Bulletin of the American Physical Society
52nd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 66, Number 6
Monday–Friday, May 31–June 4 2021; Virtual; Time Zone: Central Daylight Time, USA
Session N01: Poster Session II 4pm-6pm CDTPoster
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N01.00001: COLLISIONS AND SPECTROSCOPY
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N01.00002: Variational calculations of the bound-state energy of Ps$_2$ Sandra J Ward Quintanilla, Gabriel Medrano, Peter Van Reeth We have accurately computed the bound-state energy of Ps$_2$ using the Rayleigh-Ritz variational method with a highly correlated Hylleraas-type trial function |
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N01.00003: A Compact 0.7 T Electron Beam Ion Trap Using Radial NdFeB Magnets David La Mantia, Aung S Naing, Joseph Tan The study of multiply-ionized atoms has been greatly facilitated by the invention of the electron beam ion trap (EBIT), a device developed in the late 1980s1 for the effective production and trapping of highly-charged ions (HCIs). To produce very high charge states, an EBIT typically uses a superconducting magnet to intensify the electron beam, a costly setup to build and operate. In recent years, rare-earth permanent magnets have been used to build compact, room-temperature EBITs that are better suited for atomic clock research and other applications requiring ions with low ionization thresholds. Based on early efforts2 at NIST, a prototype miniaturized EBIT3 employed a pair of axially-magnetized NdFeB rings yoked by drift tubes of soft iron to produce a peak field of 290 mT at the trap center, demonstrating production of various highly charged ions such as Ne8+, Ar9+, Ar13+, Kr17+ and other species of HCIs with ionization potential up to 900 eV. The current work seeks to improve the performance of such miniaturized devices as sources of multiply-charged ions in the mid-Z and mid-q regime which can be extracted and subsequently recaptured for spectroscopy measurements. Simulations reveal that high electron current density and beam transmission through a permanent magnet structure4 with a peak field of 700 mT is attainable by embedding three pairs of radial ring magnets within the two end-cap drift tubes using appropriate materials. |
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N01.00004: Study of spatially confined atoms through Density functional theory Sangita Majumdar, Amlan Roy Atom trapped inside a cavity introduces alluring changes in the observable properties. While atom confined by rigid walls is a |
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N01.00005: Hydrogen-like ions in plasma environment NEETIK MUKHERJEE, Amlan Roy Behaviour of H-like atoms embedded in astrophysical plasmas in the dense plasma, strongly and weekly coupled plasmas have been investigated. In these plasmas, the change in temperature is impacted with the change in confinement radius $(r_{c})$. Two independent and generalised scaling ideas have been applied to modulate the effect of plasma screening constant ($\lambda$) and charge of ion ($Z$) on such systems. Several new equations related to various physico-chemical properties are derived to interconnect the original Hamiltonian and these two scaled Hamiltonian. A new Virial-like theorem has been established for plasma systems. Particularly, plasmas in strong spherical confinement does not obey the conventional Virial theorem. But this new form can serve the purpose successfully. In dense plasma (DP) and weekly couple plasma (WCP) these scaling idea have provided the opportunity to propose a linear equation connecting the critical screening constant $(\lambda_{c})$ and $Z$. Their ratio provides a state dependent constant, after which that particular state vanishes. Shannon entropy has been employed to understand the plasma effect on the ion. The competing effect of plasma charge density ($n_e$) and temperature in WCP is also investigated. Multipole ($k=1-4$) oscillator strength (OS) and polarizabilies for these three systems are studies considering $1s, 2s$ states. Detailed study reveals various interesting features for almost all the systems. |
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N01.00006: An Apparatus for Generation and Isolation of Highly Charged Ions with Low Ionization Thresholds Aung S Naing, David La Mantia, Joseph Tan Electron beam ion traps (EBITs) have provided access to a wide range of highly charged ions for various applications. The recent use of high-field permanent magnets—e.g., neodymium iron boron (NdFeB)—has made it possible to construct small EBITs and other traps like Penning traps. Potential applications include creating certain low ionization threshold highly charged ions, such as Pr9+ and Nd10+, proposed as interesting candidates for the development of next-generation atomic clocks, quantum information processing, or the search for variation in the fine-structure constant [1]. At NIST, a miniaturized electron beam ion trap (mini-EBIT) using a pair of NdFeB magnets has been built as a source of ions with relatively low ionization thresholds (< 1000 eV) [2]. To recapture ions of interest produced in the mini-EBIT, we discuss the design and assembly of a NdFeB permanent magnet Penning trap with a peak magnetic field of ≈ 0.77 T along with the ion transport beamline. The apparatus (both mini-EBIT and Penning trap) is designed to be portable to facilitate its use in various experiments. |
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N01.00007: Monte Carlo Studies of Radiation Therapy via X-Ray Radiosensitization of High-Z Nanomoieties and DNA Strand Breakups Alburuj R Rahman, Maximilliano Westphal, Anil K Pradhan The Monte Carlo code Geant4 was used to study methods to enhance DNA damage from tumor irradiation for cancer theranostics (therapy and diagnostics). The methods involved use of alternative X-ray sources and nanoparticles. Geant4 was used for simulations of the transmission and absorption of photons from quasi-monochromatic (QX), monochromatic (MX), and traditional broadband (BX) X-ray sources with heavy element nanoparticles, with an aim of increasing X-ray absorption [1]. The damage to cells was studied by looking at DNA strand breaks. The radiation can ionize DNA in cancer cells, creating strand breaks. DNA double strand breaks (DSB) are harder for the cell to repair than single strand breaks (SSB). The DSB to SSB ratio shows the strength of radiation therapy, indicating damage. It was found that a monochromatic x-ray sent at energy 82 keV produced the highest DNA double strand break to single strand break ratio. This work is part of a novel methodology names Resonant Nanoplasma Theranostics (RNPT) proposed by the OSU group. |
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N01.00008: Application of Monte Carlo Method to Simulate Radiation Transfer through Exoplanetary Atmospheres Michael Rothman Development is underway of an exoplanetary atmosphere simulator Geant4-EXOPlanets (G4-EXOP) based on the Monte Carlo program package Geant4, which enables modeling transmission of radiation and particles through matter. G4-EXOP will be a toolkit to model host-star radiation transmission through atmospheric layers using radiative transition data of atoms and molecules. G4-EXOP will allow observations to be compared with simulated spectra, resolving abundances in exoplanetary atmospheres. We focus on biosignatures such as H, C, N, O, P and S and molecules containing them. We report, as a test case of G4-EXOP, Gaussian convolutions of the Kurucz simulated solar irradiance and flux residual spectra. Atomic radiative transition probabilities are calculated using SuperStructure, with phosphorus sample results being reported. Transition probabilities for molecules are obtained through ExoMol. Current work is on developing the monochromatic opacity profile module. G4-EXOP will be a toolkit for modeling host-star radiation transmission through exoplanet atmospheres to characterize biosignature abundances within observations. |
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N01.00009: PRECISION MEASUREMENTS
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N01.00010: Collision strengths and rate coefficients of electron-impact excitation and photo-excitations of Ca IV Sultana N Nahar, Bilal Shafique We will report various features of collision strengths ($\Omega$) for |
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N01.00011: Electron Impact Ionization of the Lithium Atom Michael S Pindzola, James P Colgan Time-dependent close-coupling methods are used to calculate |
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N01.00012: Double Photoionization of Atomic Oxygen: Feshbach Resonances in the Two-Electron Continuum Thomas W Gorczyca, Connor Ballance, Steven T Manson, David A Kilcoyne, Wayne Stolte We describe a joint experimental and theoretical investigation on oxygen double photoionization --- the emission of two electrons from atomic oxygen following single photon absorption. High-resolution experimental measurements were performed at the Advanced Light Source, revealing sharp resonance structure superimposed on the more familiar Wannier-like, nearly-linear background. These resonance features are attributed to ionization-plus-excitation Feshbach-resonances embedded in the double ionization continuum. Such features are absent in the double photoionization cross section of He, or other quasi-two-electron systems, for which the doubly-ionized, inert atomic core that remains cannot capture a Feshbach resonance. For a corresponding theoretical analysis, the R-matrix with pseudostates (RMPS) method was invoked by calculating final-state, two-electron resonances-plus continua wavefunctions and corresponding single-photon absorption cross sections. Overall agreement is found in the direct, background double photoionization cross section. However, the RMPS method, using a small basis due to practical computational limitations, was unable to reproduce quantitatively the smooth background or the sharper resonance features observed in the measurements, showing instead large-scale oscillations about the experimental background, and characteristic pseudoresonance jitter, associated with an insufficient convergence of the pseudostate representation to the true two-electron infinite series of Feshbach resonances embedded in the two-electron continuum. The prominent resonance structure observed highlights the need to consider multiple excitation processes in atoms more complex than He or quasi-two-electron systems. |
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N01.00013: Projectile Momentum Uncertainty Effects in Electron Vortex Beam Collisions Alexander D Plumadore, Allison L Harris Ionization collisions have important consequences in many physical phenomena, and the mechanism that leads to ionization is not universal. Understanding how and why electrons are removed from atoms and molecules is crucial to forming a complete picture of the physics. Double differential cross sections (DDCS) have been used for decades to examine the physical mechanisms that lead to ionization and two separate pathways have been identified depending on the energy of the ionized electron. At low energies, the DDCS feature a broad distribution as a function of ionization angle, while at high energies, a sharp peak is observed in the distributions. The width of the DDCS peak can be directly traced to the target electron's quantum mechanical momentum distribution and the results are well-known for plane wave projectiles. However, the recent development of sculpted particle wave packets introduces the opportunity to re-examine the mechanisms that lead to ionization. We present DDCS for (e,2e) ionization of atomic hydrogen for electron vortex projectiles and show that for vortex projectiles making close collisions with the target, the DDCS are sensitive to the projectile momentum uncertainty. |
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N01.00014: A coplanar multipass laser system for a free-free apparatus Nicholas L S Martin, B.N. Kim, C.M. Weaver, B.A. deHarak A free-free experiment investigates the emission or absorption of photons when an electron scatters from an |
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N01.00015: Elastic Scattering of Electrons and Positrons from Rb and Cs atoms with relativistic effects Bidhan C Saha, D. Jakubassa-Amumdsen, A. Basak, A. K. Haque, M. Haque, M. Uddin The elastic scattering of electrons and positrons with Rb and Cs atoms is investigated theoretically employing two different approaches: i) the relativistic Dirac partial wave analysis with a complex optical-potential model (OPM) [1] and ii) the nuclear structure approach (NSA) [2] for 1 eV ≤ Ei ≤ 1 GeV. The OPM incorporates the interaction of the projectile with both the nucleus and the bound target electrons, but the NSA retains only the projectile-nucleus interaction, without the shielding effect due to the bound electrons. An overlap region connecting properly both the low- and high-energy findings is established. Comparison with experimental and other theoretical findings shows the predictive power of our approach, which can easily handle heavier targets without much numerical efforts. |
