubit Poolad Imany, Zixuan Wang, Ryan A DeCrescent, Robert Boutelle, Corey McDonald, Travis Autry, Richard Mirin, Kevin Silverman Building a long-range network of superconducting quantum computers has been an ongoing challenge owing to complications associated with transduction of quantum information between microwave and optical domains. Coherent conversion of a qubit encoded in microwave photons into an optical state has remained an outstanding challenge. Here, we encode a qubit into a coherent state of two microwave frequency levels—generating a frequency qubit. These qubits are then efficiently converted to surface acoustic wave (SAW) cavity phonons using an interdigitated transducer. The multimode nature of the SAW cavity allows enhanced interaction between both microwave frequencies and a quantum dot located at the center of the cavity. The single photon emitting capability of the quantum dot and its resonance fluorescence with sub-natural linewidth ensures coherent transduction into quantum light. We report a computational state transfer with a fidelity of 0.90±0.07. Additionally, we show coherent state transfer by measuring the phase between the two optical frequency modes with an electro-optic phase modulator, yielding a visibility of 0.70±0.07. Coherent transduction of qubits is a key step towards transmission of quantum information encoded in superconducting qubits via optical fiber networks. |
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G00.00253: First results of 2D superconducting quantum device coherence fabricated via innovative materials, substrate and passivation techniques Mustafa Bal, Arpita Mitra, Shaojiang Zhu, Mattia Checchin, Akshay A Murthy, ZuHawn Sung, Jaeyel Lee, Daniel Bafia, David Van Zanten, Grigory Eremeev, Francesco Crisa, Ivan Nekrashevich, Daniil Frolov, Roman Pilipenko, Alexander Romanenko, Anna Grassellino The past two decades has witnessed incredible enhancement of coherence time in superconducting quantum devices (SQDs). Much of this progress has been accomplished by optimization of device design and geometry. It has become clear that addressing the quality of superconducting films and interfaces in planar SQDs is of utmost importance to further improve coherence times beyond millisecond timescale. In this contribution we report the first results of superconducting transmission line resonators and transmon qubit devices fabricated at the SQMS Center (at the Pritzker nanofabrication facility at University of Chicago). A systematic investigation based on materials findings is pursued which addresses TLS losses introduced by amorphous interfaces and other new loss mechanisms which have been found recently with SQMS materials investigations [1-3] This material is based upon work supported by the U.S. Department of Energy, Office of Science, National Quantum Information Science Research Centers, Superconducting Quantum Materials and Systems Center (SQMS) under contract number DE-AC02-07CH11359. |
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G00.00254: COMPUTATIONAL PHYSICS
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G00.00255: Accelerated spin dynamics using deep learning corrections Sojeong Park, Hwee Kuan Lee, Wooseop Kwak Theoretical models capture very precisely the behaviour of magnetic materials at the microscopic level. This makes computer simulations of magnetic materials, such as spin dynamics simulations, accurately mimic experimental results. New approaches to efficient spin dynamics simulations are limited by integration time step barrier to solving the equations-of-motions of many-body problems. Using a short time step leads to an accurate but inefficient simulation regime whereas using a large time step leads to accumulation of numerical errors that render the whole simulation useless. In this paper, we use a Deep Learning method to compute the numerical errors of each large time step and use these computed errors to make corrections to achieve higher accuracy in our spin dynamics. We validate our method on the 3D Ferromagnetic Heisenberg cubic lattice over a range of temperatures. Here we show that the Deep Learning method can accelerate the simulation speed by 10 times while maintaining simulation accuracy and overcome the limitations of requiring small time steps in spin dynamic simulations. |
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G00.00256: Study the effect of acoustic and optical tweezers on a brownian particle Alireza Khoshzhaban, David Bronte Ciriza, Mehmet Burcin Unlu, Onofrio M.Marago In this study, we investigate the dynamic of a silica spherical microparticle in the presence of optical and acoustic forces. We show that the optical tweezers confine the particle around the focused beam and the acoustic tweezers apply finer force on the particle. We demonstrate the difference in the particle dynamics in the presence and absence of acoustic forces. Applying force on a trapped particle is especially useful to study collective behavior and measure minuscule force between particles and cells. Both tweezers systems have shortcomings and advantages. For example, optical tweezer has a restriction on the heavy particles since they are prone to sink. However, acoustic tweezers can levitate the particles for optical tweezers to trap them. On the other hand, the optical tweezers system can precisely trap and move the trapped particle, while acoustic tweezers are suitable for rough trapping. Combining the two systems can forge a setup that can compensate for each system's limitations. |
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G00.00257: Poles and Residues Method for Numerical Analytic Continuation Jian Wang This work is based on our previous paper, Rational function regression method for numerical analytic continuation (arXiv:1812.01817). |
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G00.00258: Coherent state description of lattice vibrations and high-temperature coherence effects Alhun Aydin, Alvar Daza, Donghwan Kim, Kobra N Avanaki, Eric J Heller Usage of coherent states to describe the electromagnetic field paved the way for comprehensive understanding of coherence in quantum optics. Here we present a new description of lattice vibrations in terms of coherent states. When lattice vibrations are treated as coherent states, the deformation potential becomes a real field acting on electrons, making the electron-phonon interaction inherently non-perturbative. In the traditional approach, electron-phonon interactions are treated as the combination of uncorrelated successive first order events. On the contrary, in our approach, the lattice creates a disordered landscape where conduction electrons can quasi-elastically scatter, which preserves electron coherence beyond single collision events. This allows us to take the coherence of electrons into account. We find that preserved coherence effects cause electrons to Anderson localize even at high temperatures for a certain timescale. Furthermore, we compare our results with the literature by calculating electrical resistivity and observe a very good match for the regimes where the electron coherence effects do not play significant role. Coherent state picture of the lattice might have a potential to shed light on the universal resistivity of strange metals. |
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G00.00259: Random phase product states for quantum Boltzmann machines at finite temperature Toshiaki Iitaka I will introduce a mathematical proof and numerical examples of the method of random phase product state (RPPS) [1] for calculating thermal average of a physical quantity A at inverse temperature β,〈Φ(w(β))| A |Φ(w(β))〉, with respect to thermal neural network wave functions (Boltzmann machines), |Φ(w(β))〉= exp[-βH/2] |Φ(w(0))〉=exp[-τH/2]n|Φ(w(0))〉, where w's are variational parameters, τ is a small imaginary time step. The initial state |Φ(w(0))〉is set to a neural network wave function of RPPS representing a state at infinitely high temperature and the imaginary time evolution exp[-τH/2] |Φ〉is approximated with the natural gradient [2]. This method is a natural extension of the RPPS method for matrix product states (MPS) [1] and the random state method for a full Hilbert space [3,4]. |
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G00.00260: Computer modeling of molecular perovskites [(C3H7)3(CH3)N]M(C2N3)3 (M = transition metal): tilt-and-shift polymorphism and vibrational/mechanical properties Shivani Grover, Stefan Burger, Keith T Butler, Hanna T B. Boström, Gregor Kieslich, Ricardo Grau-Crespo Molecular perovskites have recently gained attention in the field of ferroelectrics, multiferroics and mechanocalorics. The incorporation of molecular building blocks in the 3D ReO3-type network of the perovskite structure leads to new geometric degrees of freedom, enabling the formation of polymorphic perovskite phases with different tilt and shift systems that are close in energy, i.e. tilt and shift polymorphs. We discuss the series of molecular perovskites [(C3H7)3(CH3)N]M(C2N3)3, where different polymorphs crystallise in the perovskite structure but with different tilt systems depending on the synthetic conditions. Our computer simulations show that for the whole stability temperature range the rhombohedral polymorph is the thermodynamically more stable phase than the orthorhombic phase. The absence of imaginary modes in both phases suggests that the transformation goes through a high-energy transition state as underlying mechanism of the irreversible phase transition. Given that the bulk moduli (B) characterises the suitability of these materials for barocaloric applications, we calculated B for a wider range of compositions (M=Mn, Co, Fe, Ni, Zn, Cd, Ba, Sr, Ca, Hg, or Mg), and discuss the geometric factors determining the mechanical properties. |
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G00.00261: Efficient Crystalline Anharmonic Potential Energy Surfaces by Taking the Derivative of a Gaussian Process' Keerati Keeratikarn, Jarvist M Frost Machine learning (ML) a surrogate model is increasingly demonstrated as a useful tool for exploring potential energy surfaces (PESs). One such method is Gaussian process (GP) regression, which is particularly well suited to Bayesian (probabilistic) model construction. To obtain highly accurate PESs with a minimal number of electronic structure calculations, the GP model can be differentiated, and conditioned (trained) directly on the available forces (energy derivative). This exact transformation requires differentiating the GP kernel for the problem at hand. This could reduce the number of data points (from expensive electronic structure calculations) required for a given accuracy (at the cost of a more complex GP model). Once you have a trained GP model, force-constants (to arbitrary order) can be calculated by taking the derivative of the GP model, which as differentiation is a linear operator, yields another GP model. We apply these new techniques to inferring the anharmonic properties of crystalline materials and compare it to the more standard approach of using finite displacements. |
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G00.00262: The influence of electric fields' direction on water desalination performance Samaneh Rikhtehgaran, Luc T Wille Using molecular dynamics (MD) simulations, a nanoporous membrane is exposed to the vertical and horizontal electric fields. This project aims to investigate the influence of the electric fields’ direction on ion separation and water desalination performance. These results might help for better control of the water transport through the membrane and for the design of efficient nanoporous membranes. |
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G00.00263: Exchange-correlation functional development: Data-driven and physically-constrained Kai Trepte, Johannes Voss We present a methodology that combines data science and physical constraints for the development of new exchange-correlation functionals [1]. |
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G00.00264: First-principles study of photogalvanic effects in magnetic ferroelectrics BABU BAIJNATH PRASAD, Guang-Yu Guo Photogalvanic (Bulk photovoltaic) effects have been extensively studied in ferroelectric materials having broken inversion symmetry in past years. However, the study of magnetism-induced photogalvanic currents is still missing in magnetic ferroelectrics BiFeO3 and PbNiO3 which possess large electric polarization of 90 μC/cm2 and 100 μC/cm2 respectively. In this work, we systematically study the linear and circular photogalvanic effects, namely, linear and circular shift and injection currents. Our preliminary calculations have shown that the linear shift current conductivity can go up to 72 μA V-2 & -34 μA V-2 whereas it goes as high as -8 μA V-2 & -2 μA V-2 for circular shift current conductivity within the energy range of 0 - 6 eV for multiferroic (magnetic ferroelectrics) BiFeO3 and PbNiO3 respectively. Linear injection current susceptibility is 43 × 108 A V-2 s‑1 and 6 × 108 A V-2 s‑1 for BiFeO3 & PbNiO3 respectively in the 0 – 6 eV energy range. Circular injection current susceptibility has a large value of about 21×108 A V-2 s‑1 and -66 × 108 A V-2 s‑1 for BiFeO3 and PbNiO3 respectively within 0 - 4 eV energy range. Thus, we believe that magnetic ferroelectrics BiFeO3 and PbNiO3 will have promising applications in ferroelectric-based photovoltaic devices. |
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G00.00265: PySAGES (Python Suite for Advanced General Ensemble Simulations) Gustavo R Perez Lemus, Pablo Zubieta, Ludwig Schneider, John A Parker, Juan De Pablo Molecular Dynamics simulations are now a core component in science for understanding, prediction, and design of properties at the molecular scale, but determining the free energy of many systems requires the use of enhanced sampling techniques. In this sense, having software tools providing advanced sampling methods that can be seamlessly adapted to a broad range of complex systems is essential. Continuing with the efforts of having an open-source community supported software, we introduced PySAGES, a Python implementation of SSAGES (Software Suite for Advanced General Ensemble Simulations) with full support of GPUs for the massive parallel applications of enhanced sampling methods like adaptative forces, harmonic bias, and forward flux sampling in molecular dynamics simulations. The intuitive interface facilitates the configuration of the system, the inclusion of new collective variables, and more sophisticated free energy methods can be adapted to the software with little effort. In this work, the core features are introduced along with clear and concise examples of the capabilities of this software. |
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G00.00266: On the Role of Crystal Defects on the Lattice Thermal Conductivity of Monolayer WSe2 (P63/mmc) Thermoelectric Materials by DFT Calculation Yingtao Wang As the energy problem becomes more prominent, research on thermoelectric (TE) materials has deepened over the past few decades. Low thermal conductivity enables thermoelectric materials better thermal conversion performance. In this study, based on the first principles and phonon Boltzmann transport equation, we studied the thermal conductivities of single-layer WSe2 under several defect conditions using density functional theory (DFT) as implemented in the Vienna Ab-initio Simulation Package (VASP). The lattice thermal conductivities of WSe2 under six kinds of defect states, i.e., PS, SS-c, DS-s, SW-c, SS-e, and DS-d, are 66.1, 41.2, 39.4, 8.8, 42.1, and 38.4 W/(m·K), respectively at 300 K. Defect structures can reduce thermal conductivity up to 86.7% (SW-c) compared with perfect structure. The influences of defect content, type, location factors on thermal properties have been discussed in this research. By introducing atom defects, we can reduce and regulate the thermal property of WSe2, which should provide an interesting idea for other thermoelectric materials to gain a lower thermal conductivity. |
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G00.00267: Exchange torque in noncollinear spin-density-functional theory with a semilocal exchange functional Nicolas Tancogne-Dejean, Angel Rubio, Carsten A Ullrich We propose a novel energy functional for spin density functional theory based on the short-range expansion of the noncollinear exchange hole. |
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G00.00268: Nonreversible Markov chain Monte Carlo algorithm for efficient generation ofSelf-Avoiding Walks Hanqing Zhao, Marija Vucelja We introduce an efficient nonreversible Markov chain Monte Carlo algorithm to generate self-avoiding walks with a variable endpoint. In two dimensions, the new algorithm slightly outperforms the two-move nonreversible Berretti-Sokal algorithm introduced by H.~Hu, X.~Chen, and Y.~Deng in 2016, while for three-dimensional walks, it is 3--5 times faster. |
