Bulletin of the American Physical Society
51st Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 65, Number 4
Monday–Friday, June 1–5, 2020; Portland, Oregon
Session E01: Poster Session IOn Demand
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Room: Exhibit Hall E |
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E01.00001: Search Efforts for the Thorium-229 Nuclear Isomeric Transition Ricky Elwell, Christian Schneider, Justin Jeet, Galen O'Neil, Varun Verma, Dileep Reddy, Sae Woo Nam, Alina Heihoff, Raphael Haas, Dennis Renisch, Christoph Dullman, Lars von der Wense, Benedict Seiferle, Florian Zacherl, Peter Thirolf, Eugene Tkalya, Eric Hudson The nucleus of $^{229}$Th has an exceptionally low-energy isomeric transition in the vacuum-ultraviolet (VUV) spectrum around 8 eV [1,2]. While inaccessible to standard nuclear physics techniques, there are various prospects for a laser-accessible nuclear transition. Our ongoing direct VUV laser search for the transition using thorium-doped crystals will be supplemented by a conversion-electron M\"{o}ssbauer spectroscopy scheme [3]. In both of these direct excitation schemes, a pulsed dye laser system is used to generate the tunable VUV light. We will also report on the progress of an indirect measurement of the isomeric decay using a superconducting nano-wire single photon imager. \newline \newline [1] Seiferle, B. et al. Energy of the 229Th nuclear clock transition. Nature (2019). \newline[2] B. R. Beck et al.: LLNL-PROC-415170 (2009) \newline[3] von der Wense, L.C. et al. Hyperfine Interact (2019) [Preview Abstract] |
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E01.00002: GSNP Student Poster Competition Winner: The HUNTER Sterile Neutrino Search Experiment: 131-Cs Magneto-Optical Trap Development Eddie Chang, Francesco Granato, Paul Hamilton, Eric Hudson, Basu Lamichhane, Frank Malatino, Charles Martoff, Peter Meyers, Andrew Renshaw, Christian Schneider, Peter Smith, Xunzhen Yu The HUNTER experiment (Heavy Unseen Neutrinos by Total Energy-Momentum Reconstruction) is a search for sterile neutrinos with masses in the keV range. The neutrino missing mass will be reconstructed from 131-Cs electron capture decays occurring in a magneto-optically trapped (MOT) sample. Reaction-microscope spectrometers will detect all charged decay products with high solid angle efficiency and LYSO scintillators read out by silicon photomultiplier arrays will detect x-rays, each with sufficient resolution to reconstruct the neutrino missing mass. The short half-life of about 9.5 d of 131-Cs paired with the requirement to run the experiment over timescales on the order of one year to obtain the target sensitivity present special challenges for the MOT. We will present progress on the 131-Cs MOT development at UCLA, including development of an efficient orthotropic oven source. [Preview Abstract] |
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E01.00003: New apparatus for the measurement of the electron and positron $g$-factors to test the Standard Model Benedict Sukra, Xing Fan, Samuel Fayer, Thomas Myers, Gerald Gabrielse The comparison of the measurement of the electron magnetic moment with its predicted value from the Standard Model yields the most precise test of the Standard Model [1, 2]. This 0.9 parts per trillion comparison between measurement and theory reveals a 2.4 $\sigma $ discrepancy which warrants further investigation [3, 4]. Additionally, a comparison between the electron and positron magnetic moments provides a strong test of CPT symmetry. An apparatus currently being constructed has the goal of improving on the previous measurement of the electron and positron $g$-factors. A Penning trap has been designed with careful consideration of the microwave cavity mode structure with the aim of cooling the axial state via cavity-assisted sideband cooling. The apparatus includes a low field region about 40 cm from the electron trap for implementation of a SQUID detector. A proposed measurement procedure will be presented. 1. D. Hanneke, S. Fogwell, and G. Gabrielse, \textit{Physical Review Letters} 100 (2008) 120801 2. R. H. Parker, C. Yu, W. Zhong, B. Estey, and H. M\"{u}ller, \textit{Science} 360 (2018) 191 3. G. Gabrielse, S.E. Fayer, T.G. Myers, X. Fan,~ \textit{Atoms} 2019, 7, 45. 4. T. Aoyama, T. Kinoshita,~ M. Nio, \textit{Atoms} 2019, 7, 28. [Preview Abstract] |
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E01.00004: Towards Nondestructive State Readout of a Molecular Ion James Dragan, Qi-Ming Wu, Nia Burrell, Brian Odom Despite having “one atom too many” diatomic molecules offer a wealth of extra couplings to fundamental physics, chemical interactions and the environment. Studies of these interactions require state preparation and manipulation as well as reliable state readout. I will present our groups progress in cooling to the ground rovibrational state of silicon monoxide cation (SiO$^+$) and our work to implement nondestructive state readout. By cycling on the $B^2 \Sigma^+$ $\rightarrow$ $X^2 \Sigma ^+$ transition in SiO$^+$ with a pulsed laser whose repetition rate is matched to our ion trap’s axial mode of motion, we can perform state dependent heating. This allows us to conduct precision spectroscopy on vibrational overtone transitions in the X-state, whose levels are perturbed by the low lying $A^2 \Pi^+ $ state, furthering advancement in molecular level calculations while also probing transitions that are sensitive to time variations in the proton-to-electron mass ratio. [Preview Abstract] |
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E01.00005: Probing gravity by holding atoms for 20 seconds Victoria Xu, Matt Jaffe, Cristian Panda, Sofus Kristensen, Logan Clark, James Egelhoff, Holger Mueller Atom interferometers have proven to be powerful tools for probing fundamental physics and for inertial sensing applications. However, their performance has been limited by the available interrogation time of atoms freely falling in Earth's gravitational field. We demonstrate a trapped atom interferometer with visible interference fringes after 20 seconds of interrogation time. This coherence time is enabled by holding the spatially-separated wave packets in the resonant mode of an optical cavity, whose spatial mode filtering enforces a highly homogeneous trap geometry between the interferometer arms. This suspended interferometer geometry allows potentials to be measured by holding, rather than dropping, atoms. After seconds of hold time, the gravitational potential energy differences from micrometers of vertical separation can generate megaradians of interferometer phase. In addition, this trapped geometry can strongly suppress the phase variance caused by vibrations, thus addressing the dominant noise source in atom-interferometric gravimeters. [Preview Abstract] |
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E01.00006: GSNP Student Poster Competition Winner: Beyond the Laser Coherence Limit: Improving Frequency Ratio Measurements in Search of New Physics Ethan Clements, May Kim, Kaifeng Cui, Aaron Hankin, Samuel Brewer, David Leibrandt, David Hume Proposals that resolve outstanding problems in physics such as the nature of dark matter and dark energy could be supported by observing variations in fundamental constants [1]. Recent experiments have placed constraints on these variations using optical atomic clocks [2,3], however, tighter bounds can be made by reducing the statistical uncertainty of the frequency ratios between atoms sensitive to this new physics. Often, the measurement stability is limited by the coherence time of the local oscillator used to interrogate these systems, affecting how well these frequency ratios can be measured. This poster will present experimental demonstrations of two techniques, correlation [4,5] and differential spectroscopy [6]. These techniques utilize differential measurements which avoid or correct deviations in the local oscillator phase. As a result, these techniques can be used to probe beyond the coherence time of the local oscillator, facilitating further constraints on new physical models. [1] A. Arvanitaki et al., PRD, 91.1, 015015, 2015 [2] B. M. Roberts et al., arXiv:1907.02661,~2019 [3] M.S. Safronova et al., RMP, 90, 025008 [4] M. Chwalla et al., APB, 89, 483, 2007 [5] C.W. Chou et al., PRL, 106, 160801, 2011 [6] D. Hume et al., PRA 93.3, 032138, 2016 [Preview Abstract] |
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E01.00007: A Science Gateway for Atomic and Molecular Physics B. I. Schneider, K. Bartschat, K. R. Hamilton, O. Zatsarinny, I. Bray, A. Scrinzi, F. Martin, J. Gonzalez-Vazquez, J. Tennyson, J. D. Gorfinkiel, S. Pamidighantam We describe the creation of a new Atomic and Molecular Physics science gateway [1,2]. It is designed to bring together members of the AMP community to work collectively on making their codes publicly available and easy to use. A project such as this requires the developers to work on issues of portability, documentation, ease of input, as well as ensuring that the codes run on a variety of architectures. We present an outline of our efforts to build the gateway, the current status as discussed in a recent workshop held at NIST on Dec 11-13, 2019, and our long-range plans to further extend the functionality of the gateway. [1]~https://ampgateway.org/ [2]~https://arxiv.org/abs/2001.02286 [Preview Abstract] |
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E01.00008: Implosions in Bose-Einstein condensates quenched to large negative scattering lengths Eli Halperin, Michael Van de Graaff, Xin Xie, John Bohn, Jun Ye, Eric Cornell While much work has been done in understanding the stability and collapse of Bose-Einstein condensates in the presence of weak attractive interactions, comparatively little progress has been made in understanding the transient excitations of a highly unstable Bose gas as it collapses. We explore this less understood strongly attractive regime through a set of implosion experiments in a a harmonically trapped Bose-Einstein condensate with a weak perturbing lattice potential. The lattice induces density modulations that seed implosions which would otherwise be seeded by quantum fluctuations in the absence of the lattice. We theoretically describe the time dynamics of these density modulations in the unstable regime by decomposing into the Bogoliubov modes of the system. We give analytic formulae for of collapse dynamics for Gaussian and sinusoidal perturbations in 1D and 3D which we compare to simulations of the Gross-Pitaevskii equation. By quenching from positive to negative scattering length, we use this model to amplify our well understood density modulations in a positive scattering length gas and get an experimental signature of these seeded fluctuations which can be used as a bridge for understanding the effects of intrinsic quantum fluctuations. [Preview Abstract] |
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E01.00009: Pulsed $^{87}$Rb vector magnetometer using a fast rotating field Tao Wang, Wonjae Lee, Michael Romalis, Mark Limes, Tom Kornack, Elizabeth Foley A rotating magnetic field is applied to obtain vector magnetic field measurements using a pulsed $^{87}$Rb scalar magnetometer. The vector magnetometer provides simultaneous measurements of the total field and two polar angles defining the magnetic field vector. We study systematic effects associated with the operation of the rotating field vector magnetometer. One systematic effect is due to Berry's phase in the presence of a rotating field. Another is a systematic offset in the measured transverse magnetic field that depends on the rotation sense of the applied rotating magnetic field. We compare experimental results with a density matrix model including non-linear Zeeman effects and spin-exchange effects in order to quantitatively study these systematics. [Preview Abstract] |
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E01.00010: Ab initio - calculated direct and shakeup streaked photoemission spectra for helium Hongyu Shi, Uwe Thumm Understanding the correlated ionization dynamics in atoms has remained an important and challenging task [1]. By implementing an adaptive FE-DVR method to efficiently solve the two-electron time-dependent Schroedinger equation, we calculated attosecond time-resolved spectra for streaked XUV photoemission from helium. From the angle-differential calculated spectra we derived (directional) photoemission time delays between direct and 1s$^2$ $\rightarrow$ np$\epsilon$l shake-up ionization. [1] M. Ossiander et al., “Attosecond correlation dynamics” Nat. Phys. 13, 280 (2017). [2] A. Liu and U. Thumm, “Laser-assisted XUV double ionization of helium: Energy-sharing dependence of joint angular distributions”, Phys. Rev A 91, 043416 (2015). [Preview Abstract] |
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E01.00011: Laser ablation loading of Ba ions in a blade trap Chunyang Luan, Pengfei Wang, Zhengyang Cai, Mu Qiao, Kihwan Kim Ba ions are good candidates for using as qubits in trapped ion quantum computers or quantum simulators. The basic manipulation of Ba ions including Doppler cooling, optical pumping and detection is realized by visible laser beams. Quantum operations of Ba ions can be performed by applying 532 nm laser beams with the shelving capability to long-lived metastable 5D$_{\mathrm{5/2}}$ states. However, Ba ions are not popularly used mainly due to the difficulty in loading. Ba atoms are easily oxidized and often need to be heated to high temperature to break the oxidation layer and produce atomic beams. Laser ablation loading can be a solution for the loading problem with the high loading efficiency and negligible thermal effect[1,2]. In our blade trap, the laser ablation loading of Ba ions has been investigated with nitrogen laser pulses. Isotope selectivity of Ba ions can be also realized via resonant photo-ionization method. [1] Zimmermann, K., et al., Applied Physics B 107.4 (2012): 883-889. [2] Olmschenk, S., and P. Becker., Applied Physics B 123.4 (2017): 99. This work was supported by the National Key Research and Development Program of China under Grants No. 2016YFA0301900 and the National Natural Science Foundation of China Grants No. 11974200. [Preview Abstract] |
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E01.00012: Modification of endohedral potential after instant ionization of the inner atom. Miron Amusia, Arkadiy Baltenkov, Larissa Chernysheva We investigate the variation of endohedral A@C$_{\mathrm{N}}$ potential due to addition at the center of it a positive charge, for example, in the process of inner atom A ionization. Using a reasonable model to describe the fullerenes shell, we managed to calculate the variation that is a consequence of the monopole polarization of C$_{\mathrm{N}}$ shell. We analyze model potentials with flat and non-flat bottoms and demonstrate that the phenomenological potentials that properly simulates the C$_{\mathrm{60}}$ shell potential should belong to a family of potentials with a non-flat bottom. As concrete example, we use the Lorentz-bubble model potential. By varying the thickness of this potential, we describe the various degrees of the monopole polarization of the C$_{\mathrm{60}}$ shell by positive electric charge in the center of the shell. We calculated the photoionization cross-sections of He, Ar and Xe atoms located at the center of C$_{\mathrm{60}}$ shell with and without taking into account accompanying this process monopole polarization of the fullerenes shell. Unexpectedly, we found that the monopole polarization do not affect the photoionization cross sections of these endohedral atoms. [Preview Abstract] |
