Bulletin of the American Physical Society
53rd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 67, Number 7
Monday–Friday, May 30–June 3 2022; Orlando, Florida
Session V01: Poster Session III (4:00-6:00pm, EDT)Poster
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Room: Grand Ballroom C |
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V01.00001: ATOMIC, MOLECULAR, AND CHARGED PARTICLE COLLISIONS
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V01.00002: Laboratory Astrophysics with Highly Charged Ions Richard H Mattish, Timothy J Burke, Patrick Johnson, Steven Bromley, Mike Fogle, Chad E Sosolik, Joan Marler A detailed study of the physics of highly charged ions (HCIs) is critical for a deep understanding of observed phenomena resulting from interactions of HCIs with neutral atoms in astrophysical and fusion environments. Specifically, the charge transfer rates and spectroscopy of the subsequent decay fluorescence are of great interest to these communities. Progress towards a laboratory-based investigation of these rates will be presented. The experiment takes advantage of an energy and charge state selected beam of HCIs from the recently upgraded Clemson University EBIT (CUEBIT). |
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V01.00003: Quantum-logic detection of collisions between single atom-ion pairs Or Katz, Meirav Pinkas, Nitzan Akerman, Roee Ozeri Studies of interactions between a single pair of atoms in a quantum state are a corner stone of quantum chemistry. Yet, the number of demonstrated techniques that enable observation and control of the outcome of a single collision is still small. Hybrid atom-ion systems provide exquisite control over the physical state of both particles and allow to observe collisions of a single ultracold ion-atom pair. However, the necessary degree of control in the particles preparation and detection often severely limits the range of investigated atomic and molecular species. In this work, we report on a new technique to probe the inelastic reactions between a single ion and a single atom using the tools of quantum logic. A spectator logic ion, which is fully experimentally controlled, enables to probe a single chemical reaction that occurred on a co-trapped ion, on which we have a limited control. We demonstrate this method by measuring the exothermic hyperfine spin-exchange rate of an ultracold rubidium atom and four different isotopes of strontium ion. The reaction is detected in a single-shot with high efficiency. We show that by tuning this method, it can be used for detecting elastic and endothermic reactions. The presented technique can be implemented for detection of reaction cross-sections, quantum resonances and reaction dynamics of atomic and molecular species that have a limited accessibility. |
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V01.00004: Enhanced positron binding to molecules containing π bonds. James R Danielson, Soumen Ghosh, Clifford M Surko Observation of vibrational Feshbach resonances (VFR) in the annihilation spectra of positrons on molecules provides a direct measurement of the positron-molecule binding energy εB [1]. New annihilation measurements are presented for a series of ring hydrocarbons with different numbers of π bonds. The measurements show that adding π bonds significantly increases the positron binding energies of these molecules. This is similar to that seen in other molecules; however, for these molecules, the global molecular parameters usually considered (i.e., geometry, polarizability, and dipole moment) are approximately constant, and so the observed differences can be attributed to changes in the nature of the bonds. The molecular ionization potential (IP) is an exception: The inclusion of π bonds tends to decrease the IP, and this is well correlated with increases in εB. However, benzene does not follow this trend: both IP and εB are larger than for the other unsaturated six-carbon rings. These results will be discussed in relation to the importance of electron-positron correlation effects (such as virtual positronium formation) on εB [2]. |
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V01.00005: Positronium Scattering by CO and LiF Robyn S Wilde, Myranda K Selvage, Ilya I Fabrikant Experimental measurements of the total cross section for scattering of Positronium (Ps) by various atomic and molecular targets are very similar to electron scattering cross sections above the Ps ionization threshold [1]. Using a Free Electron Gas model [2] we have previously calculated elastic scattering cross sections for Ps scattering by the homonuclear diatomic molecules N2 and O2 as well as CO2 [3]. To obtain the total scattering cross section we added the Ps ionization cross section which was computed using the binary encounter method. Our calculations confirmed that the total cross section for electron and Ps scattering is similar above the Ps ionization threshold. In the present work we extend our calculations to include the heteronuclear diatomics CO and LiF. For CO we again see a similarity between the electron and Ps cross sections. While there are no experimental results for either molecule in the gas phase there are experimental results for Ps scattering by a LiF surface [4]. Our Ps-LiF ionization cross sections may help with the interpretation of these results. |
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V01.00006: The dynamics of a single trapped ion in a high density media: a stochastic approach Mateo Londoño, Jesús Pérez Ríos, Javier Madroñero In this work, we use a stochastic formulation, based on the Langevin and generalized Langevin equation, to describe the dynamics of a trapped ion surrounded by a cloud of ultracold atoms and in the presence of micromotion excess. This formulation allows us to explore the ion's dynamical aspects and the ion's sympathetic cooling by the atomic bath. Furthermore, stochastic force modeling using different noises enables us to explore the role of bath correlations in ion dynamics. Finally, our results bring a new perspective and novel insights with respect to traditional simulations based on hard-sphere molecular dynamics. |
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V01.00007: Anti-Alpha Particle Impact Ionization of H Michael S Pindzola, TG Lee Anti-alpha particle ionization cross sections are calculated |
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V01.00008: Effect of Continuum Electrons on Superconfiguration Electronic Structure Nathanael Gill, Christopher J Fontes, Charles Starrett Accurate calculations of opacities of plasmas often require explicit account- ing of a large number of atomic configurations in order to obtain reasonable agreement with experimental spectra. The problem of accounting for the most influential configurations can become especially difficult for plasmas at so-called warm dense matter conditions, when the charge state distribution of ions is spread over many ion stages and therefore the number of relevant atomic con- figurations can easily exceed one billion. The superconfiguration concept was developed to treat this problem by formally averaging over all possible configura- tions in order to obtain a representative atomic structure [1,2]. We present a new implementation of the superconfiguration approach which self-consistently in- cludes the influence of continuum electrons when determining the atomic struc- ture, and we analyze the impact of such an approach on spectral calculations in plasmas with significant populations of low-energy continuum electrons. |
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V01.00009: COLD ATOMS, IONS, MOLECULES, AND PLASMAS
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V01.00010: Magnetic moment reconstruction of cold atoms using direct imaging and prospects for measuring magnetic sublevel distributions Gehrig M Carlse, Alexander Pouliot, Thomas Vacheresse, Adam C Carew, Hermina C Beica, Shoshana Winter, A Kumarakrishnan We describe a simple time-of-flight technique for measuring the magnetic moment of an optically pumped magneto-optical trap.* The technique relies on free-expansion imaging of a cold atom cloud in a small magnetic field gradient without the need to detect spatial separation of magnetic sublevels. We find that the effective acceleration of the cloud can be used to characterize extreme state optical pumping. In the general case, we show that the integrated displacement of the falling cloud can be accurately modeled using rate equation simulations of magnetic sublevel populations, and knowledge of local magnetic fields, field gradients, and light intensities. The agreement between the model and the data allows the reconstruction of magnetic moments and suggests that this technique may be suitable for the measurement of population distributions over a range of optical pumping conditions. |
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V01.00011: Progress towards direct laser cooling and trapping of CaH molecules Jinyu Dai, Qi Sun, Sebastian Vazquez-Carson, Debayan Mitra, Tanya Zelevinsky The past decade has seen impressive progress in the field of direct laser cooling and trapping of molecules, extending to new candidate platforms for quantum computing, quantum simulation, precision measurement and metrology. Here we present our progress towards laser cooling and trapping of CaH molecules, which could serve as a precursor to produce ultracold hydrogen gas. We present experimental results on transverse Sisyphus cooling of a cold beam of CaH molecules. We obtain good agreement with optical Bloch equation and Monte Carlo simulations and establish that a high scattering rate (~106 photons/s) is achievable for this molecule. Next, we present our progress towards longitudinal white-light slowing of the molecular beam. With the application of the first three vibrational repumps, we expect to slow the molecular beam forward velocity to within the capture range of a magneto-optical trap (MOT) without significant loss to higher vibrational states. We describe our plan and progress towards the assembly of an ultrahigh-vacuum chamber and RF coils that will be used to generate an AC MOT of CaH molecules. Finally, we present potential dissociation pathways that could be implemented to create an ultracold sample of atomic hydrogen. |
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V01.00012: A dense magneto optical trap of cadmium atoms Simon Hofsaess, Sidney Wright, Eduardo Padilla, Sebastian Kray, Maximilian J Doppelbauer, Boris Sartakov, Jesus Perez Rios, Gerard Meijer, Stefan Truppe We present a dense magneto-optical trap (MOT) of cadmium atoms, rapidly loaded from a buffer gas cooled beam. We use the 1P1 ← 1S0 transition near 229 nm to trap all eight stable bosonic and fermionic isotopes by using a Zeeman slower. We characterize the loading rate, the trap frequency and measure the density in absorption. The lifetime of the MOT is limited by ionization but can be enhanced by detuning the laser in between shots to allow for accumulation. Cadmium is an excellent test species for our MOT apparatus as it shares many properties with the more complex case of aluminum monofluoride (AlF) molecules, which we plan to capture with this setup. |
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V01.00013: Progress Towards Programmable Strontium Atom Arrays Aaron Holman, Weijun Yuan, Siwei Zhang, Quan Gan, Chun-Wei Liu, Max Aalto, Matthew Molinelli, Xiaoyan Huang, Nanfang Yu, Minho Kwon, Sebastian Will We report on progress towards realizing a platform for programmable arrays of strontium atoms. Atom arrays have rapidly become a paradigm for exploring quantum systems, with the rich internal structure of alkaline earth atoms enabling new research avenues. On route to this goal, we demonstrate a novel dispenser-based atom source that is compact and adaptable for other experiments. Using optical tweezers generated by holographic metasurfaces, we explore trapping of atoms in a diverse set of geometries relevant to condensed matter systems, such as quasicrystals and twisted bilayer graphene. The optical tweezers operate at a magic wavelength for strontium. The setup is geared towards creating highly entangled many-body quantum states that display subradiance. In addition, our platform lends itself for applications in quantum simulation and quantum computation. |
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V01.00014: An Effective Approach for Teaching Laboratory Courses on Laser Spectroscopy and Atom Trapping Alexander Pouliot, Hermina C Beica, Gehrig M Carlse, Shoshana Winter, Carson Mok, Brynle Barrett, Robert Berthiaume, Andrew Vorozcovs, Fadi Yachoua, Nima Afkhami-Jeddi, Monika Aggarwal, Kevin B Borsos, Thomas Vacheresse, Raanan Marants, A Kumarakrishnan We present an overview of experiments covered in two semester-length laboratory courses dedicated to laser spectroscopy and atom trapping*. These courses constitute a powerful approach for teaching experimental physics in a manner that is both contemporary and capable of providing the background and skills relevant to a variety of research laboratories. The courses are designed to be accessible for all undergraduate streams in physics and applied physics as well as incoming graduate students. In the introductory course, students carry out several experiments in atomic and laser physics. In a follow up course, students trap atoms in a magneto-optical trap and carry out preliminary investigations of the properties of laser cooled atoms based on the expertise acquired in the first course. We discuss details of experiments, impact, possible course formats, budgetary requirements, and challenges related to long-term maintenance. |
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V01.00015: Apparatus for Cooling and Trapping Potassium Atoms David Loos, Mason Hayes, Jared Echternach, Jonathan P Wrubel We describe our experimental apparatus for cooling and trapping potassium at Creighton University. There are three unique aspects of our experiment: a hybrid quadrupole/octupole 3D magneto-optical trap, a high-Q radio-frequency resonator to induce a Feshbach resonance, and a modified White and Scholten compact diffraction wavemeter for laser characterization. |
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V01.00016: Simulation of Decelerating Metastable Hydrogen with the Bichromatic Force Nathaniel D McDonough, Tharon D Morrison, Gerald Gabrielse Many important measurements of atomic hydrogen's structure (for example the 1S-2S transition) are currently limited by velocity-related uncertainties like transit-time broadening and second-order Doppler shifts. Laser cooling a hydrogen beam below 4 K cryogenic temperatures will enable unprecedented measurement precision to be achieved. Independent of our Lyman-α laser cooling pursuits, we here point out the two color bichromatic force is a feasible alternative method to decelerate the atoms when specific 2S-nP Balmer transitions are used. The bichromatic force facilitates momentum exchange entirely with absorption and stimulated emission, thus it is possible to use a transition that is not closed (like a Balmer line), so long as deceleration is accomplished before spontaneous emission from the nP excited state occurs. The Balmer-ε (2S-7P) and higher lines have this rare feature, and the ≈1 m/s recoil velocity implies 102 m/s deceleration should be possible. We employ a three-state model to simulate the force on a beam of cryogenic atoms which reveals deceleration and compression of velocity space on ∼100 ns time scales. |
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V01.00017: Velocity Selective Resonances from a Novel Optical Force Yifan Fang, Edoardo Buonocore, Michael Wahl, Harold J Metcalf The strength of optical forces on atoms derives from the rate of exchange of momentum between light and atoms. We describe the use of multiple Adiabatic Rapid Passage (ARP) sequences to increase both the excitation and emission rates, and thereby strengthen the optical force to FARP » Frad Ξ ħkγ/2. This huge optical force results from coherent momentum exchange between atoms and light at a high repetition rate. It is done with counterpropagating beams of chirped, pulsed light that alternately produce absorption followed by stimulated emission [1], and has been demonstrated for atoms initially at rest. We have explored how this very strong force depends on atomic velocity and found surprising enhancement at certain velocities [1]. These will be discussed but they seem to occur when atoms travel approximately an integer number of wavelengths between ARP pulses. The current detector resolution is limited by the longitudinal velocity spread of atoms in the beam, but we are building a new velocimetry system that will ameliorate this. |
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V01.00018: Preparing a high optical depth cold atomic ensemble for a light matter interface in free space Jacob Nelson, Elohim Becerra Atomic ensembles provide a versatile light matter interface for the preparation of complex quantum states. Light-matter interfaces have allowed for the preparation of highly squeezed spin states and complex non-Gaussian states based on measurement backaction for metrology and quantum information processing. We are working towards preparing a large atomic ensemble of cold cesium atoms with high optical depth in free space to increase the efficiency for quantum state preparation based on measurement backaction. We investigate methods to optimize the optical depth of the atomic ensemble by controlling the laser parameters and magnetic fields in our magneto optical trap. Our goal is to achieve an optical depth of 300 or higher. |
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V01.00019: Towards a simple apparatus to realize a magneto optical trap of atomic Ti Jack Schrott, Dan Stamper-Kurn, Scott Eustice, Diego Novoa, Lely Tran, Yubin Hu Previous work suggests several transition metals can be laser cooled out of a metastable excited state. We propose a simple method for loading a 3D magneto optical trap of Ti from a Ti-Sublimation pump fliment with optical pumping to populate the metastable state. Ti is a refractory metal with low vapor pressures at temperatures below 1300C. Nonetheless, a resistively heated TiMo filament, commonly used in Ti-Sublimation pumps will emit a large flux of gas-phase Ti. We expect 3D MOT loading rates of up to ~1e12 atoms/sec and MOT lifetimes of ~100ms due to leakage into dark states. We report studies of optical pumping of Ti into the laser coolable metastable state and progress towards loading these atoms into a 3D MOT. |
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V01.00020: Towards Sawtooth Wave Adiabatic Passage in a grating magneto optical trap Ananya Sitaram, Peter K Elgee, Daniel S Barker, Gretchen K Campbell, Stephen P Eckel, Nikolai N Klimov Cold alkaline-earth atoms are a promising platform for a variety of mobile quantum technologies, such as atomic clocks and interferometers. Most alkaline-earth experiments use a 6-beam magneto-optical trap (MOT) for initial cooling and trapping, which requires a large optical setup, limiting fieldability. One alternative to the typical 6-beam MOT is a grating MOT, which uses one input laser beam and a nanofabricated diffraction grating to create the rest of the trap. We report our realization of a broad-line grating MOT of 87Sr. We also report on progress towards implementing sawtooth wave adiabatic passage (SWAP) in a non-orthogonal beam geometry. SWAP assisted cooling simplifies the realization of a narrow-line grating MOT with 87Sr and enhances capture of bosonic isotopes. Realization of an intercombination-line grating MOT with 87Sr is an important step towards compact clocks and interferometers using alkaline-earth atoms. |