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G00.00269: PyAMFF: A machine learning package for fitting and using atom-centered machine learning force field Jiyoung Lee, Naman Katyal, Graeme Henkelman Ab-initio calculations have been used commonly to study dynamics of complex systems and atomic-level understandings are significant to determine their barriers, reaction pathways and transition states. The high accuracy of these calculations, however, accompanies increase of computational cost and such tradeoff restricts their applicable areas. In an effort to overcome this, applying machine learning (ML) technique to learn potential energy surface (PES) of systems being studied has become one of the promising solutions for the last decades. The main advantages of using ML is that the accuracy is remained as high as ab-initio level while the computational cost is not. Especially, Behler and Parinello proposed a method of describing a system numerically in terms of atomic environment and feed the descriptor to the neural network (NN) that returns to the atomic energy of the system and allows force evaluation. PyAMFF (Python Atom-centered Machine Learning Force Field) is built off of this idea and provides user-friendly and high performance computations interfaced with the EON software, which supports long-timescale molecular dynamics. In the poster, I will present the PyAMFF code framework and its application for Li dynamics. |
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G00.00270: Identification of dyes for aggregate systems using DFT Maia N Ketteridge, Austin Biaggne, German Barcenas, Lan Li Delocalization of Frenkel excitons occurs in dye aggregates and has applications in the study of quantum information. Maximizing exciton exchange energy (J) and exciton-exciton interaction energy (K) are of particular interest for dye aggregate systems. Experimental identification of candidate dyes is time and resource intensive, however, computational methods quickly can identify candidate dyes with desired properties for further investigation. We present a method for high-throughput screening of dyes using density functional theorem (DFT) and time-dependent density functional theorem (TD-DFT). Transition dipole moment (∆d) and static dipole difference (µ) are determined, which exciton exchange energy and exciton-exciton interaction energy depend upon. The effects of solvent can also be determined. This method was applied to modified Cy5 dye, and several interesting substituents were identified for further experiment. |
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G00.00271: Quantifying Patterns of Sound Units in Languages Using Maximum Entropy Kristen P Gram, Alfred C Farris, Effrosyni Seitaridou, Jiayu Sui The frequencies of patterns of letters in words can be used to define pairwise interaction energies between letters using Jaynes’ principle of maximum entropy. By quantifying these interactions, overarching patterns in the English language can be studied [1,2]. We extend this framework to study patterns among combinations of sounds in words by investigating a phonological parametrization of texts in the English language, in addition to studying combinations of letters in words with the standard orthographic representation of these texts [1,2]. The benefit of this approach is that languages with different alphabets can be compared directly. |
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G00.00272: Spin crossover in ferropericlase: beyond ideal solid solution model Jingyi Zhuang, Yang Sun, Renata M Wentzcovitch The pressure- and temperature-induced high spin (HS) to low spin (LS) crossover of Fe2+ ions in ferropericlase (Fp), Mg(1-x)FexO, affects mantle properties such as density, elasticity, thermal properties, iron partitioning between Fp and other co-existing phases, etc. It further affects how we interpret lower mantle observations. Here, we present results of thermodynamic properties computed using a free energy model that goes beyond the ideal HS-LS solid solution framework. As in the past, ab initio calculations were performed using the DFT+ USC method with structure and electronic configuration dependent USC. Results show the influence of iron-iron interactions (elastic or exchange type) on the pressure range of the crossover. Comparison with available experimental data shows considerably improved agreement over that of the ideal solid solution model. |
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G00.00273: Arithmetic tensor network for multi-variable function integration Ruojing Peng, John C Gray, Garnet Chan Exact integration of a discretized d-variable function by summing over all grid points requires a computational cost exponential in d. On the other hand, tensor networks (TN) are known for representing high-dimensional functions with polynomial memory. We propose a TN ansatz for representing general high-dimensional functions and their integration. Unlike the standard variational/time-evolution approach well-known to the physical TN community or an optimization/fitting approach, we obtain the TN for the polynomial approximation of the high-dimensional function directly as a network of fixed small tensors. We call the resulting TN an arithmetic TN since it is analogous to the classical binary circuit which computes function value via arithmetic operation with a set of known gates. (Approximate) integration of the function is done by tracing over the external legs of the arithmetic TN and approximately contracting the resulting closed TN. We give numerical examples of approximately integrating polynomials of a specific form, quadratic Gaussians with quartic perturbations, and feed-forward neural networks -- although the same idea in principle applies to any function that admits polynomial approximation. |
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G00.00274: Prediction of mechanical and anisotropic elastic properties of Cs(Na, K)2Bi compounds under hydrostatic tension and compression and tunable auxetic properties Shahram Yalameha, Zahra Nourbakhsh, Ali Ramazani, Daryoosh Vashaee Cs(Na, K)2Bi compounds are introduced with exotic mechanical properties for application in nanoscale electromechanical devices. The mechanical properties of the compounds are investigated under hydrostatic tension and compression using first-principles calculations. We show that hydrostatic tension and compression change the isotropic and anisotropic mechanical responses of these materials. Furthermore, our results show that the auxetic nature of CsK2Bi is tunable under pressure. This compound transforms into a material with a positive Poisson’s ratio under hydrostatic compression, while it holds a large negative Poisson’s ratio of about −0.45 under hydrostatic tension. The auxetic nature is not observed in CsNa2Bi; however, an interesting phenomenon occurs in the Poisson’s ratio under hydrostatic compression, in which it exhibits completely isotropic behavior. An elastic wave velocity analysis also indicates that hydrostatic pressure effectively changes the propagation pattern of the elastic waves and switches propagation directions. Therefore, the mechanisms identified in this work to control the auxetic and anisotropic elastic behavior of these compounds provide a critical feature for the design and development of high-performance nanoscale electromechanical devices. |
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G00.00275: Theoretical design of superconducting electrides Guochun Yang Realizing the coexistence of multiple states such as electride, metallicity, and superconductivity in a compound is of great interest from basic research and practical application. Most of the electrides exhibit semiconducting or insulating properties under high pressure due to the strong localization of both interstitial and orbital electrons. We propose that the application of pressure and variable chemical composition becomes an effective way to achieve this goal. Three hitherto unknown electrides (Li5P, Li6P, and Li8P) with superconductivity are identified through first-principal swarm structural search. More intriguingly, C2/c Li6P exhibits a Tc of 39.3 K at 270 GPa, which is the highest among the already known electrides. On the other hand, we found that modifying the chemical composition, in these electrides, can not only modulate the magnitude and distribution of interstitial electrons of electrides but also have great effect on superconductivity. We also apply this strategy to lithium selenides or tellurides. More interestingly, their Li-rich compounds can achieve superconductivity at much lower pressure in comparison with lithium phosphide. |
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G00.00276: Unbiased Monte Carlo Cluster Updates with Autoregressive Neural Networks Dian Wu Efficient sampling of complicated high-dimensional probability distributions is a central task in computational science. Machine learning methods like autoregressive neural networks, used with Markov chain Monte Carlo (MCMC) sampling, provide good approximations to such distributions, but suffer from either intrinsic bias or high variance. In this paper, we propose a novel way to make this approximation unbiased and with low variance. Our method uses physical symmetries and variable-size cluster updates which utilize the structure of autoregressive factorization, and we discuss the theoretical motivation of how they help implement the ergodicity of MCMC. We test our method on classical spin systems including the Ising model and a frustrated plaquette model with a first-order phase transition, showing it significantly reduces the autocorrelation time over previous unbiased sampling methods, and alleviates the issue of metastability for MCMC methods in first-order phase transitions. |
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G00.00277: Topological evolution underlying macroscopic stress relaxation in viscous liquids Chi-Huan Tung, Shou-Yi Chang, Yangyang Wang, Jan-Michael Y Carrillo, Bobby G Sumpter, Takeshi Egami, Yuya Shinohara, Yongqiang Cheng, Changwoo Do, Wei-Ren Chen Correlations between stress relaxation and topological evolution in viscous liquids are studied by means of molecular dynamics simulation. The local topology is determined through a gyration tensor and the orientation of its principal axis is used to monitor the fluctuation of particle connectivity. In this context, decorrelation of orientational ordering is found to be highly heterogeneous in space in a peculiar manner: At the shear stress relaxation time, the orientationally corelated and decorrelated regions partition the simulated system into two mutually connected, interpenetrating interspersions without self-intersection. We found the orientationally decorrelated subdomain in this sponge-like bicontinuous structure renders a channel which promotes the stress relaxation and therefore underlies viscoelasticity of amorphous materials. |
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G00.00278: Role of anisotropic exchange and site disorder in YBaCuFeO5: A Monte-Carlo study Mukesh K Sharma, Tulika Maitra Motivated by the recent debate on the existence of type-II multiferroicity in YBaCuFeO5(YBCFO) driven by incommensurate spiral magnetic ordering up to temperatures higher than room temperature, we have investigated the magnetic phase transition of YBCFO using Monte-Carlo simulation on classical Heisenberg XXZ model. We have studied the role of anisotropic exchange and Fe-Cu site disorder on the commensurate-incommensurate magnetic phase transition. Using various exchange interactions obtained from density functional theory, our Monte-Carlo simulations show that both anisotropic exchange and site disorder play significant roles in giving rise to spiral magnetic ordering at lower temperatures. |
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G00.00279: pgm: A Python package for anharmonic free energy calculations Jingyi Zhuang, Zhen Zhang, Qi Zhang, Renata M Wentzcovitch The quasiharmonic approximation (QHA) is a powerful method for computing the free energy and thermodynamic properties of materials at high pressures (P) and temperatures (T). However, anharmonicity, electronic excitations in metals, or both, introduce an intrinsic T-dependence on the phonon frequencies, making the QHA inadequate. Here we present a Python package, pgm, for free energy and thermodynamic property calculations. It is based on the concept of phonon quasiparticles and the phonon gas model (PGM). The free energy is obtained by integrating the entropy, which can be readily calculated for a system of phonon quasiparticles. This method is useful for computing the free energy in anharmonic insulators and harmonic or anharmonic metals. The current implementation offers properties in a continuum P,T range. The necessary inputs are ab-initio Tel-dependent static energies and T-dependent phonon quasiparticle frequencies, both at several discrete volumes, and the user-specified P- and T- range. To accelerate the numerical computation, we employ techniques like just-in-time (JIT) compiling and parallel computing. We demonstrate successful applications of pgm to hcp-iron (ε-Fe) at extreme conditions [1] and cubic CaSiO3-perovskite [2], a strongly anharmonic system. |
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G00.00280: Ab Initio Study of Complex Systems: Superconductivity in Amorphous CuxZr1-x. Electronic and Vibrational Properties. Salvador Villarreal, Renela M Valladares, Alexander Valladares, Isaías Rodríguez, David Hinojosa-Romero, Ariel A Valladares Many materials that include copper in their composition have been found to be superconducting. However, pure copper does not superconduct at temperatures so far studied. Amorphous superconducting alloys are of particular interest because of the interplay between the disorder-driven Anderson’s localized states and the macroscopically coherent superconducting state, in principle two competing electronic arrangements. It is therefore remarkable that amorphous alloys in the CuxZr1-x system have been found to be superconducting while their crystalline counterparts have not. Here we revisit superconductivity in the amorphous CuxZr1-x system at various concentrations using the BCS approach as a simple mechanism to understand their properties. Ab initio DFT molecular dynamics was used, together with the undermelt-quench approach developed within our group, to generate amorphous supercells with 216 atoms. The electronic and vibrational densities of states for these structures were obtained and were used to estimate the transition temperatures of some of the specimens studied. Results will be presented and analysed and conclusions drawn. |
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G00.00281: Spectral denoising for accelerated analysis of correlated ionic transport Nicola Molinari, Yu Xie, Ian Leifer, Aris Marcolongo, Mordechai Kornbluth, Boris Kozinsky We propose a novel method for analyzing and calculating mass/charge transport in media with non-negligible correlations from atomistic simulations [1]. While widely adopted thanks to its rapid convergence, the dilute uncorrelated approximation is inaccurate. On the other hand, the exact Green-Kubo method is prohibitively expensive for complex and large systems. The approach we present automatically calculates and utilizes the collective diffusion eigenmodes of the displacement correlation matrix to denoise the calculation of the transport properties. It can also be adopted to discover collective diffusion modes in an unsupervised fashion. The approach is universally applicable and provably superior to previously available methods, exhibiting speed ups of several orders of magnitude. |
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G00.00282: Machine-Learning combined with Genetic Algorithms for Alloy Clusters Discovery Johnathan von der Heyde DFT-trained neural networks (NN) have been shown to dramatically reduce computational costs for predicting atomic properties without accuracy loss. However, this typically demands the DFT training data to be computed ahead of time. While this approach works for specialized applications, it is still infeasible for exploration into the vast configuration spaces inherent in nanoclusters of various sizes and compositions. To remedy this, we include in our methodology a Genetic Algorithm (GA) for generating structures or adsorption sites unbiasedly across configuration spaces. A self-optimizing program is developed to gradually train a single NN 'on-the-fly' for configurations generated by the GA and validated with DFT. When the self-optimization is complete, a NN capable of predicting nanocluster energies and forces for any reasonable structure or adsorption site within the configuration space is produced. This allows us to unbiasedly explore these spaces at the DFT level with relatively low computational demand automatically. The self-optimizer is tailored to explore the configuration or adsorption sites of a given nanocluster size, and composition, and can easily be extended to surface slab adsorption site exploration as well. We will present results for 13-atoms AuPd clusters. |