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E01.00013: Precise Measurement of the Electron Affinity of Thallium using Laser Photodetachment Threshold Spectroscopy C. W. Walter, N. D. Gibson, S. E. Spielman The electron affinity of thallium has been precisely measured using laser photodetachment threshold spectroscopy. The relative photodetachment cross section from the negative ion Tl$^{-}$ was measured using a narrowband tunable infrared laser over the photon energy range 300 -- 900 meV (4130 -- 1380 nm). A single s-wave threshold was observed in this range due to the Tl$^{-}$ (6\textit{p}$^{2}$ $^{3}$\textit{P}$_{0}$) to Tl (6\textit{p} $^{2}$\textit{P}$_{1/2}$) ground state-to-ground state transition, which determines the electron affinity of Tl. These results substantially improve the precision of the Tl electron affinity and resolve long-standing discrepancies in the literature between previous experimental and theoretical values. [Preview Abstract] |
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E01.00014: Fitting an Experimental Potential Energy Curve for the 10(0$^+$)[$4^3\Pi_0$] Electronic State of NaCs Andrew Steely, Rachel L. Myers, Andrew Kortyna, John Huennekens, R. F. Malenda, Carl Faust We present experimentally determined potential energy curves for the 10(0$^+$)[$4^3\Pi_0$] electronic state of NaCs. The 10(0$^+$)[$4^3\Pi_0$] state exhibits a double-minimum structure, resulting in a distinctive bound-free fluorescence signature. The perturbation facilitated optical-optical double resonance method was used to obtain Doppler-free excitation spectra corresponding to rovibrational \textcolor{red}{transitions} to the 10(0$^+$)[$4^3\Pi_0$] state. Spectroscopic constants were determined to summarize data belonging to inner well, outer well, and above the barrier regions of the electronic state. The Rydberg-Klein-Rees (RKR) and inverted perturbative approach (IPA) methods were used to construct a potential which reproduces the experimental rovibrational energies within an RMS deviation of 2.33 cm$^{-1}$. An alternative to the pointwise potential approach was also used to determine the potential energy curve by directly fitting an expanded Morse oscillator (EMO) functional form. Advantages of the two approaches as they apply to double minimum wells are discussed. [Preview Abstract] |
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E01.00015: Detection of NaRb Feshbach Molecule By Photodissociation Fan Jia, Zhichao Guo, Lintao Li, Dajun Wang We demonstrate detection of $^{23}Na^{87}Rb$ Feshbach molecule by combining molecular photodissociation and absorption imaging of the photofragments. The photodissociation process is studied by tuning the laser frequency above the Na ($3S_{1/2},|F=1,m_F=1\rangle$) to Na ( $3P_{3/2},|m_I=3/2,m_J=1/2\rangle$) transition, from which we observe a “shelf” like dissociation lineshape. Following the dissociation, the accurate number of molecules can be obtained by detecting either the resultant Rb or Na atoms. We also studied the heating effects caused by the photodissociation laser and optimized the best detection protocol for extracting accurate information of the molecular cloud. [Preview Abstract] |
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E01.00016: DFT Calculation of the Renner Coefficient for the Renner-Teller Splitting in the NCO Radical: Assessing and Characterizing the accuracy of several common functional families and basis sets. D.~O. Kashinski, T.~J. Radziewicz, E.~F.~C. Byrd Assessment of ``out of box'' DFT methods through analysis of the Renner-Teller Effect on the NCO radical is underway. This student-centered project allows us to provide an experiential portion to our undergraduate physics program with an educational focus on HPC-specific computing skills, AMO physics, and modern quantum chemistry methods. DFT functionals from the B3LYP, PBE, TPSS, M06, and M11 families with standard Correlation Consistent, 6-311G split valence family, as well as Sadlej, and Sapporo polarized triple-$\zeta$ basis sets are being assessed. The GAUSSIAN16 suite on DoD-HPCs is used for quantum chemistry calculations. Our Renner coefficients are compared with previously published theoretical and experimental results to assess the accuracy of various functional/basis set combinations. How method choice affects accuracy will be characterized. An update on the progress of this work will be given at the meeting. Early work on other linear triatomics will also be presented. [Preview Abstract] |
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E01.00017: Configuration-interaction many-body perturbation theory transition probabilities of La I and U II Dmytro Filin, Igor Savukov, James Colgan Accurate La I transition probabilities are calculated using configuration-interaction many-body perturbation theory (CI-MBPT) with 10 adjustable parameters, following the method of ref [1]. Comparison is given for energies, g-factors, and transition probabilities and lifetimes with experimental results and with other theories. Close agreement with experiment is observed for most transitions. In some cases, when two states are very close to each other, strong mixing occurs, which was difficult to predict theoretically by only energy optimization. To overcome this, we introduce a mixing angle adjustment that significantly improves the accuracy of the results. This theoretical approach can be extended to other more complex atoms. We have also applied CI-MBPT theory to calculations of energies, g-factors, and transition probabilities for the more complicated U II system. We will report the results of calculations at the conference 1. IM Savukov, PM Anisimov, Physical Review A 99 (3), 032507 (2019). [Preview Abstract] |
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E01.00018: Hyperfine structure of $^{173}\mathrm{Yb}^+$: towards resolving the $^{173}\mathrm{Yb}$ nuclear octupole moment puzzle Di Xiao, Jiguang Li, Andrei Derevianko Hyperfine structure (HFS) of atomic energy levels arises due to the interaction of atomic electrons with a hierarchy of nuclear moments. These contain magnetic dipole, electric quadrupole and higher rank nuclear moments. Recently, the octupole moment of the $^{173}\mathrm{Yb}$ nucleus was extracted from HFS measurements in the ${^3P_2}$ state of neutral Yb [PRA 87, 012512 (2013)]. However, their value, $\Omega = -34.4 \,{\mathrm{b\times{\mu_N}}}$ is four orders of magnitude larger than the nuclear theory prediction, $\Omega =0.003\,{\mathrm{b\times{\mu_N}}}$. We propose to extract $\Omega$ and higher rank nuclear multipole moments from measuring hyperfine splittings in the first excited state ($4f^{13}(^2\!F^{o})6s^2$, $J=7/2$) of $^{173}\mathrm{Yb}^+$. We present results of atomic structure calculations in support of proposed measurements. [Preview Abstract] |
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E01.00019: Analytic Dirac Large and Small Component expressions for Compton Profiles Larry LaJohn Expressions for relativistic Compton profiles (CP) were derived from Dirac large and small component hydrogen like wavefunctions. Such expressions are in the form of a rapidly converging infinite series and are functionally similar in form to the corresponding nonrelativistic (nr) expressions for CP. Such fully relativistic expressions can be used to greatly improve the accuracy of CP obtained from differential cross sections for collision processes such as photon-atom, electron-atom and proton-atom scattering processes. Such errors increase with increasing electron binding energies, as well as increasing angular momentum quantum number (l) and are spin orbit (j quantum number) dependent. Other applications for such expressions would be to model atomic processes that involve interactions with individual bound electrons such as for example positron-electron annihilation. For such applications there is a need for subshell (especially inner and middle shell) CP expressions. [Preview Abstract] |
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E01.00020: Measurement of the ratio of scalar to vector transition polarizabilities for the $6s \rightarrow 7s$ transition in atomic cesium Jonah Quirk, Amy Damitz, Carol E. Tanner, D.S. Elliott We report progress on a new measurement of the ratio of the scalar ($\alpha$) to vector ($\beta$) transition polarizabilities in atomic cesium ($^{133}$Cs) for the $6s \ ^2S_{1/2} \rightarrow 7s \ ^2S_{1/2}$ transition. This measurement is part of an effort in our laboratory to resolve the discrepancy between two determinations of the vector polarizability $\beta$ for this transition [PhysRevLett.123.073002]. For the two-pathway coherent control technique used for this measurement, the two optical pathways will be excited with a two-color two-photon transition and a Stark-induced electric dipole transition concurrently. By varying the phase of the light exciting the Stark transition and the direction of the applied electric field, we will be able to precisely measure the transition strength in each field orientation and determine the ratio $\alpha/\beta$. [Preview Abstract] |
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E01.00021: Shapes of optical molecular resonances from first principles: calculations for atmosphere-relevant molecular systems Hubert Jozwiak, Franck Thibault, Hubert Cybulski, Maciej Gancewski, Piotr Wcislo We present the results of the investigation of the line-shape parameters for two atmospheric systems based on ab initio quantum-scattering calculations. The first one is the N2-perturbed CO molecule, for which we investigated the R(0) purely rotational line. We use three recently reported potential energy surfaces (PESs), calculated by means of the state-of-the-art quantum chemistry methods, to determine the pressure broadening coefficient. We obtain reasonable agreement with the experimental data. The second system is the N2-perturbed O2 molecule. We employ the same methodology, generalized for the case of the active molecule in the $^{3}\Sigma$ electronic ground state. This is the first ab initio investigation of the line-shape parameters in the O2-N2 system. The data provided through the investigation of both systems is important for terrestrial atmospheric measurements, and can be used for populating the HITRAN database. [Preview Abstract] |
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E01.00022: Evaluation of different parameterizations of temperature dependences of the line-shape parameters based on ab initio calculations: Case study for the HITRAN database Hubert Jozwiak, Nikodem Stolarczyk, Franck Thibault, Hubert Cybulski, Grzegorz Kowzan, Bastien Vispoel, Iouli E. Gordon, Laurence Rothman, Robert Gamache, Piotr Wcislo Proper description of the temperature dependence of the line-shape parameters is essential for the spectroscopic studies of both terrestrial and extraterrestrial atmospheres. Here, we use ab initio collisional line-shape calculations for several molecular systems to compare the four temperature ranges (4TR) representation, adopted in the HITRAN database in 2016, with the double-power-law (DPL) representation. Besides the collisional broadening and shift parameters, we consider the most important beyond Voigt line-shape parameters, i.e., the speed dependence of broadening and shift parameters, and real and imaginary parts of the complex Dicke parameter. We demonstrate that not only does the DPL give better overall approximation of the temperature dependencies, but it also requires fewer parameters than the 4TR. We recommend the usage of DPL representation, and present DPL parametrization for Voigt and beyond-Voigt line profiles that will be adopted in the HITRAN database. [Preview Abstract] |
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E01.00023: Nonadiabatic dynamics in dissociative electron attachment to formic acid Daniel Slaughter, Thorsten Weber, Ali Belkacem, Robert Lucchese, Cynthia Trevisan, C. William McCurdy, Thomas Rescigno We present recent results on the dynamics of dissociative electron attachment to formic acid by anion fragment momentum imaging experiments and ab initio electron scattering theory. Anion yield measurements and electronic structure calculations reveal at least two Feshbach (doubly-excited) anion resonances between 6 and 9 eV incident electron energy. We investigate the dynamics of site-selective hydride loss for each resonance. At lower incident energies, two-body dissociation occurs by C-H or O-H break, while at higher incident energies the only significant dissociation channel involves O-H break. Structures in the H- momentum distributions illuminate the presence of two or more electronic states of the HCOO radical, which suggest the presence of a conical intersection between two metastable anion potential energy surfaces. [Preview Abstract] |
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E01.00024: Dissociative electron attachment of NO$_2$ molecule at low collision energies Emily Hendrix, Samantha Fonseca dos Santos, Nicolas Douguet, Chi Hong Yuen, Viatcheslav Kokoouline, Asa Larson, Ann Orel The work focuses on the theoretical study of dissociative electron attachment (DEA) of nitrogen dioxide, NO$_2$, which is a part of undesired air pollutants in the atmosphere produced from combustion processes. NO$_2$ molecules are emitted from combustion processes and can react with oxygen and water present in the atmosphere resulting in the formation of nitric acid that can be detrimental for the environment. Therefore, it is important to not only understand the formation mechanism of NO$_2$ molecules but also its destruction mechanisms. We investigate whether DEA is an efficient process to remove the unwanted NO$_2$ molecules at combustion level before being emitted into the environment. We report here the results of our ab initio quantum chemical studies of the geometrical and electronic structure of the NO$_2$ and and its negative ion NO$_2^-$ in our theoretical study of DEA in NO$_2$. The scattering calculations are carried out using the complex Kohn variational method. The nuclear dynamics, including dissociation, will later be treated using the MCTDH code with a three-dimensional potential energy surface. [Preview Abstract] |
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E01.00025: Theoretical study of vibrational (de-)excitation of NO$_2$ and N$_2$O by low-energy electron impact Hainan Liu, Mehdi Ayouz, Pietro Cortona, Samantha Fonseca dos Santos, Chi Hong Yuen, Viatcheslav Kokoouline We present cross sections for vibrational (de-)excitation of NO$_2$ and N$_2$O by low-energy electron impact. Calculations are performed using a theoretical approach based on a combination of the normal mode approximation for vibrational states of the target molecule, fixed-nuclei electron-target scattering matrices and the vibrational frame transformation employed to evaluate the scattering matrix for vibrational transitions. Results are presented for excitations between the ground and first two excited vibrational states for NO$_2$, and between the ground and first excited vibrational state for N$_2$O in all the vibration modes for both target molecules. Thermally-averaged rate coefficients are derived from the obtained cross sections for temperatures in the 10-10000 K interval. For NO$_2$, a comprehensive set of calculations are performed for assessing the uncertainty of the present calculations. The uncertainty assessments indicate that the computed observables for vibrational (de-)excitation is reasonable for later use in NO$_2$-containing plasma kinetics modeling. For N$_2$O, the NO and NN stretching modes cross-section behavior agrees reasonably well with the available experimental data. [Preview Abstract] |