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V01.00021: An ultracold indium machine Xianquan Yu, Jinchao Mo, Tiangao Lu, Ting You Tan, Travis L Nicholson Despite the remarkable progress made by ultracold physics in the past few decades, most atomic species have not been cooled to ultracold temperatures. Many atoms that remain unexplored in the ultracold regime have unique properties, and they could form the basis for numerous interesting measurements. Atoms in the boron group---otherwise known as the “triels”---are one such species. They contain optical clock transitions, microwave resonances, magnetic Feshbach resonances, spatial anisotropy, and many other such interesting properties never before present at once in a quantum degenerate gas of atoms. |
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V01.00022: Accurate prediction of equilibrium structures for heavy element containing molecules pertinent to laser cooling Chaoqun Zhang, Lan Cheng Accurate prediction of molecular geometries is a central subject in electronic structure theory. Accurate calculation of vibronic branching ratios for laser coolable molecules requires high-accuracy calculations of molecular geometries for both ground state and excited states. Using exact two-component theory and analytical spin-orbit coupled-cluster gradients, we present calculations of molecular equilibrium structures and vibrational frequencies for molecules containing heavy atoms with essentially quantitative accuracy, e.g., < 0.001 Å for bond lengths and ~ 1 cm-1 for vibrational frequencies. We demonstrate the accuracy and applicability of these methods using calculations for laser coolable molecules containing heavy atoms. |
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V01.00023: Rydberg-Dressed Ising Interactions for Floquet-Enhanced Spin Squeezing Jacob A Hines, Shankari V Rajagopal, Gabriel L Moreau, Nazli U Koyluoglu, Monika H Schleier-Smith Rydberg dressing provides a versatile way to create strong coherent interactions between ground-state neutral atoms. These local, optically controlled interactions can theoretically be used to create metrologically useful entanglement, such as spin squeezing in an atomic ensemble. We present progress on spin squeezing in a cesium atomic clock with Ising interactions produced by single-photon coupling to nP states. The resulting finite-range interactions generate an analog of one-axis twisting, which is well-established for squeezing in all-to-all-coupled systems. We implement optimized pulse sequences incorporating Rydberg dressing and an effective transverse field to generate strong twisting dynamics with limited decoherence. The inclusion of the transverse field additionally opens prospects for Floquet engineering to realize a modified two-axis countertwisting Hamiltonian for optimized squeezing. |
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V01.00024: Modeling Coherent Laser Excitation of Mixed Three-Atom States Near Förster Resonance Emily Hirsch, Jason Madison, Tomohisa Yoda, Lucy Shamel, Dilara Sen, Hunter Strah, Aaron Reinhard State-mixing interactions can compromise the effectiveness of the Rydberg excitation blockade near Förster resonance. We detect a significant number of atoms in dipole-coupled product states immediately after laser excitation to a target Rydberg state. Under certain conditions, this is due to excitation of mixed three-atom states. We use a rotary echo technique to demonstrate the coherence of the evolution of these three-atom states. In this poster, we describe a Monte Carlo simulation that allows us to interpret our rotary echo data. We also explain a theoretical model for laser excitation in a coupled three-atom basis,1 and show that it describes our data well for short pulse durations and low Rabi frequency. |
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V01.00025: Rotons in a bilayer Rydberg-dressed bosons Bilal Tanatar, Fatemeh Pouresmaeeli, Saeed H Abedinpour We study the dynamics of a bilayer system of bosons with repulsive soft-core Rydberg-dressed interactions within the mean-field Bogoliubov-de Gennes approximation. We find roton minima in both symmetric and asymmetric collective density modes of the symmetric bilayer. Depending on the density of bosons in each layer and the spacing between two layers, the homogeneous superfluid phase becomes unstable in either or both of these two channels, leading to density and pseudospin-density wave instabilities in the system. Breaking the symmetry between two layers, either with a finite counterflow or a density imbalance renormalizes the dispersion of collective modes and makes the system more susceptible to density-wave instability. |
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V01.00026: Towards quantum simulation with sodium atoms in Rydberg states Luheng Zhao, Mohammad Mujahid Aliyu, Krishna Chaitanya Yellapragada, Huanqian Loh Arrays of neutral atoms in optical tweezers have become a reliable platform for implementing quantum simulation and computation protocols. Their long lifetimes allow for repeated interrogations without loss, while the ability to excite the atoms to Rydberg states introduces strong interactions between particles, thereby opening the path for studies of strongly interacting systems, exotic quantum phases and quantum magnetism. So far, we have used D1 magic wavelength tweezers to scale up the atom array size. Here, we report on our progress towards realizing interactions between the singly trapped sodium atoms. After initializing the atomic state by optical pumping, we couple the atoms to the Rydberg state via two-photon transitions. These techniques combined with the scaling up of array sizes will enable us to explore intricate many-body systems with tunable interactions. |
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V01.00027: Prediction for a Dirac Spin Liquid in a Rydberg Tweezer Array Marcus Bintz, Vincent S Liu, Johannes Hauschild, Michael P Zaletel, Norman Y Yao Tweezer arrays of neutral Rydberg atoms are an increasingly capable and versatile experimental platform for studying quantum many-body physics. One alluring target for such experiments is the analog simulation of exotic phases of quantum matter. In this work, we numerically investigate a long-range antiferromagnetic XY spin model that naturally arises in tweezer arrays: the effective spin is encoded in a pair of Rydberg states, and the atoms interact through dipolar exchange. Large-scale iDMRG calculations reveal the ground state of this model on the kagome lattice to be a gapless Dirac spin liquid. We show how this highly-entangled phase can be adiabatically prepared from a simple paramagnet initial state. We also explore several avenues for experimentally characterizing the Dirac spin liquid, including detection of edge modes and Friedel oscillations by quantum gas microscopy. |
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V01.00028: Electromagnetically induced transparency in Rydberg hot atoms using polarization spectroscopy and Laguerre-Gaussian laser modes Naomy Duarte Gomes, Barbara da Fonseca Magnani, Jorge Douglas Massayuki Kondo, Luis G Marcassa In this work, electromagnetically induced transparency (EIT) is investigated in a three-level ladder of rubidium atoms at room temperature using a Rydberg state and a Laguerre-Gaussian mode laser. The probe field, which is Gaussian, couples the 5S1/2 → 5P3/2 states. The control field, which can be in either Gaussian or Laguerre-Gaussian (LG) modes, couples the 5P3/2 → nD states, with n = 42. The EIT spectrum is measured through polarization spectroscopy (PS), resulting in a dispersive signal. The dispersive EIT linewidth is narrower for the LG mode than for a Gaussian mode, which is due to the spatial distribution of the LG profile. We have implemented a probe transmission model using a simplified Lindblad master equation, which reproduces well the experimental results. The use of the PS signal eliminates the need to fit a curve when measuring EIT linewidths while still providing subnatural widths. |
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V01.00029: Resonant energy transfer within the Stark manifold Yuan Jiang, Catherine D Opsahl, Alicia Handian, Thomas J Carroll, Michael W Noel Resonant energy exchange among ultracold Rydberg atoms has been used in quantum computing, quantum simulation, and studies of dynamics in closed quantum systems. Prior studies of dipole-dipole interaction have focused on systems with few initial and final states. We have observed interactions among atoms excited to states within the Stark manifold. The harmonic nature and large number of states in the manifold allow for rich dynamics in this energy exchange process. |
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V01.00030: Effects of microwave cavity on Rb Rydberg atoms Luis G Marcassa, Naomy Duarte Gomes, Barbara Magnani, Cristian A Mojica-Casique, Marcos R Cardoso, Daniel Varela Magalhães In this work, we present lifetime measurements of Rb Rydberg states using a sample of cold atoms held in a magneto-optical trap, which is performed inside a microwave cavity. The Rydberg states are excited through a two-photon transition, and detected by pulsed field ionization. Our measurements are larger than the predictions by well established theoretical model. We have implemented a theoretical model, which considers the vacuum chamber as a lossy Fabry-Perot cavity with a discrete spectrum, and compared with experimental results. Such comparison indicates that the blackbody radiation contribution on Rydberg state lifetime can be decreased by using a small size metal cavity, without the need of cryogenic environment. This effect may have application in experiments where longer Rydberg lifetimes are required. |
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V01.00031: Excitation of Rb Rydberg atoms in MOT inside a microwave cavity CESAR R MEDERO REGUERA, Naomy Duarte Gomes, Daniel Varela Magalhães, Luis Gustavo Marcassa Rydberg atoms are extremely sensitive to electromagnetic fields. In one hand, such sensibility makes them perfect candidates for electromagnetic field sensors. On the other hand, it is very inconvenient, because it makes very challenging to excite them to a single high quantum number state (n > 80), because spurious electromagnetic field can mix the atomic states. In this work, we intend to study the interaction of cold Rydberg atoms with microwave fields inside a microwave cavity. To investigate such interaction, we will build a magneto-optical trap inside a microwave cavity. The ground state atoms will be excited to a Rydberg state two-photon transition inside such cavity, which can be tuned to an given atomic transition between two Rydberg states. The Rydberg atoms will be detected by electromagnetically induced transparency spectroscopy (EIT). The microwave cavity will shield the atoms from blackbody radiation and any other spurious field; besides it will enhance the atom-photon interaction for a given frequency, increasing the sensitivity of the microwave signal. Preliminary results will be presented. |
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V01.00032: Slow thermalization in few-body Rydberg interactions Sarah E Spielman, Alicia Handian, Nina P Inman, Thomas J Carroll, Michael W Noel Through simulation, we investigate the long-time behavior of ultracold Rydberg atoms undergoing energy exchange via two-, three-, and four-body dipole-dipole interactions. Using a simplified model of atoms in a one-dimensional lattice, we calculate the entanglement entropy, level spacing statistics, and initial state survival probability. We vary the strength of the interaction by altering the lattice spacing and add disorder by randomly perturbing the positions of the atoms. While the two-body case rapidly thermalizes, we find that the three- and four-body cases exhibit slow thermalization that suggests potential non-ergodic behavior. In addition, we find that the always resonant interactions play a critical role in impeding thermalization. |
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V01.00033: Towards making KRb - Rb* triatomic ultra-long-range Rydberg molecules Lingbang Zhu, Yi-Xiang Liu, Matthew A Nichols, MingGuang Hu, Yu Liu Ultra-long range Rydberg molecules offer large permanent electric dipole moments, on the order of kilo-Debyes, providing a new platform to study quantum physics and chemistry such as quantum sensing, many-body quantum systems, and controlled cold chemical interactions. |
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V01.00034: Toward subradiant chains of individually trapped dysprosium atoms Sam R. Cohen, Damien Bloch, Igor Ferrier-Barbut Collective radiation modes in ensembles of atoms promise exciting applications to future quantum technologies. In particular, subradiance - where collective emission occurs significantly slower than spontaneous emission - could prove useful for controlling light, and is possible when the interatomic distance d < λ/2 (the wavelength of the emitted light). Additionally, interest in using lanthanides such as dysprosium (Dy) to investigate quantum systems has grown considerably in recent years, due in part to their rich electronic structure. Many of these atoms offer a range of linewidths for optical transitions allowing for a highly flexible control of systems of lanthanides. In this work, we report on progress in the building of an experimental setup to create arrays of single Dy atoms in optical tweezers taking advantage of Dy's rich level structure. |
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V01.00035: Optimization and Stabilization of Cooling Processes of Neutral Atoms with Machine Learning Nicholas Milson, Arina Tashchilina, Logan W Cooke, Joseph Lindon, Anna Prus-Czarnecka, Lindsay J LeBlanc When trapping and cooling atomic clouds for cold-atom experiments, cycle-to-cycle variations in the number of atoms can lead to unwanted fluctuations in final measurements. External parameter fluctuations, such as in ambient temperature and stray magnetic fields, are leading contributors to these variations, in addition to instabilities within the system itself. To understand the influence of each parameter on the atom number, we seek to measure and record many parameters over many experimental cycles and construct a model of the atom-number response. |
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V01.00036: Radio-frequency magneto-optical trap of 87Rb Qian Wang, Yuqi Zhu, Thomas K Langin, Varun Jorapur, David DeMille Recent progress on direct laser cooling and trapping of ultracold molecules shows this method’s potential to reach quantum degeneracy. However, the limited molecule number and density so far achievable and short blackbody-limited lifetime still present difficulties for further collisional cooling and reaching this regime.These problems can be mitigated by sympathetic cooling with 87Rb. |
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V01.00037: Detachable 2D MOT platform as a source of cold cesium atoms Jonathan Yang, Kaiyue Wang, Colin V Parker We have designed a detachable 2D Magneto-optical Trap (MOT) platform to provide us with a continuous collimated beam of cold cesium (Cs) atoms. This detachable 2D MOT platform requires only a single laser source; this beam is split 5 ways with each beam being reflected in both the horizontal and vertical directions with polarizations being accounted for. We load this source of cesium atoms into a main 3D MOT chamber and subsequently increase the magnetic field gradient and detuning to produce a compressed MOT (CMOT). The CMOT is then pulled into an optical molasses by further increasing the detuning and removing the magnetic field gradient. At this stage, the background magnetic field is minimized through the aid of compensation coils, whose current values are adjusted by minimizing the separation of the measured peaks between adjacent microwave Zeeman transitions of the ground F = 3 F = 4 states. This transition is driven with an external microwave source amplifier and a waveguide antenna with no horn. We will present the latest results of time-of-flight imaging, as well as comparisons of optical designs and vacuum pumping techniques. |
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V01.00038: Dual-wavelength frequency stabilization scheme for high melting temperature atoms Ziting Chen, Bojeong Seo, Mingchen Huang, Mithilesh Parit, Yifei He, Peng Chen, Gyu-Boong Jo Lanthanide atoms with a large magnetic dipole moment, such as erbium and dysprosium, have attracted significant attention in quantum simulation benefitting from strong dipole-dipole interactions and rich tunability. However, high melting temperature and a narrow linewidth (Γ) of optical transition for laser cooling require a demanding task for stabilizing the frequency of cooling lasers and preparing cold atomic samples. Here, in this poster, we introduce a simple solution of frequency stabilization for high melting temperature atoms, which does not require any additional instrument such as ultra-low expansion cavity, hollow cathode lamp, or iodine cell. With saturation fluorescence spectroscopy on atomic flux, laser frequency can be stabilized to 1Γ for the narrow 583 nm transition of erbium atoms. Detailed analysis and evaluation of the saturated fluorescence spectrum and performance of frequency locking will be presented. |
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V01.00039: Fully quantum simulation of laser cooling of multilevel atoms in three dimensions Arnon R Goldberg, Jarrod Reilly, Murray J Holland In the simulation and analysis of atom-laser interactions, and in particular laser cooling processes for systems containing multiple energy levels, we have typically relied on semiclassical approximations and analytic solutions. Recently, developments in computational speed and power have allowed us to study fully quantum numeric results in more complex systems than previously possible. This maintains the ability to study the effects of superpositions and atomic coherences, important at low temperatures. We present a fully quantum Monte Carlo wavefunction simulation method that allows us to model the wave function in three dimensions, and in limited systems with arbitrary non-degenerate energy manifolds. We employ this technique to examine multiple atomic systems in three dimensions, including doppler, polarization gradient, and grey molasses cooling. Our work is motivated by the desire to understand laser cooling in complex systems such as molecules that possess many internal degrees of freedom. |
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V01.00040: Experimental Realization of Multi-ion Sympathetic Cooling on a Trapped Ion Crystal Zhichao Mao, Yuzi Xu, Quanxin Mei, Wending Zhao, Yue Jiang, Xiuying Chang, Li He, Lin Yao, Zichao Zhou, Yukai Wu, Luming Duan Sympathetic cooling in large ion crystals is a necessary technology for ion-trap-based quantum memory, large-scale quantum computing and simulation that requires long runtime. In order to resist the decoherence induced by the motional heating or background collisions, it is of crucial importance to cool large ion crystals at runtime without affecting the internal states of the computational qubits. In this work, we propose that it is feasible to achieve cooling effects near global Doppler cooling limit by optimizing the choice of several adjacent cooling ions according to the collective normal modes. We also experimentally demonstrate the cooling dynamics of multi-ion sympathetic cooling with only two cooling ions on an ion chain. With increasing the crystal scale, a tiny fraction of ions suffices to efficiently cool the whole ion crystal. Despite employing a single ion species in this work, our scheme is also appropriate for dual-type qubits or ions with small mass difference. Our proposal can directly be generalized to larger 2D and 3D ion crystals. It thus provides an important enabling step for the future large-scale trapped ion quantum computing and long-time quantum memory. |