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G00.00283: Structure and Dynamics of Supercritical Water Determined With Neural Network Quantum Molecular Dynamics Nitish Baradwaj, Aravind Krishnamoorthy, Ken-ichi Nomura, Kohei Shimamura, Rajiv K Kalia, Aiichiro Nakano, Priya Vashishta Water subjected to very high temperatures and pressures inside the Earth's Mantle exists in its supercritical form. It exhibits extraordinary properties such as having a low dielectric constant, which stems from the breakdown of hydrogen bonds at supercritical temperatures. This makes supercritical water a non-polar solvent and the basis for many innovative technologies. In this study we investigate the hydrogen bonds, its lifetime in supercritical water and its role in controlling the dielectric constant using Neural Network Quantum Molecular Dynamics (NNQMD). Two deep neural networks are constructed. The first to produce long trajectories using neural network quantum molecular dynamics (NNQMD) and the second to predict the locations of maximally localized Wannier functions (MLWF) and calculate the dielectric constant from NNQMD trajectories. |
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G00.00284: Langev(in)ference Dynamics for Heterogeneous Tissue Imaging in MRE Damian R Sowinski, Elijah E Van Houten, Keith D Paulsen We propose a novel second-order dynamical Bayesian inference method for tissue imaging using magnetic resonance elastography data. |
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G00.00285: Buoyancy and drag in Rayleigh-Taylor and Richtmyer-Meshkov linear, nonlinear and mixing dynamics Snezhana I Abarzhi, Desmond Hill, Kurt Williams, Cameron Wright Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instabilities and RT/RM interfacial mixing are omnipresent in nature and technology and are a source of paradigm shifts in mathematics. This work reports the first derivation of the buoyancy and drag for RT/RM dynamics with variable acceleration. We directly link the governing equations – the conservation laws and the boundary value and initial value problems – to the symmetry-based momentum model, precisely derive the model parameters – the buoyancy and drag – for RT/RM bubbles and spikes in the linear, nonlinear and mixing regimes, and exactly integrate the model equations. The analysis provides extensive benchmarks for future research. |
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G00.00286: Learning Transferable Neural Network Surrogates for Kohn-Sham Density Functional Theory Kyle Lennon, Sivasankaran Rajamanickam Density functional theory (DFT) is widely used to compute properties of many-body systems from first principles, and often serves as an intermediate step to computing forces on atomic nuclei in molecular dynamics (MD) simulations. However, DFT calculations are computationally intensive, and their cost becomes prohibitive for large systems or long MD simulations. Recently, efforts to circumvent expensive DFT calculations by learning system-specific neural network surrogates have been met with some success. Still, these surrogates require the generation of ab initio training data and long training times for every individual system and thermodynamic state. Here, we investigate whether this approach can be made more widely applicable by leveraging modern machine learning techniques such as transfer learning to produce surrogate models that transfer between systems and states, or adapt quickly without the need for extensive training. We develop first-of-their-kind models that are able to compute the local density of states directly from local descriptors of atomic positions across multiple temperatures, and demonstrate that the high-dimensional input descriptors may be compressed to a representation with lower information capacity without sacrificing prediction accuracy. |
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G00.00287: Richtmyer-Meshkov flows induced by strong shocks Cameron Wright, Jeremy Wright Richtmyer-Meshkov Instability is an instability that develops at the interface between fluids of distinct acoustic impedance when impacted by a shock wave. We study the effect of the adiabatic index of the fluids on the dynamics of strong-shock driven flows, particularly the amount of shock energy available for interfacial mixing. We employ Smooth Particle Hydrodynamics to ensure accurate shock capturing and interface tracking. A range of adiabatic indexes is considered, approaching limits which, to the best of the author's knowledge, have never been considered before. The simulation results are compared wherever possible with rigorous theories, achieving good quantitative and qualitative agreement. We find that the more challenging cases for simulations arise where the adiabatic indexes are further apart, and that the initial growth rate is a non-monotone function of the initial perturbation amplitude, which holds across all adiabatic indexes of the fluids considered. We also find that the velocity of the transmitted shock depends on the initial perturbation amplitude, and this dependence is non-monotone. The empiric models are elaborated to decribe our results achieveing excellent agreement with data. The applications of these findings on experiment design are discussed. |
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G00.00288: The importance of a quadratic dispersion in acoustic flexural phonons for the thermal transport of 2D materials Armin Taheri, Simone Pisana, Chandra Veer Singh Solutions of the Peierls-Boltzmann transport equation using inputs from density functional theory calculations have been successful in predicting the thermal conductivity in a wide range of materials. In the case of two-dimensional (2D) materials, the accuracy of this method can depend highly on the shape of the dispersion curve for flexural phonon (ZA). As a universal feature, very recent theoretical studies have shown that the ZA branch of 2D materials is quadratic. However, many prior thermal conductivity studies and conclusions are based on a ZA branch with linear components. In this work, we systematically study the impact of the long-wavelength dispersion of the ZA branch in graphene, silicene, and $\alpha$-nitrophosphorene to highlight its role in thermal conductivity predictions. Our results show that the predicted $\kappa$ value, its convergence, and anisotropy, as well as phonon lifetimes and mean free path can change substantially even with small linear to pure quadratic corrections to the shape of the long-wavelength ZA branch. Also, having a pure quadratic ZA dispersion can improve the convergence speed, and reduce uncertainty in this computational framework when different exchange-correlation functionals are used in the density functional theory calculations. Our findings may provide a helpful guideline for more accurate and efficient thermal conductivity estimation in mono- and few-layer 2D materials. |
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G00.00289: Fluctuations spectra in Rayleigh-Taylor interfacial mixing Kurt Williams Rayleigh-Taylor (RT) interfacial mixing plays a critical role in a broad range of processes in nature and technology, and understanding fluctuations spectra of self-similar RT mixing is in high demand. Guided by group theory, analyzing invariant properties of the fluctuations, we investigates the time series of raw data from hot-wire anemometry measurements in experiment by Akula et al. [J. Fluid Mech. 816, 619 (2017)]. We find that the power density spectrum can be modeled as a compound function represented by a product of a power law and an exponential. We apply rigorous physics-based statistical methods to estimate the model parameters, including their mean values and relative errors, to study the dependence of the parameters on the fitting interval, and to evaluate goodness-of-fit. We find that the values of the power law exponent and the exponential decay rate are distinct for fluctuations of each of the velocity components as well as of the density and the mass flux. Particularly, the power-law exponents are estimated as -2 and -1 for fluctuations of the velocity components in directions of the acceleration and the co-flowing streams, whereas they are close to -1 and-3/2 for fluctuations of the density and mass flux, achieving good agreement with group theory. |
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G00.00290: Simulations in charge of their own electrostatics: Augmenting a nucleic acid force field with fluctuating charge densities Christopher A Myers, Alan A Chen Given the recent and ongoing increases in computational resources for simulating large biomolecules, and the variety of complex environments researchers wish to study these systems in, it is worth examining how conventional molecular mechanics algorithms could be improved upon by including interactions that are historically neglected. Specifically, force fields that are based on fixed charges only implicitly incorporate polarization energies through their parameterization and other included forces, and struggle to quantitatively describe the extent to which other ab initio interactions are at play. As such, we will present our approach to augmenting AMBER based force fields for nucleic acids with the ability to explicitly account for electron polarization. Within our model, the traditionally fixed charges are replaced with fluctuating charge densities that can adjust to a molecule's geometry and environment. With the aid of density functional theory calculations of small oligonucleotides, we examine how the balance of frozen electrostatics, polarization, and charge transfer can be used to improve the description of hydrogen bonding in nucleic acid simulations. |
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G00.00291: Amazing Exponential Relationship at R2=1 for Gravity, Boltzmann, Planck Constants at ^1, ^2, ^3 with Scaling Factor *(3/2)*23 and QED Anamolous Moment Loops Arno Vigen Exploring the impossibly close R2=1 correlation of Gravity, Boltzmann, and Planck Constants when adjusted for (3/2)*23. Current theory says that all three are fully independent SI-Units. However likelihood of near perfect correlation needs further examination.
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G00.00292: LASER SCIENCE
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G00.00293: The magneto-optics of semiconducting quantum wires for designing optical amplifiers Manvir S Kushwaha, Bahram Djafari-Rouhani Quantum wires occupy a unique status among the semiconducting nanostructures with reduced dimensionality -- no other system seems to have engaged researchers with as many appealing features to pursue. This letter aims at a core issue related with the magnetoplasmon excitations in the quantum wires characterized by the confining harmonic potential and subjected to a longitudinal electric field and a perpendicular magnetic field in the symmetric gauge. Despite the substantive complexity, we obtain the exact analytical expressions for the eigenfunction and eigenenergy, using the scheme of ladder operators, which fundamentally characterize the quantal system. Crucial to this inquiry is an intersubband collective excitation that evolves into a magnetoroton -- above a threshold value of magnetic field -- which observes a negative group velocity between maxon and roton. The evidence of negative group velocity implies anomalous dispersion in a gain medium with the population inversion that forms the basis for the lasing action of lasers. Thus, the technological pathway that unfolds is the route to devices exploiting the magnetoroton features for designing the novel optical amplifiers and hence paving the way to a new generation of lasers. |
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G00.00294: Continuing Towards Real-time Programmable Photoinjector Shaping for Electron and X-ray Sources Jack E Hirschman, Randy A Lemons, Federico Belli, Peter Kroetz, Ryan Coffee, Sergio Carbajo The next generation of augmented brightness X-ray free electron lasers (XFEL), such as LCLS-II, promises to address current challenges associated with systems with low X-ray cross-sections. A key component of XFELs is the photoinjector [1], which produces the electron beams (e-beams) whose phase-space determines the performance of the XFEL [2]. Fast and active beam manipulation is required to capitalize on this new generation of XFELs. We examine e-beam shaping using a machine learning (ML) implementation of real-time photoinjector laser manipulation. Our presentation will focus on the photoinjector laser software model, the associated ML models, and the optical setup. We anticipate this approach to not only enable active experimental control of X-ray pulse characteristics but could also increase the operational capacity of future e-beam sources and accelerator facilities. |
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G00.00295: Design of tabletop high harmonic beamlines for dynamic magnetic spectro-microscopies Anna Grafov, Sinead A Ryan, Peter C Johnsen, Iona Binnie, Chen-Ting Liao, Guan Gui, Nathan Brooks, Margaret M Murnane, Henry C Kapteyn High harmonic sources in the extreme ultraviolet (EUV) region of the spectrum are being adopted for applications in magnetic spectro-microscopies, since they enable element-specific probes of the fastest spin dynamics in alloys, multilayers and topologically protected materials. Simultaneously achieving high EUV flux, stability and polarization and phase structure requires careful design. We will review two beam line designs that are optimized for resonant magnetic scattering and EUV magneto-optical spectroscopies, as well as their applications in probing multilayer, alloys, metalattice and skyrmion samples. We will also review capabilities of high harmonic generation to produce structured EUV beams. |
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G00.00296: ATOMIC, MOLECULAR, AND OPTICAL PHYSICS
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G00.00297: Shannon information entropy of atomic states in a strongly coupled plasma Young-Dae Jung, Myoung-Jae Lee The influence of shielding on the Shannon information entropy for atomic states in a strong coupled plasma is investigated using the perturbation method and the Ritz variational method. The analytic expressions for the Shannon information entropies of the ground (1s) and the first excited states (2p) are derived as functions of the ion sphere radius including the radial and angular parts. It is shown that the entropy change in the atomic state is found to be more significant in the excite state than in the ground state. It is also found that the influence of the localization on the entropy change is more significant for an ion with higher charge number. The variation of the 1s and 2p Shannon information entropies are discussed. |
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G00.00298: Something More rather than something Different Knute E Thorsgard Lip service is paid to seeking something different in order to unify the various working theories. It has been said "Something big will have to give". It will probably actually be a combination of big things. But, when things seem to be working well, change seems ridiculous. Through agreement, by convention, something more can point back to what should change. |
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G00.00299: Excitations of a strongly-correlated photon fluid stabilized via incoherent drive and dissipation Fabio Caleffi, Massimo Capone, Iacopo Carusotto We explore theoretically the spectral properties of the non-equilibrium photonic phases hosted by a lattice of coupled cavities in presence of non-Markovian driving and dissipation, as well as strong photon interactions [1, 2]. In particular, we analyse how the low-energy spectrum of the stationary state evolves across the Mott/superfluid-like transition exhibited by the model and analyse the non-trivial interplay between the diffusive Goldstone mode emerging in the symmetry-broken phase and the physical role of the remaining dissipative modes. Our study goes in the direction of investigating the potential of driven-dissipative photonic fluids to quantum simulate a wide range of many-body problems. |
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G00.00300: Reentrant localization transition in a one-dimensional quasiperiodic chain Shilpi Roy We study the effects of an onsite quasiperiodic potential on the localization properties of a dimerized chain that may mimic the structure of a polymerized acetylene molecule. An important ramification of the quasiperiodic potential is the presence of the mobility edge that segregates the energy spectrum between the localized and the delocalized phases. Interestingly, albeit stringent, for a specific assignment of the quasiperiodic potential where it alternates sign from one site to another (we refer it as a staggered scenario) and for a particular range of values for the dimerization strength, the system first undergoes a delocalization to localization transition corresponding to a certain value of the potential, which eventually gets into the delocalized phase again with further increase in the strength of the quasiperiodic potential. Thus, quite intriguingly, the system undergoes a re-entrant localization transition, a phenomenon that is unusual in electronic systems. A further increase in the potential strength will eventually push the system into a completely localized phase. We believe that the re-entrant localization phenomena, which form the central focus of our work, are very specific to an interplay of the quasiperiodic potential and a dimerized hopping. |