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N01.00016: Elastic electron scattering from Ar@C60z+: Dirac partial wave analysis AKANKSHA DUBEY Photoionization spectra of A@C60z- introduces interesting features like Coulomb confinement resonances (CCR); a new variety of confinement resonances caused due to Coulomb barrier, whereas for cationic states merely a shift of ionization potential towards higher threshold is noticed1. It is imperative to search for the electron scattering dynamics with such targets, which is not elaborately explored so far compared to that of neutral targets2-3. The present work accounts for a detailed analysis of scattering parameters using Dirac partial wave analysis, emphasizing the role of encaged Ar atom and C60z+ cage in electron scattering from Ar@C60z+ for z=1 and 6. Two contrasting types of model C60 potential with charged-shell potential are employed1. The role of Coulomb field and short-range interactions on scattering dynamics is elucidated through an analysis of the non-Coulomb scattering phase shifts. Differential cross section shows (DCS) oscillatory structures owing to interference of Coulomb and short-range interactions at the intermediate angles. DCS at backward angles comprises of interferences arising due to internal structure of the target (short-range field)4 and Coulomb field dominates near the forward angles. A piecewise scattering approximation can be proposed for charged endohedral scattering, similar to the way it was introduced earlier in electron scattering with endohedral target2. Total cross section shows solely the dominance of Coulomb field; irrespective of the size of target. Target polarization is found significant for smaller z and at low energy. |
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N01.00017: Bremsstrahlung from 5-keV electrons incident on Al2O3, MgO, and SrTiO3 targets Jonathan Heidema, Scott C Williams Bremsstrahlung emitted by 5-keV electrons incident on Al2O3, MgO, and SrTiO3 targets has been compared to results produced using pyPENELOPE (which is based on PENEPMA, the main program of the Monte Carlo code, PENELOPE). The comparisons have been made to test the accuracies of the code’s implementation of the additivity approximation (i.e. the total bremsstrahlung cross section for a molecular target is the sum of the bremsstrahlung cross sections of the constituent atoms). The results simulated using PENEPMA are consistent with the experimental data, except at energies very near the kinematic endpoint of the bremsstrahlung spectra, where the code underestimates the amplitudes. |
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N01.00018: Theoretical Studies of Dissociative Recombination of Electrons with SH+ Ions David O Kashinski, A. P. Hickman, J. Zs. Mezei, I. F. Schneider, D. Talbi We are investigating the dissociative recombination (DR) of electrons with the SH+ion, i.e. e−+ SH+ → S + H, in the interstellar medium to improve upon current astrophysical models. In 2017 we addressed the SH(2Π) potential energycurves (PECs) as a DR pathway2. We extended this work to investigate alternate DR pathways. Early results suggest that DR through a SH(4Π) pathway may resolve the low-energy (< 10 meV) discrepancy between experimentally determined rate coefficients and those determinedthrough the SH(2Π) pathway. Diabatic PECs for the SH(4Π) stateswere determined by applying the block diagonalization method to the adiabatic PECs obtained from large active space multi-reference configuration interaction (MRCI) structure calculations3. Rydberg-valencecoupling has proven to be important. Multichannel quantum defect theory (MQDT) is then used to determine the DR cross sections andrate coefficients. The diabatic PECs and preliminary results of the in-progress dynamics calculations will be presented at the conference. |
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N01.00019: ULTRAFAST AND STRONG FIELD PHYSICS
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N01.00020: Nuclear Motion in Water Ionized by 5-fs Strong Fields Andrew J Howard, Mathew Britton, Ruaridh Forbes, Nolan Peard, Philip H Bucksbaum Strong-field (multiple) ionization (SFI) experiments on molecules with small moments of inertia, such as water, have demonstrated that the large field strengths required for SFI can heavily modify the momenta of ionic fragments during the dissociation that follows multiple ionization. This has a profound effect on final state properties, such as the species, angular distribution, and kinetic energy of the fragments. We recently demonstrated that dynamic alignment and unbending are two dominant effects in the SFI of water for ionizing pulse durations of 40 fs (at 800 nm and 600 TW/cm2). These effects are significantly suppressed for ionizing pulse durations of 10 fs (at 780 nm and 400 TW/cm2). Here we show that dynamic rearrangement of molecular nuclei still occurs for pulse durations shorter than 10 fs. We compare the full three-dimensional fragment momentum distributions of multiply charged two- and three-body dissociations of H2O, D2O, and HOD for pulse durations from 5 fs to 20 fs, noting the changes in each molecule’s bend-angle and alignment with respect to the polarization and the redistribution of population between various decay channels. |
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N01.00021: Proposal for an ultrafast spin-polarized nanotip photoemission electron source based on the spin Hall effect Sam Keramati, Herman Batelaan, Timothy J Gay We propose a new ultrafast laser-driven nanotip source of spin-polarized free electrons taking advantage of the spin Hall effect. A charge current is generated in a V-shaped conducting photocathode of nanometer size scale that supports the spin Hall effect at room temperature with a suitably large Hall angle and spin diffusion length [1]. The resultant induced transverse spin currents on the photocathode surfaces are thus expected to lead to electron spins of opposing signs on opposite walls, and a fraction of the polarized electrons beneath the photoemitting convex surface at the tip of the V would be transversely polarized. The polarization direction of the output beam could be flipped simply by switching the polarity of the voltage source driving the current through the V-shaped photocathode. Search for optimal fabrication processes is underway. It is possible that such photocathodes could be fabricated from commercially-available tungsten V-shaped AFM cantilevers. |
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N01.00022: Operating Characteristics of a GaAs Tip Fast Polarized Electron Source William T Newman, Sam Keramati, Herman Batelaan, Tim Gay Previous work from our group demonstrated that through a multiphoton emission process using a Ti:Saph oscillator, with field effects from sharp tips, it is possible to create a source of polarized electrons from GaAs without a negative electron affinity (NEA) surface [1,2]. This source is fast, i.e., the photoemitted electron pulse duration is comparable to the photon pulse duration. Here, we measured the intensity and polarization of the photoemitted electrons as a function of the voltage on the GaAs shard and the average laser power. The tip voltage and average laser power were varied between -100V and -900V and 30 mW and 120 mW, respectively. The electrons were scattered by a 20 kV Mott polarimeter with an effective Sherman function characterized based on the scattered electron energy loss [3]. We observed electron polarizations varying between 5% and 15% depending on the emitting shard-tip feature. Our results show evidence of a dominant four-photon process. In addition, we have made improvements in the source’s ease of operation as well as the scattering intensity. |
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N01.00023: Pump/probe Studies of Ultrafast Dynamics using X-ray Pulse Pairs Jordan T O'Neal, Taran Driver, Elio G Champenois, Philip H Bucksbaum, James P Cryan, Peter Walter Leveraging the inherent time stability of x-ray free electron laser pulse pairs created from the same electron beam, together with the site-selectivity of x-ray wavelengths, we performed experiments at the LCLS XFEL facility tracking the dynamical evolution of molecular systems. X-ray pump/x-ray probe techniques provide sensitive probes of femtosecond molecular dynamics, and if attosecond x-ray pulses are employed, they can even be used to probe electron dynamics. We present a time-resolved study of ultrafast dissociative ionization of N2O using few-femtosecond x-ray pulse pairs. We track the electron spectrum as a function of pump-probe delay and observe spectral shifts signaling dissociation of the cation after x-ray ionization and Auger-Meitner decay. Using attosecond pulse-pairs, in a subsequent experiment, we track the electron dynamics of aminophenol following impulsive inner-valence ionization. These experiments demonstrate the utility and feasibility of x-ray pump/x-ray probe experiments for studying gas phase molecular dynamics at XFEL facilities. |
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N01.00024: Charge Transfer Dynamics in Dissociation of Halomethanes induced by Extreme Ultraviolet Free-Electron Lase Balram Kaderiya, Enliang Wang, Xiang Li, Severin Meister, Georg Schmid, Sven Augustin, Kirsten Schnorr, Yifan Liu, Hannes Lindenblatt, Florian Trost, Markus Braune, Daniel Rolles, Robert Moshammer, Artem Rudenko Electron transfer plays an important role in chemical bond formation and cleavage and is related to electron delocalization and localization. Ultrafast electron transfer in the dissociative ionization of CH3I and CH2ICl was investigated at FLASH2 by an extreme ultraviolet (EUV) pump-probe experiment. The charge transfer is traced by the yields of the dicationic species as a function of delay between the two EUV pulses. An exponential dependence of charge transfer on the internuclear distance is observed, which shows considerable deviation from the classical over-the-barrier model. Considering the thermal energy of the electrons, we develop a semi-classical model based on a reaction rate equation that quantitatively reproduces the observed behavior at sufficiently large internuclear separations. |
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N01.00025: Emergence of light-induced states in the few-photon ionization of atomic helium Aaron T Bondy, Klaus R Bartschat, Severin Meister, Robert Moshammer, Nicolas Douguet In this joint experimental and theoretical work [1], photoelectron emission from excited states of laser-dressed atomic helium is analyzed. The experiment is carried out at DESY in Hamburg using the FLASH2 free-electron laser with analysis at the reaction microscope (REMI) end station [2]. The helium atom is subject to (temporally) overlapping extreme ultraviolet (XUV) and a infrared (IR) pulses, with either parallel or orthogonal relattive polarization. The XUV pulse is scanned over excited states of helium. Dipole-forbidden transitions to light-induced states (LIS), such as nS and nD states, corresponding to multiphoton (XUV ± nIR) excitation, are observed during temporal overlap of the lasers. Studying photoelectron angular distributions (PADs) in the case where the ionization pathway of a LIS is difficult to resolve energetically allows for an unambiguous determination of the dominant LIS. Relative orientation of the two lasers is employed to study its effect on PADs and to control the suppression of certain ionization pathways. Numerical solutions of the time-dependent Schrdinger equation support the experimental observations. [1] S. Meister et al., Phys. Rev. A 102 (2020) 062809; Phys. Rev. A 103 (2021) in press. [2] S. Meister et al., Applied Sciences 10 (2020) 2953. |
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N01.00026: Deep learning reconstruction of attosecond X-ray pulses from an angularly streaked 2D photoelectron momentum distribution Paris L Franz, Rachel Margraf, Taran Driver, Zhaoheng Guo, Siqi Li, Joe Duris, James P Cryan, Agostino Marinelli We present a deep neural network (NN) to reconstruct attosecond X-ray pulses using the photoelectron momentum spectra (PEMS) from a two-color (X-ray/IR) field. A circularly polarized IR field maps the temporal profile of the X-ray pulse onto the PEMS, which is projected onto a 2D detector using a coaxial velocity map imaging spectrometer (cVMI). Our NN uses the 2D PEMS to predict the electric field of the X-ray pulse. We trained the 5-layer, fully connected network on simulated cVMI data, and tested the NN on experimental cVMI data taken at the Linac Coherent Light Source to benchmark against existing techniques. NN reconstruction of attosecond pulses from such cVMI projections allows for fast characterization of pulses, with possible application to real-time pulse diagnosis at XFELs. |
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N01.00027: Investigating the reconstruction of attosecond pulses generated by a seeded free-electron laser Jianxiong Li, Kenneth J Schafer Attosecond pulses are essential to the investigation electron dynamics on their natural timescale. In contrast to widely used methods of producing attosecond pulses using high-order harmonic generation, a recent work reports the reproducible generation of highly customizable attosecond waveforms using the seeded free-electron laser FERMI [1]. In this work, the reconstruction of the attosecond pulses was based on the interference of two and three photon processes as understood in the strong field approximation. Here we investigate how well the reconstruction works when taking into account the effect of the atomic potential of the detection atoms. We study the reconstruction using He, Ne, and Ar atoms, and find that atomic effects are most pronounced near the ionization threshold. |
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N01.00028: Extending X-ray spectral-domain ghost imaging to optically thick samples Zain Abhari, Siqi Li, James P Cryan, Taran Driver, Agostino Marinelli, Andrey Poletayev The recent development of attosecond pulses from an X-ray free electron laser has enabled a new technique using spectral domain ghost imaging (spooktroscopy) to analyze data from transient absorption spectroscopy (ATAS) for gas molecules. In this work, we introduce a variation of this correlation-based method that will allow for studying optically thick media. This new setup uses ghost imaging to reconstruct the absorption spectrum by correlating the shot-to-shot changes in the total yield of incident x-ray energy with the shot-to-shot variation in the transmitted spectrum. In simulation we inspect the dependence of the reconstruction on numerous experimental parameters. |