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V01.00041: Motion-selective coherent population trapping Sooyoung Park, Hyun Gyung Lee, Ryun Ah Kim We report progress of our experiment for sub-recoil cooling of Rb atoms in a 1D optical lattice outside the Lamb-Dicke limit. We use a cooling scheme of motion-selective coherent population trapping (MSCPT). MSCPT is our adaptation of the well-known velocity-selective coherent population trapping (VSCPT) for cooling alkali-metal atoms in an optical trap. A closed λ configuration for CPT is formed by two ground hyperfine transitions with the apex state coupled to an excited state via D transition. We use a circularly polarized trap so that the vector polarizability of Rb results in different well depths and hence different vibration frequencies for the two lower states of λ. Two-photon resonance condition for CPT then depends on the motional quantum number n, and we may tune the λ fields to select the pair of states with n = 0 for CPT. Finally, we apply Raman sideband cooling by driving the hyperfine transitions using two pairs of Raman beams tuned to the red sideband. |
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V01.00042: DEGENERATE GASES AND MANY-BODY PHYSICS
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V01.00043: Interaction Induced Motional Effects on the Facilitation Dynamics of Driven Rydberg Gases Daniel S Brady Rydberg atoms can interact strongly over very large distances leading to effects such as blockade or facilitation of excitations in a gas of atoms driven by a laser field. In the presence of slow decay processes this gives rise to complex many-body phenoma, such as self-organized criticality. Here, thermal motion of Rydberg atoms as well as mechanical effects of the interactions play an important role. |
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V01.00044: Mediated Interactions and Sound Propagation in a Degenerate 133Cs-6Li Bose-Fermi Mixture Geyue Cai, Krutik S Patel, Chang Li, Cheng Chin We present our work with Bose-Einstein condensates of 133Cs immersed in degenerate Fermi gases of 6Li. Excitations near the Fermi surface can mediate interactions between bosonic atoms, altering both the ground state and the dynamics of the condensate. Using a high-resolution microscope objective, we image and project optical potentials on the mixtures. The interspecies interactions can be tuned with a Feshbach resonance. |
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V01.00045: Spin- and atom-interactions in multimode cavity QED Brendan Marsh, Ronen Kroeze, David Atri Schuller, Jonathan Keeling, Benjamin L Lev Optical cavity QED provides a versatile platform with which to explore quantum many-body physics in driven-dissipative systems. Multimode cavities are particularly useful for exploring beyond mean-field physics. We highlight experimental progress towards simulation of driven-dissipative spin glasses. This involves demonstrating a strong, tunable-range, photon-mediated atom-atom interaction, a sign-changing interaction due to Gouy phases, and a spin-spin interaction in a spinful Bose-Einstein condensate. The joint spin-spatial degrees of freedom exhibit spinor self-organization as well as dynamical spin-orbit coupling. We highlight near-term experimental studies of few-body interacting systems exploring exotic, strongly correlated phenomena such as driven-dissipative spin glasses and quantum neural networks. |
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V01.00046: Extended mean-field theory of strongly correlated Bose polarons Nader Mostaan, Fabian Grusdt, Nathan Goldman A paradigmatic class of problems in quantum kinetic theory concerns the physics of mobile quantum impurities immersed in degenerate gases. In a condensed Bose gas, a mobile impurity leads to the formation of a quasiparticle termed Bose polaron, whose characteristics are strongly influenced by many-body effects. In particular, in the presence of an impurity-boson bound state, repulsive interaction among bosons becomes crucial for the system's stability, leading to a strongly correlated phase. We employ a novel variational ansatz to study the ground state of the Bose polaron in three dimensions, accounting for multiple occupations of the bound state and dressing by a coherent state of excitations in the Bose gas. We find that the repulsive inter boson interaction renders the ground state energy finite across a Feshbach resonance. For positive scattering lengths, a transition occurs when a single boson forms a bound state with the impurity at a scattering length significantly larger than the one predicted by non-interacting mean-field theory for the transition between attractive and repulsive polaron. Our ansatz can be readily extended to lower dimensions where the effect of quantum fluctuations becomes more prominent and to non-equilibrium settings to study the dynamics of Bose polaron formation. |
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V01.00047: Strongly interacting fluids in a Bose-Hubbard circuit Brendan Saxberg, Andrei Vrajitoarea, Gabrielle Roberts, Margaret G Panetta, Ruichao Ma, David Schuster, Jonathan Simon Synthetic photonic systems offer a robust platform for exploring the rich physics of strongly interacting and highly correlated quantum materials. We build a strongly interacting Bose Hubbard lattice with tunable on-site frequencies by capacitively coupling a 1D lattice of transmon qubits, where the anharmonicity of the transmons provides the effective onsite interaction. Individual readout resonators allow measurement access to each site and simultaneous measurements generate correlated density information about the quantum many-body state. Using these tools we study the static and dynamical properties of an adiabatically prepared fluid. We characterize the transition from the diabatic to adiabatic regime, quantify the long-range order of the lattice with two-body density correlations, and probe lattice entanglement by measuring the average purity of the lattice state. We also investigate transport properties by locally modulating the lattice potential and measuring the spectral response, probing the density of states of the strongly interacting fluid. |
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V01.00048: Few-body Physics in Microgravity Colby Schimelfenig, Jose P D'Incao, Maren E Mossman, Peter W Engels This poster discusses an experimental line of research directed towards the study of few-body physics in microgravity. Dilute quantum gasses are a prime tool for the investigation of few-body phenomena. While significant progress has been made in Earth-based experiments, a microgravity environment affords new opportunities: In the absence of a need to support atoms against gravity, ultradilute clouds and ultracold temperatures can be realized. Here, we present our studies utilizing NASA's CAL (Cold Atom Lab) facility for the investigation of Efimov physics. CAL is a quantum gas experiment installed onboard the International Space Station. In collaboration with scientists and engineers from the Jet Propulsion Lab (JPL, Pasadena), our team is conducting research directed toward the measurement of Efimov states in an ultracold cloud of potassium atoms. The current status and next steps of the experiment will be presented. |
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V01.00049: Magnetic solitons in a ferromagnetic spinor Bose-Einstein condensate XIAO CHAI, Li You, Chandra Raman Vector solitons, which are solitary waves occurring in multicomponent nonlinear media, can transport spin. In antiferromagnetic spin-1 Bose-Einstein condensates (BECs), the recently studied magnetic solitons feature themselves as a localized spin excitation traveling upon a balanced m=±1 condensate. In this work [1], we propose magnetic solitons in spinor Bose gas with ferromagnetic interaction, which in contrast, manifest themselves as a local spin-flip propagating on top of a spin-polarized background. We show that the existence of such solitons depends crucially on the ferromagnetic interaction and compare their properties with that of the well-known dark-bright solitons. Collisions between magnetic solitons in ferromagnetic spinor gas display intriguing features including bound state formation. A protocol for realizing such solitons in a 87Rb BEC is proposed for future experimental exploration. [1] Chai, X., You, L., & Raman, C. (2022). Magnetic solitons in an immiscible two-component Bose-Einstein condensate. Physical Review A, 105(1), 013313. |
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V01.00050: Energy dissipation in a binary superfluid gas by a moving magnetic obstacle Joon Hyun Kim, Deokhwa Hong, Kyuhwan Lee, Junghoon Lee, Jong Heum Jung, Yong-il Shin In this poster, we present our experimental study on the critical energy dissipation in an atomic superfluid gas with two symmetric spin components by an oscillating magnetic obstacle. Above a certain critical oscillation frequency, spin-wave excitations are generated by the magnetic obstacle, demonstrating the spin superfluid behavior of the system. When the obstacle is strong enough to cause density perturbations via local saturation of spin polarization, half-quantum vortices (HQVs) are created for higher oscillation frequencies, which reveals the characteristic evolution of critical dissipative dynamics from spin-wave emission to HQV shedding. Critical HQV shedding is further investigated using a pulsed linear motion of the obstacle, and we identify two critical velocities to create HQVs with different core magnetization. In addition, we also present our numerical study on the spin and mass current distributions near the moving magnetic obstalce in the binary superfluid. |
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V01.00051: Phases and dynamics of dipolar Bose-Einstein condensates in a rotating magnetic field Simeon I Mistakidis, Koushik Mukherjee, Panagiotis Kevrekidis, Hossein R Sadeghpour We unravel the static properties and the quench dynamics of dipolar Bose-Einstein condensates of Dysprosium atoms under the influence of a rotating external magnetic field. Relying on an extended Gross-Pitaevskii framework in 3D, we account for quantum fluctuations to the leading order and obtain the underlying phase diagram with respect to atom number and strength of contact interaction for various field orientations. For smaller values of contact interaction, a transition from a superfluid to a supersolid and then to a single or multiple dipolar droplets is captured, with the latter characterized by a non-vanishing global phase coherence. At orientation larger than the magic angle, the superfluid character dominates. These |
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V01.00052: Controllable Creation of Line Defects in Bose--Einstein Condensates with Internal Polytope Symmetries Samuel H Schulz, Arthur Xiao, Alina A Blinova, David S Hall, Tuomas Ollikainen, Magnus Borgh, Janne Ruostekoski Vorticity has played a fundamental role in physics, spanning a vast range of energy scales. Here, we experimentally create and theoretically study quantized vortices in magnetic phases of a spin-2 Bose--Einstein condensate with discrete internal polytope symmetries that we demonstrate explicitly. These vortices are non-Abelian, and are expected to exhibit unusual collision properties that leave behind conspicuous topological traces in the form of rung vortices. We show how filling the vortex line singularities with atoms in a variety of different phases leads to core structures that possess magnetic interfaces with rich combinations of discrete and continuous symmetries. We also present experimental evidence of time evolution towards fractionally quantized vortices. |
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V01.00053: Magnetically mediated hole pairing in fermionic ladders of ultracold atoms Dominik Bourgund, Sarah Hirthe, Thomas Chalopin, Petar Bojovic, Immanuel Bloch, Timon Hilker Doped antiferromagnets are prime examples of strongly correlated systems and hold the potential to shed light on the emergence of high-TC superconductivity in cuprate materials via pairing of mobile dopants. Here we report on the microscopic observation of hole pairing due to the magnetic correlations in a Fermi-Hubbard system by using quantum gas microscopy. We prepare two-leg ladders where we disable tunnelling between the rungs in order to suppress Pauli repulsion and thus drastically increase binding energy of the holes. Observing pairs of holes predominantly occupying the same rung of the ladder allows us to extract a binding energy slightly below the superexchange energy. For higher doping levels we find indications of crystallization of hole pairs. |
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V01.00054: Interaction effects on a topological spin pump Julius Bohm, Michael Fleischhauer, Dennis Breu, Maximilian Kiefer-Emmanouilidis We investigate the influence of the Hubbard interaction between spinful fermions in a one-dimensional topological spin pump using both exact diagonalization and DMRG simulations. The spin pump is realized by two Rice-Mele models for the spin components, whose parameter are varied in an adiabatic, cyclic and spin-dependent way preserving total time-reversal symmetry. |
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V01.00055: Observation of p-wave interactions between fermions in a deep optical lattice Frank Corapi, Vijin Venu, Peihang Xu, Robyn Learn, Mikhail Mamaev, Thomas Bilitewski, Jose P D'Incao, Ana Maria Rey, Joseph H Thywissen, Coraline J Fujiwara We report the first measurements of the energy spectrum of p-wave interacting fermions in a three-dimensional optical lattice. On-site p-wave interactions between a pair of ultracold spin-polarized fermionic atoms in the lattice are directly observed via RF spectroscopy. We control the interaction strength via a magnetic field and probe the interactions on both the repulsive and attractive side of a magnetic Feshbach resonance and reach the unitary regime. Measured energies are compared to solutions of two p-wave interacting particles in a simple harmonic trap. Coherent state manipulation between two free atoms and a strongly interacting doublon state is also demonstrated; wave-function overlap is extracted from the measured Rabi frequency. The measured lifetime of two interacting fermions is observed to be up to ten times larger than that of a free-space dimer. Introducing p-wave interactions into optical lattices may enable the experimental realization of new phases of matter, as well as the simulation of orbital dynamics in natural materials. |
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V01.00056: Effects of a rotating periodic lattice on coherent quantum states in a ring topology Kunal K Das, Hongyi Huang We study the landscape of solutions of the coherent quantum states in a ring shaped lattice potential in the context of ultracold atoms with an effective nonlinearity induced by interatomic interactions. The exact analytical solutions in the absence of lattice are used as a starting point and the transformation of those solutions is mapped as the lattice is introduced and strengthened. This approach allows a simple classification of all the solutions into states with periods commensurate/incommensruate with the lattice period and those with/without nodes. Their origins are traced to the primary dispersion curve and the swallowtail branches of the lattice-free spectrum. The commensurate states tend to remain delocalized with increasing lattice depth, whereas the incommensurate ones may be localized. The symmetry and stability properties of the solutions are examined and correlated with branch energies. We identify difference of significance between positive and negative nonlinearity. The crucial importance of rotation is highlighted by its utility in continuously transforming solutions, and accessing in a finite ring with a few sites the full spectrum of nonlinear Bloch waves on an infinite lattice . |
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V01.00057: Floquet Flux Attachment in Cold Atomic Systems Helia Kamal, Jack Kemp, Yin-Chen He, Yohei Fuji, Monika Aidelsburger, Peter Zoller, Norman Y Yao Flux attachment provides a powerful conceptual framework for understanding certain forms of topological order, including most notably, the fractional quantum Hall effect. The conventional picture states that strong interactions can have the net effect of binding flux quanta to underlying particles, leading to either composite fermions or bosons. Despite its ubiquitous use as a theoretical tool, directly realizing flux attachment in a microscopic setting remains an open challenge. Here, we propose a simple approach to realizing flux attachment in a periodically driven (Floquet) system of two-component spins or hard-core bosons with nearest-neighbor interactions. We do so by demonstrating that such a system naturally realizes correlated hopping interactions that have a sharp connection with flux attachment. For a hard-core bosonic model on a bipartite square lattice, we find evidence that Floquet flux attachment stabilizes the bosonic integer quantum Hall state. We further explore the surrounding phase diagram as a function of two natural parameters and discover a surprisingly rich variety of phases, including a gapless phase best characterized as a composite Fermi liquid. Finally, we propose an experimental blueprint for realizing our protocol in ultra-cold atomic systems. |
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V01.00058: Towards a Fermi Gas Microscope with Tunable Lattice Geometry Lev H Kendrick, Muqing Xu, Anant Kale, Martin Lebrat, Markus Greiner We report on progress towards a next-generation optical lattice for quantum gas microscopy of ultracold fermionic lithium. By exploiting the interference between different lattice arms, the lattice geometry may be tuned to realize hexagonal, triangular, dimerized, quasi-1D, and non-bipartite square geometries, enabling the site-resolved study and control of Fermi-Hubbard physics beyond the standard square lattice bandstructure. Such nonstandard bandstructures are a key ingredient for studying correlated phases in the Hubbard model, such as the proposed spin liquid state in the triangular lattice model or the pseudogap phase of the square lattice model. Simultaneously, we improve on the state of the art in reducing technical noise in an optical lattice, with the goal of reducing heating rates to allow for longer experimental interrogation times. In addition to providing better energy resolution for the study of low-energy phenomena, this will also improve the prospects of adiabatic state preparation schemes, which may be crucial in reducing temperatures below the limits of current experiments to study the yet unexplored low-temperature regime of the Hubbard phase diagram. |
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V01.00059: Site-resolved imaging of Mott Insulators in a novel triangular optical lattice geometry Liyu Liu, Jirayu Mongkolkiattichai, Davis A Garwood, Jin Yang, Peter Schauss The triangular lattice Hubbard model is a paradigmatic model of a strongly correlated geometrically frustrated quantum system which exhibits a rich phase diagram, including a predicted spin liquid phase. This problem is numerically difficult due to the frustration and large ground state degeneracy. Quantum gas microscopes are at the forefront of quantum simulation, providing a direct detection of experimental realization of the Hubbard model on a single-site level. Here, we report on an implementation of a site-resolved fermionic Mott Insulator in a novel triangular optical lattice. Using a recycled circularly polarized laser beam, we form a stable triangular lattice which has a factor of 1.5 larger trap frequency than our previous record [1]. In our system, the ratio of the interaction to tunneling can be tuned via a Feshbach resonance and the lattice depth. The symmetry of the tunneling along the three lattice axes are examined by evaluating density-density correlations. We compare finite-temperature correlations in the triangular Fermi-Hubbard model with calculations from a numerical linked cluster expansion we implemented in our group. |