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G00.00301: Quantum Interference in Radical and Neutral Single-Molecule Junctions Juan Hurtado, Laura Rincón-García, Nicolás Atraït Single organic molecules facilitate bottom-up functionalization and atomically precise engineering of their properties that are not accessible in other materials. Despite over a decade of development, the value for S in single organic molecules at room temperature is usually below ±20 μV/. This is because the frontier orbitals of most molecules are far from the Fermi energy (EF) of the electrodes. |
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G00.00302: Integration of single photons from a trapped ion in a programmable photonic circuit Uday Saha, James Siverns, John M Hannegan, Mihika Prabhu, Eric A Bersin, Saumil Bandyopadhyay, Jacques Carolan, Qudsia Quraishi, Dirk Englund, Edo Waks Trapped ions are one of the most promising quantum memories for scalable quantum networks and quantum computing. They can emit single photons entangled with ion’s spin states making them a promising choice to implement quantum networks. So far, bulks optics are being used to establish optical interconnects between trapped ions which lacks scalability. To establish long-distance quantum networks in a scalable way, we need to route single photons from trapped ions into integrated photonic circuits and switch them on-demand into different photonic channels. However, every trapped ion has strong dipole transitions in ultra-violet and visible wavelength and emits single photons in that regime making them incompatible for present-day photonic foundry. In this work, we route the single photons from a trapped barium ion in the silicon-nitride integrated photonic circuit. For this integration, we first generate C-band telecom single photons from barium ions. Using the thermo-optic property of silicon-nitride, we then switch the single photons in different channels of a Mach-Zehnder interferometer controlling the current of the phase-shifter. These results will enable a new generation of compact and reconfigurable integrated photonic devices that can serve as efficient quantum interconnects for quantum computers and sensors. |
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G00.00303: Phonon-polariton dynamics in sodium silicate glasses investigated by terahertz time-domain spectroscopy Yu Duan, Yasuhiro Fujii, Hiroyuki Hijiya, Suguru Kitani, Akitoshi Koreeda, Yohei Yamamoto, Tatsuya Mori We investigated phonon-polariton dynamics in the sodium silicate glass system using terahertz time-domain spectroscopy. Then, using a novel damped harmonic oscillator model in which an attenuation term with wavenumber dependence was introduced, the dielectric response in the terahertz region, especially the absorption behavior owing to the boson peak, was investigated. |
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G00.00304: Criticality and phase classification for quadratic open quantum many-body systems Yikang Zhang, Thomas Barthel We study the steady states of translation-invariant open many-body systems governed by Lindblad master equations, where the Hamiltonian is quadratic in the ladder operators, and the Lindblad operators are either linear or quadratic and Hermitian. We find that one-dimensional systems with short-range interactions cannot be critical, i.e., steady-state correlations necessarily decay exponentially. For the quasi-free case without quadratic Lindblad operators, we show that fermionic systems with short-range interactions are non-critical for any number of spatial dimensions and provide upper bounds on the correlation lengths. Lastly, we address the question of phase transitions in quadratic fermionic systems and find that, without symmetry constraints beyond particle-hole symmetries, all gapped Liouvillians belong to the same phase. |
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G00.00305: Double-trace deformation in Keldysh field theory XIANGYI MENG The Keldysh formalism is capable of describing driven-dissipative dynamics of open quantum systems as nonunitary effective field theories that are not necessarily thermodynamical, thus often exhibiting new physics. Here, given a general Keldysh action, we find that the perturbative Lindblad term responsible for driven-dissipative dynamics introduced therein has the natural form of a double-trace deformation O2, which, in the large N limit, possibly leads to a new nonthermal conformal fixed point. This fixed point is IR when Δd/2, given d the dimensions of spacetime and Δ the scaling dimension of O. Such a UV fixed point being not forbidden by Weinbergian constraints may suggest its existence and even completion of itself, in contrast to the common sense that dissipation effects are always IR relevant. This observation implies that driven-dissipative dynamics is much richer than thermodynamics, differing in not only its noncompliance with thermodynamic symmetry (e.g., the fluctuation-dissipation relation) but its UV/IR relevance as well. In particular, our results pave a new path that brings the Keldysh formalism to the gravitational side under the pronounced holographic AdS/CFT correspondence. This may lead to a refreshing perspective of how a Keldysh CFT living on the boundary corresponds to the bulk theory. |
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G00.00306: A closed-form expression for spin-exchange rate correctly predicts experimental Xe polarization values under SEOP Michele Kelley, Rosa T Branca Since its advent, the original spin-exchange optical pumping (SEOP) theory developed by Happer et al. has been adapted to predict experimental Xe polarization values. However, these adaptations have been poor predictors of Xe polarization values, leading to a search for additional depolarization mechanisms. Here, we revisit the general theory of spin-exchange optical pumping to understand the origin of such discrepancy and perform experimental measurements to validate our theoretical findings. The original theory of SEOP was used to derive a general closed-form expression for the spin-exchange between any alkali metal and noble gas atom. We then used this expression, which is different from that used in more recent theoretical models, along with previously measured constants to estimate the Rb-Xe spin-exchange cross section under different experimental conditions. We found good agreement between our theoretical cross section and the experimental cross section measured using a combination of optical absorption spectroscopy, field cycling, and NMR spectroscopy. By using the correct expression for the spin-exchange cross section, theoretical Xe polarization values that closely match those obtained experimentally are predicted for our system and for those found in the literature. |
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G00.00307: Resonance-forbidden second-harmonic generation in nonlinear photonic crystals Jicheng Jin, Jian Lu, Bo Zhen Second-harmonic generation is widely used in optoelectronics including both the classical and quantum regimes. In planar nanophotonics structures, people would expect that second harmonic waves along the vertical direction can always be generated if appropriate quadratic nonlinearities and pumping beams are present since the phase-matching condition is automatically satisfied due to the ultra-thin thickness. |
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G00.00308: Terahertz Dynamics of LiCl Aqueous Solution Measured by Terahertz Time-Domain Spectroscopy Soo Han Oh, Keito watanabe, Suguru Kitani, Shin Nakagawa, Jea-hyeon Ko, Yohei Yamamoto, Tatsuya Mori The boson peak (BP) is universal excitation of the terahertz (THz) band in glassy materials, and it appears in the display of g(ν)/ ν2 obtained by dividing the vibrational density of states (VDOS) g(ν) by the square of the frequency ν. Also, the absorption coefficient α(ν) is associated with g(ν) through the infrared light vibration coupling constant CIR(ν). Therefore, BP in infrared spectroscopy appears in the display of α(ν)/ ν2. |
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G00.00309: Controlling and probing superfluid transport through an atomic quantum point contact Philipp Fabritius, Jeffrey Mohan, Anne-Maria Visuri, Samuel Häusler, Mohsen Talebi, Simon Wili, Thierry Giamarchi, Meng-Zi Huang, Tilman Esslinger We report on the control of the superfluid transport of a strongly interacting Fermi gas flowing through a quasi-two-dimensional contact and through a quantum point contact (QPC). Using shaped light we can create almost arbitrary potential landscapes for the atoms as well as effective magnetic fields and dissipation channels to alter and probe their transport. Taking multiple absorption pictures also allows us to directly measure particle, heat and spin currents. When introducing strong interactions in fermionic Lithium-6 we find that the thermoelectric effects induced by a temperature difference across a two-dimensional channel can be tuned using an attractive as well as a repulsive gate to change the relative strength of channel and reservoir contributions. Thus changing the particle transport going from hot to cold to going from cold to hot. We find that the strong interactions reduce the Seebeck coefficient of the channel which we attribute to hydrodynamic effects and resulting superfluid correlations inside the channel. We also introduce a spin selective dissipation via an optical tweezer inside a QPC. The dissipation has a strong effect on the transport of the superfluid changing it from nonlinear to linear. Finally we can use the same tweezer at a different atomic detuning to introduce an effective magnetic field acting as a spin filter. These results open the way to studying the coupling of particle, heat and spin transport in an atomic quantum point contact. |
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G00.00310: Symmetry-protected Bose-Einstein condensation of interacting hardcore Bosons Reja H Wilke, Thomas Köhler, Felix Alexander A Palm, Sebastian Paeckel The past two decades have seen the raise of practical applications of exotic quantum many-body phases. Proving their potential to overcome classical solution strategies to relevant problem settings, one of the main obstacles nowadays is to stabilize these highly fragile quantum states against perturbations. Here, we demonstrate the stabilization of a one-dimensional quantum many-body phase, characterized by a certain wave vector k, from a k-modulated coupling to a center site via the protection of an emergent Z2 symmetry. We illustrate this mechanism by constructing the solution to the full quantum many-body problem of hardcore bosons on a wheel geometry, which is known to form a BEC. The crucial step is to map the wheel to a projected ladder geometry, where the protection of the Z2 symmetry is manifested by the choice of a particular k mode spanning the projected subspace on one leg of the ladder. The robustness of the BEC is shown numerically by adding local interactions to the wheel Hamiltonian and we identify the energy scale that controls the protection of the emergent Z2 symmetry. Since the protection is generated by gapping out an independently selectable k mode from the single-particle spectrum, our findings can be generalized, for instance to create a k≠0 BEC. |
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G00.00311: Towards Measurements of the Optical Coherence of the SnV in Diamond Ryan A Parker Recently the tin-vacancy (SnV) centre in diamond was demonstrated as a competitive spin-qubit with a spin-coherence time of 0.33ms and MHz Rabi rates [1]. This is particularly promising as these demonstrations were achieved in nanostructured diamonds, without any surface passivation engineering, in standard closed-cycle He cryostats; overcoming the charge instability and phonon-limited dephasing at these temperatures inherent to the other major defect centres in diamond: the nitrogen and silicon vacancies respectively. |
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G00.00312: Topological properties of pseudo spin-1/2 bosonic Bogoliubov-de Gennes systems with conserved magnetization in a honeycomb lattice Hong Y Ling, Ben Kain We carry out, within the 38-fold way for non-Hermitian systems, a quantitative study of the topological properties of a pseudo spin-1/2 bosonic Bogoliubov-de Gennes (BdG) system with conserved magnetization in a honeycomb lattice, which can be made to act as a topological amplifier with stable bulk bands but unstable edge modes. We find it either as two copies of symmetry class AIII + η- or two copies of symmetry class A + η depending on whether the (total) system is time-reversal-symmetric, where η is the matrix representing pseudo-Hermiticity and η- indicates that pseudo-Hermiticity anticommutes chiral symmetry. We prove that a stable bulk is characterized by the Chern number for the Haldane model, independent of pairing interactions. We construct a simple analytical edge mode description for the Haldane model in semi-infinite planes, which is expected to be useful for any models built upon copies of the Haldane model. We adapt the theorem in our recent work [Phys. Rev. A 104, 013305 (2021)] to pseudo-Hermitian (but non-BdG) Hamiltonians and apply it to highlight that the vanishing of an unconventional commutator between number-conserving and number-nonconserving parts of the Hamiltonian indicates whether a system can be made to act as a topological amplifier. |
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G00.00313: Superfluidity in the 1D Bose-Hubbard Model Thomas G Kiely Due to strong quantum fluctuations, superfluidity in one dimension is special: The superfluid state is critical, with power-law-decaying correlation functions and no Bose-Einstein condensation. In a lattice, where one can find an interaction-driven Mott insulator, the physics is even more interesting. We compute the ground state superfluid density of the 1D Bose-Hubbard model using an infinite variational matrix product state technique. We explore the scaling relationships involving the correlation functions and entanglement entropy, explicitly demonstrating the connection between superfluid density and Luttinger parameters. We compare two different algorithms for optimizing the infinite matrix product state and develop a physical explanation why one of them (VUMPS) is more efficient than the other (iDMRG). |
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G00.00314: Effect of turbulence and random scattering on complex optical beam interference Nitish Chandra, Jorge V Jose, Natalia M Litchinitser The presence of turbulence in a medium produces inhomogeneity, introducing perturbation in the amplitude and phase of waves propagating through the medium. The coherence of optical waves is reduced by the incoherent scattering from the inhomogeneity and randomness produced by the turbulence. Recently, interference of the Laguerre-Gauss beam has been used to create optical knots. Therefore, it is essential to investigate the effect of turbulence and structure of the beam on the interference to understand the stability of optical knots in the presence of perturbation and random turbulent fluctuations in the medium. As a first step, we investigate the effect of scattering and turbulence on Young's double-slit interference. Second, we use the Kolmogorov model for turbulence to quantify the changes in the amplitude and phase characteristics of a Laguerre-Gauss (LG) beam carrying orbital angular momentum. Finally, we apply the results of these studies to investigate the stability of optical knots in scattering and turbulent media. |
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G00.00315: Stoichiometric Rare-Earth Materials as a Platform for Quantum Memory and Information Processing Donny R Pearson Rare-earth atoms in crystalline solids at cryogenic temperatures are a promising platform for quantum memory and quantum information processing due to their exceptional optical and spin coherence properties, lack of motional dephasing, and potential for use in integrated photonics. A major drawback of these systems is the inhomogeneous broadening of the optical transition, which prevents utilizing the longest-lived spin coherence properties available with rare-earth atoms. This inhomogeneity is due to site-to-site variations of the local electrostatic environment, which shifts the electronic states. The dominant source of this variation is point defects in the crystal, a major contribution coming from the random dopants themselves. Rare-earth materials in which the atoms are stoichiometric in the crystal structure, rather than doped, have demonstrated substantially less broadening due to the lack of this source of disorder. A major challenge is identifying and synthesizing suitable samples with sufficiently large inter-atom spacing to remain in the weakly interacting regime. Here we present initial studies of europium-based stoichiometric materials as a platform for quantum memory devices. |