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E01.00026: Dissociative Recombination in H$_3^+$: a Scattering Matrix Approach Viatcheslav Kokoouline, Chi Hong Yuen, Joshua Forer Dissociative recombination (DR) is the main destruction mechanism of the H$_3^+$ ion in the interstellar medium, which plays an important role in the interstellar chemistry. Previously, a detailed theoretical approach could reproduce main features of the experimental cross section measured in storage-ring experiments. However, energies of Rydberg resonances resolved in the experimental data are not well reproduced by the theory. The reason could be due to the energy-independent scattering matrix employed in the theoretical approach. We are now developing a different version of the approach in which the main improvement is the use of an energy-dependent scattering matrix. In this study we present some preliminary theoretical results on the updated approach. The results are compared with the data from storage ring experiments and the previous theoretical approach. The obtained result is about a factor of two larger than the previous studies, suggesting that the autoionization of the vibrationally-excited Rydberg molecule H$_3^{**}$ may be important in the case of H$_3^+$. [Preview Abstract] |
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E01.00027: Electron transfer, ionization, and excitation in collisions between protons and the ions P$^{14+}$ and S$^{15+}$. Thomas Winter Coupled-state cross sections are being determined for electron transfer, ionization, and excitation in collisions between keV-energy protons and the hydrogenic ions P$^{14+}$ and S$^{15+}$ initially in the ground state, extending early \footnote{% T. G. Winter, Phys. Rev. A {\bf 35}, 3799 (1987)} and more recent work \footnote{% T. G. Winter, Phys. Rev. A {\bf 87}, 032704 (2013)} on the less highly charged target ions He$^{+}$, Li$^{2+}$, ..., C$^{5+}$, and work reported at recent DAMOP meetings on the target ions N$^{6+}$, O$^{7+}$, ..., Si$^{13+}$% . Considering the high asymmetry of the collisional systems, most of the recently chosen bases consist of about a hundred Sturmians on the target nucleus, only augmented by a single $1s$ function on the proton when electron transfer is considered; its contribution is otherwise negligible. The extent to which simple scaling rules with target nuclear charge $Z$ are valid is being examined further for ionization and electron transfer, and particularly for direct excitation, at intermediate energies near where the cross sections peak, as well as at higher energies. [Preview Abstract] |
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E01.00028: Deep minimum in the Ps-formation differential cross section for positron-helium collisions in the Ore gap S, J. Ward, Albandari W. Alrowaily, P. Van Reeth Using the {\it s-}, {\it p-}, {\it d-} and {\it f-}wave complex Kohn K-matrices for positron-helium collisions in the Ore gap [1] we have computed the Ps-formation differential cross section. We found a deep minimum in the cross section that corresponds to a zero in the Ps-formation scattering amplitude and a vortex in the extended velocity field [2] that is associated with this amplitude. Using the Watananbe and Greene's multichannel effective range theory [3] and polynomial fits of the K-matrices we are exploring the importance of the polarization potential in the Ps-He$^+$ channel \item{[1.]} P.~Van~Reeth and J.~W.~Humberston, J.~Phys.~B {\bf 32} 3651 (1999). \item{[2.]} A.~W.~Alrowaily, S.~J.~Ward and P.~Van Reeth, J.~Phys.~B {\bf 52} 205201 (2019). \item{[3.]} S.~Watanabe and C.~H.~Greene, Phys.~Rev.~A {\bf 22} 158 (1980). [Preview Abstract] |
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E01.00029: Charge transfer in positronium-proton collisions: Comparison of classical and quantum-mechanical theories Harindranath Ambalampitiya, Dmitry Fursa, Alisher Kadyrov, Igor Bray, Ilya Fabrikant Charge transfer in collisions of excited positronium with protons is calculated using the quantum-mechanical convergent close-coupling method and classical trajectory Monte-Carlo method. Both calculations produce the same dependence of the cross section on the center-of-mass collision energy and the principal quantum number in the initial state which is justified by analysis of classical and quantum scattering in a dipolar potential. However, the quantum cross section is systematically lower than classical one in absolute magnitude. To investigate the origin of this quantum suppression effect, we compare the charge transfer probabilities as functions of the impact parameter. We show that the quantum suppression in the cross section is mainly due to the low-impact parameter behavior of the probabilities governed by the quantum uncertainty principle. [Preview Abstract] |
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E01.00030: Efficient oil-water separation using femtosecond laser processed meshes followed with vacuum treatment Sharjeel Khan, Ganjaboy Boltaev, Rashid Ganeev, Ali Alnaser Surface structuring by femtosecond laser can alter the wetting behavior and generate micro/nanostructures with high resolution, which can find application in oil-water separation. Superhydrophobic-superoleophilic and superhydrophilic underwater-superoleophobic membranes/meshes, which we analyze in present study, are two ways to realize oil-water separation. In order to alter the wettability to superhydrophobic-superoleophilicity chemical functionalization is commonly desired, while we suggest the femtosecond pulses induced modification of surface properties. In this study surface structuring of metal meshes using 35 and 300 fs pulses yields superhydrophobic-superoleophobic structuring by utilizing a novel technique of post-ablation processing in vacuum during a few hours. Stainless steel and copper meshes are structured with laser and their oil-water separation efficiency is measured by gravity driven separation in which oil passed through the mesh repelling the water. [Preview Abstract] |
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E01.00031: Positronium scattering by molecules: free electron gas plus orthogonalizing pseudopotential model R. S. Wilde, I. I. Fabrikant Experimental total cross sections for scattering of Positronium (Ps) by various atomic and molecular targets are similar to electron scattering cross sections above the Ps ionization threshold$^1$. Below the ionization threshold measurements for rare-gas atoms exhibit small cross sections. Previously we used a Free Electron Gas (FEG) model for the exchange and correlation potentials supplemented by an Orthogonalizing Pseudopotential (OPP) to study Ps scattering with rare-gas atoms$^2$. In general, we obtained good agreement with experiment, but did not find evidence of a Ramsauer-Townsend minimum. We extend the OPP to non-spherical targets and apply the FEG plus OPP model to calculate elastic scattering cross sections for Ps scattering by the molecular targets H$_2$, N$_2$ and CO$_2$. In previous calculations, using only the FEG potentials for N$_2$, we found scattering resonances below the ionization threshold$^3$. The OPP can take account of the repulsive effect of the Pauli Exclusion Principle which can influence the shape and position of these resonances. $^1$S. J. Brawley {\it et al.}, Science {\bf 330}, 789 (2010). $^2$R. S. Wilde and I. I. Fabrikant, Phys. Rev. A {\bf 98}, 042703 (2018). $^3$R. S. Wilde and I. I. Fabrikant, Phys. Rev. A {\bf 97}, 052708 (2018). [Preview Abstract] |
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E01.00032: Coloring of metals and metal alloys surfaces by using 150 KHz fiber femtosecond laser Mazhar Iqbal, Rashid Ganeev, Ganjaboy Boltaev, Ali Alnaser Metal coloring is fascinating in scientific and non-scientific communities alike. Wheather it is for just artistic, decorative features or, and scientific functional applications, laser coloring has very promising impact. Laser based coloring technique is completely eco friendly and is quite flexible in achieving the desired results. We have used a high power fiber femtosecond laser at 150 KHz repetition rate, which reduces the processing time momentously. We have produced permanent and angle dependent colors on Aluminum, Copper, Steel and metal alloys, on smooth as well as on uneven surfaces by laser induced periodic surface structures and non-periodic nano/microstructing. Permanent and angle dependent colors of surfaces can be erased and recolored according to the desired goals. We studied the optical properties of different colors along with the wettability of the surfaces of the metals and metal alloys. The results show that we can make reflectance-controllable surfaces and surfaces varying from hydrophilic to superhydrophobic. [Preview Abstract] |
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E01.00033: Influence of molecular geometry on positron binding to molecules. J. R. Danielson, S. Ghosh, C. M. Surko The observation of vibrational Feshbach resonances (VFR) in the annihilation spectra of positrons on molecules has provided the strongest evidence to date that positrons can bind to molecules.\footnote{Gribakin, et al., {\it Rev. Mod. Phys.} {\bf 82}, 2557 (2010).} Further, the shift of these resonances relative to the underlying molecular vibrational modes provides a direct measurement of the positron-molecule binding energy, $\epsilon_b$. Here, this technique is used to study the influence of molecular geometry on $\epsilon_b$ by making measurements on isomers and conformers (i.e., molecules with the same atomic constituents but with the atoms rearranged). The molecular polarizability and dipole moment are only slightly perturbed (typically $< 2$\%), and so the largest effect will be geometrical in nature. A major result is that more spherical molecules (e.g., iso-propanol) have binding energies that are typically $\sim 10 - 20$\% larger than their chain counterparts (e.g., n-propanol). For molecules with larger molecular dipole moments, and subsequently larger binding energies, this effect is larger. Comparisons of these results to a new model by Swann and Gribakin\footnote{Swann and Gribakin, {\it J. Chem. Phys.} {\bf 149}, 244305 (2018).} will be discussed. [Preview Abstract] |
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E01.00034: New structures observed in the positron annihilation spectra of ring-alkane molecules. S. Ghosh, J. R. Danielson, C. M. Surko Annihilation spectra for molecules as a function of positron energy are typically dominated by relatively sharp features that have been identified as vibrational Feshbach resonances (VFR) involving fundamental modes.\footnote{Gribakin, et al., {\it Rev. Mod. Phys.} {\bf 82}, 2557 (2010).} The VFR spectral width is expected to be determined by the positron energy distribution (FWHM $\sim 36$ meV). This is found to be true for some molecules, including small alkane chains. However, for cyclo-alkanes and larger chain alkanes, the observed spectra are significantly broader than that expected for fundamental vibrations. Details of the measured beam distribution will be presented along with measurements of spectral widths for a range of ring and chain alkanes. Preliminary results for cyclopentane using a new high-resolution cryogenic beam (FWHM $\sim 20$ meV)\footnote{Natisin, et al., {\it Appl. Phys. Lett.} {\bf 108}, 024102 (2016)}, show the broad resonance separates into two distinct peaks, one of which is not due to any known fundamental vibration. Possible physical interpretations of the observed broadening and identification of the new peak will be discussed. [Preview Abstract] |
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E01.00035: Probing many-electron resonances by the positronium formation spectroscopy Himadri Chakraborty, Paul-Antoine Hervieux Positronium (Ps) formation studies of atoms, molecules, polymers, solids, liquids, surfaces/films, metal-organic-frameworks and embedded nanostructures are abundant. Our recent calculations [1,2] of Ps formation from fullerene molecules predicted target-geometry dependent diffraction resonances, which are of single-electron character and may be measured by available laboratory technology [3]. The current study, on the other hand, accesses the many-electron resonances, which are known to have been successfully described in photoelectron studies of atoms and fullerenes, by the Ps formation spectroscopy (PsFS). We model the ground state and the many-body linear response of the targets to the positron field by density functional methods [4] and the Ps formation is treated by the continuum distorted-wave final-state approximation [5]. The results, that will be presented, may motivate applications of PsFS to probe resonance signatures. [1] Hervieux \textit{et al.}, \textit{Phys. Rev. A} \textbf{95}, 020701 (R) (2017); [2] Hervieux \textit{et al}., \textit{Phys. Rev. A} \textbf{100}, 042701 (2019); [3] Hervieux \textit{et al}., \textit{Euro. Phys. J. D} \textbf{73}, 262 (2019); [4] Choi \textit{et al}., \textit{Phys. Rev. A} 95, 023404 (2017); [5] Fojon \textit{et al}., \textit{Phys. Rev. A} \textbf{54}, 4923 (1996). [Preview Abstract] |
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E01.00036: Photoemission studies of Spin Polarized Electrons from Chiral Tungsten N. K. Lewis, K. J. Ahrendsen, Y. Lassailly, I. Vobornik, J. Fujii, T. J. Gay, W. R. Flavell, E. A. Seddon We have measured the spin polarization of photoemission from two-dimensionally chiral W surfaces. Theoretical studies indicate that the surface of an oblique crystal lattice can produce a spin polarization parallel to the direction of the electron crystal momentum that inverts between enantiomorphs [1]. Using the APE-LE beamline at the Elettra synchrotron facility in Italy, we probed the electronic structures of W(321) and W(-3-2-1) surfaces using spin- and angle-resolved photoemission. These measurements are the first of their kind for this crystal surface. We first systematically varied incident photon energy that identified 65 eV as optimal for observing a spin polarization. With this photon energy, we then identified locations of interest in E-k space. For our selected points of interest, significant polarizations were observed for all three spin components and a value as high as 20{\%} was observed in a particular case. Further studies are under way to disentangle the various possible origins of our spin polarization results. [1] N. K. Lewis, P. J. Durham, W. R. Flavell, and E. A. Seddon, Physical Review B \textbf{97}, (2018). [Preview Abstract] |
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E01.00037: Temporal symmetries in XUV+IR photoionization Renata Della Picca, Marcelo Ciappina, Diego Arb\'o The laser-assisted XUV photoelectric effect (LAPE) occurs when extreme ultraviolet (XUV) and infrared (IR) lasers overlap in space and time. The simultaneous absorption of one high-frequency photon and the exchange of several additional photons from the IR field, lead to equally spaced sideband (SB) peaks in the photoelectron spectra (PES) [1]. It is known that the temporal symmetry of the IR field is the responsible of the SB formation [2]. We have found, however, an additional symmetry in certain configurations (inherent to each half cycle) that gives rise to a destructive interference, resulting in only odd or even number of exchanged IR photons [3]. In the present work we theoretically investigate the LAPE in Ar $3s$, with an emphasis on the analytic properties deduced from the SFA transition matrix element. We show that, in several XUV+IR configurations, the PES can be described as a function of the time integral during the first IR optical cycle, not only for the sidebands but also (i) in the streaking regime and (ii) in the case for several XUV attosecond pulses [4]. [1] V\'eniard V et al 1995 Phys. Rev. Lett. 74 4161 [2] Gramajo A A et al 2018 J. Phys. B 51 055603 [3] Della Picca R et al 2020. J Phys Conf. Series. In press. [4] Della Picca R et al 2020. In preparation [Preview Abstract] |