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V01.00060: Bilayer microscopy of spin and charge in a Fermi-Hubbard lattice Botond Oreg, Thomas R Hartke, Carter Turnbaugh, Ningyuan Jia, Martin W Zwierlein Quantum gas microscopes have provided unique opportunities to investigate correlations and thermodynamics of strongly interacting fermionic systems with unprecedented accuracy, including in-situ measurement of magnetic order with repulsive interactions and charge-density wave order with attractive interactions. In this work, we demonstrate the ability to extract the full charge information of a single band Fermi-Hubbard model. The method provides access to local correlations of the total density, enabling model-independent thermometry of low entropy samples through the fluctuation-dissipation theorem. We here also extract both spin and charge simultaneously from images of large, strongly-correlated systems by creating an additional spin-dependent potential during the separation of atoms. In addition, we show that this perpendicular superlattice can be used to coherently prepare equilibrium many-body states, and explore the crossover from single-layer to bilayer Fermi-Hubbard systems. |
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V01.00061: A programmable 2D Fermi-Hubbard simulator Max Prichard, Benjamin M Spar, Sungjae Chi, Hao-Tian Wei, Eduardo Ibarra Garcia Padilla, Kaden R Hazzard, Zoe Yan, Waseem S Bakr Fermi-Hubbard models are paradigmatic models for studying strongly correlated lattice fermions which can be cleanly realized in cold atom experiments. However, so far optical lattice experiments have been limited in both the attainable entropies and available geometries. Here we present an alternative quantum simulation platform based on optical tweezer arrays which combines deterministic single tweezer ground state loading and tunnel coupling between nearest neighbor sites. Building on prior work in 1D, we present a novel technique using a stroboscopically modulated tweezer array towards realizing the 2D Fermi Hubbard model in arbitrary lattice geometries. Combined with a bilayer imaging procedure which provides full spin-charge readout, this method allows us to load perfect band insulators in triangular, Lieb and ring geometries with up to 30 fermions. Our experiment opens the door to study Fermi-Hubbard physics in unexplored geometries which are predicted to host novel properties such as ferromagnetic ground states and quantum spin liquids. |
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V01.00062: Discontinuous Phase Transition in a Strongly Correlated Driven Lattice Lee C Reeve, Shaurya A Bhave, Jr-Chiun Yu, Emmanuel Gottlob, Georgia Nixon, Bo Song, Ulrich Schneider Discontinuous (first-order) phase transitions and the associated metastability play fundamental roles in nature, from ferromagnetism in solids to the false-vacuum decay in the early Universe. However, their underlying mechanism is poorly understood, particularly in many-body systems. |
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V01.00063: Realizing Correlated Electron States of Twisted Bilayer Graphene in an Optical Lattice Model Rahul Sahay, Stefan Divic, Daniel E Parker, Tomohiro Soejima, Shubhayu Chatterjee, Johannes Hauschild, Michael P Zaletel, Norman Y Yao Experiments on magic-angle twisted bilayer graphene (MATBG) have found that it hosts a plethora of strongly correlated phases as well as superconductivity. Owing to the size of the moiré unit cell and the resultant complexity of unbiased numerical simulation, a complete theoretical understanding of these phases remains an outstanding challenge. Here, we propose and numerically investigate a bilayer optical lattice model that captures the essential elements of MATBG. Namely, we study a spinful bilayer system of quarter-flux Hofstadter lattices subjected to opposite magnetic fields, equipped with both local Hubbard interactions and interlayer tunneling. We explore its phase diagram using the infinite density matrix renormalization group, finding numerous correlated phases at integer and fractional fillings of the lowest Hofstadter bands including phases analogous to the generalized quantum Hall ferromagnets of MATBG. We conclude by providing an experimental blueprint for realizing this model in near-term optical lattice setups. |
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V01.00064: Towards quantum many-body physics in two-dimensional triangular atom arrays Weikun Tian, Wen Jun Wee, Billy Jun Ming Lim, An Qu, Huanqian Loh Scalable, programmable triangle arrays of neutral atoms trapped in optical tweezers form a promising platform for quantum simulation of frustrated antiferromagnetic systems. Here we present a 20-by-20 triangle tweezer array with a loading rate of 78%, and the ability to image release and recapture single Rb atoms with fidelities exceeding 99%. We introduce a rearrangement protocol that allows us to generate a 16-by-16 defect-free triangle array in tens of ms and 40 moves on average. We also present our progress towards inducing Rydberg excitations between the trapped atoms. The combination of these techniques allows us to explore quantum many-body phases and dynamics in two-dimensional spin-frustrated systems. |
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V01.00065: Towards the implementation of extended Hubbard models in an erbium quantum gas microscope Lin Su, Alec Douglas, Robin Groth, Aaron Krahn, Anne H Hebert, Furkan Ozturk, Ognjen Markovic, Markus Greiner Quantum gas microscopes are a powerful tool for controlled single-site resolved studies of many-body quantum systems. In our erbium quantum gas microscope, we combine technical improvements such as fast cycle time and fast high-resolution imaging with the ability to implement extended Hubbard models with dipolar interactions between erbium atoms. Here we present the progress on creating a lattice system of erbium atoms by loading them into a low-disorder, 266 nm spacing optical lattice. Single-site resolution imaging is enabled by transferring the atoms into a variable-spacing accordion lattice, where we demonstrate single-site imaging with >99.5% fidelity imaging with less than 10 microseconds of resonant pulses. Finally, we discuss how we can leverage these capabilities for quantum simulation of exotic phases in a lattice system. |
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V01.00066: Manipulating non-Hermitian skin effect via electric fields Jianwen Jie, Yi Peng, Yucheng Wang, Dapeng Yu In non-Hermitian systems, the phenomenon that the bulk-band eigenstates are accumulated at |
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V01.00067: Domain wall dynamics of multi-domain spin structures in an ultracold Rb-87 gas Mehdi Pourzand, Olha Farion, Lindsay E Babcock, Jeffrey McGuirk We explore dynamics of a pseudo-spin-½ non-degenerate gas of Rb-87 atoms initialized in a state with three spin domains. We experimentally study how the interplay of coherent spin currents and diffusive pressure drives motion of the domain walls and dynamic generation of new domain walls as the system evolves in a spin-independent potential. Further, we explore the roles of symmetry and domain size on spin transport by comparing the dynamics of these domain walls with a two domain system in which the single wall is initialized away from the trap center. |
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V01.00068: Eccentric magnetic skyrmions generated from a magnetic domain wall with spin current in the ferromagnetic phase of spin-1 Bose-Einstein condensates Hiromitsu Takeuchi Spinful superfluids of ultracold atoms are ideal for investigating the intrinsic properties of spin current and texture because they are realized in an isolated, nondissipative system free from impurities, dislocations, and thermal fluctuations. This study theoretically reveals the impact of spin current on a magnetic domain wall in spinful superfluids. An exact wall solution is obtained in the ferromagnetic phase of a spin-1 Bose-Einstein condensate with easy-axis anisotropy at zero temperature. The bosonic-quasiparticle mechanics analytically show that the spin current along the wall becomes unstable if the velocity exceeds the critical spin-current velocities, leading to complicated situations because of the competition between transverse magnons and ripplons. Our direct numerical simulation reveals that this system has a mechanism to generate an eccentric fractional skyrmion, which has a fractional topological charge, but its texture is not similar to that of a meron. This mechanism is in contrast to the generation of conventional skyrmions in easy-axis magnets. The theoretical findings can be examined in the same situation as in a recent experiment on ultracold atoms. In terms of the universality of spontaneous symmetry breaking, unexplored similar phenomena are expected in different physical systems with the same broken symmetry. |
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V01.00069: GENERAL PRECISION MEASUREMENTS
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V01.00070: AC Stark Shift Cancellation in Hydrogen 2S-nS Spectroscopy Ryan Bullis, Cory Rasor, Samuel F Cooper, Adam Brandt, Dylan C Yost Hydrogen precision laser spectroscopy can provide a test of fundamental physics with the ability to determine constants such as the Rydberg constant and the proton charge radius. However, to rigorously test theory, multiple transitions need to be measured with a small fractional uncertainty. Unfortunately, many two-photon transitions require large laser intensities to acquire adequate signal-to-noise, resulting in significant AC Stark shifts. The AC Stark shift broadens the resonance in a beam style experiment and limits the fractional uncertainty with which the transition can be measured. Here, we present a method to mitigate the AC Stark shift in Hydrogen 2S-nS transitions through the addition of a laser with an opposite AC Stark shift coefficient to that of the spectroscopy laser. Simulations conducted using a density matrix model show that distortion of the lineshape due to the AC Stark shift can be significantly reduced with the addition of AC Stark shift cancelling radiation. In particular, our results show that resonance widths on the order of 50 kHz can be obtained and linecenter frequencies can be determined at the 100 Hz level with such a method. |
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V01.00071: Hunting for Hidden Photons in the Wilderness: the Search for Non-Interacting Particles Experiment (SNIPE Hunt) Michael A Fedderke, Saarik Kalia, Peter Graham, Jason E Stalnaker, Ibrahim Sulai, Erik B Helgren, Ryan P Smith, Arran T Phipps, Madison Forseth, Andres Interiano-Alvarado Recently, it was proposed that the Earth itself could act as a transducer for ultralight dark-matter detection [1]. In particular, interaction of kinetically mixed hidden-photon dark matter with the Earth and the surrounding space environment (e.g., the ionosphere) generates a characteristic coherent magnetic field signal pattern across the surface of the Earth that can be searched for using unshielded magnetometers [2]. We plan to search for signals from hidden-photon dark matter with Compton frequencies in the 0.1-100 Hz range by performing correlated measurements with a network of atomic magnetometers in relatively quiet magnetic environments (in the wilderness far from human-generated magnetic noise). |
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V01.00072: Search for exotic low-mass fields with a global magnetometer network Sami S Khamis, Ibrahim Sulai, Paul Hamilton The Global Network of Optical Magnetometers for Exotic physics searches (GNOME) is a network of geographically separated, time-synchronized, optically pumped atomic magnetometers searching for correlated transient signals that might herald exotic physics [1]. Quantum sensor networks provide an additional tool in multi-messenger astronomy to probe high-energy astrophysical events for signals by beyond-standard-model theories. We present a method to use the GNOME to search for coherent, intense bursts of exotic low-mass fields (ELFs) that could be produced alongside gravitational waves (GWs) [2] and fast radio bursts (FRBs). Candidate events are identified with a model agnostic excess power search [3] and subjected to a generalized likelihood test. Empirical distributions are employed to remove explicit assumptions about noise characteristics. We construct Feldman-Cousins confidence belts [4] to constrain detectable ELF signal amplitudes and couplings to standard-model fermions. |
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V01.00073: Helium-3 nuclear-spin oscillator for detection of exotic spin couplings Heather R Pearson, Dhruv Tandon, Jason E Stalnaker We report on a helium-3 nuclear-spin oscillator that uses a feedback mechanism to self oscillate in the presence of a leading magnetic field. Hybrid pumping of Rb atoms was used to polarize potassium and helium-3 spins in a vapor cell through spin-exchange collisions. The nuclear spins were tipped to start their precession about the leading field. The precession was detected via optical rotation of light detuned from the D1 transition in potassium. This signal was fed back to magnetic field coils surrounding the cell to sustain the oscillation of the helium-3 spins. We investigated the sensitivity of this system to the measurement of exotic spin couplings for potential application to the Global Network of Optical Magnetometers for Exotic physics (GNOME). |
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V01.00074: Towards King - plot nonlinearity measurements in Pd and Pd+ Ibrahim Sulai, Yicheng Wang King plots are the graphical representations of the linear relationships of the isotope shift of two transitions of the same element. Deviations of linearity in these plots may be sensitive to beyond the standard model (BSM) interactions of some new light boson to neutrons. As hyperfine structure and second order field shifts serve as sources of non BSM King plot nonlinearities, an ideal element to use in a King plot nonlinearity search is one with (1) a long chain of spin-zero isotopes, (2) measureable narrow transitions, and (3) small nuclear deformation. Palladium (Z= 46) is one such element with its five stable spin-zero isotopes. We describe our plans to carry out isotope shift measurements in Pd and Pd+ towards performing a King Plot nonlinearity test. |
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V01.00075: Search for Boson Stars Using the Global Network of Optical Magnetometers for Exotic Physics (GNOME) Dhruv Tandon, Heather R Pearson, Perrin C Segura, Sami S Khamis, Ibrahim Sulai, Derek F Jackson Kimball, Jason E Stalnaker Since the discovery of dark matter in our universe, numerous possible candidates have been proposed to explain its existence and composition. One of the candidates is the Ultralight axion-like particles, existing in the form of domain walls or boson stars, caused by topology or self-interactions. The Global Network of Optical Magnetometers to search for Exotic Physics (GNOME) looks for a transient signal caused by exotic-spin couplings as the Earth passes through such composite dark matter objects. We describe an analysis method for the GNOME data that is sensitive to bosons stars based on the excess power technique. |
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V01.00076: Developing a vector EIT magnetometer Mario Gonzalez Maldonado, Alex Toyryla, Daniel Rodriguez Castillo, Isaac Fan, Yang Li, John E Kitching, Jamie McKelvy, Andrey B Matsko, Eugeniy Mikhailov, Irina B Novikova We experimentally study a novel technique of detecting the magnitude and orientation of DC magnetic fields using electromagnetically induced transparency (EIT) resonances. Magnetic fields modify the separation between EIT spectrum peaks, independently of their orientation, allowing for magnetic field magnitude measurements. However, the resonance amplitudes depend on the field orientation relative to the light wave vector and polarization direction, making this system capable of vector measurements. Here we assess short-term stability and sensitivity of magnitude and field orientation measurements in 87Rb hot atomic vapor, using phase-modulated linearly polarized coherent light. |
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V01.00077: All-In-One Quantum Diamond Microscope for Rapid Sample Characterization. Connor Roncaioli, Donald P. Fahey, Matthew J Turner, Connor A Hart Negatively-charged nitrogen-vacancy (NV) defects in diamond possess optically pumpable spin states with long coherence times at room temperature useful to building highly-sensitive and robust magnetometers. For NV ensembles, a variety of factors can impact magnetometry performance, e.g. strain or nitrogen concentration, and numerous distinct setups are often required to fully characterize a sample. We present an all-in-one apparatus which combines many optical detection schemes into one platform, shortening the time required for characterization. Additionally, this design allows us to switch between multiple modalities and wide-field imaging, allowing us to correlate sample-wide parameter variation with performance. |
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V01.00078: Toward multi-channel magnetic resonance imaging with radio-frequency atomic magnetometers Igor M Savukov, Young Jin Kim Radio-frequency atomic magnetometers (RF AMs) can operate in a broad frequency range from kHz to MHz with a magnetic field tuning. Their sub-fT sensitivity is promising for many applications, especially in magnetic resonance imaging (MRI). At Los Alamos, we have designed a multi-channel RF AMs with the goal of applications in |
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V01.00079: A Tunable, High Power Interferometer Beam with Reduced Pointing Fluctuations and Wavefront Aberrations for 100-Meter Baseline Atom Interferometry (MAGIS-100) Jonah Glick, Yiping Wang, Zilin Chen, Natasha Sachdeva, Tejas Deshpande, Kenneth DeRose, Timothy 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 and 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 aberrations in the wavefront of the laser limits the ultimate sensitivity. We present the design and prototype test of a beam delivery system for MAGIS-100 informed by numerical simulations addressing the impact of laser wavefront aberrations on the atom cloud interference pattern, as well as a plan for measuring laser wavefront aberrations with the atoms on site. |
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V01.00080: Upgrades for the optical lattice atom interferometer Miguel Ceja, James Egelhoff, Cristian D Panda, Andrew Reynoso, Matthew Tao, Victoria Xu, Holger Mueller Atom interferometers are powerful tools for probing fundamental physics |
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V01.00081: Matter-wave Fabry-Pérot Interferometer for Gravimetry Patrik Schach, Alexander Friedrich, Enno Giese One promising candidate for high-precision gravimetry is atom interferometry. In contrast to light in optical interferometers, matter waves consisting of massive particles couple strongly to gravity, making them a tool suitable for gravimetry. In addition to gravity, the motion of atomic wave packets is manipulated by optical potentials that trap, guide or diffract the atoms. Contrary to classical waves, quantum physics allows for tunneling through forbidden regions and thus offers an additional tool to influence the atomic motion. |