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G00.00316: Robust Atom Optics for Large Momentum Transfer Atom Interferometry with Strontium-88 Garrett Louie, Tejas Deshpande, Zilin Chen, Tim Kovachy Large momentum transfer (LMT) atom interferometry requires atom optics with precise population and phase control, which are limited by factors such as cloud expansion, stray magnetic fields, and laser fluctuations. To allow greater momentum transfer under a broad range of experimental conditions, we use the quantum optimal control Python package developed by Q-CTRL to engineer amplitude and phase-modulated pulses for the 461 nm and 689 nm transitions of Sr-88. We have simulated pulses that maintain well over 99% population transfer and phase stability across several static and time-dependent noise channels, which couple as power, frequency, and polarization errors. We also report on progress towards implementation of the 689 nm pulses for point-source interferometry (PSI) with a hot (~1 mK) cloud [1][2]. The 6W output from a pair of Ti:sapphire lasers is shaped into arbitrary pulses via AOMs driven by an IQ modulated rf signal. Such pulses could also be used as wavefront diagnostics during operation of colder interferometers such as MAGIS-100 [3]. |
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G00.00317: Electronic, and Optical Properties of Small Clusters of Methylammonium Tin Bromide (CH3NH3SnBr3) Chiranjivi Lamsal, Jonathan Sinopoli In this work, we studied the ground-state optimized geometry of CH3NH3SnBr3 monomer, dimer, trimer, and tetramer using ab initio quantum mechanical calculations. HOMO-LUMO (∆EL-H) gap was studied and found to be redshifted with increasing size of (CH3NH3SnBr3)n from n =1 to 4. Optical gap and Maximum Absorption wavelength, λmax, were calculated. The values of (∆EL-H) and Optical gap for CH3NH3SnBr3 clusters were approximated to be 3.622 and 3.091 electron volts respectively. Major electronic transitions observed from vertical excitation calculations show that the transitions occur from ground state to first excited state due to the excitation of one electron mainly from HOMO to LUMO. The (∆EL-H) value of (CH3NH3SnBr3)n clusters approximated using density of states is 2.19eV, which is close to the experimentally reported optical gap of 2.15eV. Contribution of individual atomic units to frontier orbitals was studied. |
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G00.00318: "Vanadyl phthalocyanine: A computational study of a molecular scaffold for long-lived molecular spin states on surfaces" Maria C Urdaniz, Maria C Urdaniz, Young Namgoong, Andreas J Heinrich, Christoph Wolf Achieving quantum coherent control of spins on surfaces at the atomic scale is the goal for quantum coherent nanoscience. A good surface spin system requires two components: a localized spin and a buffer layer to isolate that spin from the metallic substrate. |
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G00.00319: Tomography of phonons in one-dimensional gases Marek Gluza, Thomas Schweigler, Bernhard Rauer, Christian Krumnow, Joerg Schmiedmayer, Jens Eisert Quantum simulators allow to explore static and dynamical properties of otherwise intractable quantum many-body systems. In many instances, however, it is the read-out that limits such quantum simulations. In this work, we introduce a new paradigm of experimental read-out exploiting coherent non-interacting dynamics in order to extract otherwise inaccessible observables. Specifically, we present a novel tomographic recovery method allowing to indirectly measure second moments of relative density fluctuations in one-dimensional superfluids which until now eluded direct measurements. We achieve this by relating second moments of relative phase fluctuations which are measured at different evolution times through known dynamical equations arising from unitary non-interacting multi-mode dynamics. Applying methods from signal processing we reconstruct the full matrix of second moments, including the relative density fluctuations. We employ the method to investigate equilibrium states, the dynamics of phonon occupation numbers and even to predict recurrences. The method opens a new window for quantum simulations with one-dimensional superfluids, enabling a deeper analysis of their equilibration and thermalization dynamics. |
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G00.00320: Ubiquitous quantum scarring does not prevent ergodicity Miguel A Bastarrachea-Magnani, Saúl Pilatowsky-Cameo, David Villaseñor, Sergio A Lerma-Hernández, Lea F Santos, Jorge G Hirsch We discuss the connection between quantum scarring, localization in phase space, and ergodicity in the Dicke model. This model is used to describe interacting light-matter systems and has been realized with different AMO platforms. We show that all the eigenstates of the Dicke model in the chaotic region are scarred, although with different degrees of scarring and different levels of phase-space localization. We also explain that ergodicity is an ensemble property, achievable only through temporal averages. Therefore, scarring, localization and lack of ergodicity are not synonyms, although connections exist. |
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G00.00321: Goldstone mode in a quantum fluid of polaritons. Ferdinand Claude, Michiel Wouters, Iacopo Carusotto, Elisabeth Giacobino, Quentin Glorieux, Alberto Bramati Goldstone modes appear as a consequence of a spontaneous breaking of a continuous symmetry. In driven-dissipative systems, they emerge in the long-wavelength limit of elementary excitations spectra in the form of overdamped modes whose linewidths tends to zero. We study Goldstone modes physics in exciton-polariton quantum fluids which are a coherent superposition of cavity photons with quantum well excitons in planar semiconductor microcavities. In the optical parametric oscillation (OPO) regime of these systems, the crossing of the oscillation threshold, with the generation of signal and idler modes, constitutes a spontaneous symmetry breaking transition. Using a new experimental method based on Bragg spectroscopy with a high spectral resolution, we present here the appearance of the Goldstone mode in the spectrum of elementary excitations of the polariton signal mode. Moreover, by fixing the phase of the signal mode by injecting an additional laser which breaks the initial U(1) symmetry, we observe the suppression of the Goldstone mode. |
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G00.00322: The interplay of quasi-bound states of black holes and the Hawking effect in a dissipative quantum fluid analogue black hole Ferdinand Claude, Malo Joly, Luca Giacomelli, Iacopo Carusotto, Quentin Glorieux, Elisabeth Giacobino, Alberto Bramati, Maxime J Jacquet Analogue gravity enables the laboratory study of the Hawking effect, the emission of correlated waves on either side of a sonic horizon. |
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G00.00323: AlCl Precursor Optimization and Hyperfine Characterization Towards Laser Cooling John R Daniel, Chen Wang, Taylor Lewis, Madhav Dhital, Shan-Wen Tsai, Brian K Kendrick, Chris Bardeen, Boerge Hemmerling Cooling atoms to the ultracold regime has allowed for studies of physics, ranging from many-body physics of quantum degenerate gases, quantum computing, precision measurements and tests of fundamental symmetries. Extending these experiments to polar molecules has the prospect of enhancing the sensitivity of such tests and of enabling novel studies, such as cold controlled chemistry. However, applying traditional laser cooling techniques to molecules is rendered difficult due to their additional degrees of freedom which result in a limited photon scattering budget. Here we study the 261.5nm X1Σ+ to A1Π transition in aluminum monochloride (AlCl) as a promising candidate for laser cooling and trapping. Our spectroscopy results indicate the Franck-Condon factors of 99.88% of the v=v’=0 manifold to be amenable to laser cooling, in agreement with our ab-initio calculations. Furthermore, we present our detailed study on maximizing the yield of AlCl molecules by laser ablation of KCl + Al mixture targets, while monitoring the K, Al and AlCl yields, and discuss a nonequilibrium recombination model of the process. We will also present preliminary work towards theoretically modeling the slowing and trapping process of AlCl. |
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G00.00324: A Tunable, High Power Interferometer Beam with Reduced Pointing Fluctuations and Wavefront Aberrations for 100-Meter Baseline Atom Interferometry (MAGIS-100) Jonah Glick, Natasha Sachdeva, Tejas Deshpande, Zilin Chen, Kenneth DeRose, Yiping Wang, Tim Kovachy MAGIS-100 is a 100 meter baseline atom interferometer which will search for wavelike dark matter, serve as a prototype gravitational wave detector in the 0.3-3 Hz frequency range, and realize large scale quantum superpositions. The interferometer will be assembled in the vertical MINOS access shaft at Fermilab, where the interferometer beam will split the wave function of an atom cloud via the strontium clock resonance. The space-time area enclosed by the interferometer arms can be increased with large momentum transfer pulse sequences, but jitter in the pointing of the interferometer beam and inhomogeneity in the laser phase and intensity profiles limits the ultimate sensitivity. We present the design and prototype test of a beam delivery system for MAGIS-100 which provides spatial mode cleaning by free-space in-vacuum propagation, minimizes subsequent induced aberrations with ultra-high-quality in-vacuum optics, provides Coriolis force compensation with piezo-controlled tip-tilt mirrors, and uses stable support structures to suppress the pointing jitter and frequency noise response of the interferometer beam from seismic drives. |
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G00.00325: Quantum Many-body Dynamics in a Squeezing-while-rotating Scheme Zeyang Li, Simone Colombo, Edwin Pedrozo Penafiel, Chi Shu, Mikhail Lukin, Vladan Vuletic An ensemble of atomic spin interacting with an optical cavity mode is widely studied and attracts many interests from quantum metrology to quantum many-body physics. The optical cavity can generate a coherent long-ranged spin-spin interaction among atomic ensembles via the one-axis twisting Hamiltonian. The dynamics of the spin system are significantly affected and exhibit rich quantum many-body phenomena by exposing the ensemble to an additional transverse field. In addition, by using a recently achieved time-reversal toolbox, one also has a probe of more non-trivial collective spin states, especially those with high quantum Fisher information. We will report here our experimental and theoretical progress in this direction and an outlook for exploring other exotic quantum properties. |
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G00.00326: Open system dynamics with a Hagedorn bath Yunfei Wang, Albion Lawrence We study the open system dynamics of a harmonic oscillator "system" coupled to an "environment" of oscillators with an exponential density of states, motivated by holographic models of non-gravitational "little" string theories. We present the Heisenberg equations of motion and the quantum master equation for the system, and develop a renormalization procedure to manage the divergences, which are exponential in the cutoff. We provide evidence that the renormalized system dynamics is Markovian even when the initial state of the environment is the instantaneous ground state. |
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G00.00327: Structure and Statistics of the Traid Group Franscesca J Ark, Nathan L Harshman, Adam C Knapp Topological exchange statistics given by the traid group Tn can occur in one-dimensional particle systems with hard-core three-body interactions. The traid group, also known as the twin group or planar braid group, is a strand group, similar to the braid group, whose generators are self-inverses and obey locality. We compare the structures of low-order traid groups and braid groups by analyzing their conjugacy classes, normal subgroups, and word problems. Exchange statistics given by strand groups have possible applications in quantum computing and physical systems such as ultracold atoms in optical traps. |
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G00.00328: Hyperfine spectroscopy toward microwave quantum memory using rare-earth materials Safura Sharifi, Donny R Pearson, Elizabeth A Goldschmidt A solution for practical quantum information processing is to develop quantum memories that store microwave photons. Today, most quantum memories work on optical modes while many quantum information systems operate in the microwave regime and are limited by relatively short coherence times. Rare-earth atoms in solids are a promising platform for both optical quantum memory and microwave to optical quantum transduction due to their extremely long coherence times, high densities of emitters, and more. In particular, certain isotopes with GHz-scale hyperfine splittings (including 167Er3+, 145Nd3+, and 171Yb3+) in yttrium-oxide crystalline hosts are well-suited for microwave quantum memory due to their minimal inhomogeneous broadening and optical addressability for spectroscopic investigations. For most microwave-regime quantum memory protocols, minimizing the inhomogeneous broadening of the spin transition is vital. We will present spectroscopic investigations of the hyperfine states of rare-earth ensembles at cryogenic temperatures to determine the dependence of the inhomogeneous broadening on temperature, magnetic field, doping concentration, and host material. We will discuss the implications on future microwave quantum memories with rare-earth doped crystals. |
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G00.00329: Integrated hybrid quantum system as quantum simulator Abasalt Bahrami Recently, the interactions between neutral atoms and charged ions have been addressed for investigations of low temperature chemical reactions [1, 2, 3], the study of polaron physics [4], but also to allow for novel types of quantum simulation [5]. From the experimental side, the challenge is to combine both trapping techniques into a hybrid atom-ion trap to study the atom-ion system. We introduced a novel integrated atom-ion system, which traps both ions and neutral atoms simultaneously under the ion chip [6]. Atom-ion mixtures have similarities to a natural crystalline where atoms play the role of electrons; this allows our system to function as a quantum simulator to study the dynamics of many-body atom-ion systems. |
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G00.00330: Abstract Withdrawn
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G00.00331: Enhancing atomic dark matter and gravitational wave detectors with optimal quantum control Zilin Chen, Garrett Louie, Tim Kovachy Large scale atom interferometers using strontium atoms are promising for searching for ultralight dark matter and gravitational waves in a currently unexplored frequency range. In atom interferometry, the atomic superposition states are created and controlled by transferring momentum from laser pulses. The interferometer sensitivity can be enhanced by implementing large momentum transfer (LMT) atomic beam splitters with hundreds or even thousands of pulses which drives atomic transitions between ground and excited states. Deviation from ideal transitions limit the control efficiency and lead to significant atom loss after numerous pulses. During the driving process, deviations can be induced by various factors such as location deviation of atoms in the cloud, non-zero initial velocity spread of atoms respective to the rest-frame, intensity, phase fluctuations and polarization aberration in the laser pulses, and non-zero environmental electromagnetic fields. We manage to drive transitions of the 87Sr atoms in simulation with high fidelity by employing the optimal quantum control techniques which increase the robustness and efficiency of driving pulses against nonideal factors by detuning the amplitude and phase instantaneously and constantly in the pulse duration timescale. |
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G00.00332: Rotation Sensing with Nuclear Spins in Diamond Sean Lourette, Andrey Jarmola, Victor Acosta, Anthony G Birdwell, Peter Blümler, Dmitry Budker, Tony Ivanov, Vladimir S Malinovsky We demonstrate a solid-state rotation sensor based on the 14N nuclear spins intrinsic to nitrogen-vacancy (NV) color centers in diamond [1]. The operation of diamond rotation sensors are analogs of vapor-based NMR devices, constituting a scalable and miniaturizable solid-state platform, capable of operation in a broad range of environmental conditions. The sensor employs direct optical polarization and readout of the 14N nuclear spins and a radio-frequency double-quantum pulse protocol that monitors 14N nuclear spin precession. This measurement protocol suppresses the sensitivity to temperature variations in the 14N quadrupole splitting, and it does not require microwave pulses resonant with the NV electron spin transitions. The nuclear spin interferometric technique developed in this work may find application in solid-state frequency references and in extending tests of fundamental interactions at micro- and nanoscale to those involving nuclear spins. With further improvements, it may also find use in practical devices such as miniature diamond gyroscopes for navigational applications. |