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E01.00038: Ultrafast hydrogen migration and induced fragmentation dynamics in propanol Razib Obaid, Juan Gonzalez, Debadarshini Mishra, Sergio Díaz-Tendero, Nora Kling, Aaron LaForge, Fernando Martín, Nora Berrah Carbon backbones play an important role in ultrafast electronic relaxation processes following photoexcitation, particularly in the presence of another functional group such as -OH. We investigated the photoinduced single and double hydrogen migration, leading to formation of H$_{\mathrm{2}}$O$^{\mathrm{+}}$ and H$_{\mathrm{3}}$O$^{\mathrm{+}}$ respectively, through excitation by intense, ultrashort (\textasciitilde 10 fs), 800 nm laser pulses in two structural isomers of propanol. Our results show changes in the pathways of the time-resolved formation of H$_{\mathrm{2}}$O$^{\mathrm{+}}$ and H$_{\mathrm{3}}$O$^{\mathrm{+}}$, and the mediated bond dissociation observed at the dicationic states of the two propanol conformers. Using coincidence recoil ion momentum spectroscopy and state-of-the-art molecular dynamics simulations, we show the role of carbon chains in the time-resolved energy redistribution and relaxation mechanisms of photoexcited prototypical hydrocarbons. [Preview Abstract] |
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E01.00039: Disentangling Rescattering Interference Structures in High Fidelity Laser-Induced Photoelectron Imaging Nicholas Werby, Adi Natan, Ruaridh Forbes, Robert Lucchese, Philip Bucksbaum Velocity-map imaging (VMI) is a useful tool for probing the dynamic structures of atoms and molecules. This poster presents high fidelity VMI data of the laser-induced photoelectron momentum spectrum of argon gas. By employing an energy filtering with Legendre decomposition algorithm we filter out the characteristic above threshold ionization (ATI) rings, resulting in the approximate single cycle direct ionization spectrum. We observe angle and energy dependent interference patterns in the rescattering regime and we suggest that these patterns are from the interference of long trajectory rescattered electrons. We compare our data to calculations of an electron elastically scattering from a Hartree-Fock ion target and find strong agreement with our measurements at high electron momenta. Our methodologies of data acquisition and processing greatly improve the fidelity of VMI measurements, and may uncover momentum interference structures that are unexplored in earlier studies, further unraveling strong field ionization processes. [Preview Abstract] |
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E01.00040: Dynamic Alignment of Water in the Few-Cycle Limit Andrew J. Howard, Ruaridh Forbes, Gregory A. McCracken, Ian Gabalski, Philip H. Bucksbaum Dynamic alignment refers to the phenomenon by which the anisotropy in the polarizability of a molecule causes it to experience a torque when in the presence of a strong field. This occurs most commonly in linear molecules. Water, in its ground state, is bent and its polarizability is very nearly isotropic. However, strong field ionization of an electron from the 3a$_{\mathrm{1}}$ molecular orbital causes rapid unbending of the molecule and an enhancement in the polarizability along the H-H axis. If the ionizing pulse has a duration greater than the time it takes the molecule to unbend (\textgreater \textasciitilde 10 fs), dynamic alignment can play a significant role in realigning the molecule with the laser polarization axis before dissociation occurs. Here, we demonstrate the dependence of this dynamic alignment effect on the duration of the ionizing pulse. An effusive molecular beam of water is multiply ionized using Ti:Sapphire pulses with a central wavelength of 800 nm and a pulse duration of 40 and \textless 10 fs. The trajectories of the dissociated ions are studied using a momentum imaging spectrometer. [Preview Abstract] |
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E01.00041: Photo-ion photo-electron coincidence study of methanol fragmentation by XUV pump and NIR probe pulses Seyyed Javad Robatjazi, Shashank Pathak, Anbu Venkatachalam, Kanaka Raju P, Jeffery Powell, Surjendu Bhattacharyya, Daniel Rolles, Artem Rudenko Ionization and fragmentation of a methanol molecule has been studied in a pump probe experiment employing coincident velocity map imaging of resulting photoions and photoelectrons. The molecules photoionized by a 30 fs XUV high harmonics pulse were dissociated or further ionized by a near-infrared (790 nm) probe pulse arriving at variable time delays. The channel-selective yields, kinetic energies and angular distributions of the photoions and photoelectrons were recorded as a function of XUV-NIR delay. We compare the results obtained employing a single (13$^{\mathrm{th}})$ harmonic or a train of harmonics (13$^{\mathrm{th}}$ to 27$^{\mathrm{th}})$. While in the former case the outcome of the experiment is dominated by the dynamics in low-lying cationic states and the final products are mainly singly charged, the latter configuration often results in double ionization and populates many highly-excited cationic states. We observe H$_{\mathrm{3}}^{\mathrm{+}}$ ion formation in both singly or doubly charged final states, and trace signatures of hydrogen migration resulting in the ejection of OH$_{\mathrm{2}}^{\mathrm{+}}$ and OH$_{\mathrm{3}}^{\mathrm{+}}$ fragments. [Preview Abstract] |
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E01.00042: Semi-classical approach for solving the time-dependent Schr\"{o}dinger equation in inhomogeneous electromagnetic pulses Jianxiong Li, Uwe Thumm To solve the time-dependent Schr\"{o}dinger equation in spatially inhomogeneous pulses of electromagnetic radiation, we propose an iterative semi-classical complex trajectory approach, termed ACCTIVE (Action Calculation by Classical Trajectory Integral in Varying Electromagnetic pulses) [1]. In numerical applications, we validate this method against \emph{ab initio} numerical solutions by scrutinizing (a) electronic states in combined Coulomb and spatially homogeneous laser fields and (b) streaked photoemission from hydrogen atoms and plasmonic gold nanospheres. In comparison with streaked photoemission calculations performed in strong-field approximation, we demonstrate the improved reconstruction of the spatially inhomogeneous induced plasmonic infrared field near a nanoparticle surface from streaked photoemission spectra [2].\\ \\ [1] J. Li, and U. Thumm, Phys. Rev. A. \textbf{101}, 013411(2020).\\ [2] J. Li, E. Saydanzad, and U. Thumm, Phys. Rev. Lett. \textbf{120}, 223903 (2018). [Preview Abstract] |
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E01.00043: Control of the population and phase dynamics of two-level systems by a single frequency-chirped laser pulse Andras Csehi We present an analytical electric field expression to simultaneously control the population and phase dynamics of two-level quantum systems. The presented electric field is obtained by a reverse engineering technique after the desired population and phase evolution pathways of the system have been specified. Upon application of this laser field, the system is driven from an arbitrary quantum state superposition to the desired population distribution; meanwhile the phase of one of the states proceeds according to a predefined path (J. Phys. B: At. Mol. Opt. Phys. 52 195004, 2019). The robustness of the engineered electric field is demonstrated by numerical simulations on the example of the 3s-3p transition of atomic sodium. Furthermore, the limitations of the presented technique, which arise due to the application of the rotating wave approximation, are thoroughly analyzed and discussed. [Preview Abstract] |
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E01.00044: Echo in a single vibrationally excited molecule Ilia Tutunnikov, Junjie Qiang, Peifen Lu, Kang Lin, Wenbin Zhang, Fenghao Sun, Yaron Silberberg, Yehiam Prior, Ilya Averbukh, Jian Wu Echo is a ubiquitous phenomenon found in many physical systems, ranging from spins in magnetic fields to particle beams in hadron accelerators. Here, we report experimental observation of quantum wave packet echoes in a single isolated molecule [1]. In contrast to conventional echoes, here the entire dephasing-rephasing cycle occurs within a single molecule without any inhomogeneous spread of molecular properties, or any interaction with the environment. In our experiments, we use a short laser pulse to impulsively excite a vibrational wave packet in an anharmonic molecular potential, and observe its oscillations and eventual dispersion with time. A second delayed pulsed excitation is applied, giving rise to an echo - a partial recovery of the initial coherent wavepacket. The vibrational dynamics of single molecules is visualized by time-delayed probe pulse dissociating them one at a time. Interplay between the optically induced echoes and quantum revivals of the vibrational wave packets is observed and theoretically analyzed. The single molecule wave packet echoes may lead to the development of new tools for probing ultrafast intramolecular processes in various molecules.\\ {[}1{]} Nature Physics (2020). https://doi.org/10.1038/s41567-019-0762-7 [Preview Abstract] |
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E01.00045: Enabling momentum-imaging studies of competing proton and hydrogen elimination channels initiated by a strong laser field T. Severt, Bethany Jochim, K. D. Carnes, I. Ben-Itzhak We are interested in imaging and controlling proton versus atomic hydrogen elimination in the strong-field induced dissociation of hydrocarbon molecular ions, such as H$^+ + $ C$_2$H and H + C$_2$H$^+$ from C$_2$H$_2^+$. To permit kinematically complete measurements of these processes, we employ ``fast" (few keV) molecular ion-beam targets, allowing the detection of both neutral and charged fragments [1]. However, measuring breakup channels with large mass asymmetries simultaneously is difficult [2]. We present an upgrade of our coincident three-dimensional momentum imaging method to overcome these challenges and measure the proton and hydrogen elimination channels. \newline [1] I. Ben-Itzhak \emph{et al.}, Phys. Rev. Lett. \textbf{95}, 073002 (2005). \newline [2] L. Graham \emph{et al.}, Phys. Rev. A \textbf{91}, 023414 (2015). [Preview Abstract] |
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E01.00046: Suppressed and enhanced tunneling ionization of transition metal atoms and cations: a TDDFT study on nickel Xi Chu We study the tunneling ionization (TI) of Ni, Ni$^+$, and Ni$^{2+}$ with a TDDFT method and reproduce the puzzling suppression of the TI of Ni and Ni$^+$ and the enhancement of TI in Ni$^{2+}$. Numerical results reveal that for all three species the electron tunnels from a $4s$ orbital, i.e., excitation precedes tunneling for both of the cations, for which the highest orbitals are $3d$. The effective radial potentials for the $d$ orbitals have a centrifugal barrier, while there is no such barrier for the $s$ orbitals. At the classical turning point for the $3d$ orbital, the $3d$ to $4s$ excitation energy is lower than the centrifugal potential for the $d$ orbitals. Two factors of opposite nature are identified in this work. On one hand, electrons moving away from the nucleus in the intense laser fields induce an attractive potential that effectively lowers the energy level and thus suppresses tunneling. Excitation, on the other hand, has the opposite effect and enhances tunneling. The energy gap between $4s$ and $3d$ is small for Ni$^+$ and therefore suppression wins. As the charge of the cation increases, the excitation energy becomes much greater and for Ni$^{2+}$ enhancement dominates. Based on similar analysis, we expect enhanced TI for several other cations. [Preview Abstract] |
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E01.00047: Numerical studies of interaction of bicircular laser pulses with atoms. Yonas Gebre, Joel Venzke, Andreas Becker, Agnieszka Jaron-Becker We perform numerical studies of the interaction of atoms with intense bi-circular laser pulses. We study the interaction by numerically solving the time dependent Schr\"{o}dinger equation (TDSE). The numerical methods used for our calculations will be discussed, particularly the choice of gauge for the TDSE. We demonstrate the convergent behavior of length and velocity gauge for a variety of TDSE calculations, and the resolution of excitation to high Rydberg states. [Preview Abstract] |
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E01.00048: Nonlinear Compton scattering from bound electrons Akilesh Venkatesh, Francis Robicheaux A recent experiment by Fuchs et al.\footnote{\textbf{Nat. Phys.} 11, 964 (2015)} of non-linear Compton scattering revealed an anomalous frequency shift of high-intensity X-rays by electrons in solid beryllium. This frequency shift was at least 800 eV to the red of the values predicted by analytical free-electron models for the same process. Here, we describe a theoretical method for simulating non-linear Compton scattering from bound electrons in a local spherical potential to explore the role of binding energy in the frequency shift of scattered Xrays.\footnote{\textbf{Phys. Rev. A} 101, 013409 (2020)} The calculations do not reveal an additional redshift in the scattered Xrays beyond the nonlinear Compton shift predicted by the free-electron model. Two alternate causes for the anomalous redshift consisting of electron-electron correlation effects and a case of linear Compton scattering from a photoionized electron followed by electron recapture are examined and ruled out. [Preview Abstract] |
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E01.00049: Double photoionization of the Be isoelectronic sequence Stephane Laulan, Marc-Andre Albert, Samira Barmaki We investigate the removal of the two outer electrons in the Be-like ions by using x-ray free electron laser pulses. Our theoretical approach to describe the interaction of the electrons with the laser pulse is based on solving the time-dependent Schr\"odinger equation with a spectral method of configuration interaction type \footnote{S. Barmaki et al., \textbf{Chem. Phys.} 517, 24 (2019)}, \footnote{S. Barmaki et al., \textbf{Phys. Rev. A} 89, 063406 (2014)}. We present the first theoretical results of double-to-single photoionization cross sections ratios for Be-like ions in support of possible photofragmentation experiments with x-ray free electron lasers \footnote{S. Barmaki et al., \textbf{J. Phys. B} 51, 105002 (2018)}. We also present results of the probe of the mutual interaction between the outer electrons at different photon energies and give details about the subsequent redistribution of the excess photon energy among them. [Preview Abstract] |