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V01.00082: Next generation measurement of the fine-structure constant Andrew O Neely, Zachary R Pagel, Yair Segev, madeline r bernstein, Jack C Roth, Ocean Zhou, Stephanie Bie, Holger Mueller We present a next-generation atomic fountain designed to measure the fine-structure constant (alpha) as a test of the Standard model. Previous measurements in our group (Parker et al 2018) and at CNRS (Morel at al 2020) reported an accuracy of 200 parts-per-trillion and 80 parts-per-trillion respectively. Our improved atomic fountain seeks sensitivity to the 20 parts-per-trillion level. By driving Bragg diffraction using a beam with a large beam waist, systematic effects such as Guoy phase and effects from thermal motion of the atoms are minimized. A 5 meter tall, 50 cm wide vacuum chamber with optical baffles reduces the amount of scattered light and associated systematic effects. Offset simultaneous conjugate interferometer geometry cancels phase shifts from the gravity gradient and from diffraction phases. In order to achieve high momentum transfer with a larger beam area, we are constructing a kW-level quasi-CW laser system at 852 nm based on a high-efficiency free-space optical parametric amplifier. |
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V01.00083: Magnetic shield design for atom interferometry over a 100m baseline Yijun Jiang, Mahiro Abe, Samuel P Carman, Ben E Garber, Megan Nantel, Jan Rudolph, Hunter Swan, Thomas Wilkason, Jason M Hogan MAGIS-100 is a next-generation atom interferometer detector with a 100-meter baseline, currently under construction at Fermilab, that is designed to search for ultralight dark matter and to serve as a prototype for a future gravitational wave detector. Magnetic shielding over the entire baseline length is crucial to suppress unwanted phase shifts from the background magnetic field. Due to the segmented nature of the detector, our magnetic shield design consists of 17 identical sections, each with an octagonal cross section. Optimized overlap of multiple mu-metal sheets minimizes field inhomogeneity within each shield segment. Field penetration at the gaps between the segments is addressed by a combination of additional mu-metal couplers as well as active compensation coils. This design is compatible with the modular assembly procedure required by MAGIS-100, and accommodates structural, vacuum, and cable penetrations through the shield without unacceptable degradation of shielding performance. |
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V01.00084: Design and Characteristics of a Shaken Lattice Interferometer Incorporating Optical BEC Catie LeDesma, Kendall Mehling, Liang-Ying Chih, Murray J Holland, Dana Z Anderson Shaken lattice interferometry (SLI) utilizes ultracold atoms confined to an optical lattice. Sensing of inertial forces, for example, is achieved by modulating the lattice in a way that achieves the functionality of an interferometer – effectively splitting, propagating, reflecting, again propagating and then recombining the atomic wavefunction. The protocol for shaking is derived through machine learning techniques. For general sensing applications, shaking can consist of phase modulation of the optical lattice in which we consider the short-time average of the lattice position as unchanging, and also frequency modulation, which can be viewed in terms of transport of the atomic wavefunction. This work presents a shaken lattice system in which the lattice is loaded from an optical BEC system consisting of a crossed dipole trap. We present the apparatus for both phase- and frequency-modulation of the lattice that can be used to carry out inertial sensing. The system allows for tradeoffs in sensitivity and dynamic range that can be dynamically altered. Moreover, when combined with machine learning techniques, the signal transfer function can be tailored to achieve optimum performance for a specific application scenario. |
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V01.00085: Work on Improving the Precision of Helium Laser Spectroscopy Garnet Cameron, Jeffrey Pound, Jr., David C Shiner Precision measurements of the fine structure of the helium 2P state provides a proving ground for various experimental techniques as well as a test of the bound state quantum electrodynamics of the electron-electron interaction. Additional applications are to nuclear few-body physics and possible input to the fine structure constant determination. We update the study and status of: (1) Circular polarized atomic beam preparation pumping, with 99.3% purity, achieved with a custom, miniature, annular NdFeB magnet assembly [1], (2) Submicroradian stability and automated picomotor control of a coupled pair of fiber to free-space laser custom assemblies, and (3) In-house manufacture and filling of an iodine cell applied to an iodine stabilized HeNe 633 nm reference laser. Data collection to further identify sources of uncertainty which limit precision will be examined. |
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V01.00086: Exploring possibilities for dark matter detection via atomic interactions Ashlee Caddell, Ben Carew, Victor V Flambaum, Benjamin M Roberts We investigate low mass WIMPs (at the GeV scale) and their potential for direct detection via atomic interactions. Due to these WIMPs having masses comparable to nucleons, detection of any nuclear recoil in scintillation experiments proves difficult. Instead, a WIMP-electron interaction resulting in atomic ionisation could be detected in conventional scintillators due to an enhanced scattering rate [1, 2]. Considering this possibility is important for assessing recent experimental results and upcoming scintillator-based dark matter searches. |
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V01.00087: The force that started the universe - the vacuum force Han y yong Quan Vacuum force: F=δρ(Vv)——(1), δ proportional constant, ρ is the density of non-empty space, V is vacuum space, v is non-vacuum space, deformation (1) formula F=δ(ρV-m)= δρV -δm——(2), m is the mass of the universe without the beginning, δ is a proportional constant, that is, δm is a constant, so the magnitude of the vacuum force is determined by the size of the vacuum space and the density of the non-vacuum space. We can see from equations (1) and (2): when the particle volume v tends to zero, the magnitude of the vacuum force F=δρV. The density of the particle forms a vacuum, and the vacuum makes the density of the particle. The two complement each other, and in extreme cases, they jointly form a vacuum force. The vacuum space is proportional to the density of the particle, namely V=kρ, where k is the proportionality constant, ρ is the density of the particle, the size of the vacuum force F can be written as: F=δkρ2, δk is also a constant, the vacuum force is rewritten as: F=zρ2 , let z=1, this condition is not Newton. In the case of defining z=1, the unit of force is the Newton power. Vacuum force: F=ρ2. The density of the singularity is: 1097kg/m3, and the vacuum force at the big bang: F=ρ2=(1097)2=10194 Newton power. It can be seen that the vacuum force was very huge at the beginning of the universe. |
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V01.00088: Background magnetic field automatically compensated atomic magnetometer for bio-magnetic field sensing Yao Chen, Libo Zhao We described an atomic co-magnetometer which could effectively suppress the background fluctuating magnetic field as sensing the fast changing bio-magnetic field such as magnetic field from the brain. In the co-magnetometer, the hyper-polarized nuclear spin could produce a magnetic field which will shield the electron spin from the background fluctuation DC magnetic field. The nuclear spins like an automatic magnetic field shields and dynamically compensate the fluctuated background magnetic field. The magnetic field suppression effect is studied and we find that the suppression is closely related to several parameters such as the electron spin magnetic field, the nuclear spin magnetic field and the holding magnetic field. We show the magnetic field suppression ability of the magnetometer and magnetic field sensitivity is measured. Finally, we do a simulation for the magnetometer as it is utilized for detecting brain magnetic field under fluctuation background magnetic field. |
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V01.00089: LASERS AND QUANTUM OPTICS
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V01.00090: Frequency conversion through Rydberg states Erik G Brekke We demonstrate progress towards frequency conversion using four-wave mixing through Rydberg states in rubidium vapor. Excitation is accomplished through the intermediate 6p state using light at 420 nm generated through parametric four-wave mixing in combination with a 1015 nm laser. We demonstrate Electromagnetically Induced Transparency as a result of the Rydberg excitation transition. The application of microwaves then allows transitions between neighboring Rydberg states. When combined with a 780 nm laser, four-wave mixing through the Rydberg state can generate a beam at 480 nm. Even more promising is the potential to use six-wave mixing to accomplish microwave to optical frequency conversion. Microwaves resonant with a transition between nearby Rydberg states can cause the creation of light in the infrared. Several possible methods for accomplishing this conversion are outlined. |
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V01.00091: Quantum optics with hot atoms Robert Loew, Artur Skljarow, Benyamin Shnirman, Xiaoyu Cheng, Max Maeusezahl, Florian Christaller, Felix Moumtsilis, Harald Kuebler, Charles Adams, Hadiseh Alaeian, Tilman Pfau Strong interactions between atoms are known to cause nonlinearities at a few photon |
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V01.00092: Quantum networking and vortex field experiments with Strontium ions Mika Chmielewski, Denton Wu, Raphael Metz, Hao Wang, Andrei Afanasev, Norbert M Linke The strontium ion is an ideal candidate for medium-distance quantum networking due to an atomic transition at 1.1 μm, a wavelength compatible with existing fiber optic infrastructure. This transition eliminates the need for lossy photon conversion processes, allowing for direct remote entanglement on the kilometer scale. We discuss the design and assembly of a strontium trapped-ion system and report on current progress towards remote entanglement. The final qubit states in our photon-generation scheme lie in the D3/2 level and differ by Δmj = 2. We propose a scheme for driving this dipole-forbidden transition using a microwave vortex field, which carries a unit of orbital angular momentum in addition to the unit of photon spin. It will also allow us to make a first measurement of the ratio of E2 and M1 multipoles in this transition. |
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V01.00093: Towards quantum communication and entanglement distribution using solid-state defects integrated into a diamond nanophotonic system Can M Knaut, Daniel Assumpcao, Aziza Suleymanzade, Yan-Cheng Wei, Erik Knall, Pieter-Jan C Stas, Yan Qi Huan, Bartholomeus Machielse, Denis D Sukachev, Mihir K Bhaskar, David Levonian, Hongkun Park, Marko Loncar, Mikhail Lukin Silicon vacancy (SiV) centers integrated into diamond nanophotonic crystal cavities provide a high-efficiency spin-photon interface, strong spin-photon interaction, and access to auxiliary memory qubits. This platform recently has demonstrated memory enhanced quantum communication, efficient generation of shaped single photons, and high-fidelity gates between the SiV electron and the auxiliary 29Si nuclear spin, all using a single quantum network node. In this work, I will report on progress towards realizing a quantum link constituted by two SiV-based quantum nodes spatially separated by 20 meters and connected via optical fiber. Specifically, I will discuss methods of entanglement distribution, entanglement purification, and progress towards realizing a full quantum-repeater architecture. |
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V01.00094: An integrated Bell-state analyzer for high fidelity entanglement between trapped ion quantum computers Uday Saha, Edo Waks Trapped ions are excellent candidates for quantum computing and quantum networks because of their long qubit coherence times, ability to generate photons entangled with the ion’s qubit states, and high-fidelity single- and two-qubit gates. To connect multiple trapped ion quantum computers in a scalable way, we need an integrated Bell-state analyzer that can herald high fidelity entanglement between remote ions. Thin-film lithium niobate is an attractive platform to implement integrated Bell-state analyzer because its large transparency window and high electro-optic coefficient. However, trapped ions emit polarization-encoded photonic qubits, while thin-film lithium niobate devices are polarization-sensitive due to the large mode anisotropy created during the fabrication process. In this work, we design a photonic Bell-state analyzer on a thin film lithium niobate platform for polarization-encoded qubits. We optimize the device dimensions and input coupler to achieve polarization-insensitive operation. We achieve high fidelity entanglement between two trapped ions and determine > 99.99% fidelity in the final optimized device. The proposed Bell-state analyzer can scale up trapped ion quantum computing as well as other optically active spin qubits, such as color centers in diamond, quantum dots, and rare-earth ions. |
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V01.00095: A Dual Laser Frequency-Locking Module for NIR and Telecom Transitions in Alkali Atoms Rourke Sekelsky, Alexander N Craddock, Yang Wang, Mael Flament, Mehdi Namazi Precise laser frequency stabilization is critical to many atom-based applications including metrology, sensing, and quantum networking. Warm vapors of alkali atoms are attractive candidates for long-distance quantum networking because they possess transitions in the telecom wavelength that are naturally suited for transmitting over existing telecom infrastructure. However, unlike the well-developed saturated-absorption spectroscopy that provides a stable frequency reference for D-line transitions, accessing the telecom line (e.g., 5P to 6S) requires a two-photon transition, and a reliable locking method is yet to be developed. Here, we present a compact, polarization-agnostic module that provides spectra for both ground-state hyperfine transitions and two-photon telecom transitions in alkali atoms, allowing us to lock laser frequencies simultaneously to relevant NIR and telecom transitions with sub-linewidth precision. We report the locking mechanism (double-resonance optical pumping (DROP)), basic setup and operation, and locking characteristics including linewidth, precision, and long-term stability. |
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V01.00096: Atom recoil in collectively interacting dipoles using quantized vibrational states Deepak Aditya Suresh, Francis J Robicheaux Densely packed atom arrays have been shown to be useful in coherent control and quantum information, especially due to their high reflective properties. But as we move towards denser arrays, the forces due to the collective interactions become larger and cause unwanted decoherence in the system. Hence, we study the recoil resulting from the forces due to the near-field collective dipole interactions and far-field laser and decay interactions using quantized vibrational states for the atomic motion. Results show that the recoil effects are especially pronounced in highly subradiant systems which can lead to substantial decoherence. The contributions to the recoil and the dependence on the trap frequency of the different terms of the Hamiltonian and Lindbladian are also studied. These calculations are compared with previous results using the impulse model in the slow oscillation approximation. |
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V01.00097: Multichannel photoelectron phase lag across atomic barium autoionizing resonances Yimeng Wang, Chris H Greene Phase lag associated with coherent control where an excited system decays into more than one product channel has been subjected to numerous investigations. |
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V01.00098: Rapid Quantum Squeezing by Jumping the Harmonic Oscillator Frequency Mingjie Xin, Wui Seng Leong, Zilong Chen, Shau-Yu Lan Quantum sensing and quantum information processing use quantum advantages such as squeezed states that encode a quantity of interest with higher precision and generate quantum correlations to outperform classical methods. In harmonic oscillators, the rate of generating squeezing is set by a quantum speed limit. Therefore, the degree to which a quantum advantage can be used in practice is limited by the time needed to create the state relative to the rate of unavoidable decoherence. Alternatively, a sudden change of harmonic oscillator's frequency projects a ground state into a squeezed state which can circumvent the time constraint. Here, we create squeezed states of atomic motion by sudden changes of the harmonic oscillation frequency of atoms in an optical lattice. Building on this protocol, we demonstrate rapid quantum amplification of a displacement operator that could be used for detecting motion. Our results can speed up quantum gates and enable quantum sensing and quantum information processing in noisy environments. |
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V01.00099: Optical Recording of Bioelectric Signals Using Electrochromic Materials Burhan Ahmed, Kenneth Nakasone, Yuecheng Zhou, Erica Liu, Felix S Alfonso, Victoria Xu, Eric A Copenhaver, Bianxiao Cui, Holger Mueller Non-invasive methods with high spatial and temporal resolution are highly desirable in the study of electrical signals in biological cells. Developing such methods can help uncover how a network of interconnected neurons receives, stores and processes information. Optical recording through voltage-sensitive fluorescent probes provides a flexible method for measuring neuronal activity, but these methods often suffer from photobleaching and phototoxicity, limiting their application in studying these activities for longer durations. Here, we report on electrochromic optical recording (ECORE) which uses the electrochromic properties of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) to detect electrical activity in biological cells. We demonstrate the optically-recorded spontaneous action potentials in cardiomyocytes, cultured hippocampal and dorsal root ganglion neurons, and brain slices. ECORE provides a non-invasive, highly flexible method to study electrical activities in biological cells, while also enabling the long-term recording of these activities. |
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V01.00100: Creation of Singlet Strontium Rydberg States Using ULE-stabilized Laser Systems Robert A Brienza, Chuanyu Wang, Yi Lu, Soumya K Kanungo, F B Dunning, Tom C Killian The development of stable laser systems for creation of high-n strontium singlet Rydberg states via two-photon 5s2 1S0 → 5s5p 1P1 → 5sns 1S0 transitions is described. The required radiation at 461 and 413 nm is generated using frequency-doubled diode laser systems whose fundamental outputs are stabilized using a single very-high-finesse ultralow expansion (ULE) cavity. The lasers are tuned by directing a fraction of their fundamental output powers through fiber electro-optical modulators (EOMs) to generate sidebands that are then locked to the ULE cavity. This allows the lasers to be tuned over frequency ranges of up to ~1GHz by varying the EOM drive frequency. Whereas a similar scheme has been used to generate triplet strontium Rydberg atoms, the use of singlet Rydberg atoms results in a simpler excitation spectrum and, since S=0, simplifies the interpretation of observed phenomena. |