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N01.00029: Molecular Modes of Attosecond Charge Migration Aderonke Folorunso, Francois Mauger, Kyle A Hamer, Robert R Jones, Louis F DiMauro, Mette B Gaarde, Kenneth J Schafer, Kenneth Lopata Charge migration (CM) is a coherent mechanism in which a localized hole created by sudden ionization of a molecule travels across the molecular backbone in the time scale of a few hundred attoseconds. In this work, we use first-principles simulations to develop a set of heuristics for charge migration. Halogenated hydrocarbons are studied because they are promising targets for ionization-triggered charge migration experiments and they support the creation of a localized hole via strong-field ionization (SFI). Using constrained density functional theory (cDFT) to emulate SFI, a localized hole was created on the halogen followed by time dependent density functional theory (TDDFT) simulations. After which, we explored the relationship between obtained CM modes and molecules’ length, bond order, and halogenation. Our results show that the CM speed is largely independent of molecule length (~4Å/fs) and hole behaves like a particle as the atomic number of the halogen increases. These heuristics will be useful in identifying molecules and optimal CM detection methods for future experiments. |
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N01.00030: Quantum Charge Migration in Light-Harvesting Chromophores Ruben A Fernandez Carbon, Luca Argenti Mounting experimental evidence suggests that the high efficiency of energy conversion in living beings relies on the quantum nature of charge transfer [1]. Attosecond laser technology allows us to study these ultrafast processes at the molecular level and at their natural time scale. Here, we present an ab-initio method to simulate the evolution of the correlated electronic state of a molecule under the action of arbitrarily polarized ultrashort light pulses in the presence of decoherence and apply it to organic molecules of biological relevance. The molecular excited electronic states are obtained from MCSCF calculations [2] while the effects of driving pulses and decoherence are taken into account by solving numerically the time-dependent Lindblad equation [4] for the density matrix of the system. The migration of charge is tracked using Becke’s charge-partitioning algorithm [5]. Finally, from the dipolar response of the light-dressed molecule, we reconstruct the observable susceptibility and relate it to specific charge migration modes predicted by theory. We demonstrate the potential of this method and show that decoherence favors a few modes, which can be controlled with light pulses to localize charge fluctuations on specific moieties. |
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N01.00031: QUANTUM INFORMATION AND QUANTUM OPTICS
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N01.00032: Microwave to Optical Transducer with Single NV Centers Vinodh Raj Rajagopal Muthu, Michal Bajcsy In this work we aim to develop a quantum interface between microwave and optical photons. This is an essential component in realising a hybrid quantum network where information needs to be efficiently interfaced between superconducting microwave circuits, for quantum information processing, and optical photons, for communication and memories. Our work investigates the potential of micro-fabricated devices with integrated optical and microwave cavities that use individual three-level solid-state emitters, such as NV centres, for the efficient conversion between the microwave and optical regimes. We present analytical and numerical simulation results that explore the required characteristics of the microwave and optical cavities to achieve high conversion efficiency between the microwave and optical regimes. |
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N01.00033: An Elementary Trapped-Ion Quantum Network Dougal Main Trapped ions are a promising candidate for quantum information processing. Hybrid quantum networks based on photonic interfaces have been proposed as a modular architecture for trapped ion processors. In this work, two 88Sr+ ions in separate traps are entangled via the polarisation degree of freedom of spontaneously emitted 422 nm photons. We are able to generate Bell states with a fidelity of 94%, at a rate of 182 s-1 [1]. Using mixed species gate techniques developed by Hughes et al. [2], we aim to incorporate 43Ca+ qubits, which have excellent coherence properties, to create a hybrid quantum network, and we discuss possible applications. |
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N01.00034: Enhancing associative memory recall and storage capacity using confocal cavity QED Brendan Marsh, Yudan Guo, Ronen Kroeze, Sarang Gopalakrishnan, Surya Ganguli, Jonathan Keeling, Benjamin L Lev We introduce a near-term experimental platform for realizing an associative memory that outperforms the standard Hopfield neural network. It can simultaneously store many memories by using spinful bosons coupled to a degenerate multimode optical cavity. The associative memory is realized by a confocal cavity QED neural network, with the cavity modes serving as the synapses, connecting a network of superradiant atomic spin ensembles, which serve as the neurons. Memories are encoded in the connectivity matrix between the spins, and can be accessed through the input and output of patterns of light. Each aspect of the scheme is based on recently demonstrated technology using a confocal cavity and Bose-condensed atoms. The platform represents a new form of random spin system that can be controllably tuned between a ferromagnetic and a spin-glass regime. We find that the native spin dynamics, a form of discrete steepest descent, enhance the network's ability to store and recall memories beyond that of the standard Hopfield model. Surprisingly, the cavity QED dynamics can retrieve memories even when the system is deep in the spin glass phase, a regime in which associative memory was not thought to be possible. |
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N01.00035: Towards a high-performance photonic quantum memory using Bose-Einstein condensate Anindya Rastogi, Erhan Saglamyurek, Taras Hrushevskyi, Benjamin D Smith, Logan W Cooke, Lindsay J LeBlanc The future quantum Internet relies on the long-distance distribution of quantum information via single-photon-level light that needs to be stored in quantum memories. However, developing a long-lived quantum memory, simultaneously featuring efficient, high-speed, and low-noise operation, has been an open challenge due to the intrinsic limitations of both storage platforms and light-matter interaction techniques. Here, we propose and experimentally demonstrate that the fundamentally distinct features of a Bose-Einstein condensate (BEC) platform in combination with the unique advantages of the Autler-Townes-Splitting (ATS) technique overcomes this obstacle. In particular, the non-adiabatic character of the ATS protocol (leading to high-speed and low-noise operation) in conjunction with the intrinsically large atomic densities and ultra-low temperatures of the BEC platform (offering highly efficient and long-lived storage) opens up a new avenue towards high-performance quantum memories. Together with the recently developed space-based BEC systems, our approach brings satellite-based quantum networks closer to reality. |
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N01.00036: Cryogenic Rydberg Optical Tweezer Array Zhenpu Zhang, Ting-Wei Hsu, Adam Kaufman, Cindy A Regal Scalable ultracold Rydberg atom arrays provide an intriguing platform for programmable quantum simulation and computation. We present a new design for a 2D Rydberg qubit array embedded in a low-vibration cryostat. Cryopumping will improve the atom vacuum lifetime to fully leverage the scalability of Rydberg platforms, and a 30 K environment will extend the Rydberg lifetime to its natural linewidth. To create a large and controlled array, we will utilize a 2D optical lattice with the site-resolved addressability and interaction control aided by optical tweezers. To address the effect of motion of Rydberg atoms, we will harness a bi-chromatic magic lattice to provide identical confinement for both ground and Rydberg states, which, together with single photon Rydberg excitation scheme, reduces the phase error in a classic two qubit gate operation. A lossless spin-selective imaging protocol will be explored to maximally exploit the long trap lifetime of the atom array. |
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N01.00037: Experiments on a Quantum Matter Synthesizer Mingjiamei Zhang, Jonathan Trisnadi, Cheng Chin The ``Quantum Matter Synthesizer" integrates single-site imaging with moving optical tweezer arrays for dynamical re-arrangement of atoms in an optical lattice. We first load pre-cooled Cs atoms in a 2D triangular lattice stochastically. After initial imaging of site occupancies, an array of moving tweezers will re-arrange atoms into a desired configuration. In this poster we report progress towards the completion of this apparatus, including the trapping and cooling of atoms at microscope focus, as well as technique to improve the streaming rate of a digital micromirror device to kHz scale for fast implementation of a moving tweezer array. |
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N01.00038: The effect of laser noise on Rabi oscillation fidelity Xiaoyu Jiang, Mark G Friesen, Jacob Scott, Mark Saffman We study the effect of laser noise on one- and two-photon Rabi oscillations with realistic noise models with the goal of quantifying the influence of laser noise on neutral atom quantum gate fidelity. First we study the relation between self-heterodyne measurements, the laser lineshape, and its underlying phase noise features, and power spectral density. There is a universal relation satisfied between the two quantities for locked and well-filtered lasers with low noise, which is useful for practical experiments. Noise spectra that include servo bump features are modeled analytically. |
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N01.00039: Control of directional photocurrent through interference of one- and two-photon ionization Yimeng Wang, Chris H Greene Coherent control of interfering one- and two-photon processes has been the subject of extensive research to achieve phase-controlled redirection of photocurrent. The present study develops two-pathway coherent control of above-threshold photoionization(ATI) of the helium atom ground state, for final state energies up to the $N=2$ ionization threshold, described by a multichannel quantum defect(MQDT) and R-matrix calculation. Three parameters are controlled in our treatment: the optical interference phase $\Delta\Phi$, the reduced electric field strength $\chi=E_2^2/E_1$ (with $E_{2}$ and $E_1$ the respective electric fields of the fundamental and the second-order harmonic), and the final state energy $\epsilon$. Our analysis identifies the $\Delta\Phi$ and $\chi$ parameters that can maximize the degree of control of the directional photoejection asymmetry, and we propose a new frequency-sensitive controlling scheme, by which a small energy change near resonances can flip the direction of scattering electron with high efficiency. An example of the frequency-sensitive coherent control is presented, where 90% of the photoelectrons flip their emission direction when the final state energy is changed from within the $2p^2\ ^1S^e$ resonance to just outside it. |
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N01.00040: QUANTUM INFORMATION SCIENCE
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N01.00041: Non-linear trapped-ion spin-motion coupling with orthogonal geometric phase gates Robert T Sutherland, Raghavendra Srinivas Non-linear boson interactions are essential for quantum metrology and continuous variable quantum computation (CVQC). In trapped ions, subsets of such interactions can be generated for phonons through higher-order spatial derivatives of applied fields. Unfortunately, no scheme exists that enables a broad set of non-linear interactions in an "all-in-one" experimental setup. Here, we propose a new method of generating such interactions that uses two (linear) non-commuting geometric phase gates. We show how this can be used to produce various types non-linear interactions including, among others, one and two mode squeezing, beam splitting, and trisqueezing operations. |
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N01.00042: Quadrupole-quadrupole interactions between three Rydberg atoms Jianing Han Similar to van der Waals interactions, interactions between dipoles, quadrupole-quadrupole interactions are interactions between quadrupoles. In this presentation, we study the quadrupole interactions between highly excited atoms or Rydberg atoms. In addition, unlike many other calculations, in which the primary focus was on the one-dimensional two-body quadrupole-quadrupole interactions, the primary aim of this article is to study the two-dimensional few-body interactions. Specifically, the two-dimensional three-body interactions are investigated. This research has many applications, such as quadrupole-blockade for quantum computing, creating molecules based on quadrupole interactions. |