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E01.00050: Kinematically-complete measurements of laser-induced dissociation of C$_2$H$_2^q$ Bethany Jochim, T. Severt, K. D. Carnes, I. Ben-Itzhak, E. Wells We examine intense femtosecond laser-induced fragmentation of acetylene dications and monocations [1]. Probing these molecules as keV ion-beam targets and focusing on dissociation ensure that the dynamics occur in a single charge state. We observe both acetylene-like breakup (CH$^{q_1}$~+~CH$^{q_2}$) and vinylidene-like breakup (C$^{q_1}$~+~CH$_2^{q_2}$) of the initially linear HCCH configuration C$_2$H$_2^q$ molecules (where $q=q_1+q_2$). For the acetylene dication, the triplet electronic states play a dominant role in the CH$^+$~+~CH$^+$ channel, in contrast to previous photofragmentation studies of neutral C$_2$H$_2$ targets, e.g., [2,3], wherein the singlet states are likely the main contributors. Plausible pathways leading to CH$^+$~+~CH fragmentation of the acetylene monocation are also discussed. The dynamics underlying the vinylidene-like breakup channels are less clear and call for more complete structure calculations and better understanding of the isomerization process. \\ {[1]} B. Jochim \emph{et al.}, Phys. Rev. A \textbf{101}, 013406 (2020); {[2]} A. S. Alnaser \emph{et al.}, J. Phys. B \textbf{39}, S485 (2006); {[3]} T. Osipov \emph{et al.}, J. Phys. B \textbf{41}, 091001 (2008). [Preview Abstract] |
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E01.00051: Redistribution effects in single photon ionization of Rydberg states with IR laser pulses Joel Venzke, Edward Macdonald, Yonas Gebre, Agnieszka Jaron-Becker, Andreas Becker Rydberg states have been shown to survive multi-photon ionization induced by intense IR laser pulses. In this poster, we study the impact of high intensity IR laser pulses on highly excited states in the hydrogen and helium atoms through numerical solutions of the Time Dependent Schrodinger equation. By starting the calculations in a highly excited state, we can analyze the interplay between one photon ionization, few-photon stabilization (e.g. lambda processes), de-excitation, and other higher order processes as a function of angular momentum quantum numbers, laser intensity, and wavelength. [Preview Abstract] |
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E01.00052: Fully correlated two electron calculations interacting with intense laser fields in hyperspherical coordinates Joel Venzke, Agnieszka Jaron-Becker, Andreas Becker Simulations of fully correlated multi electron systems are computationally difficult. When coupled with an intense laser pulse, both the bound and continuum states must be represented, which further complicates the calculations. By expanding the two electron wavefunction in hyperspherical coordinates, the number of radii that must be discretized reduces. In this poster, we present progress towards and current status of our two electron hyperspherical code. [Preview Abstract] |
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E01.00053: Tracking the non-linear optical response in plasmonic nanoparticles with strong-field photoemission spectroscopy Jianxiong Li, J. Powell, A. Summers, S.J. Robatjazi, M. Davino, P. Rupp, C.M. Sorensen, D. Rolles, M.F. Kling, C. Trallero-Herrero, A. Rudenko, Uwe Thumm Femtosecond optical interactions with nanometer-sized metallic structures hold strong promise to enhance our understanding of the transient electronic response of solid matter and enable novel applications in ultrafast electro-optical devices [1]. In order to probe the transient optical response of such structures, we exposed solid gold nanospheres and gold spherical shells with silica cores to intense pulses of infrared light and measured the emitted photoelectron cut-off energy [2]. To better understand the measured photoelectron cut-off energy spectra as functions of intensity, we employed Mie theory to simulate intensity-dependent plasmonic fields, with the inclusion of the non-linear optical effects. We found conclusive evidence that, for thin-layered nanostructures, the non-linear optical response has a significant impact on the plasmonic fields and photoemission process. This intensity-sensitive nonlinear effect in thin layered structures can be exploited to constitute an ultrafast optical switch. [1] J. Li et al., \textit{Phys. Rev. Lett.} 120, 223903 (2018). [2] J. Powell et al., \textit{Opt. Express} 27, 27124 (2019). [Preview Abstract] |
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E01.00054: The imaginary part of the high-order harmonic cutoff Emilio Pisanty, Marcelo F. Ciappina, Maciej Lewenstein High-harmonic generation - the emission of high-frequency radiation by the ionization and subsequent recollision of an electron driven by a strong laser field - has been explained over the past two decades using a semiclassical formalism, derived from a saddle-point approximation, where each saddle corresponds to a complex-valued trajectory. The classification of these saddles into separate families is a central task when using saddle-point methods, but it has received comparatively little attention since the discovery of the approach. In this work we present a novel scheme to classify the different trajectories, based on an identification of the (complex) time that corresponds to the cutoff, given by a zero of an appropriate derivative of the action. We demonstrate this method on bicircular fields of varying intensities, where the different trajectories morph and re-connect to form nontrivial topologies. In addition, we show that this interpretation of the harmonic cutoff coincides with the known scaling laws, and allows them to be easily extended to nontrivial fields. Moreover, this approach provides a natural interpretation to the imaginary part of the high-harmonic cutoff, which controls the strength of quantum-path interference between the trajectories it separates. [Preview Abstract] |
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E01.00055: Many-body quench dynamics in trapped-ion quantum simulators Lei Feng, Wen Lin Tan, Arinjoy De, Harvey B. Kaplan, Kate Collins, Patrick Becker, Antonis Kyprianidis, William Morong, Guido Pagano, Christopher Monroe Trapped-ion quantum simulators are pristine platforms to study out-of-equilibrium many-body systems. We engineer such a simulator embedded with tunable long-range spin-spin interaction using qubits encoded in the hyperfine clock state of $^{\mathrm{171}}$Yb$^{\mathrm{+}}$ atomic ions. With precise laser control, long coherence times, and individual single-shot readout capability, we explore the out-of-equilibrium dynamics after a quantum quench in a transverse Ising Hamiltonian. We first investigate the domain-wall confinement effect on the spin dynamics after the sudden quench. We observe that the spreading of correlations is confined since low-energy excitations are bounded to meson-like quasiparticles. We further study how a weakly nonintegrable many-body system thermalizes after a quantum quench by looking at the temporal fluctuations of the spins [1]. Such fluctuations are exponentially suppressed by increasing the system size as a result of many-body dephasing. We also introduce EIT cooling to simultaneously cool many motional modes of a long chain of ions across a large bandwidth, which is particularly useful for low-frequency modes. [1] H. B. Kaplan, et al., arXiv: 2001.02477 (2020). [Preview Abstract] |
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E01.00056: Topological structures in spinor Bose--Einstein condensates and optical fields Maitreyi Jayaseelan, Justin T. Schultz, Azure Hansen, Joseph D. Murphree, Janne Ruostekoski, Nicholas P. Bigelow We explore the mathematical and physical connections between the topological structures that we create in a $^{87}$Rb Bose--Einstein condensate and those found in optical polarization. We sculpt the spinor wavefunction with a coherent Raman imprinting technique to create fractional and non-Abelian vortices in the F=1 and F=2 atomic ground state manifolds. Mobius strip and torus knot topologies emerge as we characterize the topology of the spinor condensate through the orientation of the order parameter around these singularities. These topologies also occur in optics; we show that the F=1 and F=2 atomic ground state phases correspond to states of monochromatic and bichromatic optical polarization when explored in the language of angular momentum. Transformations between different phases in the atomic ground state manifolds are governed by SU(2) subalgebras of the full symmetry groups of these manifolds. Of these, the subalgebra that involves rotations around the quantization axis is found to govern transformations between the corresponding states of paraxial optical polarization. This points to connections between superfluid flows and flows in optical angular momenta as well as extensions to non-paraxial optical fields and higher spin systems. [Preview Abstract] |
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E01.00057: quantum dynamics in the kicked top model and its generalizations Chenwei Lv, Changyuan Lyu, Yangqian Yan, Qi Zhou The kicked top model has been extensively studied for exploring classical and quantum chaos. Typically, the normalized quadratic interaction, where the strength inversely scales with the size of the system, is considered to avoid the divergent energy density. Here, we show that such a constraint can be relaxed by considering an alternative means of realizing the kicked top model and its generalizations. As a result, new quantum chaotic behaviors emerge and enable precision measurements beyond the standard quantum limit. [Preview Abstract] |
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E01.00058: Tight-Binding Kondo Model and Spin-Exchange Collision Rate of Alkaline-Earth Atoms in a Mixed-Dimensional Optical Lattice Ren Zhang, Peng Zhang We study the two-body problem of ultracold fermionic alkaline-earth (like) atoms in the electronic $^1$S$_0$ state ($g$-state) and $^3$P$_0$ state ($e$-state) which are confined in a quasi-one-dimensional (quasi-1D) tube simultaneously, where in the axial direction the $g$-atom experiences a 1D optical lattice and the $e$-atom is localized by a harmonic potential. Due to the nuclear-spin exchange interaction between the $g$- and $e$-atom, one can use such a quasi-(1+0)D system to realize the Kondo effect. We suggest two tight-binding models for this system, for the cases that the odd-wave scattering between the $g$- and $e$-atom is negligible or not, respectively. Moreover, we give a microscopic derivation for the inter-atomic interaction parameters of these models, by explicitly calculating the quasi-(1+0)D low-energy scattering amplitude of the $g$- and $e$-atom in this system and matching this exact result with the ones given by tight-binding models. We illustrate our results for the experimental systems of ultracold $^{173}$Yb and $^{171}$Yb atoms and show the control effect of the confinement potentials on these model parameters. Furthermore, the validity of the simple ``projection approximation" is examined. In this approximation, one derives the interaction parameters [Preview Abstract] |
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E01.00059: Experiments on Quantum Matter Synthesizer Mingjiamei Zhang, Jonathan Trisnadi, Cheng Chin Scalable atom-by-atom assembly of many-body states is a key progression in the direction of quantum simulation experiments. In this poster we detail the technical aspects of a new apparatus, the ``Quantum Matter Synthesizer", which uses a pair of high-numerical aperture microscope objectives to both image and address atoms on single sites of a 2D lattice. Pre-cooled cesium atoms are first stochastically loaded into a magic-wavelength 2D triangle lattice and then simultaneously cooled and imaged. After detecting the initial site occupancy, an array of moving optical tweezers will re-arrange atoms into a pre-desired configuration. In this poster we report performance updates on the transport, trapping, and cooling of atoms at the microscope focus, as well as details on our implementation of a moving tweezer array. A future upgrade is integrating Optical Feshbach Resonance (OFR) technique into the system, which enables control of local interaction strength and potentially engineering of more exotic quantum phases. [Preview Abstract] |
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E01.00060: Towards Quantum Simulation of Light-Matter Interfaces with Strontium Atoms in Optical Lattices Neven Santic, Andre Heinz, Annie Jihyun Park, Jan Trautmann, Eva Casotti, Florian Wallner, Immanuel Bloch, Sebastian Blatt In the last two decades, quantum simulators based on ultracold atoms in optical lattices have successfully emulated strongly correlated condensed matter systems. With the recent development of quantum gas microscopes, these quantum simulators can now control such systems with single-site resolution. Within the same time period, atomic clocks have also started to take advantage of optical lattices by trapping alkaline-earth-metal atoms such as Sr, and interrogating them with precision and accuracy at the $10^{-18}$ level. Here, we report on progress towards a new quantum simulator that combines quantum gas microscopy with optical lattice clock technology. We have developed in-vacuum buildup cavities with large mode volumes that will be used to overcome the limits to system sizes in quantum gas microscopes. We measure the spatial overlap of two orthogonal cavity modes of the in-vacuum buildup cavity by loading ultracold strontium atoms in a lattice created by those modes. By using optical lattices created in this buildup cavity that are state-dependent for the clock states, we aim to emulate strongly-coupled light-matter-interfaces in parameter regimes that are unattainable in real photonic systems. [Preview Abstract] |
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E01.00061: Probing and controlling dimensionality of strongly interacting spin ensembles Thomas Mittiga, Chong Zu, Simon Meynell, Bingtian Ye, Francisco Machado, Satcher Hsieh, Prabudhya Bhattacharyya, Soonwon Choi, Ania Jayich, Norman Yao Understanding the decoherence of a strongly interacting spin ensemble remains an important challenge at the interface of basic science and quantum technology. Here, we experimentally investigate the electronic spin coherence of nitrogen-vacancy (NV) centers in a nitrogen-14 enriched delta-doped diamond. In this sample, the average spin-spin spacing (\textasciitilde 5 nm) is close to the thickness of the delta-doped layer, leading to a quasi-two dimensional spin system. Compared to conventional 3D samples, we observe an improvement of NV coherence times with a distinct temporal profile. We provide a theoretical model for the observed spin coherent dynamics as a function of dimension. Our work provides new opportunities for exploring novel non-equilibrium physics. [Preview Abstract] |
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E01.00062: Towards a synthetic lattice of Rydberg levels for quantum simulation Jackson Angonga, Bryce Gadway Rydberg atoms in optical tweezer arrays present a versatile platform for quantum simulation, metrology and quantum information processing. We present a scheme that extends the capabilities of this platform by adding a synthetic dimension where several Rydberg levels are coupled by microwave fields to create a lattice. The near arbitrary ability to engineer a generic tight-binding Hamiltonian in the synthetic dimension, in addition to strong dipole-dipole interactions present in Rydberg atomic gases, allows new capabilities for the exploration of interaction effects in topological and disordered systems. [Preview Abstract] |