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V01.00101: Intra-Cavity Frequency-Doubled VECSEL System for Narrow Linewidth Rydberg EIT Spectroscopy Joshua C Hill, William Holland, David Meyer Stable, frequency-tunable lasers are crucial tools throughout various quantum science disciplines including computing, sensing, and timekeeping. Many of these applications require hundreds of milliwatts of output power at visible frequencies approaching the UV that are challenging to achieve directly. Such requirements are often met by using tapered amplifiers, frequency doubling and/or injection locking of additional lasers. Vertical external-cavity surface-emitting lasers (VECSELs) augmented by nonlinear optical frequency conversion offer an alternative method of producing such light with a reduced number of components and excellent output mode quality. Here, we demonstrate the use of such a laser with 690mW of output power at 480nm for Rydberg-state spectroscopy via electromagnetically induced transparency (EIT) in a room temperature vapor of 85Rb atoms, observing narrow linewidth EIT with full-width half-maximum of 1.75MHz. We also characterize the laser's frequency stability via the delayed self-heterodyne technique and direct comparison to a commercial external-cavity diode laser (ECDL). To our knowledge, this is the first spectroscopic demonstration of atomic features with widths on the order of 1MHz using an intra-cavity frequency-doubled VECSEL. |
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V01.00102: Characterization and Applications of Auto-locked Vacuum Sealed Diode Lasers for Precision Metrology Alexander Pouliot, Hermina C Beica, Adam C Carew, Andrew Vorozcovs, Nima Afkhami-Jeddi, Thomas Vacheresse, Gehrig M Carlse, Patrick Dowling, Boris Barron, A Kumarakrishnan We demonstrate the performance characteristics of a new class of vacuum-sealed, autolocking diode laser systems and their applications to precision metrology*. The laser is based on adaptations of a design that uses optical feedback from an interference filter and it includes a vacuum-sealed cavity, an interchangeable base-plate, and an autolocking digital controller. A change of the base-plate allows operation at desired wavelengths in the visible and near infrared spectral range, whereas the autolocking ability allows the laser to be tuned and frequency stabilized with respect to atomic, molecular, and solid-state resonances without human intervention using a variety of control algorithms programmed into the same controller. We characterize the frequency stability of this laser system based on the Allan deviation (ADEV) of the beat note and of the lock signal. We find that the ADEV floor of 2 × 10−12 and short-term linewidth of ∼200 kHz are strongly influenced by current noise and vacuum sealing. Reducing the current noise and cavity pressure decreases the ADEV floor and increases the averaging time at which the floor occurs, which is a signature of long-term stability. We also show that evacuating the cavity to ∼1 Torr reduces the range of the correction signal of the feedback loop by approximately one order of magnitude, thereby increasing the lock range of the controller. The long-term stability allows the laser to be incorporated into commercial gravimeters and lidar systems. |
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V01.00103: A 6-cm Cryogenic Silicon Cavity at 4 K with Crystalline AlGaAs Coatings Alexander Staron, Dhruv Kedar, Eric Oelker, William R Milner, John M Robinson, Jun Ye, Jialiang Yu, Thomas Legero, Daniele Nicolodi, Fritz W Riehle, Uwe Sterr Advancements in ultra-stable lasers locked to cryogenic resonators have enabled the rapid characterization of optical lattice clocks [1] and aided in setting new limits in tabletop investigations of fundamental physics [2]. The performance of these ultra-stable laser systems is fundamentally limited by Brownian thermal noise. For cryogenic cavities, the Brownian noise of the optical mirror coatings is the primary limitation, so characterizing coatings with low mechanical loss is an important step towards building narrower-linewidth lasers. We have developed a 6-cm single-crystal silicon cavity at 4 K with Al0.92Ga0.08As/GaAs crystalline mirror coatings [3]. We expect a fractional frequency instability of 1.3 x 10-17, a 5-fold improvement over an equivalent cavity geometry with dielectric coatings [4]. Frequency noise associated with the large birefringent mode splitting of these crystalline mirror coatings is identified [5]. We employ dual-tone probing of the two polarization eigenmodes of the cavity to cancel this birefringent noise. We present recent improvements to this ultra-stable laser system and investigations into the character of this observed birefringent noise. |
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V01.00104: A python-based software for wavelength stabilization of external cavity diode lasers Jacob B Thompson, Thomas E Zodda, Jack T Landrigan, Paul W Hess The Middlebury College ion trapping group is building a lab to trap atomic ytterbium ions for quantum information and spectroscopy experiments. We report on the development of a software program to wavelength stabilize our lab's multiple external cavity diode lasers (ECDLs) using feedback from a commercial wavemeter. By connecting to a Fizeau wavelength meter and multiplexed fiberoptic switch (Bristol Instruments), the python-based and open-source software can monitor the wavelength of multiple lasers simultaneously relative to their respective lock points. A proportional-integral-derivative (PID) algorithm calculates a correction voltage, generates it through connection to a DAC device (LabJack), and sends it to the ECDL piezo for feedback at rates of up to 30 Hz. The software includes robust features, including independent control of up to four lasers through a graphical user interface, the ability to rapidly toggle each laser between two different lock points, and wavelength monitoring via trend plots. The software has been demonstrated on both commercial and home built ECDLs, effectively eliminating their long-term wavelength drift. This long-term stability may be accompanied by an increase in the short-term noise by to 33% compared to when the lock is off, although additional testing relative to other frequency references is still needed to verify these results. |
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V01.00105: A Custom Design Stainless Steel Hot Sodium Vapor Cell with Sapphire Viewports for the Generation of Resonant Twin Beams Hio Giap Ooi, Qimin Zhang, Saesun Kim, Daniel P Petit, John E Moore-Furneaux, Alberto M Marino, Arne Schwettmann Four-wave mixing (FWM) is a non-linear process that can produce quantum correlated twin beams of light with noise properties below the shot noise limit. This makes them useful for quantum-enhanced sensing, as has been shown by recent experiments at the LIGO interferometer. We are interested in narrowband near or on atomic resonance squeezed light at 589 nm to enhance density measurements of our sodium Bose-Einstein condensate. One of the techniques to generate twin beams is by employing a nonlinear crystal inside a cavity, i.e. an optical parametric oscillator (OPO), but this technique leads to technical challenges, such as engineering the nonlinear crystal to operate at a desired wavelength. Therefore, we generate the twin beams with an atomic ensemble. In particular, we use FWM in a double-lambda configuration to generate twin beams of light, known as probe and conjugate, in hot sodium vapor. However, the high temperature required to obtain the necessary atomic density for an efficient FWM process also leads to complications. Owing to a strong chemical reaction between Pyrex glass and alkali atoms at high temperatures, we design a stainless-steel heat pipe that will allow temperatures of up to 400 degrees Celsius. The high temperature, enabled by employing sapphire viewports, will lead to the higher vapor densities needed to obtain large FWM gains, and thus larger levels of intensity-difference squeezing in the generated twin beams. We present the design of our home-built hot sodium vapor cell and preliminary results on the dependence of the FWM gain on temperature, pump beam intensity, detunings and other experimental parameters. |
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V01.00106: QUANTUM INFORMATION SCIENCE
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V01.00107: A dipolar quantum gas microscope Sean Graham, Paul Uerlings, Kevin Ng, Jens Hertkorn, Jan-Niklas Schmidt, Ralf Klemt, Tim Langen, Tilman Pfau Magnetic quantum materials can be simulated with dipolar atoms arranged in a two-dimensional lattice. Such a system would enable quantum simulations of extended Bose- and Fermi-Hubbard physics that would be critical in furthering our understanding of high-temperature superconductivity and other magnetic quantum materials. By combining dipolar atoms with the single-site resolution of a quantum gas microscope, we aim to measure site-to-site correlations and the effect of interactions between next-nearest neighbours in a lattice. Our experimental design will populate an ultraviolet optical lattice with dipolar atoms, which requires the use of super-resolution techniques and precise magnetic field control for efficient readout of site populations. We present these necessary techniques and our experimental progress in constructing a dipolar quantum gas microscope. |
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V01.00108: Exponentially slow heating in a periodically driven 3D disordered dipolar spin ensemble in diamond Guanghui He, Ruotian Gong, Bingtian Ye, Chong Zu Periodically driving has recently emerged as a versatile tool to engineer non-equilibrium phases of matter. However, a generic many-body system will inevitably absorb energy from the drive and heat up to a featureless thermal state. Fortunately, when the driving frequency is high, the heating process may be exponentially suppressed, leading to an extremely long-lived state, known as prethermalization. Whether prethermalization exists in a system with long-range interactions and disorder still remains an open question. Here, we report the observation of prethermalization in a 3D disordered dipolar spin ensemble in diamond. In particular, we show that the heating timescales of the many-body system grow exponentially with driving frequencies. Our result demonstrates the possibility of robust Floquet engineering in disordered 3D systems with long-range interactions. |
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V01.00109: Exchange of a single motional quantum between trapped ions in a 2D RF microtrap array Nathan K Lysne, Justin F Niedermeyer, Jonas Keller, Katherine C McCormick, Susanna L Todaro, Andrew C Wilson, Daniel H Slichter, Dietrich Leibfried Two-dimensional arrays of trapped ions with control over individual sites are promising systems for quantum computation and simulation of many-body phenomena. We have developed a microfabricated surface-electrode trap, fabricated by Sandia National Labs and operated at cryogenic temperatures, to realize a minimal two-dimensional array. This device creates a triangular array of individual trapping sites spaced 30 µm apart with sufficient degrees of freedom to independently control the motional mode frequencies and orientations of an ion trapped in each potential. In this poster we will discuss technical details of how the microtrap array is operated, and report on work developing protocols for selective manipulation and readout of the state of an ion in a particular trapping site through controlled reintroduction of excess micromotion. We also demonstrate tunable single-phonon exchange between ions in adjacent sites of the array through precise control of the site curvatures that determine the motional mode frequencies. This level of control over a single motional quantum can be used for simulations of systems such as bosons evolving in synthetic magnetic fields. |
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V01.00110: Analog-Digital Quantum Simulations with Trapped Ions William N Morong, Kate S Collins, Arinjoy De, Christopher R Monroe Quantum simulators combining Hamiltonian evolution with gate operations represent a powerful approach towards probing many-body physics with NISQ devices. We apply a platform based on a linear chain of trapped 171Yb+ ions to demonstrate some of the uses of this hybrid strategy, such as characterizing slow correlation growth arising from Stark many-body localization, certifying quantum many-body chaos, and studying non-equilibrium criticality in quench dynamics. |
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V01.00111: Towards the analog quantum simulation of field theories with trapped ions Visal So, Roman Zhuravel, Abhishek Menon, Midhuna Duraisamy Suganthi, April Sheffield, Guido Pagano The high controllability, scalability, and long coherence times of trapped ions make them a promising platform for the analog simulation of quantum spin ensembles. We can study quantum field theories of condensed matter, nuclear, and high energy systems by mapping them to spin models. We will present our experimental progress on the construction of an analog quantum simulator for field theories with a trapped Ytterbium ion chain. Our trap assembly consists of a segmented four-blade Paul trap that allows for a quasi-uniformly spaced ion chain with a homogenous radiofrequency confinement field along the trap axis and large numerical apertures for high-resolution imaging (NA~0.6) and individual addressing (NA~0.3). This setup serves as a prototype design for the future monolithic three-dimensional trap with high precision electrode alignment using laser writing and controlled glass etching techniques for universal accessibility to ion trapping. We will report the characteristics of our trap performance and the stability of our system. Furthermore, we will propose an experimental scheme to simulate the U(1) lattice gauge field theory in 1+1 dimensions via three-body interactions with trapped ions. |
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V01.00112: Quantum simulations of open molecular systems with trapped ions Ke Sun, Mingyu Kang, Kenneth Brown, Jungsang Kim, Jungsang Kim The quantum dynamics of a molecular system are complicated to simulate due to the coupling between the system and the surrounding environment. The environment is often treated as harmonic oscillators coupled to the electronic states of the system. The trapped-ion simulators provide the opportunity of studying the effects of a quantum environment, as their native operations consist of controlling the coupling between spins and their quantized motional degrees of freedom. Moreover, dissipation of motion can be engineered by using ancilla ions, which enables us to simulate a wide range of phenomena, from a coherent, low-temperature regime to a dissipative, high-temperature regime. We explore trapped-ion simulations of molecular dynamics with a toy model and compare the results with classical simulations. |
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V01.00113: Measuring Arbitrary Physical Properties in Analog Quantum Simulation: Ancilla-Assisted Classical Shadow Tomography Minh C Tran, Daniel Mark, Wen Wei Ho, Soonwon Choi Extracting physical properties that are not directly accessible from the standard measurement basis is one of the central challenges in existing analog quantum simulation platforms. Here, we propose and analyze a novel approach to efficiently extract many physical properties without having to apply sophisticated controls. Our protocol simply involves introducing ancillary degrees of freedom in a predetermined state and evolving the joint system under its natural dynamics. Since quantum many-body dynamics is generally ergodic in nature, a subsequent measurement of the joint system in the fixed, standard basis amounts to an effective random-basis measurement on the original system, from which nontrivial properties can be extracted via classical data processing. Under certain conditions, our method approaches an information-theoretically optimal method called classical shadow tomography. We numerically demonstrate our protocol in systems of spins and itinerant particles, and extract quantities such as the entanglement entropy and many-body Chern number which are otherwise difficult to measure. Our protocol constitutes an example in which the ergodicity of quantum dynamics — a ubiquitous feature of nature — is leveraged as a resource, enabling a quantum application. |
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V01.00114: Universal random statistics in quantum many-body systems and their applications Joonhee Choi, Adam L Shaw, Ivaylo S Madjarov, Xin Xie, Ran Finkelstein, Jacob Covey, Jordan Cotler, Daniel Mark, Hsin-Yuan Huang, Anant Kale, Hannes Pichler, Fernando Brandao, Soonwon Choi, Manuel Endres
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V01.00115: Benchmarking quantum simulators using quantum chaos Daniel Mark, Joonhee Choi, Adam L Shaw, Manuel Endres, Soonwon Choi Benchmarking a quantum device is a central task in quantum science and technology, but remains experimentally challenging. In particular, existing methods either require prohibitively many experimental runs or are not suitable for analog quantum simulators with limited controllability. We propose a benchmarking protocol to estimate the fidelity between an experimentally prepared state and a target state, applicable to any analog quantum device. Our approach utilizes universal statistical fluctuations arising from quantum chaos (suitably defined in our context), which are generically present in many-body dynamics. Therefore, our protocol does not require fine-tuned dynamics, state preparation or measurements. It has a small sample complexity and improves in accuracy with increasing system size. The dominant cost is the computational cost of simulating the target state. We numerically demonstrate our protocol for a variety of quantum simulators such as itinerant particles on optical lattices, trapped ions, or neutral atoms, and discuss applications of our method for parameter estimation. |
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V01.00116: Non-equilibrium steady states in an open tricritical Dicke model Diego A Fallas Padilla, Youjiang Xu, Han Pu The Lindblad formalism has been successfully employed to determine the non-equilibrium steady states (NESS) of Dicke-like models under a semiclassical description, predicting non-equilibrium superradiant phase transitions occurring in the thermodynamic limit. High tunability and control in AMO experimental setups allow us to construct more complex light-matter interacting Hamiltonians with richer properties, however, the conventional semiclassical approximations might not be suitable for these systems, and a more general method is required to determine if these exotic features survive in an open description. In this work, we explore the implementation of the density matrix form of the Lindblad equation in order to describe the steady-state behavior of more intricate light-matter interacting quantum open systems. Here we describe the effect of photon losses in the critical properties on a recently proposed generalization of the Dicke Hamiltonian that exhibits a quantum tricritical point. |
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V01.00117: Prototype quantum simulator of structured environment-assisted energy transfer Kristian D Barajas, Joseph Broz, Hartmut Haeffner, Wes Campbell As much as we like to complain about noise, classical and quantum noise are relevant to energy capture, storage, and conversion processes. To extend the capability of experimental platforms to probe complex structured environments in open quantum systems, we study the the interplay of classical and quantum (stationary Gaussian) noise on energy transfer dynamics. We characterize a prototype open quantum system simulator consisting of a phase damped quantum oscillator interacting with a noisy classical environment on a trapped-ion quantum computer. D. J. Gorman et al. (2018) experimentally demonstrated how a simple quantum environment of a single thermalized harmonic oscillator enables transport and simulates vibrationally-assisted energy transfer (VAET). Recent fidelity improvements in encoding VAET dynamics allow for observation of more subtle noise interplay effects. The prototype simulator uses VAET dynamics where the controllable bosonic modes approximate a quantum reservoir, the classical noise is injected by the control laser, and each noise source can be encoded with near arbitrary spectral properties. We analyze the preliminary experimental and numerical simulation results using IonSim.jl and compare them to recent theoretical predictions by Li et al. (2021). |