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N01.00043: Proposed Beamsplitter Network for Heralded 4-ion W-state Remote Entanglement Zachary S Smith, David Hucul, William Grant, Paige Haas, Michael Macalik, Justin Phillips, Harris Rutbeck-Goldman, Boyan Tabakov, James Williams, Carson Woodford, Kathy-Anne Soderberg The number of families of entanglement, such as Bell, W, and GHZ states, grows as the number of entangled qubits increases. These families of entanglement cannot be transformed into another using only local operations and classical communication, and many families of entanglement have different useful properties. For example, W-states maximize residual entanglement under qubit loss. Ion based qubits may be entangled by simultaneously sending a photon emitted from each qubit through a shared interferometer. The design of the interferometer must be chosen to produce and herald successful entanglement. Here we show beamsplitter networks can be used to herald 3- and 4-qubit GHZ- and W-states via 3- and 4-photon coincident detection without the use of other ancilla qubits. Though slower than other proposed methods, as the speed and size of quantum networks grows, the interferometers shown could enhance connectivity without requiring operations at intermediate nodes. Distribution Statement A. Approved for public release: distribution unlimited. Case number AFRL-2021-0178. |
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N01.00044: Analysis of a neutral atom surface code with two atomic species Xiaoyu Jiang, Matthew Otten, Mark Saffman We report on analysis of a neutral atom implementation of the surface code using two atomic species. Quantum error correction using the surface code, or other codes, relies on ancilla qubits that detect an error syndrome and measurement of the ancillas without disturbing data qubits, followed by correction of the data qubits. A challenge for many architectures, including neutral atoms, is measurement crosstalk that corrupts data qubits when measuring ancillas. We have analyzed a two-species implementation using Cs atoms for the data, and Rb atoms for the ancilla. The difference in resonant wavelengths of the two species makes crosstalk free optical measurement practical. A novel repumping scheme is used to mitigate leakage errors to Zeeman states outside the computational basis. Using a numerical code that implements surface 13 we will report on code performance with realistic gate parameters. |
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N01.00045: Quantum Computing with Circular Rydberg Atoms Sam R. Cohen, Jeff D Thompson Rydberg atom arrays are a leading platform for quantum computing and simulation, combining strong interactions with highly coherent operations and flexible geometries. Despite recent improvements, achievable two-qubit gate fidelities are limited by the finite lifetime of the Rydberg states as well as technical imperfections. In this work, we propose a novel approach to quantum computing with Rydberg atom arrays based on long-lived circular Rydberg states in individual optical traps. Based on the extremely long lifetime of these states (exceeding seconds in cryogenic microwave cavities) and gate protocols that are robust to finite atomic temperature, we project that arrays of hundreds of circular Rydberg atoms with two-qubit gate errors below 10-5 can be realized with current technology. |
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N01.00046: Photon-recoil and laser-focusing limits to Rydberg gate fidelity Francis J Robicheaux, Trent Graham, Mark Saffman Limits to Rydberg gate fidelity that arise from the entanglement of internal states of neutral atoms with the motional degrees of freedom due to the momentum kick from photon absorption and re-emission are quantified[1]. The Schrödinger equation that describes this situation is presented and two cases are explored. In the first case, the entanglement arises because the spatial wave function shifts due to the separation in time between excitation and stimulated emission. In the second case, there is a reduction in gate fidelity because the photons causing absorption and stimulated emission are in focused beam modes. This leads to a dependence of the optically induced changes in the internal states on the center of mass atomic position. In the limit where the time between pulses is short, the decoherence can be expressed as a simple analytic formula involving the laser waist, temperature of the atoms, the trap frequency, and the atomic mass. These limits on gate fidelity are studied for the standard π-2π-π Rydberg gate and a protocol based on a single adiabatic pulse with a Gaussian envelope. With realistic parameters and atoms cooled below 5 microK, entanglement fidelity better than 0.99 appears possible in a dense array of atomic qubits. |
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N01.00047: Fermionic ytterbium tweezer arrays for quantum information processing Joanna W Lis, Alec Jenkins, Adam Kaufman Neutral atom tweezer arrays emerged as a prominent platform for quantum computing, quantum simulation and quantum-enhanced metrology. Their scalability and the potential to generate entanglement in a controlled manner are only a couple of the appealing aspects. While the first generation of experiments involved alkali species, recent work with the alkaline-earth and alkaline-earth-like atoms offers an alternative approach, taking advantage of the rich electronic structure the two-valence-electron species have to offer. A promising atomic candidate is the spin-1/2 Yb171 isotope. Its decoupled nuclear and electronic degrees of freedom and the presence of the long-lived excited clock states allow for storage of quantum coherence in the nuclear qubit, while optically manipulating electronic states for lossless state detection. Here, we will report on the progress towards realization of the Rydberg Yb171 optical tweezer arrays. Our platform will incorporate features such as fast, local control of the nuclear qubit and the clock transition, spin-sensitive detection and long-range dipole-dipole interactions accessed through microwave dressing of the Rydberg states, to aid the generation of large and robust entangled states for quantum information processing. |
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N01.00048: A Simplified Projected Optical Trap Array Preston Huft, Yunheung Song, Mark Saffman Arrays of optical traps are ubiquitous in cold atom experiments, including quantum computing and quantum simulation, due to their stability and versatility. However, the optical trains for creating these traps are often complicated, space-consuming, and expensive, requiring active electro-optical devices. Here we present an approach for trapping cold atoms in a 2D optical trap array generated with a novel 4f filtering scheme and custom transmission mask without any active device. The approach can be used to generate arrays of bright or dark traps, or both simultaneously in customizable configurations. Using blue-detuned light, single atoms are loaded into regions of near-zero intensity in an approximately Gaussian profile trap. Moreover, we demonstrate a simple solution to the problem of out-of-focus trapped atoms, which occurs due to the Talbot effect in periodic optical lattices. In such cases, atoms trapped out-of-focus lead to higher background in fluorescence measurements, complicating single atom imaging and control. By using a relatively inexpensive spectrally and spatially broadband laser, out-of-focus interference is mitigated, leading to near perfect removal of Talbot plane traps. |
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N01.00049: High-Fidelity Quantum Memory for the Silicon-vacancy Defect in Diamond Pieter-Jan C Stas, Bartholomeus J Machielse, David Levonian, Ralf Riedinger, Mihir K Bhaskar, Can M Knaut, Erik Knall, Daniel Assumpcao, Rivka Bekenstein, Yan Qi Huan, Mikhail Lukin, Marko Loncar, Hongkun Park Implementation of long range quantum networks requires network nodes with multiple interacting qubits which can be used to store and process information communicated via itinerant photons. We report significant progress towards deterministic realization of such nodes via the implantation of Silicon-29 ions into high quality factor diamond nanophotonic cavities. Silicon-vacancy color centers formed from these ions demonstrate strong interactions between the color center electron spin and the nuclear spin of the silicon atom, constituting a 2-qubit register. The constituent qubits and their interactions can be coherently controlled with microwave and RF signals sent using on-chip coplanar waveguides. We show the realization of high-fidelity gates including CNOT and SWAP gates between these long-lived quantum memories. By leveraging the efficient spin-photon interface enabled by the nanophotonic cavity this demonstration can be extended to a full implementation of the quantum repeater protocol. |
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N01.00050: High-fidelity mixed-species entangling gates for ion-trap quantum computing Oana Bazavan Working with mixed-species ion crystals is advantageous for scaling up trapped ion systems for quantum computing and networking. A high-fidelity entangling gate between ions of different species gives the freedom to select ions with preferable attributes for different tasks, and to coherently map the information from one to the other depending on the required task. |
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N01.00051: Hardware-Efficient, Fault-Tolerant Quantum Computation with Rydberg Atoms Iris Cong, Shengtao Wang, Harry Levine, Mikhail Lukin, Alexander Keesling While neutral atom setups have emerged both theoretically and experimentally as attractive systems for quantum information processing, one important remaining roadblock for achieving large-scale quantum computation with these platforms is the decay of the finite-lifetime Rydberg states during entangling operations. Because such Rydberg state decay errors can result in many possible channels of leakage out of the computational subspace or correlated errors from unwanted blockade effects, they cannot be addressed directly through traditional proposals for fault-tolerant quantum computation. Here, we present a complete analysis of the effects of these intrinsic sources of errors on a neutral-atom quantum computer and propose fault-tolerant quantum computation schemes that address these errors. By making use of the specific structure of the error model, the multi-level nature of atoms, and dipole selection rules, we find that the resource cost for fault-tolerant quantum computation can be significantly reduced compared to existing, general-purpose schemes, even when additional types of errors must be considered. We illustrate the experimental feasibility of our protocols through concrete examples with qubits encoded in 87Rb or 85Rb atoms, and we discuss important considerations for near-term and scalable implementation. |
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N01.00052: Ytterbium Rydberg Atom Arrays Shuo Ma, Jack Wilson, Samuel Saskin, Alex Burgers, Jeff D Thompson Arrays of laser-cooled neutral atoms in optical tweezers have emerged as a promising platform, because of their flexibility and the potential for strong interactions via Rydberg states. We will present our progress with a new platform based on Yb atoms. In particular, we will discuss results on cooling, trapping and imaging Yb atoms in defect-free tweezer arrays, novel spectroscopy of Yb Rydberg states, and trapping of Yb Rydberg states leveraging the polarizability of the Yb$^+$ ion core in a standard, red-detuned optical tweezer. Using these traps, we realize coherence times between two Rydberg levels exceeding the lifetime of un-trapped Rydberg atoms, overcoming a limitation in existing alkali experiments, where Rydberg states are not trapped by the same potential that confines ground state atoms. We will discuss ongoing progress towards gates and quantum dynamics in many-body systems. |
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N01.00053: Fault-Tolerant Operation of a Quantum Error-Correction Code Laird Egan, Dripto Debroy, Crystal Noel, Andrew Risinger, Daiwei Zhu, Debopriyo Biswas, Michael Newman, Muyuan Li, Kenneth Brown, Marko Cetina, Christopher R Monroe We experimentally demonstrate fault-tolerant preparation, measurement, rotation, and stabilizer measurement of a Bacon-Shor logical qubit using 13 trapped ion qubits. Comparing these fault-tolerant protocols to non-fault tolerant protocols, we see significant reductions in the error rates of the logical primitives in the presence of noise. The result of fault-tolerant design is an average state preparation and measurement error of 0.6% and a Clifford gate error of 0.3% after error correction. Additionally, we prepare magic states with fidelities exceeding the distillation threshold, demonstrating all of the key single-qubit ingredients required for universal fault-tolerant operation. |
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N01.00054: Demonstration of a symmetry-protected fermion pair qubit Botond Oreg, Thomas R Hartke, Ningyuan Jia, Martin W Zwierlein Quantum simulation of large scale fermionic systems with ultracold atoms has shown great success in recent years. In situ manipulation and readout have been achieved using optical tweezers and quantum gas microscopes, removing the last roadblocks to performing digitized quantum computation on such platforms. Here we propose and demonstrate a novel way of storing and manipulating quantum information using a pair of fermionic neutral atoms in an optical lattice as the quantum register. The fermion pair forms a spin singlet in a quasi-harmonic trap, and the qubit is formed by a set of symmetry-protected two-particle motional states. The two pair states of the qubit are separated by a gap equal to the atomic recoil energy, providing robust protection from laser intensity noise. Coupling between the states is provided by tunable atomic interactions, controlled via the magnetic field. We observe seconds long coherence times, with gate speeds tunable over orders of magnitude by converting one of the pair states into a tightly bound Feshbach molecule. Individual readout of each qubit is achieved in parallel using fluorescence imaging under a quantum gas microscope. These results open the door towards digital quantum computation based on physical fermions, combining the paradigms of quantum simulation and quantum computation. |