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G00.00333: Towards Raman Cooling in Erbium Doped Microresonators Danielle Woods, Safura Sharifi, Josephine Melia, Gaurav Bahl, Elizabeth A Goldschmidt Optical excitation of matter commonly results in heating processes due to light absorption and inelastic phonon production processes such as Raman scattering. Spontaneous optical cooling has been achieved for certain materials through processes dependent on the sample’s electronic structure or through optical engineering. However, fluorescent cooling of any solid remains a challenge that has not been fully solved. We propose a new approach for achieving optical cooling in solids using whispering gallery modes. Optical absorption of rare-earth dopants in a micro-resonator is used to eliminate the Purcell enhancement of the heat-producing Stokes light scattering in a high-Q resonator with large Purcell enhancement of the phonon-absorbing Anti-Stokes scattering. We use several methods to fabricate erbium-doped Silica microsphere resonators with Q factors of 10^7, evanescently coupled to a biconical tapered fiber waveguide. Our initial results demonstrate that the erbium dopants substantially reduce the quality factor of our resonators at the erbium absorption wavelengths, which is where we will then position the silica Stokes peak, thus reducing the ratio of Stokes to Anti-Stokes emission in our sample and leading towards possible net cooling effects. |
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G00.00334: Simulation Study of Laser Aberrations for MAGIS-100 Yiping Wang, Natasha Sachdeva, Jonah Glick, Tim Kovachy The MAGIS-100 experiment is a 100-m tall atom interferometer being built at Fermilab with a goal of searching for ultralight dark matter and serving as a prototype gravitational wave detector in a frequency range between the peak sensitivities of LIGO and LISA. Wavefront aberrations in the laser used to manipulate the atoms cause phase distortions across the Sr atom cloud and result in loss of contrast and systematic errors in the interferometer phase. In this poster, we present simulation studies of the effect of wavefront aberration from the beam delivery system throughout the interferometry process. The effects of these aberrations are simulated by numerically evaluating the Rayleigh-Sommerfeld diffraction integral using the FFT convolution theorem. The aberrations are then included in a Monte Carlo simulation for determining the final interferometry phase. As a final step, we include the simulation of the imaging process. The complete simulation informed the design of the MAGIS-100 beam delivery system to minimize the aberrations experienced by the atoms, and the point-source interferometer we are simulating will be used between experimental cycles to measure wavefront aberrations. |
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G00.00335: Characterization of a photonic crystal mirror for quantum optomechanics John Omnik, Charles A Condos, Aman Agrawal, Dalziel J Wilson The ability to control nanomechanical devices using radiation pressure is the foundation for quantum optomechanical technologies. We have fabricated Si3N4 membranes with embedded photonic crystal (PtC) reflectors to enhance their susceptibility to radiation pressure at near-infrared wavelengths. In this poster we present efforts to characterize the optical properties of the PtC-etched Si3N4 membrane with sub-100 nm thickness, with the objective of achieving 99% reflectivity at a wavelength of 850 nm. Characterizations were made by measuring the reflectance across a broad spectrum of wavelengths using a tunable Titanium-Sapphire laser and a custom reflectometer employing a quadriaxial sample mount. Unpatterned 90 nm thick Si3N4 membranes were found to reflect ~35% of light at 850 nm. PtC membranes with the same thickness were found to have a reflectance of ~90% at 861 nm, for an incident beam with a spot size of 100 µm. These results are consistent with previous sub-100-nm-thick PtC reflectors at near-infrared wavelengths, suggesting the need for thicker membranes. Ultimately, the PtC mirror will be integrated into an optical microcavity as a platform for quantum-limited force sensing and electro-optic conversion applications. |
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G00.00336: Optical coherence and relaxation dynamics in a thulium-doped yttrium gallium garnet crystal for quantum memory applications Antariksha Das, Mohsen Falamarzi Askarani, Jacob Davidson, Neil Sinclair, Joshua A Slater, Sara Marzban, Daniel Oblak, Charles W Thiel, Rufus L Cone, Wolfgang Tittel Rare-earth ion-doped crystals with a long optical coherence lifetime are of great interest to serve as solid-state multimode quantum memories in frequency-multiplexed quantum repeater architectures. Towards this end, spectroscopic investigation on yttrium gallium garnet -YGG crystal cooled to 500 mK and doped with 1% Tm3+ is presented. At low magnetic fields (a few hundreds of Gauss), this crystal offers an optical coherence lifetime exceeding one millisecond and ground-state Zeeman level lifetime as long as tens of seconds. Furthermore, we characterize and model the time evolution of spectral holes at different magnetic fields for various temperatures in the view of spectral diffusion which is crucial to understand in order to build an efficient long-lived quantum memory. |
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G00.00337: Elastic positron versus elastic electron scattering off Mn Valeriy K Dolmatov, Miron Y Amusia, Larissa V Chernysheva Earlier [1, 2], we demonstrated the specific multielectron features of elastic electron scattering by Mn atom due to its 3d5 semifilled subshell. We now study [3] to what extent the elastic scattering of positrons by Mn can differ from the scattering of electrons by this atom. This is all the more interesting and important, since today little is known about the elastic scattering of positrons by atoms possessing a multielectron half-filled subshell in the ground state, as far we know. The problem is theoretically complex. This due to both the need to accurately take into account the correlation effects affecting the scattering of the projectile by such atoms, and accounting for the formation of virtual Ps in the scattering of positrons by the atom. In the present study, we fairly accurately account for correlation effects using the Dyson formalism for both the electron and positron Green’s function in the framework of the RPAE theory. As for the formation of virtual Ps in the e+ + Mn scattering, we take into account the latter in a reasonable, albeit simplified, approximation, as in [4]. One of the key findings of this study is that the e+ + Mn and e− + Mn elastic scattering cross sections follow different paths at lower energies, with the result that the low-energy e+ + Mn cross section domiantes the e− + Mn cross section to the degree not previously observed or predicted for other atoms such as alkali and noble atoms. [1] V. K. Dolmatov 2017 Phys. Rev. A 96 052704. [2] V. K. Dolmatov, M. Ya. Amusia, and L. V. Chernysheva 2013 Phys. Rev. A 88 042706. [3] M. Ya. Amusia, V. K. Dolmatov, and L. V. Chernysheva 2021 J. Phys. B (Accepted manuscript). [4] M. Ya. Amusia et al., 2003 JETP 97 34. |
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G00.00338: Entanglement entropy production at early times Rishabh Kumar, Eugenio Bianchi We study the early-time evolution of interacting subsystems initially prepared in a non-entangled state. We show that the entanglement entropy initially grows as $-\alpha t^2 \log(\alpha t^2)$ and determine the scale $\alpha$ in terms of the interaction strength for the following cases: (i) random-matrix Hamiltonians, (ii) random quadratic Hamiltonians, and (iii) Hamiltonians with a finite number of interactions. The result shows that, in these systems, the entanglement entropy reaches its equilibrium value on a time-scale much shorter than the decoherence time. |
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G00.00339: Fabrication of photonic crystal mirror into a silicon nitride membrane resonator Bre' Anna Sherman, Aman Agrawal, Dalziel J Wilson High Q silicon nitride membrane resonators have enabled a diversity of |
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G00.00340: Toward Quantum Computing Experiments Using Trapped Electrons Kayla J Rodriguez, Qian Yu, Alberto M Alonso, Jackie Caminiti, Kristin M Beck, Dietrich Leibfried, Madhav Dhital, Hartmut Haeffner, Boerge Hemmerling
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G00.00341: DFT random phase approximation needs to be revisited Mohammad Alidoust, Erlend E Isachsen, Klaus B Halterman, Jaakko E Akola Here we compare and contrast the dispersive permittivity tensor, using both a low-energy effective model and density functional theory (DFT) [1]. As a representative material, phosphorene subject to strain is considered. Employing a low-energy model Hamiltonian with a Green's function current-current correlation function, we compute the dynamical optical conductivity and its associated permittivity tensor. For the DFT approach, first-principles calculations make use of the first-order random-phase approximation. Our results reveal that although the two models are generally in agreement within the low-strain and low-frequency regime, the intricate features associated with the fundamental physical properties of the system and optoelectronic device implementation such as band gap, Drude absorption response, vanishing real part, absorptivity, and sign of permittivity over the frequency range show significant discrepancies. Our results suggest that the random-phase approximation employed in widely used DFT packages should be revisited and improved to be able to predict these fundamental electronic characteristics of a given material with confidence. Furthermore, employing the permittivity results from both models, we uncover the pivotal role that phosphorene can play in optoelectronics devices to facilitate highly programable perfect absorption of electromagnetic waves by manipulating the chemical potential and exerting strain and illustrate how reliable predictions for the dielectric response of a given material are crucial to precise device design. |
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G00.00342: Gauge Sensitive Features of Quantum States on a Cylindrical Lattice Kunal K Das, Caelan Brooks We examine the spectrum and the quantum states on small lattices with cylindrical topology subject to gauge potentials, natural or synthetic, that introduce position-dependent phase in the hopping terms. General gauge invariance assumed in open or infinite lattices is lost due to the periodic boundary condition and the spectrum and eigenstates can become sensitive to specific gauge assumed. This can have significant effects on the behavior of the system, such as those relevant in phenomena associated with the quantum Hall effect. We examine several distinctive features in the spectrum including avoid crossings and persistent intersections, and their dependence on the choice of gauge and other system parameters. The origins of those features are traced by comparison with systems with different boundary conditions and configurations. We correlate the impact of those spectral features with the behavior of the quantum states of the system. We determine under what conditions invariance under specific gauge choices can be restored. |
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G00.00343: Stationary Quantum States Associated with Nonlinear Scattering in One Dimension Kunal K Das, Allison Brattley Quantum scattering dynamics can be reduced to a description in terms of stationary states. In the presence of nonlinearity, this is not typically possible, but stationary states exist and provide a framework for understanding the dynamics. We do a comprehensive analysis of the quantum states for a step potential and for a barrier potential in one dimension in the presence of nonlinearity, such as induced by interatomic interactions for coherent quantum states associated for example with Bose-Einstein condensates (BEC). In the mean field limit, using analytical expressions involving Jacobi elliptic functions, we find the full range of allowed solutions, which span a substantially larger variety than in the linear case used to model scattering in one dimension. We use a system based on the nature of the roots of the hydrodynamic equations to classify and characterize the solutions and determine the associated range of allowed physical parameters. We consider these stationary solutions in the context of nonlinear scattering dynamics at potential barriers. The intricate sensitivity of the stationary solutions to small changes in the physical parameters in certain critical regimes open possibilities of high precision metrology based on quantum coherent states. |
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G00.00344: Experimental exploration of fragmented models and non-ergodicity in tilted Fermi-Hubbard chains Bharath Hebbe Madhusudhana, Sebastian Scherg, Thomas Kohlert, Pablo Sala de Torres-Solanot, Frank Pollmann, Immanuel Bloch, Monika Aidelsburger Thermalization of isolated quantum many-body systems can be understood a redistribution of quantum information within the system in such a way that macroscopic variables acquire a thermal value, which is independnet of the initial state, and remain experimentally accessible and microscopic variables, that contain most of the details of the initial state recede into experimentally inaccessible parts of the observable space. Therefore, a question of fundamental importance to quantum information theory is when do quantum many-body systems fail to thermalize, i.e., feature non-ergodicity. One of the paradigmatic examples of ergodicity breaking is many-body localization, which occurs in the presence of disorder. Recently a new form of ergodicity breaking was proposed, which occurs without disorder. A useful test-bed for the study of this type of non-ergodicity is the tilted Fermi-Hubbard model, which is directly accessible in experiments with ultracold atoms in optical lattices. Here we experimentally study non-ergodic behavior in this model by tracking the evolution of an initial charge-density wave over a wide range of parameters, where we find a remarkably long-lived initial-state memory [1]. In the limit of large tilts, we identify the microscopic processes which the observed dynamics arise from. These processes constitute an effective Hamiltonian and we experimentally show its validity [2]. This effective Hamiltonian features the novel phenomenon of Hilbert space fragmentation. In the intermediate tilt regime, while these effective models are no longer valid, we show that the features of fragmentation are still vaguely present in the dynamics. |
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G00.00345: Bifurcation of avoided crossing at an exceptional point in the Lorentz oscillator model Alexei A Maznev Physical phenomena associated with exceptional points of non-Hermitian operators are subject of active research in photonics and other fields. I will show that an exceptional point occurs already in the classic Lorentz oscillator model of optical dispersion. The reason that this feature of the Lorentz dispersion equation has remained unnoticed is that normally the wavevector is regarded as a complex function of the real frequency, in which case the exceptional point is not encountered. However, if the frequency is treated as a complex function of the real wavevector, the Lorentz dispersion equation describes the transition between the strong and weak coupling regimes through the bifurcation of an avoided crossing at the exceptional point. These two situations correspond to two classes of experiments: while transmission measurements imply a real frequency, scattering experiments impose a real wavevector. In the latter class of experiments, exceptional points will be encountered in many physical systems generally described by Lorentz-oscillator-type models. |
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G00.00346: Floquet lattice engineering and thermodynamics with ultracold lthium Eber Nolasco-Martinez, Ethan Q Simmons, Roshan Sajjad, Jeremy Tanlimco, Alec J Cao, Hector Mas, Toshihiko Shimasaki, Hasan E Kondakci, David M Weld We present recent results on experiments using ultracold lithium BECs to study quantum thermodynamics and thermalization. We explore the robustness of dynamical localization in the atom-optics kicked rotor realized with a pulsed optical lattice. We observe the breakdown of localization and a prethermal plateau via tunable interactions and establish the role of these interactions in destroying reversibility. We then report the first experimental observation and characterization of the quantum boomerang effect using a second, phase-shifted lattice. We also discuss our progress in studying quantum heat engines and atom interferometry in Floquet-Bloch bands. |
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G00.00347: Visible-wavelength optomechanical cavity for realizing spin-phonon coupling of the silicon vacancy center in diamond Graham D Joe, Kazuhiro Kuruma, Michael Haas The silicon vacancy center in diamond (SiV) is a promising candidate for use as a node in a quantum network, in part due to its ability to emit indistinguishable single photons from nano-cavities, its high cooperativity as a spin-photon interface, and its high spin-strain susceptibility. The latter opens the door for the SiV spin state to be manipulated via a spin-phonon interface, which has been investigated using classical surface acoustic waves in bulk diamond. Alternatively, a spin-phonon interface can be probed using an optomechanical cavity, in particular one that is resonant with the optical transition of the SiV to allow efficient spin readout. With this in mind, we have designed and fabricated a visible-wavelength optomechanical cavity in diamond. In particular, we have utilized a novel cavity design that results in a small mechanical mode volume, which is beneficial towards producing high spin-phonon coupling rates. Our work is a step towards strong spin-phonon coupling of the SiV center for hybrid quantum networks. |