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V01.00118: Quantum simulation of Hubbard-type model with trapped ions Bowen Li, Quanxin Mei, Yukai Wu, Minglei Cai, Ye Wang, Lin Yao, Zichao Zhou, Luming Duan Quantum simulation provides important tools in studying strongly correlated many-body systems with controllable parameters. Among them two prototypical many-body models with spin-boson interactions are the Jaynes-Cummings-Hubbard(JCH) model and the Rabi-Hubbard(RH) model, both of which originate from cavity quantum electro-dynamics systems but are also well-suited for the trapped ions. Both demonstrate rich physics through the competition between local spin-boson interactions and long-range boson hopping. The RH model breaks the U(1) symmetry and thus shows non-trivial distinctions from other generalizations like Bose-Hubbard model and Jaynes-Cummings-Hubbard(JCH) model. The JCH model possessed U(1) symmetry thus demonstrates essentially different properties in the ground state phase diagram. |
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V01.00119: Impurity dephasing in a Bose–Hubbard model Fabio Caleffi, Massimo Capone, Inés de Vega, Alessio Recati We study the dynamics of a two-level impurity embedded in a two-dimensional Bose–Hubbard (BH) model at zero temperature from an open quantum system perspective. Results for the decoherence across the whole phase diagram are presented, with a focus on the critical region close to the transition between superfluid and Mott insulator. In particular we show how the decoherence and the deviation from a Markovian behaviour are sensitive to whether the transition is crossed at commensurate or incommensurate densities. The role of the spectrum of the BH environment and its non-Gaussian statistics, beyond the standard independent boson model, is highlighted. Our analysis resorts on a recently developed method (Phys. Rev. Res. 2 033276, 2020) – closely related to slave boson approaches – that enables us to capture the correlations across the whole phase diagram. This semi-analytical method provides us with a deep insight into the physics of the spin decoherence in the superfluid and Mott phases as well as close to the phase transitions. |
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V01.00120: Schemes of Engineering Nodal Surfaces with an Open Four-Level Quantum System Chuan-Hsun Li, Shih-Wen Feng, Felicia Martinez, Qi Zhou, Yong Chen Quantum systems coupled to the environment with gain and loss can often be described by non-Hermitian Hamiltonians. Such open systems can exhibit phenomena difficult to observe in closed systems, such as the emergence of novel topological matter induced by non-Hermiticity. For example, in two-dimensional momentum space, a Hermitian Weyl node can become a Weyl exceptional ring when subject to non-Hermitian perturbations. Whereas such nodal points and lines have already led to extensive studies of topological (semi)metals, nodal surfaces may further enrich topological physics but are not well-understood. Here, we propose realizing various nodal surfaces by utilizing an open four-level quantum system. Take atomic systems for example, one can choose four pseudospin states and couple them with microwaves or radio-frequency waves, whose coupling strengths, phases, and detunings constitute a parameter space. With engineered gain and loss, we show that nodal surfaces such as spheres, hyperboloids, cones, and cylinders can emerge in the parameter space. Our results may provide insights into exploring high-dimensional topological defects in synthetic quantum matter. |
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V01.00121: Continuous versus discrete truncated Wigner approximation for driven, dissipative spin systems Christopher D Mink, David Petrosyan, Michael Fleischhauer We present an alternative derivation for the recently proposed discrete truncated Wigner approximation (DTWA) for the description of the many-body dynamics of interacting spin-1/2 systems. The DTWA is a semi-classical approach based on Monte-Carlo sampling in a discrete phase space which improves the classical treatment by accounting for lowest-order quantum fluctuations. |
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V01.00122: STRUCTURE AND PROPERTIES OF ATOMS, IONS, MOLECULES, AND PLASMAS
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V01.00123: Absolute Single Photoionization Cross-Section Measurements of Br+ David A Macaluso, A.L. David Kilcoyne, Jonah Britton, Alex Aguilar, Rene C Bilodeau, Nicholas C Sterling, Antonio M Juarez, Manuel A Bautista Absolute single photoionization cross-section measurements of Br+ ions were performed using the photo-ion, merged-beams technique with synchrotron radiation at the Advanced Light Source at Lawrence Berkeley National Laboratory. Measurements of Br+ were made in the photon energy range 17.0 eV to 32.5 eV with a photon energy resolution of 29.2 meV. These measurements span the 3P2 ground state ionization threshold as well as the 3P1, 3P0, 1D2, 1S0 metastable state ionization thresholds. We identified multiple Rydberg resonance series in the auto-ionization resonance structure of Br+ and used these identifications to verify the reported ionization potential of Br+ and accurately determine the excited-state energy levels of low-lying metastable states of both Br+ and Br2+. The ionization potential of Br+ and the metastable-state energy levels were found to agree with the tabulated energy levels reported by NIST to within the energy uncertainties of the NIST values and the present measurements. The measurements are also compared to Breit-Pauli R-matrix calculations with positive agreement between theory and experiment. |
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V01.00124: Photoionization of doublet and quartet boron states as benchmarks for NewStock and ASTRA Siddhartha Chattopadhyay, Nolan Vild, Luca Argenti Boron, a pervasive element in nature, is the simplest atom featuring three active electrons in the valence over an appreciably polarizable core. For these reasons, it is also an interesting system for benchmarking ab initio photoionization codes and their ability to investigate the effects of core-core, core-valence, and valence-valence correlation on observables characteristic of the electronic continuum such as the position and Auger decay rate of autoionizing states, photoionization cross-sections, and resonant asymmetry parameters. Here we present a comparison between calculations, for the doublet and quartet states of the boron atom, conducted with an ad-hoc high-precision three-active-electron code [1], with the results obtained with the NewStock atomic and the new ASTRA molecular polyelectronic ionization codes. In NewStock and ASTRA, resonance parameters are determined by diagonalizing the multi-channel close-coupling in the presence of exterior-complex scaling and complex absorbing boundaries, respectively. |
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V01.00125: Electron transfer and level crossing induce anomalous photoionization along halogen@C60 series Ruma De, Esam Ali, Taylor O’Brien, Dakota W Shields, Andrew Dennis, Maia Magrakvelidze, Mohamed El-Amine Madjet, Steve Manson, Himadri Chakraborty Our earlier study finds that the photoionization properties of the configurations Cl−@C60+, Br−@C60+ and I−@C60+ are insensitive to the C60 level where the vacancy is formed following the electron transfer [1,2]. This is because, before the transfer, the neutral halogen np level is energetically above the 2p level of empty C60, so the transfer induced screening separates the levels further. The situation is different if the free atomic level locates below 2pC60 as is the case for the halogen F. In forming F−@C60+, therefore, the screening from the transfer causes 2pF to rise and move toward 2pC60 from below it. This creates the condition of a reduced level-separation leading to a crossing, instead of the increase as happens for other halogens. The effect sensitizes the atom-C60 hybridization mechanism. As a result, the transfer of a hybrid versus a pure C60 electron makes a difference [3]. Many body DFT calculations for the photoionization of pure and hybrid levels along this halogen series will be presented to showcase this novel but anomalous phenomenon. |
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V01.00126: Towards Vibrational Spectroscopy of Single Polyatomic Molecules Scott Eierman, Zeyun Peng, Aaron Calvin, Dave Patterson Molecular ions are of fundamental importance to fields from biochemistry to atmospheric chemistry. High resolution spectroscopy is challenging, however, as large number densities are difficult to achieve in the gas phase. Action spectroscopy methods enable high resolution structural studies otherwise inaccessible with absorption methods, but most all commonly reported action techniques destroy the molecules being studied. We are pursuing a novel action technique in which molecular ions are co-trapped with laser-cooled atomic ions and complexed with weakly bound, neutral "messenger" atoms. Messengers can be selectively removed by optically exciting vibrational transitions, and co-trapped atoms can be used as a probe to monitor this messenger ejection process, thus indirectly recording the vibrational spectrum of the trapped molecule. The instrument which we are building to perform these measurements will open up new pathways for non-destructive, high-resolution spectroscopy and structural analysis of molecular ions. |
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V01.00127: Inner-Shell Photodetachment of Na- using R-matrix Methods Thomas W Gorczyca, Hsiao-Ling Zhou, Alan Hibbert, M. Fatih Hasoglu, Steven T Manson Inner-shell photodetachment of Na- near the L-edge threshold is investigated using the R-matrix method. Significant structure in found in the cross section and this structure is shown to be related to the complicated correlated electron dynamics endemic in negative ions. Comparison with experiment suggests that the absolute values of the measured cross section might be too small by a factor of two. |
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V01.00128: Absolute Single Photoionization Cross-Section Measurements of Rb3+ David A Macaluso, Alex Aguilar, Rene C Bilodeau, Nicholas C Sterling, Manuel A Bautista, Zachary Taylor, A.L. David Kilcoyne, Antonio M Juarez Absolute single photoionization cross-section measurements of Rb3+ ions were performed using the photo-ion, merged-beams technique with synchrotron radiation at the Advanced Light Source at Lawrence Berkeley National Laboratory. Measurements of Rb3+ were made in the photon energy range 46.52 eV to 62.51 eV with a nominal photon energy resolution of 30 meV. These measurements span the 3P2 ground state ionization threshold as well as the 3P1, 3P0, 1D2, and 1S0 metastable state ionization thresholds. We identified multiple Rydberg resonance series in the auto-ionization resonance structure of Rb3+ and used these identifications to verify the reported ionization potential of Rb3+ and accurately determine the excited-state energy levels of low-lying metastable states of both Rb3+ and Rb4+. The ionization potential of Br+ and the metastable-state energy levels were found to agree with the tabulated energy levels reported by NIST to within the energy uncertainties of the NIST values and the present measurements. The measurements are also compared to Breit-Pauli R-matrix calculations with positive agreement between theory and experiment. |
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V01.00129: Benchmark of Few-Level Quantum Theory vs. ab initio Numerical Solutions for the Strong-field Autler-Townes Effect in Photo-Ionization of Hydrogen Daniel Younis, Joseph H Eberly The temporal and spectral consequences of an intermediate resonance en route to strong-field photoionization [1] are investigated theoretically in two ways: by solving few-level model equations and by ab initio numerical solution of the time-dependent Schrödinger equation, in both cases for hydrogen in three dimensions. The model is designed to include field-dressed atomic states via resonance in a three-level reduction of the hydrogen atom consisting of the 2p-3d (Balmer) transition and one energetically-distant continuum state. The model's level occupation probabilities are derived from three Schrödinger amplitude equations, and are benchmarked against the ab initio numerical solution under the same strong field. We examine contrasts between the results of the two approaches with a particular focus on Autler-Townes doublets [2] that appear in the photoelectron spectrum. |
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V01.00130: L-shell Auger electron generation across the Kr K-edge Shuai Li, Stephen Southworth, Dimitris Koulentianos, Gilles Doumy, Linda Young, Donald A Walko, John Bozek, Ralph Püttner, Maria Novella Piancastelli, Renaud Guillemin, Marc Simon, Sergei Sheinerman We have used high-resolution electron spectroscopy at the Advanced Photon Source to study resonance and threshold variations of the 1611-eV L2-M4,5N2,3 Auger line as the x-ray energy is scanned across the 14327.2-eV Kr K-edge. X-ray absorption excites the Kr 1s-np Rydberg series below threshold and the 1s continuum above threshold. The Auger line is only weakly generated by direct L2 photoionization and strongly enhanced by K-L2 x-ray emission. Consequently, the yield of the L2 Auger electron follows the K-edge absorption cross-section, including the 1s-np Rydberg states, resulting in resonant Auger lines. Above threshold, small energy shifts of the Auger line result from post-collision-interaction (PCI) with 1s photoelectrons. Due to the 2p-1s fluorescence time delay [1], modeling PCI effects requires combining the 0.24-fs 1s lifetime with the 0.50-fs 2p1/2 lifetime. The results demonstrate the sensitivity of high-resolution electron spectroscopy combined with synchrotron x rays for inner-shell studies of heavy atoms. |
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V01.00131: Confinement induced enhancement of photoionization cross-section of an alkali-metal cluster inside a giant fullerene Rasheed Shaik, Hari Varma Ravi, Himadri Chakraborty Giant fullerenes encasing atoms, clusters and nanocrystals have recently been developed [1] allowing researchers to investigate aspects of the dynamical response of an atom/cluster inside a fullerene cage to external stimuli. These endohedral systems hold the prospects of exciting applications. Thus, investigation of the influence of confining cage on the spectroscopy of atoms/cluster inside is a matter of significant interest [2]. In the present work, we investigate photoionization of Nax inside a gigantic fullerene Cn. The ground state of the endohedral systems, Nax@Cn (x=20, 40 and n=240, 540 respectively), is studied using a jellium-based density functional theory (DFT) approach with a gradient corrected exchange-correlation functional (LB94). Their photoionization (PI) dynamics is probed within an independent particle (IP) framework called linear-response DFT [3]. The results and comparisons with those of their isolated Nax counterparts [4] show a significant enhancement in cross-sections owing to the confinement, even at the IP level. |
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V01.00132: Comparative study of plasmon-resonance properties as a function of fullerene size using density functional theory Rasheed Shaik, Hari Varma Ravi, Himadri Chakraborty Fullerenes, the most stable finite-size carbon formations with a cage-like structure, exhibit unique spectroscopic properties. The occurrence of plasmon in such systems resulting from the collective excitations of its delocalized electrons, driven by an external electromagnetic field, makes the study of these systems very interesting [1, 2] with important applications in the field of plasmonics. In this study, the ground state of the fullerenes, Cn (n=60, 240 and 540), is investigated using a jellium-based density functional theory (DFT) approach with a gradient corrected exchange-correlation functional (LB94) [3]. A linear response framework of time-dependent DFT [3] is then employed to study the photoionization (PI) dynamics of these systems to probe the characteristics of plasmon resonances. The comparison among PI results of these fullerenes provide a comprehensive picture of the effect of the fullerene size on evolutions of plasmon properties and their underlying mechanism. |
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V01.00133: Photoionization time delay of Hg 6s subshell at higher energies: RMCTD calculations Aarthi Ganesan, Sourav Banerjee, Ankur Mandal, Pranawa C Deshmukh, Steven T Manson The study of photoionization of atomic mercury highlights the importance of electron correlation in high-Z atoms [1-3]. Attosecond time delay [4-5] in photoionization processes [4] is an excellent probe to understand the dynamics of the highly correlated atomic systems. Earlier studies have shown that dipole and quadrupole photoelectron angular distributions are dramatically affected near the 6s dipole Cooper minimum in atomic mercury [2]. Photoionization time delay has been reported [6] in the near threshold region of 6s using the relativistic-random-phase approximation (RRPA) [7], RRPA with relaxation (RRPA-R) [8] and the relativistic multiconfiguration Tamm Dancoff approximation (RMCTD) [9, 10] techniques and the time delay was found to be very sensitive to how correlations are treated. The present work reports the 6s photoionization cross section, photoelectron angular distribution and Wigner time delay using RMCTD [11] in the energy region well above the 6s threshold near the second Cooper minimum (~130 eV) and non-RPA correlations [10] that are included in RMCTD are found to be important. Significant time delay is predicted in Hg 6s in the region of second Cooper minimum. [1] D. Toffoli, et al., Phys. Rev. A 66, 012501 (2002); [2] T. Banerjee, P.C. Deshmukh and S.T. Manson, Phys. Rev. A 75, 042701 (2007); [3] B. H. McQuaide, et al., Phys. Rev. A 35, 1603 (1987) [4] A. S. Kheifets and I. A. Ivanov, Phys. Rev. Letts. 105, 233002 (2010); [5] P.C. Deshmukh et al., Phys. Rev. A 89, 053424 (2014); [6] A. Ganesan et al., BAPS 60(7), 128 (2015); [7] W. R. Johnson and C. D. Lin. Phys. Rev. A 20, 964 (1979); [8] V. Radojevic, et al., Phys. Rev. A 40, 727 (1989); [9] V Radojevic and W. R. Johnson, Phys. Rev. A 31, 2991 (1985); [10] J. Jose, et al., Phys. Rev. A 83, 053419 (2011). |
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V01.00134: Angular Dependence of the Transition from Dipole to Quadrupole Photoionization Time Delay in Atoms Rezvan Hosseini, Steven T Manson, Pranawa C Deshmukh Wigner time delay [1] in atomic photoionization is sensitive to the transition dynamics of atomic electrons on the attosecond time scale, the natural time scale of atomic electron motion [2]. Time delay generally has an angular dependence and calculations have been performed including only dipole transitions [3,4]. The amplitude for dipole photoionization vanishes at certain angles as a result of angular momentum geometry. In such a case, quadrupole transitions dominate; specifically, where the dipole amplitude vanishes, the time delay is quadrupole photoionization time delay, and the attosecond dynamics of quadrupole transitions can be investigated. Relativistic expressions have been derived showing where quadrupole channels determine the time delay. Relativistic random phase approximation (RRPA) [5] calculations for the angular dependance of time delay of s-subshells of noble gas atoms for the angular distribution of time delay including both dipole and quadrupole channels have been performed as a function of the angle between the photoelectron momentum and photon polarization and the transition from dipole to quadrupole time delay is exhibited. [1] E. P. Wigner, Phys. Rev. 98, 145 (1955); [2] R. Pazourek, S. Nagele and J. Burgdörfer, Rev. Mod. Phys. 87, 765 (2015); [3] J. Wätzel, et al, J. Phys. B 48, 025602 (2015); [4] A. Mandal, et al, Phys. Rev. A 96, 053407 (2017); [5] W. R. Johnson and C. D. Lin, Phys. Rev. A 20, 964 (1979). |