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E01.00063: Bringing Rydberg Atom Array Quantum Simulators Online Kent Ueno, Caroline Laure Tchouawou Mbakob, Ho June Kim, Jeremy Flannery, Alexandre Cooper Rydberg atom arrays based on alkali and alkaline-earth elements have recently emerged as a competitive platform for simulating quantum many-body systems formed by hundreds of interacting particles assembled in reconfigurable structures with tunable dimensionality, geometry, and interaction strengths. Democratizing access to such quantum simulators will impact not only quantum information science, but also condensed matter physics, e.g., by facilitating the exploration of Ising spin models and lattice gauge theories. In this poster, we outline our progress in bringing our first-generation rubidium-87 system online and describe our effort to develop a low-latency closed-loop feedback control system for calibrating and optimizing control parameters. [Preview Abstract] |
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E01.00064: Exploring Dynamical Phase Transitions with a Cavity-QED Platform Dylan Young, Juan Muniz, Diego Barberena, Robert Lewis-Swan, Julia Cline, Ana Maria Rey, James Thompson Rich quantum spin models and phases can arise from cavity-mediated interactions between laser-cooled atoms confined inside an optical cavity. These systems can offer unique opportunities to study out-of-equilibrium dynamical phases of matter precluded from existence at equilibrium. Here, we report the observation of distinct dynamical phases of matter in a nearly unitary implementation of the collective XY spin model with transverse and longitudinal fields simulated via an ensemble of one million $^{88}$Sr atoms. We probe the dependence of the associated dynamical phase transitions on parameter space, system size and initial state. In the spirit of quantum simulation our observations can be linked to similar dynamical phases featured in a range of related systems, including the Josephson effect in superfluid helium, coupled atomic and solid-state polariton condensates, with complementary types of control including the magnitude and sign of Hamiltonian parameters. Moreover, our system offers potential for the generation of metrologically useful entangled states in optical transitions, which can enable real metrological gains via quantum enhancement in state-of-the-art atomic clocks. [Preview Abstract] |
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E01.00065: Spin transport in a tunable Heisenberg model Niklas Jepsen, Jesse Amato-Grill, Ivana Dimitrova, Wen Wei Ho, Mikhail Lukin, Eugene Demler, Wolfgang Ketterle We report on the first realization of the anisotropic Heisenberg model using ultracold atoms with fully tunable anisotropy. So far, only the isotropic Heisenberg model had been realized. We demonstrate this tunability by measuring the transport properties of the Hamiltonian as function of anisotropy in 1D-chains. With increasing anisotropy, we observe a ballistic and a diffusive regime, which are smoothly connected by a super-diffusive regime and followed by a sub-diffusive regime. While we observe this anomalous diffusion for positive anisotropies, negative anisotropies show a behavior which is more reminiscent of transport in a classical gas: ballistic at short relaxation times and diffusive at long relaxation times. We also probe the broken rotational symmetry of the Hamiltonian by rotating the initial state and we find the emergence of an additional relaxation mechanism: local dephasing, which can be controlled by the anisotropy. Finally we directly observe the effective magnetic term in the Hamiltonian, which has its origin in the mapping form the Hubbard model and which has never been observed before. [Preview Abstract] |
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E01.00066: Laser-free trapped-ion entangling gates with simultaneous insensitivity to qubit and motional decoherence R. T. Sutherland, R. Srinivas, S. C. Burd, H. M. Knaack, A. C. Wilson, D. J. Wineland, D. Leibfried, D. T. C. Allcock, D. H. Slichter, S. B. Libby The dominant error sources for state-of-the-art laser-free trapped-ion entangling gates are decoherence of the qubit state and the ion motion. The effect of these decoherence mechanisms can be suppressed with additional control fields, or with techniques that have the disadvantage of reducing gate speed. Here, we propose using a near-motional-frequency magnetic field gradient to implement a laser-free gate that is simultaneously resilient to both types of decoherence, does not require additional control fields, and has a relatively small cost in gate speed. [Preview Abstract] |
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E01.00067: Progress in entangling atoms in 3D for quantum computation Tsung-Yao Wu, Felipe Giraldo, Peng Du, Aishwarya Kumar, David S. Weiss We will report our recent progress towards implementing entangling operations in our 3D neutral atom quantum computer. To date, we have demonstrated deterministic preparation of qubits through 3D sorting and cooling [Nature 561, 83 (2018)], high-fidelity single qubit gates [Phys. Rev. Lett. 115, 043003 (2015)], and high-fidelity state measurement [Nature Physics 15, 538 (2019)]. We are developing two types of entangling operations. The first is the creation of cluster states (in 1D, 2D and 3D) through cold atom collisions [Phys. Rev. Lett. 86, 910 (2001)]. We are currently improving our cooling by temporarily transferring atoms to a closer-detuned, deeper trap. Preliminary results show a 3D vibrational ground state occupation \textgreater 98{\%}. By using this enhanced cooling and our state-dependent lattices, we will prepare all the atoms in a superposition and entangle them all together through controlled collisions with neighboring atoms. This will enable us to create cluster state of up to 50 qubits in 3D. The other entangling operation currently being developed is a site-addressable Rydberg gate within the 3D, which we project can exceed 99.9{\%} fidelity. [Preview Abstract] |
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E01.00068: Quantum gates and algorithms in a 2D neutral atom array Trent Graham, Minho Kwon, Cody Poole, Xiaoyu Jiang, Alphonse Marra, Brandon Grinkemeyer, Josh Cherek, Matthew Ebert, Mark Saffman We present progress towards designing and constructing a neutral atom quantum computer. Atoms are loaded into a blue-detuned array constructed from a 16 X 16 array of cross-hatched lines which define a 15 X 15 grid of optical traps. These lines are created using acousto-optic modulators, which allow us to reconfigure site number and trap spacing. Optical tweezers are used to load atoms into targeted sites and form defect-free trapping regions, greatly increasing experimental repetition-rate. We perform CNOT gates between qubits based on Rydberg blockade. Novel CNOT gate protocols based on adiabatic rapid passage excitation of Rydberg states will be presented; such gates may prove more robust to variations in Rabi frequency over the trapping region. In addition, we present improved CNOT gate fidelity using previously implemented gate protocols. Using these upgrades, we demonstrate variational quantum algorithms and use them to estimate ground state energies of the Lipkin Hamiltonian. [Preview Abstract] |
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E01.00069: Towards robust single qubit gates on a trapped-ion quantum computer Ming Li, Nikodem Grzesiak, Reinhold Blumel, Yunseong Nam As fundamental building blocks of digital quantum computation, single qubit gate operations need to be implemented with high fidelity and efficiency for any quantum computing architecture to be scalable. In trapped-ion quantum computers, the implementation utilises spin-changing transitions driven by an electromagnetic field, which could also couple to motional sidebands of the ion chain. Such off-resonant couplings are usually neglected in theoretical studies by applying the rotating wave approximation. As the number of motional modes increases with the number of qubits, and as the frequencies of some modes lower, the validity of the approximation becomes questionable. We theoretically investigate coherent errors and decoherence induced by these off-resonant couplings. To mitigate the resulting infidelity, we implement pulse shaping techniques and study their behaviors in terms of phase space closure, power requirement, and more. [Preview Abstract] |
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E01.00070: System Stability Optimization and Gate Operations in a Compact Cryogenic Ion Trap Setup Zhubing Jia, Robert Spivey, Ismail Inlek, Ke Sun, Stephen Crain, Mark Kuzyk, Rachel Noek, Kenneth Brown, Jungsang Kim We describe one- and two-qubit operations in a compact ion trapping system at cryogenic temperature. A low-vibration closed-cycle cryostat is utilized with all optics mounted on machined plates for operations with higher stability. We use Sandia High-Optical Access (HOA) surface traps and install the trap into a compact package, enabling easier system integration and characterization. The surface trap is mounted on a ceramic pin grid array (CPGA) package and covered with a copper lid with a meandering channel for differential pumping. The whole package is cooled down to a base temperature of 7K. We set up a Michelson interferometer to characterize and optimize the vibrations from the cryostat to the ion trap with respect to control lasers and give a quantitative analysis on the effect of vibrations on gate fidelity. We show the latest result of M{\o}lmer-S{\o}rensen gate fidelity with an analysis of the source of errors, which are dominated by motional decoherence. [Preview Abstract] |
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E01.00071: Characterizing the Coherence of Trapped Ion Qubits in the Software-Tailored Architecture for Quantum co-design (STAQ) Hardware Jacob Whitlow, Junki Kim, Mark Kuzyk, Stephen Crain, Tianyi Chen, Brad Bondurant, Samuel Phiri, Ken Brown, Jungsang Kim The goal of STAQ is to build a vertical stack for quantum computing composed of applications, software, and hardware integrated together. Our team focuses on the hardware implementation, which consists of building a trapped ion quantum computer large enough to perform calculations of practical use. The system itself utilizes a Sandia high-optical access trap placed in a mechanically stable cryostat. This presentation will provide updates on the quality of our $^{171}$Yb+ qubits, including the T2 coherence time. [Preview Abstract] |
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E01.00072: Metastable Qubit in $^{171}$Yb$^{+}$ Patrick McMillin, Thomas Dellaert, Anthony Ransford, Conrad Roman, Wesley Campbell Metastable qubits in trapped ion arrays offer an alternative to multi-species traps by preserving the advantage of qubit indistinguishability, and by reducing the challenge associated with adding an additional species to a trapped ion experiment. We have shown that the ground state ($^{2}$S$_{1/2}$) hyperfine qubit in $^{171}$Yb$^{+}$ has excellent state preparation and measurement (SPAM) fidelity (F$\geq$0.999), and is thus a good candidate for trapped ion quantum computation. Additionally, the $^{2}$F$_{7/2}$ state is ideally suited to host a metastable qubit due to its approximately 5 year lifetime and its large optical frequency separation from the transitions used in the $^{2}$S$_{1/2}$ qubit operations. We perform single-qubit gates and measure the $^{2}$F$_{7/2}$ clock-state qubit SPAM fidelity of this metatable qubit as F$\geq$0.95. By coherently mapping the population between the $^{2}$S$_{1/2}$ (“operational”) and $^{2}$F$_{7/2}$ (“storage”) qubits through an electric octupole transition, one may perform operations on a set of qubits while others are unaffected. In combination with coherent mapping, the ability to use metastable qubits in a multi-qubit array provides promising schemes for the implementation of gate operations. [Preview Abstract] |
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E01.00073: An efficiently-verifiable test of quantum advantage Gregory D. Kahanamoku-Meyer, Soonwon Choi, Umesh V. Vazirani, Norman Y. Yao Recently, quantum hardware has started to outperform classical computers at certain computational tasks (so-called quantum supremacy). Many protocols designed to demonstrate quantum advantages in computation have the undesirable feature that they are difficult to verify---checking whether or not a quantum machine produced correct results is as difficult as solving the problem classically. We propose a new test protocol that is efficiently verifiable and provably secure: the correctness of the results can be checked quickly (in polynomial time) by a classical machine, while passing the test with a classical machine is as hard as integer factorization. Such a protocol is essential in order to verify the performance of the first large-scale quantum devices; to our knowledge this protocol requires the least quantum resources of any proposal until now. In particular, we show that the resources are much less than those needed to run Shor's algorithm, allowing its efficient implementation in near-term devices. We present multiple ways to realize our protocols using trapped ions and Rydberg atoms systems, and explicitly analyze qubit and gate counts. Finally, we discuss the protocol's relevance in the broader landscape of quantum algorithms. [Preview Abstract] |
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E01.00074: Realizing Quantum Computation Using Continuous Variables in Trapped Ions Jeremy Metzner, Alex Quinn, Daniel Moore, Dave Wineland, David Allcock Instead of encoding quantum information in the internal electronic ``spin'' states of trapped ions, it is possible to encode solely within the ions' harmonic vibrational modes. Like spin qubits, this system is capable of universal quantum computation given an appropriate set of operations. Operations such as phase shift, displacement, squeezing$^{\mathrm{[1]}}$, and ``beam splitting''$^{\mathrm{[2]}}$~have been performed quickly and with high fidelity, using only electric fields acting on the ions' charge. Part of our investigation will be to put this set of operations together and demonstrate a basic computation algorithm. However, to have full realization of universal continuous variable quantum computing, there is a need for a non-gaussian operation. In order to produce such an operation, a Hamiltonian that is at least third order in the bosonic-mode raising and lowering operators, is needed. In principle higher order potentials can create this type of operation, for example, generation of a quartic potential will create a non-linear phase shift, but typical ion traps are inefficient at generating these potentials. We will be working on design and detailed simulations of microfabricated surface-electrode traps to see if this approach is feasible. ~ [1]- S. C. Burd et al. Science~Vol. 364, Issue 6446, pp. 1163 [2]- D. J. Gorman et al. Phys. Rev. A 89, 062332 (2014) [Preview Abstract] |
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E01.00075: Implementation of the Variational Quantum Eigensolver algorithm to estimate the ground state energy of the Lipkin model using atomic qubits. Cody Poole, Trent Graham, Minho Kwon, Michael Cervia, Peter Love, Susan Coppersmith, Baha Balantekin, Mark Saffman We present progress in executing the Variational Quantum Eigensolver (VQE) algorithm with neutral atom qubits. The VQE algorithm is used to estimate the ground state energy of the Lipkin-Meshkov-Glick (LMG) Hamiltonian for systems of two and three spins where the state of each spin in the LMG system is encoded in the state of a single hyperfine-ground state encoded cesium atom qubit. The LMG model is exactly solvable and so serves as a useful tool for validating the operations of a quantum computer. Once validated, the quantum computer could potentially implement VQE to model interactions of various dark matter candidates with detectors to aid in dark matter searches. [Preview Abstract] |