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G00.00348: High-power and Frequency-Agile Laser System for Gravitational Wave and Dark Matter Detection Using Atom Interferometry (MAGIS-100) Kenneth DeRose, Tejas Deshpande, Tim Kovachy MAGIS-100 is 100-meter-tall atom interferometer currently being built at Fermilab which will leverage modern laser manipulation techniques to search for oscillations in fundamental constants and time-dependent, equivalence-principle-violating accelerations of test masses: key signatures of several ultra-light dark matter candidates. Generation and precise control of meter-separated quantum atomic superpositions within the interferometer requires an agile laser system able to rapidly shift the optical frequency up to a rate of 100 GHz/s while maintaining a phase lock to our static frequency comb. To meet the power requirement of the experiment, two lasers coherently locked must be robust to these rapid frequency shifts. Here, we share test data of our lasers both operating coherently with a 90 % coherence fidelity and reliably surviving the rapid frequency shifts while preserving phase lock. In addition to dark matter searches, the interferometer can adapt toward searches for new fundamental forces outside the Standard Model and tests on the coherence limits of spatially separated wave packets. It will also serve as a prototype gravitational wave detector in frequency band between the peak sensitivities of LIGO and LISA. |
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G00.00349: Vibrational spectroscopy of dimer radical cation of thioureas in water Susmita Bhattacharya Time-resolved resonance-enhanced Raman spectra of thiourea dimer radical cation, (Tu)2•+, and its methyl substituted analogues prepared by pulse radiolysis, have been obtained and interpreted in conjunction with theoretical calculations to provide detailed information on the molecular geometry and bond properties of these class of species. Seven Raman bands of (Tu)2•+ observed in the 80-1600cm-1 region are assigned in terms of the strongly 212cm-1 and weakly enhanced 719cm-1 fundamentals, their overtones and combinations. Upon substitution of labile protons of (Tu)2•+ with deuterons in D2O solutions frequencies of fundamental vibrations observed in H2O decrease slightly to 208 and 668cm-1, respectively, and two additional fundamentals become apparent at 380 and 410cm-1 overlapping overtone of 208cm-1 band. Calculations by range-separated hybrid density functionals support the spectroscopic assignments of the 212(208)cm-1 vibration to a predominantly symmetric SS stretching mode and the feature at 718.6(668)cm-1 to symmetric SC stretching mode, respectively. Our findings are compared to analogous symmetric SS hemibonded methyl substituted thiourea dimer radical cations to provide insights about relation between their structure and properties. |
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G00.00350: FLUID DYNAMICS
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G00.00351: Correlation lags give early warning signals of approaching tipping points Cristina Masoller, Giulio Tirabassi Identifying upcoming tipping points from observations is an important challenge in time series analysis with practical applications in many fields of science. Well-known indicators are the increase in spatial and temporal correlations. However, the performance of these indicators depends on the system under study and on the type of approaching bifurcation, and no indicator provides a reliable warning for any system and bifurcation. Here we propose an indicator that simultaneously takes into account information about spatial and temporal correlations. By performing a bivariate analysis of signals recorded in pairs of adjacent spatial points, and analyzing the distribution of lag times that maximize their cross-correlation, we find that the variance of the lag distribution consistently decreases as a bifurcation approaches. We demonstrate the reliability of this indicator using different types of models that present different types of bifurcations, including local bifurcations (transcritical, supercritical and subcritical saddle-node and Hopf bifurcations), and global bifurcations. |
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G00.00352: Observations of Cross-Shelf Nitrate Fluxes on the Oregon Continental Shelf Andrew L Scherer, Thomas Connolly The United States Pacific Northwest ocean ecosystems are primarily limited in growth from nitrate supply. The nitrate supply that drives the highly productive marine growth in this region is primarily a result of wind driven coastal upwelling. This work investigates cross-shelf nitrate fluxes over the Oregon continental shelf using new data made available through the installation of the Ocean Observatories Initiative Endurance Array. The primary onshore flow of nitrate-rich water over the continental shelf is found to originate at the middle depths, consistent with previous research in the region. However, the upwelling transport and cross-shelf nitrate fluxes on the continental shelf are found to be in poor agreement with common upwelling indices and a variety of physical forcings (e.g., wind stress). This suggests the need for additional dynamics (e.g., large-scale pressure gradients) to fully explain the observed surface transport and nitrate fluxes. Near the coast, an empirical model is found to be successful at predicting the nearshore nitrate concentrations from onshore wind stress measurements. The primary results from this research are laying the groundwork for future analytical modelling of nitrate and water transport on the Pacific Northwest continental shelf. |
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G00.00353: Determining the correlation between particulate matter emissions, greenhouse gas emissions and respiratory disease risk in large cities Siona Prasad The emission and distribution of particulate matter (PM) among numerous atmospheric gases is a growing problem in large cities. Particulate matter is correlated with declining air quality and increasing respiratory disease risk. An accurate and efficient measurement strategy to estimate PM emissions from large cities does not currently exist. However, particulate matter tends to be co-emitted with other common pollutants such as carbon dioxide and methane. Existing sensor networks and modeling techniques are capable of quantifying and pinpointing urban CO2 sources. In this project, I discuss the correlation between PM emissions and CO2 emissions. The existing sensor network and dispersion models are used to predict total PM emissions from urban sources in Washington DC. Results are validated through comparison with state-of-the-art instruments. Together, we construct the tools for comprehensive prediction of PM emissions via correlation with abundant greenhouse gas emissions. PM emission levels have established associations with emergency hospital visits for respiratory disease and negative health impacts for those with existing respiratory and cardiovascular risk factors. Quantification of PM sources is a crucial first step to designing effective mitigation strategies and improving city-wide air quality. |
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G00.00354: CLIMATE PHYSICS
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G00.00355: A Parallel Least Squares, Conjugate Gradient, Finite Element Method Solver for Velocity-Current MHD Equations A.J. Meir, Keith D Brauss Due to the symmetry of weak formulations for the Navier-Stokes equations and the velocity-current MHD (magnetohydrodynamics) equations, we propose a least squares formulation and numerical approximation mdethod for the velocity-current MHD equations that is based on work by Roland Glowinski and fellow authors. A parallel, finite element method solver was developed that utilizes the open-source, C++ software library deal.II and wraps into the libraries p4est and Trilinos. A block-diagonal preconditioner is utilized for convergence of the conjugate gradient method. The weak formulation, finite-dimensional approximation, and algorithm implementation are discussed with application interest toward optimization of crystal growth processes. |
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G00.00356: Capillary Action as seen in Trees, may be a manifestation of the Photo Electric Effect, and may have caused long periods of Cooling of the Earth RICHARD M KRISKE One of Einstein's first paper is rather unknown, titled "Conclusions Drawn from the phenomena of Capillarity." It seems that water rose in trees without any work being done. This author put forward a theory, that must have been realized by Einstein. Einstein proposed, that the flow of two fluids, accounted for Capillary Action, before he went on to write the "Photoelectric Effect." It can be seen that the water rises in the capillary of the tree, and as the water evaporates at the top of the capillary, a hole id sent from the top of the column to the bottom, producing a sort of "negative energy" field, that draws more water from the soil. Before Einstein, apparently subconsciously, applied this same idea to Electrons being ejected from the surface of a metal (and what we would now call an electron hole being transmitted through the metal, attracting more Electrons, he proposed that a gas of some sort flowed through the capillary tube. Knowing what we know now, we can surmaise that not only "electrons" have positive conterparts in "holes", but so do atoms and molecules. Water "holes" are transmitted into the soil, and cool it, and the surrounding environment. The taller the tree, or even seaweed for that matter, the more it cools the environment, because it would have a greater "work function", just as in the photoelectric effect. The plants cool using the Photoelectric effect. What is wrong with this theory? The problem with it is, that it shows explicitly how 'negative energy" works and how it gives a type of "antigravity", in that the water rises with no work being done. It also shows that the Earth is greatly influenced, cooled into several ice ages, by "negative energy." Particle Physics would also be somewhat in error, in that almost everything has an "anti." Yet the whole of it is in plain site, with little or nor mystery involved. With "climate change" being the major problem on Earth, perhaps it is time to make this correction to Physical Laws. |
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G00.00357: Energy dissipation when internal, ocean-type waves reflect from a solid boundary Bruce E Rodenborn, Luke Payne, Michael Allshouse, Yichen Guo Determining the energy flux of an internal wave from the experimentally measured velocity field was made possible by the work of Lee et al. (Lee et al., Phys. Fluids, 26, 2014). This method is used in our work to measure the amount of energy dissipated when internal waves reflect from sloping boundaries by comparing the incoming energy flux to the outgoing energy flux through a surface near to the reflection region. We also use numerical simulations of the Navier-Stokes equations in the Boussinesq limit where the energy flux is known from the pressure and velocity fields. There is good agreement between our experimental and numerical simulation data, and we find that there are high rates of energy dissipation during reflection process. We also find that there is a wave reflected back from the boundary towards the generation site, which has not been reported previously. |
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G00.00358: Modeling 3D Printing Ink Flow and Drying for Battery Applications Zhuolin Xia, Dilip Gersappe 3D printing is a promising method in fabricating battery cells with higher energy density at low cost due to its controllability of architecture and simplicity of process. The ink for battery electrodes is a complicated mixture of particles and different interaction energies. In order to understand the dynamics and design inks with good flowability and conductivity, numerical simulations were carried out. We present a hybrid model used the lattice Boltzmann Method(LBM) and the kinetic Monte Carlo(KMC) to simulate ink flow and drying processes. The model includes shear thinning behavior and hydrodynamic interactions of the ink suspension. Velocity profiles at different shear rates were obtained. The results indicate that the flowability is greatly improved when viscosity drops below certain value during printing. The drying process was modeled by considering the evaporation of solvent and the aggregation of different particles including active particles, binders, conductive additives. The influence of evaporation rate on the dried ink morphology was investigated. The smaller evaporation rates lead to more aggregated microstructures having larger conductive interfaces, while the higher evaporation rates result in more scattered microstructures with larger active interfaces. |
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G00.00359: Two-Dimensional evaporation dynamics of a respiratory droplet in context of COVID-19 Saptarshi Basu, Sreeparna Majee, Abhishek Saha, Swetaprovo Chaudhuri, Dipshikha chakravortty Respiratory droplets are considered the primary mode of transmission of COVID-19. The droplets ejected through the exhalation process during cough, sneeze, speech consist of a complex mixture of volatile and non-volatile substances. While transmitted and translated in air with perturbations, these complex liquid droplets undergo a series of coupled thermo-physical processes. Contemplating an individual airborne droplet in a cloud of infectious droplets interacting with air vortices, boundary layers and wakes develop on account of relative motion between the droplet and the ambient air. The mathematical description of the coupled subprocesses, including droplet aerodynamics, heat, and mass transfer, which controls the evaporation dynamics, were solved to obtain the solution. The two-dimensional model gives a complete analysis encompassing the gas phase coupled with the liquid phase responsible for the airborne droplet kinetics' complex evaporation phenomenon in the ambient environment. The transient inhomogeneity of temperature and concentration gradient in the liquid phase of the respiratory droplet caused due to the convective and diffusive transports are captured in the 2D model. |
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G00.00360: Numerical simulation of gas migration in a cement slurry in a wellbore annulus NDRI A KONAN, Eilis Rosenbaum, Mehrdad Massoudi Gas migration in cement slurries is regarded as one of the more serious problems encountered in the wellbore cementing operations, as this results in about 25-30% of the operation failures [Vazquez et al., 2005]. One approach to mitigate the gas migration is to allow enough time for the cement to develop sufficient gel strength, which describes the phase change from the cement slurry to a gel-like material. Cement slurries, in general, exhibit yield stress, which can depend on the shear rate, concentration of the cement particles, etc. [see Tao et al, 2020]. Their rheological properties are also affected by temperature, pressure, etc. [see Banfill, 2006]. To gain a better understanding of the air bubbles' distribution in the well and their sizes, we simulate using CFD approach, 3D flows of a cement slurry in a laboratory scale annulus representative of real wellbore operations with continuous injection of air. The dynamics of the slurry and the air bubbles are modeled using a two-phase approach, where the volume fraction (concentration of the cement particles), mass and linear momentum conservation equations are solved. We assume that the cement suspension can be modeled as (1) a Bingham fluid and (2) a Herschel-Bulkley visco-plastic fluid. Furthermore, (3) the viscous stress of the cement slurry is assumed to exhibit a dependence on the volume fraction and can account for the shear-thinning or shear-thickening behavior of the slurry. The thixotropy effects are neglected. As for the yield stress, we assume that it depends on the volume fraction as well as the ratio of water-to-cement [see Tao et al., (2020)]. These equations are implemented as customized non-Newtonian viscosity libraries and are solved along with the governing equations in the open-source toolbox/library, OpenFOAM. The simulation results are compared with available measurements, and the statistics of the bubble sizes and their distributions are also analyzed and discussed. |