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N01.00055: Modeling a dynamical purification phase transition in a trapped-ion quantum computer Crystal Noel, Pradeep Niroula, Marko Cetina, Daiwei Zhu, Andrew Risinger, Laird Egan, Debopriyo Biswas, Alexey V Gorshkov, Michael Gullans, David A Huse, Christopher R Monroe
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N01.00056: DEGENERATE GASES AND MANY-BODY PHYSICS
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N01.00057: Spin dependent optical potentials for transport measurements in 6Li ultracold gases Alessandro Muzi Falconi, Giulia Del Pace, Woo Jin Kwon, Giacomo Roati, Francesco Scazza Spin drag is a widespread concept in physics, its implications ranging from spintronics to the exploration of quantum many body correlations. In particular, quantum correlations are expected to give rise to collisionless and non dissipative spin currents which are yet to be observed experimentally. Due to their high degree of controllability, ultracold quantum gases provide an ideal platform for both testing theories and observing new spin transport related phenomena. One of the main advantages of these systems is the possibility to manipulate single atomic spin states in a controlled way. For this reason, we developed an optical scheme which exploits near resonant DMD-shaped light to generate spin-dependent optical potentials for the manipulation of Zeeman spin states in a degenerate 6Li gas. In particular, we observed that these states can be selectively addressed by finely tuning the light polarization and frequency between the D1 and D2 lines of 6Li. Through this new tool we intend to explore the dynamical response of our system in presence of a spin dependent external perturbation, and to determine the role of spin correlations in different quantum regimes across the BEC – BCS crossover, from three to two dimensions. |
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N01.00058: Ferromagnetism and Phase-Separation in Confined Fermionic 1D Systems Georgios Koutentakis Lieb and Mattis have shown that ferromagnetism is impossible to achieve in the ground state of fermionic systems, our work focusses on identifying stable ferromagnetic correlations emanating in the excited states of 1D ultracold systems of few fermions. The stability of such correlations can be attributed to the Hund exchange interaction inherent in those setups. However, these ferromagnetic correlations are connected to neither the stability of the magnetization nor the phase separation of the spin-components, contrary to the well enstablished framework of the Stoner instability. |
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N01.00059: Design of a High Numerical Aperture Vacuum Chamber for Optical Lattice Experiments Bhagwan D Singh, Jacob A Fry, Randall G Hulet In our previous experiments, optical lattices have been used to study the behavior of ultra-cold fermions in a 3D realization of the Hubbard model1. The necessity of small lattice beams, however, leads to inhomogeneous confinement. We previously used blue-detuned (anti-trapping) beams to flatten the confining potential2 in order to detect antiferromagnetic (AFM) spinordering1. Finer details in the confinement potential can be realized by implementing a vacuum chamber with a large numerical aperture (NA) for the compensation beams. As a result, the AFM phase region can be enlarged through improved flattening of the potential and sharpening of the walls separating the various phases. More specifically, entropy redistribution may be achieved by imposing entropy storing reservoirs surrounding the main region of interest. |
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N01.00060: Andreev-Bashkin Effect: A Cold Atom / Nuclear Analogy Ryan Corbin, Michael Forbes Superfluid entrainment is a frictionless drag effect predicted to be present in a wide variety of multi-component systems. Though proposed by Andreev and Bashkin in 1975, it has yet to be measured directly. Recent advances in cold-atom experiments make miscible superfluids attractive candidates for investigation, but it has proven difficult to design experiments to observe this effect. In contrast, entrainment plays a significant role in nuclear dynamics, with measurable effects through the giant-dipole resonance (GDR). In this poster, I will discuss how proton-neutron entrainment affects the GDR in density functional models of nuclei. Specifically, entrainment is included in a two-component superfluid model of nuclei through a modified Galilean invariant kinetic term. This analogy with nuclei may provide insight about how similar effects could be seen in cold-atom systems. |
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N01.00061: Vortex Filament Dynamics in the Unitary Fermi Gas Edward Eskew, Michael Forbes Quantum turbulence, characterized by quantized vortices which tangle and interact in a "turbulent" manner, plays a key role in neutron stars, and may hold the key to puzzling phenomena such as pulsar glitches. To understand if neutron superfluids explain glitches, however, one needs to simulate dynamics in macroscopic volumes of nuclear matter, which is prohibitively expensive using microscopic quantum dynamics. The vortex filament model – well-studied in Helium – tracks individual vortices, expressing the bulk superfluid flow with the Biot-Savart law, and can be scaled to much larger volumes relevant for glitches. However, applications of the vortex filament model to the unitary Fermi gas and dilute neutron matter are not as well studied. In this work, we examine vortex dynamics and interactions in the unitary Fermi gas, comparing the vortex filament approach to full simulation of microscopic quantum dynamics using time-dependent density functional theories (TDDFT). Because the unitary Fermi gas is a good approximation to the neutron superfluid in neutron star crusts, this project makes valuable progress towards understanding neutron stars. |
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N01.00062: Pauli blocking of light scattering in degenerate fermions Yu-Kun Lu, Yair Margalit, Furkan Top, Wolfgang Ketterle Pauli blocking occurs when free atoms scatter light elastically and the final external momentum states are already occupied. Suppression of the total rate of light scattering requires a quantum-degenerate Fermi gas with a Fermi energy larger than the photon recoil energy. Pauli blocking was predicted 30 years ago, but the experimental realization was elusive due to the difficulty of prepare cold fermi gas at high density. Here we report the creation of a dense Fermi gas of ultracold lithium atoms and show that at low temperature light scattering is suppressed. We also demonstrated the suppression of inelastic light scattering when two colliding atoms emit light shifted in frequency. Our platform enables future studies of light-matter interaction at high density. |
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N01.00063: Observation of a strongly ferromagnetic spinor Bose-Einstein condensate SeungJung Huh, Kyungtae Kim, Kiryang Kwon, Jae-yoon Choi In this poster, we introduce a new experimental platform of spinor condensate of Lithium-7 atoms with strong ferromagnetic spin interaction. After efficient evaporation cooling in a magnetic trap, we are able to produce condensates in an optical trap without using magnetic Feshbach resonance so that the system has spin degrees of freedom. Studying the nonequilibrium spin dynamics, we have measured the ferromagnetic spin interaction energy to be 160 Hz, which is about 50% of the condensate chemical potential. This implies a strong collision-channel dependence, which leads to a large variation in the condensate size with different spin compositions. In the experiment, radial breathing is excited after a spin-flip transition from mF=0 to mF=1 state, where we can estimate the scattering length ratio among total spin channels. From these experiments, the scattering length for each channel is determined aF=2 = 7(2) and aF=0 = 25(5) Bohr radii, respectively. |
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N01.00064: Effect of domain wall width on spin wave dynamics in a non-degenerate Bose gas Lindsay E Babcock, Mehdi Pourzand, Olha Farion, Jeffrey McGuirk Collisions between indistinguishable atoms in ultracold systems above quantum degeneracy can collectively give rise to spin waves via the identical spin rotation effect. We present experimental results to characterize the effect of domain wall width on lifetime and oscillation frequency of spins waves in a two-domain magnetically trapped ultracold gas of Rb-87. Further, we investigate how application of a spin-dependent optical potential can stabilize domain walls of a certain width and produce long-lived spin domains. |
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N01.00065: Spin dynamics in a 3-domain non-degenerate Bose gas Mehdi Pourzand, Lindsay E Babcock, Olha Farion, Jeffrey McGuirk We explore the spin dynamics of a magnetically-trapped weakly-interacting non-degenerate ultracold Bose gas. In this atomic system, macroscopic spin oscillations are created due to the identical spin rotation effect in binary collisions between indistinguishable atoms. We create quasi-one-dimensional spin structures with three domains and study the effect of the domain widths and domain wall widths on the behavior of spin oscillations in a gas of Rubidium-87. |
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N01.00066: Phase Diagram of Solitons in the Polar Phase of a Spin-1 Bose-Einstein Condensate I-Kang Liu, Shih-Chuan Gou, Hiromitsu Takeuchi We theoretically study the structure of a stationary soliton in the polar phase of spin-1 Bose--Einstein condensate in the presence of quadratic Zeeman effect at zero temperature. The phase diagram of such solitons is mapped out by finding the states of minimal soliton energy in the defining range of polar phase. The states are assorted into normal, anti-ferromagnetic, broken-axisymmetry, and ferromagnetic phases according to the number and spin densities in the core. The order of phase transitions between different solitons and the critical behaviour of relevant continuous transitions are proved within the mean-field theory. |
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N01.00067: Formation and characterization of matter-wave soliton breathers Yi Jin, De Luo, Ricardo Espinoza, Randall G Hulet, Vladimir Yurovsky, Boris Malomed, Oleksandr Marchukov, Vanja Dunjko, Maxim Olshanii Solitons are non-dispersive wave packets which arise as solutions to the 1D nonlinear Schrodinger equation (NLSE). Due to the integrability of the NLSE, higher-order solitons, known as breathers, can be formed from fundamental solitons by a specific interaction quench. A n-soliton breather is composed of constituent solitons of mass ratios 1:3:...:2n-1, and is formed when the attractive interactions are quenched by a factor of n2, where n is an integer. A breather’s density profile oscillates in time at a frequency determined by the chemical potential difference of its constituent solitons. While the relative velocity and positions of the solitons are conserved quantities in the mean-field (MF) limit, quantum manybody theory predicts that quantum fluctuations break integrability and lead to breather dissociation1,2. In this work, we form solitons from a Bose-Einstein Condensate of 7Li atoms in a quasi-1D harmonic potential formed by a focused laser beam. Breathers are formed following an interaction quench controlled through the Feshbach resonance. We observe density profiles of 2- and 3-soliton breathers, and characterize their breathing frequencies with respect to atom number and confinement aspect ratio. Our findings agree well with a quasi-1D MF theory. We report the progress made towards observing breather dissociation. |
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N01.00068: Ultracold dysprosium in 1D optical lattice Pierre Barral, Li Du, Alan Jamison, Wolfgang Ketterle Ultracold dysprosium presents a frontier of study that combines the simplicity of atoms with a dipolar interaction strength approaching that of less polar molecules. We report the creation of a dysprosium BEC and its subsequent loading into an optical lattice. Lifetime and losses of the condensate in the lattice are studied. |
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N01.00069: Topological pumping of a 1D dipolar gas into strongly correlated quantum many-body scar states Kuan-Yu Lin, Wil Kao, Kuan-Yu Li, Sarang Gopalakrishnan, Benjamin L Lev Long-lived excited states of interacting quantum systems that retain quantum correlations and evade thermalization are of great fundamental interest. We create nonthermal states in a bosonic one-dimensional (1D) quantum gas of dysprosium by stabilizing a super-Tonks-Girardeau gas against collapse and thermalization with repulsive long-range dipolar interactions. Stiffness and energy-perparticle measurements show that the system is dynamically stable regardless of contact interaction strength. This enables us to cycle contact interactions from weakly to strongly repulsive, then strongly attractive, and finally weakly attractive. We show that this cycle is an energy-space topological pump (caused by a quantum holonomy). Iterating this cycle offers an unexplored topological pumping method to create a hierarchy of increasingly excited quantum many-body scar states. |