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E01.00076: Investigation of Five-Level Excitation Schemes for Rydberg Atom-based Radio Frequency Field Metrology Amy Robinson, Matthew Simons, Christopher Holloway, Georg Raithel Electromagnetically-induced transparency (EIT) techniques have been used to successfully detect and characterize radio frequency (RF) fields. This approach typically uses a four-level excitation scheme, which include a probe laser (levels $|1\rangle \rightarrow |2\rangle$), a coupling laser to Rydberg states ($|2\rangle \rightarrow |3\rangle$), and an RF source to couple two Rydberg states ($|3\rangle \rightarrow |4\rangle$). In this talk we explore five-level excitation schemes. In the first scheme we add a fifth level, which is another Rydberg state, that is coupled by a second RF source ($|4\rangle \rightarrow |5\rangle$). The second scheme is a five-level ``Y'' scheme, which includes two ground state transitions, $|1\rangle \rightarrow |2\rangle$ (5S$_{1/2,F=3}$ $\rightarrow$ 5P$_{3/2,F=3}$), and $|3\rangle \rightarrow |2\rangle$ (5S$_{1/2,F=2} \rightarrow$ 5P$_{3/2,F=3}$). A coupling laser generates Rydberg states ($|2\rangle \rightarrow |4\rangle$), and RF couples two Rydberg states ($|4\rangle \rightarrow |5\rangle$). We show experimental results for the two different 5-level schemes and discuss novel features observed in the spectra of these five-level schemes. We describe their dependence on frequency detuning and power variations, and compare with theoretical models. [Preview Abstract] |
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E01.00077: Microwave-to-optical transduction and microwave-controlled optical switch in a vapor cell inside a room-temperature high-Q microwave cavity Andrei Tretiakov, Clinton Potts, Timothy Lee, Matthew Thiessen, John Davis, Lindsay LeBlanc Information transfer from microwave to an optical domain in classical and quantum regimes have significant applications for modern communication systems and quantum information devices. Here we use a thermal Rb vapor cell enclosed by a room-temperature high-Q microwave cavity as an interface between microwave and optical fields. Through magnetic-dipole coupling greatly enhanced by the cavity, the microwave field affects the optical density of the vapor for a resonant optical transition. In this set up we experimentally demonstrate transduction of an audio signal encoded in microwave modulation to the optical intensity and show that applying a microwave field in the presence of a strong optical pump, can drive the medium from full absorption to full transmission of a weak optical probe, thus acting as an optical switch. [Preview Abstract] |
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E01.00078: Towards quantum sensing at megabar pressures using nitrogen vacancy centers in diamond Prabudhya Bhattacharyya, Satcher Hsieh, Thomas Mittiga, Chong Zu, Thomas Smart, Zachary Geballe, Nicholas Rui, Tim Hoehn, Bryce Korbin, Francisco Machado, Brian Chase Chandler, Viktor Struzhkin, Raymond Jeanloz, Norman Yao The nitrogen vacancy (NV) color center in diamond has emerged as a robust and versatile sensor for a wide range of applications. The recent incorporation of NV centers into diamond anvil cells - the workhorse technology of high pressure science - has enabled the direct imaging of pressure-driven phenomena. In particular, by implanting a shallow layer of NV centers near the anvil cell's culet, one can map the magnetic field vector and the stress tensor with diffraction limited spatial resolution. Despite this progress, a number of challenges remain. Most importantly, prior experiments suggest that NV sensing cannot be performed above \textasciitilde 60 GPa of pressure owing to a sharp reduction of the NV center's contrast as a function of increasing pressure. To this end, we introduce a new approach that enables NV spectroscopy to be performed at well above 100 GPa (megabar) pressures, opening the door for the exploration of high-temperature, pressure-induced superconductivity in the hydrides. [Preview Abstract] |
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E01.00079: Realization of a universal quantum pressure standard Pinrui Shen, Kirk Madison, James Booth We have reported the realization of the first cold atom primary pressure standard for the high- and ultra-high vacuum (UHV) regimes. This standard is a fundamentally different approach to vacuum metrology as it is based on a universal law governing quantum diffractive collisions between particles. We show that a measurement of the collision-induced loss rate of trapped atoms versus trap depth provides the velocity averaged total collision cross section - the only parameter required to quantify the pressure or flux of particles impinging on the trapped atoms. Using a sensor ensemble of $^{87}$Rb atoms we demonstrated that this new quantum pressure standard can be applied to gases of both atomic species (He, Ar, and Xe) and molecular species (N$_2$, CO$_2$, and H$_2$), surpassing the scope of existing orifice flow pressure standards. The accuracy of this new standard was verified against an N$_2$ calibrated ionization gauge traced back to an orifice flow standard. Moreover, using this standard we were able to observe and quantify the performance limits of the ionization gauge. We also demonstrated the use of a magneto-optical trap (MOT) as a transfer standard to extend the operational range of the cold atom pressure standard by a factor of 100. [Preview Abstract] |
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E01.00080: Spin State-Dependent Relaxation Rates in Nitrogen-Vacancy Centers in Diamond Aedan Gardill, Matthew C. Cambria, Yanfei Li, Shimon Kolkowitz Nitrogen-vacancy centers (NVs) in diamond are widely used for their easily accessible quantum properties in the solid-state at room temperature. Understanding the origins of decoherence in NVs is vital to extending their coherence times and unlocking their full potential. We present findings of spin-state dependent relaxation rates at room temperature for NVs deep in bulk diamond and for NVs in nanodiamonds. We measure the relaxation rate on both the qubit transition (between the ms $=$ 0 state and one of the energy eigenstates composed of the ms $=+$/-1 states) and the qutrit transition (between the two eigenstates composed of the ms $=+$/-1 states). For deep, native NVs in ultrapure bulk diamond we find that spin-state dependent two-phonon processes result in a qutrit relaxation rate that is \textasciitilde 2 times the qubit relaxation rate, providing an estimate of the strength of a previously unmeasured electric dipole-coupling term in the NV Hamiltonian. We also present measurements of fast relaxation on qutrit transitions in \textasciitilde 40 nm nanodiamonds under ambient conditions. We observe a strong falloff of the qutrit relaxation rate with applied on-axis magnetic field, and conclude that surface electric field noise is a major source of decoherence for NVs in nanodiamonds. [Preview Abstract] |
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E01.00081: Building a Portable, Cold-Atom Pressure Standard Perrin Waldock, Pinrui Shen, James Booth, Kirk MAdison Both science and industry require vacuum pressure measurement, with applications including residual gas analysis, semiconductor device manufacturing, and atmospheric modeling. Remarkably, no primary pressure standard existed for the high and ultra-high vacuum regimes (below $10^−7$ Pa) until recently, when a UBC-BCIT collaboration succeeded in producing the first primary vacuum pressure standard. Based on collision-induced loss rates of trapped 87Rb atoms, this new technique uses only fundamental constants and immutable atomic properties to measure pressure. It takes advantage of quantum diffractive universality (QDU) associated with trap loss, rendering it self-defining and able to measure the pressure of any gas. This is a significant advance over the existing orifice flow standard, which only works with inert gases, and is a based on a mechanically-fabricated orifice. We are building a portable Rb-based pressure standard to compare against other devices. Following our lead, the National Institute of Standards and Technology (NIST) is building a Li-based pressure standard, which we will compare our device against. This will allow us to test the limits of QDU, refine the atom-based definition of pressure, and investigate the short-range collision interaction to atom loss rates. [Preview Abstract] |
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E01.00082: Metrology and many-body physics with strontium in a 2D tweezer array Nathan Schine, William Eckner, Aaron Young, William Millner, Dhruv Kedar, Matthew Norcia, Jun Ye, Adam Kaufman Arrays of neutral atoms trapped in optical tweezers are a powerful platform for single-particle-controlled quantum gas assembly, entanglement generation, and many-body physics. Alkaline-earth atoms, such as strontium, offer a rich singlet-triplet electronic structure which enhances the capabilities of tweezer arrays---principally via high-fidelity low-loss imaging and ultra-narrow `clock' transitions with direct applications in metrology and quantum information science. Indeed, our tweezer array clock establishes a new, state-of-the-art platform for comparisons of atomic ensembles' clock frequencies. Now, we are working to introduce off-resonant Rydberg excitation---Rydberg dressing---of the clock state introduces strong long-range interactions between atoms in a low-entropy two-dimensional array. The resulting transverse field Ising Hamiltonian enables spin-squeezing on the clock transition, leveraging quantum entanglement for improved metrological sensitivity. This also offers a rich many-body system in which entanglement may propagate beyond the range of the underlying interactions. These goals demonstrate the power and versatility of combining controllable long-range interactions with single particle manipulation of highly coherent quantum systems. [Preview Abstract] |
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E01.00083: Enhanced Electric Field Sensing with Nitrogen-Vacancy Ensembles Bryce Kobrin, Maxwell Block, Andrey Jarmola, Nataniel Figueroa, Victor Acosta, Satcher Hsieh, Chong Zu, Joaquin Minguzzi, Jeronimo Maze, Dmitry Budker, Norman Yao Nitrogen-vacancy (NV) centers in diamond have shown promise as inherently localized electric field sensors, capable of detecting individual charges with nanometer resolution. Here, we demonstrate that a detailed understanding of the internal electric field environment in NV ensembles enables enhanced sensitivity in the detection of external electric fields. We follow this logic along two complementary paths. First, using excitation tuned near the NV’s zero-phonon line, we perform optically detected magnetic resonance (ODMR) spectroscopy at low temperatures in order to precisely measure the NV center’s excited state susceptibility to electric fields. In doing so, we show that a characteristically observed contrast inversion arises from an interplay between spin-selective optical pumping and the NV centers’ local charge distribution. Second, motivated by this understanding, we propose and analyze a novel scheme for optically enhanced electric field sensing using NV ensembles; we estimate that our approach should enable an improvement in DC sensitivity by two orders of magnitude. [Preview Abstract] |
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E01.00084: Compact devices for atomic spectroscopy and quantum technologies: applications in electromagnetic field sensing, measurement, and imaging. Luis Felipe Goncalves, Georg Raithel, David Anderson Quantum phenomena in atomic, molecular, and optical systems continue to enable fundamentally new technological advances with broad impact across different industries, from science research and metrology to communications and defense. The realization of devices and instruments based on quantum technology requires both the development of new hardware to perform specialized tasks as well as advanced engineering for hardware miniaturization and operation in real-world harsh environments. Here we present the development of compact, plug-and-play devices for high-resolution optical frequency tracking and absolute frequency referencing for narrow-line lasers made for use as either stand-alone components in AMO laboratory experiments or as integrated OEM components in higher-level instrument assemblies. Features and capabilities of these devices are highlighted in their application to atomic electromagnetic field sensing, receiving, and imaging technology. Recent developments in high magnetic field measurement technology and SI-traceable, self-calibrated broadband RF field imaging and antenna characterization with a portable Rydberg field probe (RFP) and measurement system (RFMS) will be presented. [Preview Abstract] |
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E01.00085: A portable Rydberg RF field probe and measurement instrument for SI-traceable, self-calibrated, broadband RF field sensing, measurement, and imaging. David Anderson, Rachel Sapiro, Georg Raithel We present a self-calibrating, SI-traceable broadband Rydberg-atom-based radio-frequency (RF) electric field probe (the Rydberg Field Probe or RFP) and measurement instrument (Rydberg Field Measurement System or RFMS) [1]. The RFMS comprises an atomic RFP and a remote portable mainframe control unit with a software interface for RF measurement and analysis, rendering real-time RF field readouts and allowing rapid RF waveform visualization. The instrument employs electromagnetically induced transparency (EIT) readout of spectral signatures from RF-sensitive Rydberg states of an atomic vapor for continuous, pulsed, and modulated RF field measurement. The RFP atomic probe has been characterized by polar field and polarization patterns at 12.6 GHz RF; the patterns have been obtained in the far-field of a standard gain horn antenna. A detailed calibration procedure and uncertainty analysis are presented. The effects of hardware choices and other systematic effects are accounted for in the procedure, providing an absolute-standard SI-traceable calibration of the RFP. Pulsed and modulated RF field measurement, and time-domain RF-pulse waveform imaging are also demonstrated. [1] Anderson, D.A. et al., arXiv:1910.07107v2 [physics.atom-ph] (2019). [Preview Abstract] |
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E01.00086: Dynamics of a 3D Bose gas in an optical lattice driven by local particle loss Christopher Mink, Axel Pelster, Michael Fleischhauer We study both the steady states and the dynamics of a weakly interacting Bose gas, which is confined by an optical lattice in one spatial dimension as well as an isotropic harmonic trap in the two transveral dimensions and is driven by a local particle loss. To this end we start from first principles and use coherent phase space methods in order to derive the underlying stochastic Gross-Pitaevskii description of the emerging Bose-Einstein condensate. Afterwards we neglect at first quantum fluctuations and determine approximately the condensate wave functions at each lattice site with a suitable variational ansatz. Then we take quantum fluctuations into account and study numerically their impact upon the time evolution of the system. With this we aim at reproducing the experimental results of Ref. [1] concerning the refilling dynamics of an empty site without any free parameters. Finally, we discuss the strengths of this model and demonstrate the limits of its applicability. [1] R. Labouvie, B. Santra, S. Heun, and H. Ott, Phys. Rev. Lett. 116, 235302 (2016) [Preview Abstract] |