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G00.00361: Flow through an array of flexible hairs Sri Savya Tanikella, John P Raimondi, Emilie Dressaire Numerous biological systems rely on hair-like structures to filter or sense disturbances in their surroundings. These hair-like structures can cover external surfaces like in the lateral fish line or internal cavities such as cilia inside the oesophagus. Most of the elongated structures found in nature are flexible and deform when placed in a flow field. This observation is consistent with models of elastic beams that demonstrate their ability to act as strain sensors and amplifiers by deforming their substrate. This experimental study investigates the deformation of a flexible hair, isolated or in an array in a viscous flow. The experiments are conducted in a rectangular channel once a steady-state Poiseuille flow has developed in it. For the single hair, we vary the geometry and Young's modulus, and we measure the deformation of the hair and the surrounding flow field using particle image velocimetry. We then repeat the experiments with arrays of varying sizes, geometry, and hair spacing. We measure the flow field and hair deformation to model the effects of deformation on the flow through and around the array. Finally, we compare our experimental results with numerical simulations coupling the fluid flow and elastic deformation. |
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G00.00362: Modelization of dispersion of swimming bacteria in Poiseuille flow Harold Auradou, Carine Douarche, Marco Dentz This work reports 3D Langevin simulations of swimming bacteria modelled as an active Brownian rod experiencing rotational and translational motion when subject to Poiseuille flow. We perform the simulations for large number of particles, and sufficiently long time so that effective steady state longitudinal, transverse dispersion coefficients and mixing time across the gap can be determined. The influence of the particle aspect ratio, flow velocity, gap size and the competition between the Brownian motion and the swimming characteristics of the particle on the macroscopic dispersion coefficient is studied. Three different regimes are observed : (i) at low shear rate, rotational diffusion dominates, and classical Taylor dispersion regime is observed (ii) an intermediate regime where reorientation of the bacteria by the shear increases the mixing time in the gap and in turn increases longitudinal dispersion, (iii) a final "new" Taylor regime where mixing in the gap is set by the Brownian thermal diffusion. Three Péclet numbers are identified to capture the transition and the range of observation of those regimes. |
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G00.00363: Splash-cups and rain dispersal of Marchantia polymorpha gemmae Valentin LAPLAUD, Christophe F Josserand, Camille Duprat, Arezki Boudaoud In many plant species seedlings are dispersed in nature by the way of wind or animals. This in not the case for Marchantia polymorpha whose gemmae are ejected from a splash-cup organ by the fall of raindrops. This splash-cup is a small conical cavity of a few milimeters that contains the plants gemmea. When a raindrop falls on this cup in a non centered way there is formation of a jet that carries a few gemmea with it. This dispertion mechanism if very efficient as a single drop can eject gemmea up to a meter away from the plant. |
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G00.00364: Driven two-phase fluid displacements through a localized constriction Ido Lavi, Lauren Rose, Ramon Planet, Jaume Casademunt, Jordi Ortin, Stephane Santucci The manner in which a two-phase interface propagates through a porous medium is of major utilitarian interest and has been the subject of extensive research, specifically in the limit of quasi-static flow rates. However, the effects of a finite driving velocity, pending in any practical application, have not been carefully looked at nor clarified theoretically. Such non-equilibrium phenomena can already be observed in very simple devices that contain isolated defects. Here, as a model system, we study the driven displacement of an oil-air interface through a localized 'mesa' constriction in a Hele-Shaw cell. Using controlled experiments, theory, and finite element simulations, we find—in noteworthy quantitative agreement—that the driving velocity dramatically and nonlinearly modifies the resultant interface deformations. My talk will focus on the mathematical physics of this free boundary problem, demonstrating, without fitting parameters, how increasing levels of analysis progressively draw better comparisons to experiments. |
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G00.00365: Separating diffusion from dilation in the adsorption of surfactants. Brandon Ortiz, Mario R Mata Arenales, Santiago Ricoy, Han-Jae J Cho Surfactants are often employed in highly dynamic environments, such as in the oil and gas industry, where large variations in both surfactant concentrations as well as distortions of bubble and foam geometries can exist. In such scenarios, the surface tension changes are a result of surfactants diffusing to the interface and/or being spread apart due to interfacial dilation. While previous studies have mainly focused on diffusion-driven adsorption, we use surface-area-controlled bubble tensiometry to characterize dynamic surface tension in terms of separate diffusion and dilation effects during surfactant adsorption to the liquid-vapor interface. Distinguishing these behaviors provides a more specific characterization of dynamic surfactant behaviors that can ultimately provide a better insight into how to better select and utilize surfactants for a variety of applications. |
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G00.00366: Effects of Electrical Image Potentials in Porous Materials and in Narrow Nanotubes Jeffrey B Sokoloff Electrical image potentials can be important in small spaces, such as nanoscale pores in porous electrodes, which are used in capacitive desalination and in supercapacitors, as shown by Bazant’s group at MIT. It will be shown here that inside pores in porous metallic materials the image potentials can be considerably larger than near flat walls, as a result of the fact that the dielectric constant for an electric field perpendicular to a wall is much smaller than the bulk dielectric constant of water. Calculations will be presented for the image potential in spherical and cylindrically shaped pores. The calculations for cylindrical pores can also be applied to nanotubes. It has been believed for a long time, on the basis of molecular dynamics simulations, that in order to push a salt solution through a small radius nanotube, work must be done against the solvation energy of the ions, which is larger inside a narrow nanotube than it is in the bulk. The relatively large image charge potential in narrow nanotubes, however, tends to oppose this increase in the solvation energy. The degree to which the image potential facilitates the flow of the salt ions through nanotubes will be discussed. |
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G00.00367: Application of Method-of-Lines Numerical Solutions to Nernst-Plank-Diffusion-Binding Mass Transport Equations to Quantum Dot Accumulation in Bacillus Subtilis Biofilms Joshua Prince Interactions between biofilms and nanoparticles (NPs) have gotten increasing interest amongst scientists for applications in medicine, ecotoxicity and biogeochemical cycling. Comprehensive health and safety assessments in these areas require models which quantify nanoparticle uptake into biofilms and consequent toxic effects, or nanoparticle-biofilm interaction models. To develop the nanoparticle-biofilm interaction models necessary for these applications, a mass-transport model for nanoparticle transport in biofilms was developed which accounts for nanoparticle diffusion and macro/microscale electrostatic interactions within biofilms. Nanoparticle diffusion and macroscale electrostatic interactions were captured using a modified Nernst-Plank equation. Microscale electrostatic interactions were accounted for using protein-type binding kinetics. Dimensionless mass-transfer relations were developed from this model for different rate-limiting assumptions by solving the general component balance using both analytical and numerical techniques. These relations were then applied to charged quantum dots diffusing in B. subtilis biofilms to predict qualitative behaviors of this system. |
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G00.00368: Marangoni Convection-Driven Laser Fountains on Free Surfaces of Liquids Feng Lin, Aamir Nasir Quraishy, Tian Tong, Runjia Li, Guang Yang, Mohammadjavad Mohebinia, Yi Qiu, Talari Vishal, Junyi Zhao, Wei Zhang, Hong Hong Zhong, Hang Zhang, Zhongchen Chen, Chaofu Zhou, Xin Tong, Peng Yu, Jonathan Hu, Suchuan Suchuan Dong, Dong Liu, Zhiming Zhiming Wang, John R. John R. Schaibley, Jiming Bao It is well known that an outward Marangoni convection from a low surface tension region will make the free surface of a liquid depressed. Here, we report that this established perception is only valid for thin liquid films. Using surface laser heating, we show that in deep liquids a laser beam pulls up the fluid above the free surface generating fountains with different shapes, and with decreasing liquid depth a transition from fountain to indentation with fountain-in-indentation is observed. High-speed imaging captures a transient surface depression before steady elevation is formed, and computational fluid dynamics simulations reveal the underlying flow patterns and quantify the depth-dependent and time-resolved surface deformations. Systematic investigation of the effect of laser parameters, surface tension and area of the fluid on its surface deformation further confirms that the laser fountain is a result of dynamic competition between outgoing Marangoni convection and the upward recirculation flow. Experiments and simulations also reveal that a smaller surface area can dramatically strengthen laser fountain. The discovery of laser fountain and the development of related experimental and simulation techniques have upended a century–old perception and opened up a new regime of interdisciplinary research and applications of Marangoni-induced interface phenomena. |
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G00.00369: Role of oil conductivity in electrocoalescence of a droplet David Van Assche, Jean-Christophe Baret Electrocoalesence is a widely adopted method in droplet microfluidics, used for the controlled merging of droplets to manipulate the drop content. |
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G00.00370: FPGA based control electronics for quantum applications with ultra-low latency Nicholas Bornman, Silvia Zorzetti, Salvatore Montella, Gustavo Cancelo, James B Kowalkowski, Shefali Saxena, David Schuster, Leandro Stefanazzi, Chris Stoughton, Sara F Sussman, Ken Treptow, Neal Wilcer The long coherence time quantum systems, in the focus of the Superconducting Quantum Materials and Systems (SQMS) research center, require high resolution and dedicated electronics to measure and control the states of superconducting qubits coupled with record high photon lifetime cavities. Hardware acceleration using field programmable gate arrays (FPGAs) has a key role in the improvement of the speed and the efficiency of the quantum systems characterization and controls. Custom hardware design translates into robust controls and high-fidelity readouts, ultimately leading to the achievement of high performances and accurate results. We will present dedicated instrumentation to engineer quantum controls with ultra-low latency to enable future applications. |
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G00.00371: Investigating multiscale empirical mode decomposition of density fluctuation near critical point of SF6 David Dorf, Ana Oprisan, Sorinel Oprisan, Dereck Morgado, Seth Zoppelt, Carole Lecoutre, Yves Garrabos, Daniel Beysens We use a multiscale approach to investigate the dynamics of fluctuations near the critical point of |
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G00.00372: The effect of salt on the interaction between contact surfaces and COVID-19 droplets Meng Shen, Alex Kemnitz Fomite transmission through contact surfaces is implicated as an important transmission route for viral pathogens. For COVID-19, the role of fomite transmission through surfaces in the recent outbreak is not clear yet and leads to wide debating. In particular, the effect of the Covid-19 droplet composition, such as salinity, on the transmission at contact surfaces is unknown. Here we use molecular dynamics to investigate the interaction between Covid-19 in droplets of varied salinity and hydrophobic/hydrophilic surfaces. We choose cellulose membrane as the hydrophilic surface and graphite as the hydrophobic surface. Our results show that Covid-19 spike protein interacts more strongly with graphite than with cellulose membrane, and both interactions are reduced at increased salinity. We attribute the reduction in interaction to the screening effect. The research provides sheds light on the factors influencing the fomite transmission of Covid-19 via contact surfaces and the potential of viral transmission in different environment. |
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G00.00373: Thickness dependent superconducting properties of FeTe0.55Se0.45 thin films grown on YSZ substrates HIMANSHU CHAUHAN, Shivam K Miglani, A Mitra, G. D Varma The discovery of new high-temperature superconductors has long been a significant research issue in condensed matter physics. Iron-based superconductors (IBSs) have generated much research interest as the topological states in IBSs have been reported, suggesting a promising direction to realize topological superconductivity and great potential in various applications. Many attempts have been made to understand the origin of topological states in Fe-chalcogenide thin films in recent years. From this approach, we have fabricated superconducting thin film of different thicknesses (59 nm and 78 nm) from polycrystalline target FeTe0.55Se0.45 on YSZ single-crystalline substrates using pulse laser deposition (PLD) technique to study the structural, topological, and superconducting properties. Temperature-dependent resistivity curves show TC ~ 15 K. The magnetotransport data have been used to calculate the upper critical field (HC2) and coherence length (ξ) of grown thin films. From the magnetoresistance (MR) results, we have observed thickness dependence non-saturating linear magnetoresistance (LMR) in superconducting thin films, suggesting the presence of the possible topological superconducting state in the grown thin films. |
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G00.00374: Connectivity and dynamics in the olfactory bulb David E Kersen Dendrodendritic interactions between excitatory mitral cells (MCs) and inhibitory granule cells (GCs) in the olfactory bulb create a dense interaction network, reorganizing sensory representations of odors and, consequently, perception. Large-scale computational models are needed for revealing how the collective behavior of this network emerges from its global architecture. We propose an approach where we summarize anatomical information through dendritic geometry and density distributions which we use to calculate the probability of synapse between MCs and GCs, while capturing activity patterns of each cell type in the neural dynamical systems theory of Izhikevich. In this way, we generate an efficient, realistic large-scale model of the bulbar network. Our model reproduces known connectivity and functional properties of the bulb, and in turn predicts testable relationships between these two aspects of the bulb. Importantly, this allows us to explore the influence of the cortex on bulbar activity, demonstrating possible mechanisms by which centrifugal feedback to MCs or GCs influences bulbar activity, as well as how neurogenesis improves decorrelation without invoking cell death. Additionally, the methodology we describe here provides a tractable tool for other researchers. |
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G00.00375: Gamifying a Simulation to Improve Understanding and Attitudes Towards Electric Fields Ted K Mburu, Colleen Countryman, Liana R Rodelli Because electric fields cannot be touched or seen, simulations are often utilized to enhance students' understanding of them by providing them with a visual representation of electric fields and the motion of test charges within them. We built and tested an electric field "sandbox" simulation that dynamically represents the electric field lines, field vectors, equipotential lines, and the voltage of the charges that the user places anywhere on the screen. After building this, we gamified the simulation with the intent of further improving motivation and engagement in the material. The goal of the game is to guide a test charge through a racetrack using an electric field that the player creates. Both the game and the simulation that we created before it are built in JavaScript, so they will run on most browsers on a computer or mobile device. Results and student feedback from a subsequent controlled study of the efficacy of these instructional tools will also be discussed. The results indicated that no individual tool was significantly more effective than the others, but pre- to post-diagnostics were significant across all three groups. |
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