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N01.00070: Direct Observation of Spin-Charge Separation in a Tomonaga-Luttinger Liquid Ruwan Senaratne, Danyel Cavazos-Cavazos, Ya-Ting Chang, Randall G Hulet We demonstrate the first observation of spin-charge separation in a Tomonaga-Luttinger Liquid (TLL) with tunable interaction strength. We measured the low-energy dynamic density response in the charge- and spin-modes by selectively exciting these modes using Bragg spectroscopy. By adjusting the detuning of the Bragg light, we selected whether this spectroscopy was spin-independent (charge-mode), or spin-sensitive (spin-mode). We prepared an effective spin-1/2 system consisting of the lowest and third-to-lowest hyperfine sublevels of 6Li, trapped in a 2D optical lattice, which created an array of quasi-1D tubes. Repulsive inter-species interactions were tuned via a magnetic Feshbach resonance. We observed distinct spectra for the two modes in the strongly interacting regime, which implies that the two modes have distinct propagation speeds. The speed of the charge-mode increased with interaction strength, whereas that of the spin-mode decreased, as predicted for a TLL via exact results for a homogenous gas using Bethe ansatz methods. In the weakly interacting limit, we observed similar excitation spectra for the two modes, and therefore no evidence of spin-charge separation. This disagreement with TLL theory perhaps indicates that the system has effectively 3D behavior for weak interactions. |
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N01.00071: Engineered entanglement in a tweezer-loaded Hubbard-regime optical lattice William J Eckner, Aaron W Young, Nathan A Schine, William R Milner, Dhruv Kedar, Eric Oelker, Jun Ye, Adam Kaufman Arrays of neutral-atoms loaded into optical tweezers with single-particle control have provided a versatile platform for quantum simulation, quantum information, and optical frequency metrology. Building on previous work with tweezer-trapped arrays of ground-state cooled strontium atoms and half-minute atomic coherence times [1], we present results on interfacing our tweezer array with a 3D optical lattice. This hybrid design provides an optical-power efficient method for generating potentials deep enough for low-loss imaging, and high fidelity rotations on strontium’s clock transition. It also opens the door to quantum simulations of Hubbard-model physics, and as a first demonstration of tunneling dynamics on this platform we use the tweezer array to load a single plane of the 3D lattice; we then ramp down the lattice confinement in the plane of the tweezers, and observe quantum random walks of single atoms in two dimensions, as well as 2D Bloch oscillations. Additionally, we present results that introduce long-range, Van-der-Waals type interactions between Rydberg-dressed atoms. Leveraging the flexibility of tweezer-array geometries, we create arrays of atom pairs and use this Rydberg-interaction to perform two-qubit gates on the optical-clock transition. These advances should enable future studies of spin squeezing for quantum enhanced metrology, investigations into the nature of long-lived entanglement on an optical-clock qubit, as well as simulation of extended Hubbard models and transverse-field ising models. |
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N01.00072: Relaxation of a Single Dopant in a 2D Antiferromagnetic Insulator: Interplay of Tunneling and Superexchange Lev H Kendrick, Geoffrey Ji, Muqing Xu, Anant Kale, Christie S Chiu, Justus Bruggenjurgen, Daniel Greif, Annabelle Bohrdt, Fabian Grusdt, Eugene Demler, Martin Lebrat, Markus Greiner The interplay between spin and density underlies much of the emergent phenomena in the doped Hubbard model, including bad metallic phases and possibly d-wave superfluidity. Quantum simulation of the Hubbard model using quantum gas microscopy offers site-resolved readout and manipulation, enabling detailed exploration of the relationship between density and spin. Here we report on the time- and position-resolved dynamics of a single hole in a 2D Hubbard insulator with short-range antiferromagnetic correlations using a cold-atom quantum simulator of about 400 sites. We observe an initial hole expansion determined by the tunnelling rate, followed by a slowdown that strongly depends on the spin exchange energy instead. Concurrent measurements of the spin correlations reveal a dynamical dressing of the hole by its spin environment, indicating the formation and spreading of a magnetic polaron. This work enables the study of out-of-equilibrium emergent phenomena in the Fermi-Hubbard model, one dopant at a time. |
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N01.00073: COLD ATOMS, IONS, MOLECULES, AND PLASMAS
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N01.00074: Normal Modes and Gates in Interspecies Trapped-Ion Chains Jameson O'Reilly, Allison L Carter, Ksenia Sosnova, Sagnik Saha, Yao De George Toh, Christopher R Monroe Scaling up ion trap quantum information processors will likely require at least two co-trapped ion species. Using different species for computation and for sympathetic cooling or photonic interconnects provides spectral isolation that prevents decoherence of the computation ion. However, the different charge to mass ratios of distinct ion species cause their motion to decouple in the radial normal modes that are often used for entangling gates in trapped-ion systems. This decoupling increases the required laser power for these gates and hurts their fidelity by hampering sympathetic cooling. We study the general mass dependence of mutual mode participation in interspecies chains and the laser power required to drive entangling gates with amplitude modulation and amplitude-frequency modulation. We find that co-trapping different isotopes of the same element may be most desirable. |
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N01.00075: Closed-cycle gas flow cryogenic ion trap apparatus Andrew Laugharn, Joseph Britton Trapped atomic ions are a leading platform for quantum information processing. Scaling to processors with 1000’s of ions is expected to require entanglement distribution using ion-photon interfaces mediated by small mode volume photonic structures. We report on the design and testing of a closed-cycle gas flow cryogenic apparatus for ion trapping that will enable rapid prototyping on integration of traps with novel photonic structures. The cryostat is designed to minimize vibration, mechanical drift, and temperature instability[1, 2, 3]. With an eye toward pursuing large qubit registers required for long-distance quantum networking, we note that cryogenic traps enable long ion chains[2], with reduced background gas collisions and motional heating. Our cryostat is rigidly mounted in an 11 inch bore of an optics table. It is mechanically decoupled from a Gifford-McMahon cryo-cooler that lies several meters away in an acoustic isolation box. Eight optical ports 4 inches above the table provide 360○ optical access. All UHV vacuum components, electrical penetrations and cryogenic ports lie under the optics table. We present measurements of the vibration, cooling power, and temperature stability of the apparatus. |
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N01.00076: Progress towards large-scale parallel quantum information processing with trapped Be+ ions Qiming Wu, Melina Filzinger, Yue Shi, Umang Mishra, Jiehang Zhang Trapped atomic ions can be entangled with the Molmer-Sorensen gate scheme, a prevalent approach for quantum computing and quantum simulations. Despite high-precision qubit manipulations with small systems, the current limits for scaling up system sizes come from technical and control challenges: digital systems need extensive individual control; the analog limit suffers from the slow gate speeds; both suffer from collisional losses of ion chains due to residual background gas collisions, which can be solved brute-force by cryogenic ion traps at the cost of introducing significant system complexities and vibration-induced decoherence. We present progress towards parallel gates with long ion strings using combined theoretical, numerical, and experimental approaches. We propose fast gates in the non-adiabatic region using laser frequency modulations with spin-phonon error mitigation and robustness against motional heating. We perform extensive numerical searches and compare with experiments to solve the collisional many-body loss mechanism. Finally, we improve the vacuum level by up to an order of magnitude compared to state-of-the-art setups, without the added complexity of cryogenics. Integrating these advantages, the light mass of Be+ should enable fast parallel quantum gates with a hundred qubits and beyond. |
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N01.00077: Minimal Overhead Detection of 171Yb+ Micromotion in 3D Connor Goham, Joe Britton Atomic ions stored in RF Paul traps exhibit driven motion at the trap frequency known as micromotion [1]. This modulates optical fields seen by the ions, presenting a nuisance for their use in metrology and quantum information [2,3,4]. In heavier ions, the cooling linewidth and trap frequency are often commensurate, complicating measurement of the induced sidebands. In Yb+, the standard 935 nm repump transition has a natural linewidth of 2π×4.2 MHz in comparison to the cooling linewidth of 2π×19.6 MHz and standard trapping frequencies of ΩRF~2π×30 MHz, allowing resolution of the micromotion spectrum without inducing Doppler heating. In-line fiber EOM permits rapid laser control allowing easy measurement along three directions without increasing detection background scatter or inducing trap charging. The result is a rapid method for probing and minimizing micromotion in 3D with very low operational overhead. |
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N01.00078: Optically-heated atomic sources for compact ion traps William J Hughes, Shaobo Gao, Emil Ostergaard, Oliver Lowe, Jacob Blackmore, David Lucas, Joseph Goodwin The drive towards scalable ion trap systems for quantum technology applications places an increasing imperative on compact and reliable subsystems with low power consumption and simple construction, particularly for vacuum-side components. We present a design for an efficient, optically-heated atomic oven, which produces a beam of calcium atoms of suitable for rapid ion loading with modest requirements on heating laser power, easily satisfied by inexpensive diode lasers. In comparison with Joule heated ovens, the absence of low-resistance electrical connections permits excellent thermal isolation of the source, reducing energy delivered to the surrounding system during loading and making the source suitable for use in miniaturised or cryogenic vacuum systems. |
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N01.00079: Design and Assembly of a Compact Penning Trap with In-Vacuum, Thermally-Stable Permanent Magnets Jonathan R Jeffrey, Brian J McMahon, Brian Sawyer We present an updated design of a compact permanent-magnet Penning trap for atomic sensing and quantum information applications. Design advances include the in-vacuum placement of a pair of SmCo alloy magnets with low temperature coefficients to achieve a magnetic field stable to temperature fluctuations. The new design also includes a pair of printed circuit boards with a 12-fold segmented ring electrode for trapping, harmonic compensation, and the creation of various 'rotating wall' potentials. We describe the characterization of the magnetic field and the shimming process used to optimize magnetic field uniformity at the trap center. Plans for the addition of high-finesse mirrors for cavity-enhanced applications are also presented. |
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N01.00080: Quantum networking and vortex field experiments with Strontium ions Mika Chmielewski, Denton Wu, Raphael Metz, Eunji Ko, 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 um, 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. In this poster we discuss the design and current progress towards the assembly of a strontium trapped-ion system for 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 that of the photon spin. It will also allow us to measure the ratio of E2 and M1 multipoles in this transition, which has not previously been measured. |
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N01.00081: Towards a robust system for cryogenic multi-species ion trapping Kyle DeBry, Felix W Knollmann, Trevor J McCourt, Xiaoyang Shi, Jules M Stuart, Susanna Todaro, Jasmine Sinanan-Singh, Gabriel Mintzer, Colin D Bruzewicz, Jeremy Sage, John Chiaverini, Isaac Chuang The increasing complexity of modern trapped ion quantum information processing experiments requires a stable and adaptable system designed for rapid turnaround. We present a robust cryogenic ion trapping apparatus for complex quantum computing experiments. Modular optical systems are integrated on custom-machined baseplates to stabilize and miniaturize the laser system. Light delivery is enabled by chamber-referenced optical couplers with parabolic mirrors and photonic crystal fibers for simplified alignment and identical focus of multiple wavelengths on an ion chain. We demonstrate trapping, initial quantum control, and high-fidelity state detection of 88Sr+ and present work towards trapping 133Ba+. These two species have visible and infrared transition wavelengths and a favorable atomic structure for quantum information experiments. |