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V01.00135: 6p Cooper minima in the photoionization in high-Z atoms Saumyashree Baral, Jobin Jose, Pranawa C Deshmukh, Steven T Manson A zero in the photoionization transition matrix element is well-known as the Cooper minimum (CM) [1,2]. Owing to the spin-orbit forces, the non-relativistic CM splits to two or more zeros. The 6p→εd Cooper minimum splits into three, i.e., 6p1/2→εd3/2 ,6p3/2→εd3/2, 6p3/2→εd5/2; there is no zero in 6p→εs transition matrix element. In past, CM in the photoionization from the 6p subshell was investigated up to Z=100 with the application of Dirac-Slater methodology [3,4]. In this work the dynamics of the 6p CM in atoms up to Z=120 are studied including both relativity and many-particle correlations. The Dirac-Fock (DF) independent particle approximation [5] and the correlated relativistic random phase approximation (RRPA) [6] are employed for calculating the dipole photoionization matrix elements for Rn (Z=86), Ra (Z=88), No (Z=102), Cn(Z=112), Og (Z=118), and Ubn (Z=120). [1] J. W. Cooper, Phys. Rev. A, 128, 681 (1962). [2] W. R. Johnson and K. T. Cheng, Phys. Rev. A 20, 978 (1979). [3] S. T. Manson, C. J. Lee, R. H. Pratt, I. B. Goldberg, B. R. Tambe and A. Ron, Phys. Rev. A, 28,2885 (1983). [4] P. C. Deshmukh, B. R. Tambe and S. T. Manson, Austral. J. Phys. 39, 679 (1986). [5] M. Reiher and A. Wolf, Relativistic Quantum Chemistry: The Fundamental Theory of Molecular Science, 2nd Edition (Wiley-VCH, Wertheim, Germany, 2015). [6] W.R. Johnson and C.D. Lin, Phys. Rev. A, 20, 964 (1979).] |
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V01.00136: Nondipole Time Delay in the Photoionization of Atomic Systems Pratikshya Parajuli, Pranawa C Deshmukh, Steven T Manson It has recently been shown that, owing to their opposite parities, dipole and quadrupole contributions to attosecond photoionization time delays behave differently as a function of detection angle; specifically, one is symmetric under a transformation from θ to 180- θ while the other in antisymmetric, so that by adding or subtracting the time delay at the complementary angles, the dipole contribution cancels out and the quadrupole contribution can be observed [1]. In the light of this understanding, it is useful to study the quadrupole time delays. A theoretical investigation has been initiated using the relativistic-random-phase approximation (RRPA) [2] to investigate quadrupole time delays in a variety of atomic systems. As a first step, the situation for Ne has been explored for all subshells over a broad range of energies from threshold to several keV. The quadrupole time delays in Ne show tendencies similar to dipole results [3]. The calculations will be extended to other atomic systems including the other noble gas atoms, various atomic ions, and confined atoms. [1] M. Amusia and L. Chernysheva, JETP Lett. 112, 673 (2020). [2] W. R. Johnson and C. D. Lin, Phys. Rev. A 20, 964 (1979). [3] A. S. Kheifets, et al Phys. Rev. A 92, 063422 (2015). |
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V01.00137: The Iron Project \& The Opacity Project: Iron ions at the solar radiative-convection boundary - Fe~XVII, Fe~XVIII, Fe~XIX Sultana N Nahar, Werner Eissner, Lianshui Zhao, Anil K Pradhan Iron is the dominant heavy element that determines radiation transport |
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V01.00138: ULTRAFAST AND STRONG FIELD PHYSICS
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V01.00139: Photoionization dynamics of Na 3s in the Cooper minimum region Nishita M Hosea, Jobin Jose, Hari R Varma, Pranawa C Deshmukh, Steven T Manson The photoionization cross section of 3s orbital of sodium atom has a Cooper minimum (CM) near its threshold region [1]. It is known that photoionization parameters are very sensitive to the presence of CM [2, 3]. Also, in the region of CM, the effects of quadrupole transitions are important while determining the angular distribution parameters. Here we report the effect of quadrupole transition near the 3s dipole CM [4,5] on the angular distributions of Na 3s which is an open shell system. We also include the study of spin polarisation of photoelectrons in this region [6]. The required transition amplitudes for these calculations are obtained from RATIP [7]. The wavefunctions of the initial and ionised state of the system are obtained from GRASP [8]. [1] J. W. Cooper, Phys. Rev. 128, 681 (1962); [2] S. T. Manson and A. F. Starace, Rev. Mod. Phys., 54, 389 (1982); [3] M. S. Wang, et.al, Phys. Rev. A 25, 857 (1982); [4] W. R. Johnson and C. D. Lin. Phys. Rev. A 20, 964 (1979); [5] W. R. Johnson, et.al, Phys. Rev. A 59, 3609 (1999); [6] K.-N. Huang, Phys. Rev. A 22, 223 (1980); [7] S. Fritzsche, Comp. Phys. Comm. 183, 525 (2012); [8] F.A. Parpia, C. Froese Fischer, I P. Grant, Comp. Phys. Comm. 94, 249 (1996), |
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V01.00140: Attosecond-Scale Charge Migration Studies using a Water-Window X-ray Source Chase E. Geiger, Quynh V. Le, Zenghu Chang, W. T. Hill III Quynh v Le, Chase E Geiger Charge migration is an electronic ultrafast process – unlike charge transfer which involves a slower redistribution of electrons and nuclei – and requires tools with sub-femtosecond temporal resolution to observe. This research involves the use of a broadband, Carrier Envelope Phase (CEP)-stable, femtosecond pulsed 1.7-micron infrared source to generate attosecond pulses through High Harmonic Generation (HHG) in a target gas. These X-ray attosecond pulses have sufficient photon energy (284-543 eV) to perform studies at the Carbon and Nitrogen K-edge, and have been used to probe vibrational, rotational, and electronic dynamics in atoms, molecules, and condensed matter on attosecond, femtosecond, and picosecond timescales. It is planned to use the 1.7-micron Optical Parametric Chirped Pulse Amplifier (OPCPA) as the driving laser for the X-ray source in an attosecond transient absorption spectroscopy (ATAS) setup to observe electronic and nuclear motion during photoinduced charge migration in propiolic acid molecules. This study will provide valuable information about the coupling between electrons and nuclei. |
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V01.00141: Simulations for x-ray imaging of wave packet dynamics Akilesh Venkatesh, Francis J Robicheaux Previous work on imaging wave packet dynamics with x-ray scattering revealed that the scattering patterns deviate substantially from the notion of instantaneous momentum density of the wave packet. Here it is shown that when the final state of the scattered electron and the scattered photon momentum are measured simultaneously, the scattering probability is found to be proportional to the modulus square of the Fourier transform of the instantaneous spatial wave function weighted by the final state of the electron. Several cases for the choice of final state of the electron are explored. First, the case where the final state can be measured up to a given principal quantum number n and orbital angular momentum l are presented. Next, the case where the final states can only be determined up to a given energy is discussed. Finally, the case of a wave packet consisting of a large amount of a known stationary state and a small amount of an unknown stationary state is examined and the scattering profile is used to determine the properties of the unknown state in the wave packet. |
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V01.00142: Observation of Quantum beats in two photon ionization of argon. Miguel Alarcon, Chris H Greene, Alexander C Plunkett, James K Wood, Arvinder S Sandhu An accompanying experimental study uses two asynchronous lasers to create and ionize a wave packetof low lying states of argon. It was observed that by varying the wavelength, starkly different photoionization signals were obtained. This technique has been used before when studying autoionizing statesin argon [1]. Here we theoretically study one and two photon ionization from one such wavepacket bymeans of multichannel quantum defect theory treating the delayed laser as a time dependent perturbation.We find that two the processes posses a remarkably different photo electron spectrogram and that, asobserved in the experiment, both signals show quantum beats in the delay between the lasers. Wealso explore here the importance of the intermediate states that give rise to this difference and someproperties, in both phase and amplitude, of the asymmetry coefficients in the angular distribution aswell as the photo electron signal. |
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V01.00143: Imaging Molecular Motion During the Strong-Field Enhanced Ionization of Water Andrew J Howard, Mathew Britton, Joshua Reynolds, Chuan Cheng, Ian Gabalski, Ruaridh Forbes, Thomas Weinacht, Philip H Bucksbaum There exists an enhancement in the strong-field (multiple) ionization (SFI) of water that leads to an increased trication (H2O3+) yield at certain “critical” internuclear geometries. Here we investigate this enhancement by studying the three-body dissociations of the trication and dication. To produce these charge states, we performed SFI using two schemes: 1) 800-nm pulses of variable duration, and 2) 6-fs 800-nm pulse pairs of variable interpulse delay. In scheme 1, we found that the ratio of triply to doubly charged three-body dissociations increases exponentially with pulse duration from 5 to 20 fs (at constant peak intensity). This trend suggests that longer durations allow the molecule more time to distort within the field and reach the critical geometry. In scheme 2, we identify a similar, though smaller, enhancement in this ratio at particular delays. This observation indicates that the critical geometry may be reached via field-free internuclear motion manifesting in the time between formation of the dictation and the arrival of the second pulse. In either scheme, after formation of the trication, the molecule undergoes a Coulomb explosion. The 3D momentum of each resulting fragment is measured in coincidence and used to reconstruct the molecule’s internuclear geometry. |
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V01.00144: A Quantum Rattleback Effect in Rotationally Asymmetric Molecules Robert R Jones, Madeline C Killian, Varun S Makhija The rattleback is a boat shaped toy with a non-uniform mass distribution. As a result, its principal axes of rotation do not coincide with geometrical symmetry axes. A rattleback exhibits unidirectional rotation when spun about a symmetry axis. Here we computationally investigate the rotational dynamics of C2H3Cl after interaction with a non-resonant, femtosecond laser pulse. C2H3Cl lacks an axis of rotational symmetry, as a result of which the principal axes of its moment of inertia and polarizability tensors do not coincide. The interaction with the laser pulse torques the molecule about the principal axes of the polarizability tensor, initiating rotation that is not about any one of the principal axes. We compute the time evolving probability distribution of molecular axes during and after this interaction by solving the Time Dependent Schrodinger Equation in the rigid rotor approximation. This probability distribution evidently exhibits a unidirectional rotational motion about the most polarizable molecular axis, similar to that of the classical rattleback. The effect can be traced back to Raman transitions occurring during interaction with the laser pulse that change the parity of K - the projection of the rotational angular momentum on the most polarizable axis. |
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V01.00145: Field Free Dimensional Algnment of Molecules with Varying Degrees of Symmetry Henry Mills, Varun S Makhija A number of methods have been developed to achieve aligned or oriented distributions of polyatomic molecules. Nonetheless, achieving strong alignment of all three molecular axes remains a challenge. Furthermore, most studies have focused on prolate-type asymmetric top molecules with their most polarizable and fastest axis being the same, such as Iodobenzne. Here, we computationally investigate the application of multiple laser pulses with different polarizations to molecules with varying symmetry in their moment inertia and polarizability tensors. We find that a pulse sequence previously demonstrated to produce three-dimensional alignment (3DA) of Iodobenzene under field-free conditions fails do so in general. We find new pulse sequences that generate 3DA for molecules with different symmetry properties, and prescribe a strategy for 3DA of asymmetric top molecules. |
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V01.00146: A Coupled Volterra Integral Equation Approach to Solving the Time-Dependent Schr\"odinger Equation Barry I Schneider, Ryan Schneider, Heman Gharibnejad Most approaches to solving the time-dependent Schr\"odinger (TDSE) involving time-dependent interactions invoke the short-time approximation. In essence, one propagates the TDSE over a sufficiently short time interval that one can ignore the time dependence of the interaction. It is possible to improve these approaches, for example, as is done in the Magnus expansion, but they often require the evaluation of commutators which are not always easy to compute. A new and simple approach to overcome both of the aforementioned problems, is based on rewriting the TDSE as; |
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V01.00147: Probing molecular autoionization and dissociation using photoelectron spectroscopy Dipayan Biswas, James K Wood, Alexander C Plunkett, Arvinder S Sandhu We studied the ultrafast dynamics of Rydberg states of polyatomic molecules near conical intersection using differential pump-probe photoelectron spectroscopy and Raman electron interferometry. Attosecond XUV pump was used to excite the carbon dioxide molecule to the Rydberg states above the first ionization threshold. While participating in conical intersection dynamics, these Rydberg states can undergo neutral predissociation or they can autoionize to lower lying continuum thresholds of the molecule with a very different evolution timescale. The competition between neutral predissociation and autoionization is studied using a second time delayed infrared probe that can further ionize the molecular Rydberg states as well as their dissociated fragments to their continuum limit. Velocity map imaging spectrometer was used to collect the photoelectrons generated by Rydberg autoionization and IR induced photoionization. From the differential photoelectron signal and Raman interferences we obtain both high spectral and temporal resolution to monitor the autoionizing wavepacket dynamics, allowing us to extract autoionization and dissociation lifetimes. |
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V01.00148: Attosecond transient absorption spectroscopy in ionic systems Nisnat Chakraborty, Islam S Shalaby, Sergio Yanez-Pagans, Arvinder S Sandhu We investigated ionized wavepackets in Xenon and Krypton using attosecond transient absorption spectroscopy. The ionized system was prepared using a strong near-infrared pump pulse, while a time-delayed extreme ultraviolet attosecond pulse train acted as the probe in a non-collinear geometry. The hole wavepacket evolves with time and this is monitored using 11th or 13th high harmonics which serve to excite the system further to high-lying ionic states. The polarization and intensity of near-infrared pulse were varied, and quantum beating of the hole wave packet is monitored in the process. This approach also allows us to probe the evolution of neutral autoionizing states that exist between two spin-orbit split ionization thresholds, to gain insight into the strong-field induced decay dynamics and modification of the ionic population. These results open the door to study ionized atomic and molecular systems, as well as plasmas using the attosecond transient absorption techniques. |
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V01.00149: Ultrafast hot-carrier relaxation in photoexcited Ca@C60 molecule Esam Ali, Mohamed El-Amine Madjet, Ruma De, Himadri Chakraborty We investigate the processes of hot-carrier relaxation in photoexcited Ca@C60 molecule at room temperature by using a scheme based on ab initio nonadiabatic molecular dynamics simulations and time-dependent density functional theory [1-3]. The methodology is underpinned by a combination of the fewest-switch surface hopping approach and Kohn−Sham single-particle description. Results indicate that the relaxation of the excited population to the band edges occurs on the ultrafast time scale driven by the dynamical electron-phonon coupling. We will investigate the population lifetimes for unoccupied orbital states near the energy gap and study the role of spin multiplicity in the hot-carrier relaxation process in Ca@C60. Some results will be presented in the conference. |
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V01.00150: Focused-ion-beam-milled GaAs nanotip: A semiconducting ultrafast photoemission electron source Sam Keramati, William T Newman, Herman Batelaan, Timothy J Gay We report fabrication and characterization of a GaAs nanotip that is carved out of a shard from a GaAs wafer using focused-ion-beam-milling. GaAs-based electron photoemission tips have been shown to produce spin-polarized electrons [1], and ultrashort nanoscale pulses of polarized free electrons from such tips are of interest in time-resolved electron microscopy as well as fundamental research on quantum mechanics [2]. In the present work, we demonstrate multiphoton photoemission from an ion-milled GaAs nanotip using an ultrafast near-IR Ti:Sa laser oscillator with a repetition rate of 90 MHz. Moreover, using a Cs dispenser installed in the proximity of the tip, we show that the photocathode work function can be systematically lowered and controlled at residual gas pressures of 10-7 Torr by changing the Cs emission rate from the dispenser which enhances the electron emission while lowering the photon number needed for emission. About 8 photoelectrons per pulse was achieved this way with a moderate Cs deposition rate and the laser pulses focused to a free-space intensity of 1010 W/cm2. [1] E. Brunkow, et al., Appl. Phys. Lett. 114, 073502 (2019). [2] S. Keramati, et al., Phys. Rev. Lett. 127, 180602 (2021). |
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V01.00151: Dissociation dynamics of ethylene (C2H4) probed by time-resolved coincident ion momentum imaging Keyu Chen The dissociation dynamics of ethylene (C2H4) induced by double-photon absorption of the deep UV (DUV) pulse is probed by the near-infrared (NIR) laser pulse at a peak intensity of 6.4 x 1014Wcm-2. Hydrogen migration channel leading to ethylene(C2H4+) -ethylidene (HC-CH3+) isomerization are observed. Delay-dependent effects are observed in dominant CH2+ + CH2+ (symmetric breakup) and weak CH+ + CH3+ (hydrogen migration) two-body dissociation channels. The yields of these two channels are compared at the different pump and probe power to understand the mechanistic aspects of the dissociation dynamics. |
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