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N01.00082: Ion-trapping lab setup for quantum information experiments Sean Brudney, Alexander Quinn, Jeremy Metzner, Isam D Moore, Vikram Sandhu, David J Wineland, David T Allcock The new laboratory for the Oregon Ions, the trapped ions group at the University of Oregon, is in the final stages of setup for initial experiments. Here we present our progress. The group’s main focus is to trap 43Ca+ ions and use them for quantum information experiments. We are currently building and integrating: a macroscopic, linear Paul trap (electrode-to-center spacing of 0.75 mm) that will operate at room temperature; an ultra-high vacuum system; and a compact, rack-mounted laser system for ion cooling, state preparation, state readout, and qubit state manipulation. The apparatus includes a control system based on ARTIQ hardware, gateware, and software, for implementing and analyzing experiments. In addition, we are studying the use of Light Induced Atomic Desorption (LIAD) to load traps by photoionizing neutral atoms that are at lower temperatures than typical for oven and laser ablation methods. |
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N01.00083: Continuous Variable Quantum Computing with Trapped Ions Gabriel Mintzer, Jasmine Sinanan-Singh, Susanna Todaro, Kyle DeBry, Felix W Knollmann, Xiaoyang Shi, Jules M Stuart, Colin D Bruzewicz, Jeremy Sage, John Chiaverini, Isaac Chuang The standard approach to quantum computation uses qubits, which are well-described as a two-level system. An alternative approach is continuous-variable quantum computation (CVQC), which uses observables with a continuum of values such as the position and momentum of a particle. In this work, we use the motional modes of trapped ions as our continuous variable. CVQC has been explored in other physical platforms, such as superconducting qubits and photonic systems, but there remain open questions about the feasibility and implementation for trapped ions. We report progress simulating the motional coherence of CVQC operations implemented with electric fields. Further, we explore using composite sideband laser pulses, which provide a Jaynes-Cummings-like interaction, to read out information stored in the ion's bosonic modes. We present a computational framework for simulating CVQC operations in a realistic trapped-ion system with realistic noise sources, as well as preliminary experimental results implementing these operations on $^{88}Sr^+$ ions. |
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N01.00084: Towards single site addressing and detection in rotating crystals of ions in a Penning trap Jennifer F Lilieholm, Matthew J Affolter, Bryce Bullock, Elena Jordan, Kevin Gilmore, Anthony Polloreno, Ana Maria Rey, John J Bollinger We discuss plans for establishing programmable single qubit rotations on large, single-plane trapped-ion crystals (~200 ions) stored in a Penning ion trap. These crystals rotate (rotation frequency ~180 kHz), making single site addressing challenging with focused laser beams. Previous work has established global rotations of the ion qubits (or spins) and a global entangling gate generated by a spin-dependent force implemented with a moving 1D optical lattice. We discuss how wave front deformations of the 1D optical lattice combined with a lattice frequency that is a multiple of the crystal rotation frequency can generate programmable ion qubit rotations without the need to rotate the lattice. We will implement the wave front deformations with a deformable mirror (DM). Currently, we are characterizing a 137-actuator DM and preparing to add it to the trap’s optical system. In this first iteration we anticipate addressing small neighborhoods of ~6 ions occupying an area of 40 μm diameter. We are also working on improving the detection of individual ions in the crystal with an imaging photon-counting camera that is capable of processing more than 106 photon detection events/s. |
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N01.00085: A guided-light individual addressing scheme for trapped Ba+ ions in an open-access quantum information processor Nikolay N Videnov, Matthew Day, Noah Greenberg, Ali Binai-Motlagh, Nathan Snider, Richard Rademacher, Elijah Durso-Sabina, Virginia Frey, Crystal Senko, Rajibul Islam Trapped ion quantum devices have been used as a proving ground for quantum technologies throughout the last 20 years. To keep the trapped ion platform at the forefront of quantum computing an increased focus must be placed on scaling into the Noisy Intermediate Scale Quantum (NISQ) era. QuantumION is a project at the University of Waterloo's Institute for Quantum Computing (IQC) which aims to improve scalability by providing an open-access quantum computer for the research community. All users will have access to the full control stack and the ability to submit experiments for autonomous execution. To accommodate the breadth of experiments across different user types each of the planned 16 Ba+ ion's quantum state must be individually controllable. To date, ion trap quantum processors have been limited in their qubit numbers due to the challenge of generating large arrays of switchable laser beams with low crosstalk to neighboring sites. To overcome this, a novel guided-light approach is presented in this poster which makes use of state-of-the-art glass micromachining techniques. A single laser beam is split into 16 individual channels using a path length matched Femtosecond Laser Direct Write (FLDW) waveguide. A fibre V-Groove Array (VGA) is butt coupled to the waveguide breaking each channel out into an individual fibre optic cable. Commercial fibre optic Acousto-Optic Modulators (AOMs) are then used to provide independent phase, frequency, and intensity control for each beam. This approach removes any crosstalk inherent to the AOMs. The pitch and beam waist at the ions is set by recombining the fibre optic cables into a VGA with a custom Micro-Lens at the output facet of each fibre. The output is re-imaged onto the corresponding equally spaced ion chain using a single telescope. This poster will present results on route to implementing this setup for QuantumION. |
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N01.00086: The 2F7/2 state in 171Yb+ as a resource for high SPAM fidelity Thomas Dellaert, Patrick J McMillin, Conrad H Roman, Anthony Ransford, Wes Campbell The unique metastable 2F7/2 state in 171Yb+ is a powerful tool for achieving low state preparation and measurement (SPAM) errors in trapped ion qubits. Narrow-band optical pumping from one of the ground-state hyperfine qubit levels to the 2F7/2 manifold allows SPAM of 171Yb+ qubits at state of the art fidelity. As this scheme is based on frequency-selective optical pumping, it is simple to implement and does not require exceptionally fine laser control. Within the 2F7/2 state in 171Yb+, we also implement a metastable qubit on the zero-field clock transition between the F=4 and F=3 sublevels. This "m-type" qubit features separate dissipative channels to out-couple population from either qubit state to the ground state on demand. This allows null-measurement-driven and null-measurement-certified gates in the metastable qubit, which can be used to achieve perform and validate calculations in the presence of noise. |
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N01.00087: Towards Quantum-Enabled Spectroscopy of Highly Charged Ions for Improved Optical Clocks and Tests of Fundamental Physics. Alessandro L Banducci, David Fairbank, Samuel M Brewer In the past few decades, high-precision atomic, molecular, and optical (AMO) experiments have offered a complementary approach to accelerators in the search for new physics. Due to enhanced relativistic effects, highly charged ions (HCIs) provide a unique platform for studies of fundamental physics including tests of quantum electrodynamics (QED) and searches for time-variation of the fundamental constants (e.g. ̇α/α). Here, we present the status of an experimental program to perform high-precision, quantum-enabled laser spectroscopy of trapped HCIs for tests of fundamental physics. We also demonstrate an improved form of the boundary element method (BEM) used for ion trap simulations and highlight applications to the development of high-performance HCI-based optical clocks. |
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N01.00088: Metastable Qubit Operations in 171Yb+ Patrick J McMillin, Thomas Dellaert, Conrad H Roman, Wes Campbell The use of metastable ("m-type'') qubits in trapped ion experiments allows for the development of single-species ion arrays that eliminate the complications that arise from multi-species trapping. The 2F7/2 manifold in 171Yb+ is well suited to host an m-type qubit due to its year-scale lifetime and large optical frequency separation from transitions used in the operation of the ground state ("g-type") hyperfine qubit. We perform single qubit operations of a zero-field clock state m-type qubit, and quantify its coherence and the effect of g-type qubit lasers on qubit coherence and energy splitting. In addition we report high fidelity SPAM of the m-type qubit by heralded state preparation, and investigate the possibility of directly coupling the m-type qubit to motion via stimulated Raman and electric quadrupole transitions. |
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N01.00089: Supersolidity in Trapped Two-Dimensional Dipolar Droplet Arrays Jens Hertkorn, Jan-Niklas Schmidt, Mingyang Guo, Fabian Boettcher, Kevin Ng, Sean Graham, Paul Uerlings, Hans Peter Büchler, Tim Langen, Martin W Zwierlein, Tilman Pfau We theoretically investigate the ground states and the spectrum of elementary excitations across the superfluid to droplet crystallization transition of an oblate dipolar Bose-Einstein condensate. Using scaling properties that arise from beyond mean-field quantum fluctuations, we systematically identify regimes where spontaneous rotational symmetry breaking leads to the emergence of a supersolid phase with characteristic collective excitations. We find a low-energy Goldstone as well as a Higgs amplitude mode arising from the symmetry breaking. Furthermore, we study the dynamics across the transition and show how these supersolids can be realized with standard protocols in state-of-the-art experiments. |
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N01.00090: Additive and nonadditive potentials in a hybrid system: Ground state atom, excited state atom, and ion Pei-Gen Yan, Li-Yan Tang, Zong-Chao Yan, James F Babb The long-range additive and nonadditive potentials for a three-body hybrid atom-ion system composed of one ground S state Li atom, one excited P state Li atom and one ground S state Li+ ion are studied theoretically. The interaction coefficients are evaluated with highly accurate wave functions calculated variationally in Hylleraas coordinates. We find for this hybrid system in particular geometrical arrangements the two-body additive interactions sum to zero leaving only three-body nonadditive collective interactions. We also present a precise evaluation of the coefficients up to order R-6 in the long-range potentials for electronic states of Li2+ correlating to Li+ (1 S) - Li(2 P). |
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N01.00091: GENERAL PRECISION MEASUREMENTS
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N01.00092: Toward a two-dimensional array of ultracold molecular ions controlled with quantum logic to perform precision measurements of time-reversal and parity violating effects Matthew C Cooper, Timothy Chung, Trevor Taylor, Antonio Bernardino, Yan Zhou Molecular ions can be used as quantum sensors of new physics beyond the Standard Model (SM). Low-energy, high-precision measurements on these molecules could provide crucial information about new particles and new forces at the TeV energy scale. TaO+ is chosen in our experiment because of its sensitivity to the effects of the electron’s Electric Dipole Moment (eEDM) and the Nuclear Magnetic Quadrupole Moment (NMQM), which both violate parity (P) and time-reversal (T) symmetry. Additional sources of T violation beyond those included in the SM are required to explain the matter-antimatter imbalance in the universe. We are constructing a new experimental platform that includes a quantum logic scheme to control and detect quantum states of the ions, a two-dimensional array of traps to multiply experimental throughput, and an integrated photonic device to make light delivery and signal detection both efficient and scalable. This new method has the potential to achieve high frequency accuracy of the measurements by efficient state preparation and readout. It is also expected to achieve a one minute or beyond coherence time which will not only support higher measurement accuracy but will also be beneficial for exploring and eliminating a variety of systematics. In addition, this platform can be used for other molecular species that are sensitive to different theories of fundamental physics without substantial modification to the experimental setup. |
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N01.00093: Progress towards a nuclear Schiff moment measurement using TlF molecules in CeNTREX Oskari Timgren, Michael P Aitken, David P DeMille, Olivier O Grasdijk, Jakob Kastelic, David M Kawall, Steve K Lamoreaux, Konrad Wenz, Tristan Winick, Tanya Zelevinsky The prevalence of matter over antimatter – the baryon asymmetry of the universe (BAU) - is an observation that cannot be explained by the Standard Models of particle physics and cosmology. Models aiming to explain the BAU typically require time-reversal symmetry violation at a level far exceeding that of the Standard Model. CeNTREX (Cold molecule Nuclear Time-Reversal EXperiment) is a molecular beam experiment utilizing the Ramsey method of separated oscillatory fields to investigate time-reversal symmetry-violating interactions that are associated with the Schiff moment of the 205Tl nucleus in thallium fluoride (TlF) molecules. This poster gives an overview of the current status of the experiment. We present measurements of the properties of the cryogenic buffer gas beam, and of rotational cooling of the molecular beam. We also discuss proposed state preparation and manipulation schemes for the experiment, which utilize microwave adiabatic passage and/or Rabi pulses. Progress on the main interaction region, including its high-voltage electrodes and magnetic shielding, is reported. |
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N01.00094: Phenomenological model for electric dipole and magnetic moment experiments Peter Porshnev, Vladimir Baryshevsky Relaxing P- and T- reversal symmetries is typically captured by adding electric dipole moment (EDM) and new interaction terms to phenomenological models. We argue that removing symmetry constraints might lead to more physical effects compared to what is currently included into conventional phenomenology. In several recent studies we developed the new phenomenological model which includes new pseudoscalar corrections. It can potentially help in matching QFT predictions with high precision measurements of electric and magnetic moments. Considering the EDM and AMM problems in the single framework, our approach could explain why the electric moment continues to escape detection while the gaps between experimental and theoretical predictions of magnetic anomaly emerge. |
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N01.00095: Silicon photomultiplier module as a photon detector for ACME III Electron EDM search Takahiko Masuda, Daniel G Ang, David DeMille, John M Doyle, Gerald Gabrielse, Zhen Han, Bingjie Hao, Peiran Hu, Nicholas Hutzler, Daniel D Lascar, Zack Lasner, Siyuan Liu, Cole Meisenhelder, Cristian D Panda, Noboru Sasao, Satoshi Uetake, Xing Wu, Koji Yoshimura A search for the electron electric dipole moment (eEDM) is one of the powerful ways to probe for the existence of physics beyond the Standard Model of particle physics. The current upper limit of |de| < 1.1×10-29 e·cm has been achieved by the ACME II which used cold ThO polar molecules. One of the upgrade plans for the ACME III is a new light-induced-fluorescence detection system based on a silicon photomultiplier (SiPM) instead of photomultiplier tube (PMT). SiPMs have higher quantum efficiency, ~50% at 512 nm, than the normal PMTs used in ACME II. We report here a design of the SiPM module and the characterization of the performance. |
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N01.00096: The Buildup to JILA Gen. III eEDM Experiment Anzhou Wang, Kia Boon Ng, Tanya Roussy, Noah Schlossberger, Sun Yool Park, Trevor Wright, Antonio Vigil, Gus Santella, Luke A Caldwell, Jun Ye, Eric A Cornell The third-generation (Gen. III) apparatus for the measurement of the electric dipole moment of the electron (eEDM) at JILA utilizes ThF+. ThF+ has several potential advantages over HfF+ used in the second-generation experiment: (i) the eEDM-sensitive state (3Δ1) has a longer coherence time of about 20 seconds suggested by [1,2]; (ii) ThF+’s effective electric field (35 GV/cm) is 50% larger than that of HfF+ [3], which promises a direct increase of the eEDM sensitivity. To fully exploit the advantage of ThF+’s long coherence time while enhancing the measurement count rate, we introduce a new multiplexing strategy, which would continuously load and read out ThF+. With this strategy, we expect Gen. III to reach a limit of |de| < 10-31 e·cm. However, the price for achieving a long coherence time and the multiplexing strategy is highly homogeneous electromagnetic field during Ramsey oscillation and complicated ion trap structure. We will present the current status of the field simulation and the ion trap design. |
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N01.00097: Characterization of systematic shifts in the 2nd generation JILA eEDM experiment Luke A Caldwell, Tanya Roussy, Trevor Wright, Kia Boon Ng, Noah Schlossberger, Sun Yool Park, Anzhou Wang, Tanner Grogan, Yan Zhou, Yuval Shagam, Antonio Vigil, Gustavo Santaella, Madeline Pettine, Jun Ye, Eric A Cornell Generation II of the JILA eEDM experiment aims to set a new limit on the electron electric dipole moment below 10-29 e cm. The experiment uses hundreds of trapped HfF+ ions, polarized by a rotating electric field and evolving coherently for more than 1 second. We report on our ongoing efforts to study and control systematic shifts in this unique environment for precision metrology. We discuss characterization and suppression of the leading order systematic effects from Generation I as well as new effects that must be considered at our improved sensitivity. |
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N01.00098: Improving Optical Pumping Methods for Nuclear Beta Decay John A Behr, Anastasia Afanassieva, James C McNeil, Alexandre Gorelov, Melissa Anholm, Gerald Gwinner, Dan G Melconian To improve our nuclear beta decay asymmetry experiment [B. Fenker et al. Phys. Rev. Lett. 120 062502 (2018)]), we are trying to improve the vector polarization of our laser-cooled atoms from our present 99.1 +- 0.1% [B. Fenker et al. New J. Phys 18 073028 (2016)]. We cycle on and off a MOT, and optically pump 37K atoms with trap off. We use circularly polarized light on the 4S1/2 → 4P1/2 transition, using RF sidebands on a diode laser to excite transitions from both F=1 and F=2 ground states. We test techniques with stable 41K atoms, which have very similar hyperfine splitting to 37K. Upgrades to improve our systematic uncertainties include: use of twisted nematic liquid crystal rotators for better spin flips; replacing in-vacuum 0.25 mm thick SiC substrate mirrors in front of the beta detectors with 0.004 mm unprotected Au-covered kapton to minimize beta straggling; higher-power laser diode closer to saturation intensity to better overcome Larmor precession around stray B fields. Diagnostics of the polarization include the time dependence of the excited state population after optical pumping light is applied, probed by measuring fluorescence and by nonresonant photoionization. The improvements project to vector polarization 99.6%. |
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N01.00099: Simulation of interactions of cesium atoms with an rf cavity mode for measurement of the nuclear anapole moment Amy Damitz, Jonah Quirk, Daniel Elliott, Carol E Tanner We report simulations of a cesium, 133Cs, atomic beam interacting with an rf field. The rf field will drive a weak electric dipole interaction between the hyperfine components of the ground state of cesium (6s2S1/2 F=3→ 6s2S1/2 F=4), which is weakly allowed due to the nuclear anapole moment. We use detailed numerical calculations of the rf field modes in a cavity and numerical integration of the equations of motion of the state amplitudes to calculate the expected magnitude of precession of the Bloch vector. We show sinusoidal modulation of the relative population of the two ground states with the phase of the rf field, relative to the phase of the initial superposition state. The magnitude of this modulation is ∼5 x 10-6, which we show to be measurable in the laboratory. |
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N01.00100: Field Plates for ACME III Electron EDM Search Peiran Hu, Zhen Han, David P DeMille, Daniel G Ang, John M Doyle, Gerald Gabrielse, Bingjie Hao, Ayami Hiramoto, Nicholas Hutzler, Daniel D Lascar, Zack Lasner, Siyuan Liu, Takahiko Masuda, Cole Meisenhelder, John Mitchell, Cristian D Panda, Noboru Sasao, Satoshi Uetake, Xing Wu, Koji Yoshimura The measurement of electron Electric Dipole Moment (eEDM), de, is a powerful probe for physics beyond Standard Model. The current most stringent limit of |de|<1.1×10-29 e·cm was reported by the ACME II experiment (Nature, 562(2018), 355). A primary source of systematic error in the first two generations of ACME was the polarization imperfection of the state preparation and readout lasers used to detect electron spin precession in the H 3△1 state of ThO molecules. Most of this imperfection comes from stress-induced birefringence of the optical components along the laser path, including vacuum chamber windows and field plates. For ACME III we aim to reduce birefringence and here report on progress towards new field plates and window designs. In order to take advantage of longer precession time in our molecular beam, we are working to develop methods for fabricating larger field plates. Use of a specialized glass material with ultra-low stress-optics coefficient has been examined, and a technique for joining multiple pieces of glass with smooth surfaces at the interface has been developed. A self-calibrating polarimeter was also developed to measure small birefringence in field plate components (arXiv:1703.00963). |
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N01.00101: Progress Towards the ACME III Search for the Electron Electric Dipole Moment Cole Meisenhelder, Daniel G Ang, David P DeMille, John M Doyle, Gerald Gabrielse, Zhen Han, Bingjie Hao, Ayami Hiramoto, Peiran Hu, Nicholas Hutzler, Daniel D Lascar, Zack Lasner, Takahiko Masuda, Cristian D Panda, Noboru Sasao, Satoshi Uetake, Xing Wu, Koji Yoshimura, Siyuan Liu Measurements of the electron electric dipole moment (eEDM) serve as a powerful test for theories of physics beyond the standard model involving high energy time-reversal violating interactions. The ACME II measurement in 2018 reported the current best limit of the eEDM of |de| < 1.1 × 10−29 e · cm (Nature, 562 (2018) 355-360), probing energy scales on the order of 10 TeV (J. High Energ. Phys., 2019 (2019) 59). The ACME collaboration is currently developing a new measurement with the goal of improving the experiment sensitivity by at least an order of magnitude. This new measurement will rely on improvements of the statistical sensitivity of the experiment, and suppression of known systematic error sources. These statistical upgrades include improvements to the molecular beam flux, the detection system, and the experiment precession time. In order to suppress known error sources, we are developing an improved magnetic shielding system, and new glass electric field plates for the precession region. We report here a general overview of the upgrades being developed, and the status of the ACME III measurement of the eEDM. |
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N01.00102: Magnetic characterization of the rotation system for the ARIADNE axion experiment Chloe E Lohmeyer, Nancy Aggarwal, Zhiyuan Wang, Huan Zhang, Andrew A Geraci
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N01.00103: UHV Compatible Power Build-up Cavity for Francium Spectroscopy Tim Hucko, Seth Aubin, John A Behr, Eduardo Gomez, Alexandre Gorelov, Gerald Gwinner, Mukut R Kalita, Luis A Orozco, Matthew Pearson, Anima Sharma, Andrea Teigelhoefer Studying the highly forbidden 7s→8s magnetic dipole (M1) transition is key for future atomic parity-violating (APV) experiments in francium. Relativistic effects and hyperfine interactions give rise to an extremely weak M1 transition, with oscillator strength f ~ 10-13(100× larger than in cesium). To increase the M1 transition rate, one can use a power build-up cavity (PBC) to increase the overall intensity of the spectroscopy laser within the interaction region. At the Francium Trapping Facility located at TRIUMF, Canada's Particle Accelerator Center, we collect neutral francium atoms using magneto-optical traps. These laser-cooled and trapped francium atoms are then used in 7s→8s (506 nm) spectroscopy experiments. We have designed a high finesse PBC that will increase the power of the spectroscopy laser by a gain factor of 4034 ± 50 (preliminary) within the interaction region. This cavity uses the Pound-Drever-Hall locking technique and is UHV compatible. Here we will discuss the design and construction of the PBC, as well as the required stability needed for locking. Further discussion will review measurements of the gain factor and losses of the PBC and compare it to theoretical calculations. |
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N01.00104: Towards measuring the ratio of scalar to vector transition polarizabilities in 7S → 8S transition in francium. Anima Sharma, Gerald Gwinner, Tim Hucko, John A Behr, Mukut Kalita, Matthew Pearson, Andrea Teigelhoefer, Alexandre Gorelov, Luis A Orozco, Eduardo Gomez, Seth Aubin Our group is working on measuring the strength of highly forbidden atomic transitions induced by the parity violating (PV) exchange of Z bosons between electrons and quarks in francium (Z=87), the heaviest alkali, at TRIUMF where we capture Fr atoms in a magneto-optical trap (MOT) online to ISAC. The atomic parity violation (APV) signal in Fr is ≈ 18 × larger than in Cs. Working on the atomic 7S-8S transition, the PV observable will be the interference between a parity-conserving amplitude, the “Stark induced” E1 amplitude created by applying a DC electric field, E, to mix S and P states, and the vastly weaker PV-induced amplitude. The 7S → 8S Stark spectroscopy is a precursor to atomic parity violation tests. We intend to explore the Stark amplitude, in particular the ratio of its scalar, α, (ε || E) and vector, β, (ε ⊥ E) components, where ε is the laser polarization. APV tests will require an accurate value for β , and the measurement of α/β will provide an important benchmark for theory providing β. The poster will present our plans for the precision determination of this ratio, including the challenges of producing spin-polarized Fr in a MOT environment and the sub-ms switching of magnetic fields. |
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