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E01.00087: Quantized topological transport in open systems induced by topology transfer Lukas Wawer, Michael Fleischhauer Topological states of matter have fascinated physicists since a long time. Motivated by topological charge pumps, we introduced a classification of topological phases of matter in finite-temperature as well as stationary states of driven, dissipative, systems of non-interacting fermions based on a many-body invariant [1]. While the integer-valued transport of particles in topological charge pumps breaks down at finite temperatures, the winding of the topological invariant remains strictly quantized. Here we show that quantized particle transport can be restored by transferring the topological properties of the finite-temperature system to an auxiliary system of free fermions, initially prepared at $T=0$. Cooling the auxiliary system continiously to low temperature realizes a temperature robust topological charge pump. It also allows us to detect the topological invariant of the open system in a direct way. Finally the quantized transport in the auxiliary system could also be used to define topology of mixed states of interacting systems. \newline [1] C.E. Bardyn, L. Wawer, A. Altland, M. Fleischhauer, S.Diehl, Phys. Rev. X 8, 011035 (2018) [Preview Abstract] |
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E01.00088: Engineering Strong Interactions between mm-wave and Optical Photons using Rydberg Atoms Aishwarya Kumar, Aziza Suleymanzade, Mark Stone, Lavanya Taneja, Jasmine Kalia, David Schuster, Jonathan Simon We describe progress towards an experimental system to couple single photons in the mm-wave and optical regimes. Such a system can enable realization of exotic photonic states, as well as open doors for new techniques in quantum information and communication. At the heart of our design is a high-Q, monolithic, superconducting cavity crossed with an optical resonator and with optical access to trap and cool atoms at the center. Quality factors of $\sim 10^{7}$ at 100 GHz and 1K temperature have recently been demonstrated in these cavities. Along with the strong electric dipole couplings between Rydberg states, exceptionally high single atom cooperativities are achievable. Here we show trapping and cooling of atoms, observation of Rydberg Electromagnetically Induced Transparency (EIT), and progress towards generating mm-wave induced optical non-linearity in such a cavity in a 3K cryostat. [Preview Abstract] |
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E01.00089: Sympathetic Cooling of Levitated Nanospheres using Cold Atoms William Eom, Eduardo Alejandro, Daniel Grass, Apryl Witherspoon, Cris Montoya, Gambhir Ranjit, Andrew Geraci Trapped silica nanospheres cooled to the ground state of their center of mass motion can be used to explore the interface between the quantum and classical world in search of new physics. Rubidium atoms are stored in a MOT, while a lone silica nanosphere is trapped in a separate chamber with optical tweezers. The systems are then coupled through radiation pressure forces mediated by a 1-D optical lattice for sympathetic cooling. The atoms, cooled with well-known techniques such as molasses cooling, can sympathetically reduce the center of mass motion of the trapped sphere. Such cooled spheres can be used for precision sensing, matter-wave interferometry, and tests of quantum coherence in the mesoscopic regime. [Preview Abstract] |
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E01.00090: Toward Room-Temperature Mechanical Motion Driven by Quantum Radiation Pressure Noise. Jiaxing Ma, Vincent Dumont, Simon Bernard, Thomas Clark, Jack Sankey We present progress toward an optomechanical system in which the motion of a "trampoline" mechanical system is overwhelmingly determined by the quantum radiation pressure noise (QRPN) of laser light circulating in a microns-long fiber cavity. As of January, we have developed a flexure-based chip-mount capable of maintaining the trampoline's high Q-factor, and a monolithic piezo-actuated mount for the fiber mirrors. The next steps are to assemble the device in a vibration-isolated UHV chamber and stabilize it. If successful, this experiment will provide access to measurements at the standard quantum limit and the generation of broadband squeezed light in a room-temperature apparatus. [Preview Abstract] |
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E01.00091: A new Na-K apparatus for simulating quantum many-body phenomena Jan Kilinc, Lilo Hoecker, Rohit Prasad Bhatt, Fred Jendrzejewski Ultracold atomic gases allow a precise control over experimental parameters enabling the simulation of complicated physical processes in nature. Quantum mixtures expand these horizons by covering an even greater range of many-body phenomena. In this poster, we present the new Na-K experiment at Heidelberg, which we are setting up as a platform to study problems in High Energy Physics (dynamical gauge fields), Condensed Matter Physics (Kondo effect) and Quantum Thermodynamics (quantum heat engines). [Preview Abstract] |
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E01.00092: Theory of radio-frequency spectroscopy of impurities in quantum gases Weizhe Liu, Zhe-Yu Shi, Meera Parish, Jesper Levinsen We present a theory of radio-frequency spectroscopy of impurities interacting with a quantum gas at finite temperature. We show that the impurity spectral response is directly connected to the finite-temperature equation of state (free energy) of the impurity. We consider two different response protocols: “injection”, where the impurity is introduced into the medium from an initially non-interacting state; and “ejection”, where the impurity is ejected from an initially interacting state with the medium. We show that there is a simple mapping between injection and ejection spectra, which is connected to the detailed balance condition in thermal equilibrium. We specialize in the case of the Fermi polaron, corresponding to an impurity atom that is immersed in a non-interacting Fermi gas. For a mobile impurity with a mass equal to the fermion mass, we find a striking non-monotonic dependence on temperature in the impurity's free energy, the contact, and the radio-frequency spectra. For the case of an infinitely heavy Fermi polaron, we derive exact results for the finite-temperature free energy, thus generalizing Fumi’s theorem to arbitrary temperature. [Preview Abstract] |
(Author Not Attending)
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E01.00093: Abstract Withdrawn
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E01.00094: Spin- and atom-interactions in multimode cavity QED Ronen Kroeze, Yudan Guo, Brendan Marsh, Jonathan Keeling, Benjamin Lev Optical cavity QED provides a versatile platform with which to explore quantum many-body physics in driven-dissipative systems. Multimode cavities are particularly apt for exploring beyond mean-field physics. After previously having demonstrated strong, tunable range, photon-mediated, atom-atom interactions, we now present three other recent experimental advances. Firstly, we have endowed these interactions with a sign-changing feature. In a confocal cavity, Gouy phase effects result in non-local, sign-changing interactions, and enriched symmetries. We demonstrate this using holographic detection of the cavity emission, after crossing a superradiant, self-organization phase transition. In the same context of a non-equilibrium Dicke-like phase transition, we realize joint spin-spatial (spinor) organization of a two-component Bose-Einstein condensate, as driven by spinor-spinor interactions. Lastly, we present results on dynamical spin-orbit coupling, where a chiral spin spiral emerges. Uniquely, it is quantum fluctuations that drive this spin-orbit coupling, enabling studies of dynamical gauge fields. Together, these advances enable us to explore exotic, strongly correlated systems such as quantum liquid crystals, driven-dissipative spin glasses, and quantum neural networks. [Preview Abstract] |
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E01.00095: Spin-Resolved Quantum Gas Microscopy with Bilayer Readout Pimonpan Sompet, Joannis Koepsell, Sarah Hirthe, Dominik Bourgund, Guillaume Salomon, Jayadev Vijayan, Immanuel Bloch, Christian Gross Ultracold atoms in optical lattices with single-site resolved detection has enabled the study of the interplay between charge and spin in strongly correlated systems. Here, we report on a high fidelity of vertically spin-resolved method in our two-dimensional (2D) Fermi-Hubbard systems. To achieve this, we employ the Stern-Gerlach splitting which separates two different spins into two different sublayers of a fully-controllable bichromatic vertical superlattice. For imaging the two layers (or spins), we use geometric charge pumping to increase the distance between the layers, and therefore achieve the single-site-resolution images of individual layers. We benchmark this technique by measuring the spin correlation in our 2D systems and observe strong antiferromagnetic correlations in undoped regime. [Preview Abstract] |
(Author Not Attending)
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E01.00096: Measuring Many-body Coherence in Weakly Interacting Fermi Gases Saeed Pegahan, Ilya Arakelyan, John E. Thomas We study a coherently prepared, weakly interacting Fermi gas of $6\times10^4$ $^6$Li atoms, which offers a new foundation for understanding complex spin dynamics induced by the interplay between spin interactions and motion in many-body systems. Using phase-controlled radio-frequency (rf) pulses, we prepare an x-polarized collective spin state and implement a many-body echo: After an evolution time $\tau$, we apply a rotation by an angle $\phi$ about the x-axis. This is followed immediately by a $\pi$ rotation about the y-axis and inversion of the s-wave scattering length, which reverses the sign of the Hamiltonian. The rf detuning is sufficiently stable to measure the final collective spin vector as a function of $\phi$ for $2\tau$ up to 1 second. This system provides a powerful tool to study many-body coherence and entanglement spreading in quantum many-body systems. [Preview Abstract] |
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E01.00097: Selected applications of ultracold strontium: quasicrystals, anyons, and compact atom sources Max Prichard, Toshihiko Shimasaki, Peter Dotti, Enrique Morell, Jared Pagett, David Weld Ultracold strontium in a bichromatic lattice can serve as a quantum simulator which probes the effects of quasiperiodicity on many-body quantum systems. We present recent work demonstrating phasonic spectroscopy of Strontium in an optical lattice [1], and describe experiments exploring dynamical localization in driven optical crystals and quasicrystals. Separately, we report progress on efforts to realize non-Abelian anyons in a biased zig-zag lattice, and describe a compact cold atom source in which a magneto-optical trap of strontium is loaded by laser illumination of strontium oxide. [1] Rajagopal, Shankari V., et al. PRL 123.22 (2019): 223201. [Preview Abstract] |
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E01.00098: Observation of Multiple Dark Antidark Solitons in Two-Component Bose Einstein Condensates Garyfallia Katsimiga, Simeon Mistakidis, Thomas Bersano, Md Kamrul Hoque Ome, Sean Mossman, Koushik Mukherjee, Peter Schmelcher, Peter Engels, Panayotis Kevrekidis We report on the experimental observation of multiple dark-antidark (DAD) solitons in two-component 87Rb Bose-Einstein condensates. Particularly, our experimental efforts suggest the spontaneous generation of multiple such structures in two different formats. Namely, we present settings in which the multiple dark solitons are all in the same component and the antidark solitons are all in the second component (sorted case), as well as ones where there is an alternating sequence of darks and antidarks (in a complementary fashion) between the two components. The above observations are corroborated by theoretical predictions regarding the existence of stationary states consisting of either sorted or alternating configurations upon varying the intercomponent coupling. It is found that only ensembles of few sorted DADs exist as stable configurations, while for larger DAD arrays windows of stability are identified and discussed. On the contrary, bound states of alternating DAD solitons do not exist and thus we can infer solely their dynamical formation and interactions. [Preview Abstract] |
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E01.00099: Rabi oscillations and Ramsey-type pulses in ultracold bosons: Role of interactions Q. Guan, T. M. Bersano, S. Mossman, P. Engels, D. Blume Double-well systems loaded with one, two or many quantum particles give rise to intriguing dynamics, ranging from Josephson oscillation to self-trapping. This work presents theoretical and experimental results for two distinct double-well systems, both created using dilute rubidium Bose-Einstein condensates. The first is realized by creating an effective two-level system through Raman coupling of hyperfine states. The second is realized by creating an effective two-level system in momentum space through the coupling by an optical lattice. Even though the non-interacting systems can, for a wide parameter range, be described by the same model Hamiltonian, the dynamics for these two realizations differ in the presence of interactions. The difference is attributed to scattering diagrams that contribute in the lattice coupled system but vanish in the spin-orbit coupled system. The internal dynamics of the Bose-Einstein condensates for both coupling scenarios is probed through a Ramsey-type interference pulse sequence. The results have important implications for lattice calibration experiments and momentum space lattices. [Preview Abstract] |
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E01.00100: Unraveling the role of long-range coherence for superfluid dynamics by disorder quenches Sian Cardoso Barbosa, Benjamin Nagler, Jennifer Koch, Artur Widera Quantum fluids exhibit a well-defined phase, which can be interferometrically measured. The direct connection of long-range coherence with superfluid transport and expansion dynnamics is, however, challenging to access experimentally. I report on experimentally revealing the role of long-range coherence for superfluid flow in an interacting gas of lithium-6 atoms along the BEC-BCS crossover, quenched into and out of optical disorder. I will describe the experimental apparatus including the creation of disorder by laser speckle pattern. Then, I will present our investigations about the density and superfluid-expansion response of a molecular Bose-Einstein condensate after quenching. We measure the breakdown and reoccurrence of superfluid hydrodynamics. We track the response times on which the system relaxes to a new equilibrium and relate the time scales to fundamental energy scales of the system. Our results shed light onto the importance of long-range phase coherence for superfluid flow, and also suggest a possible route of studying complex phase dynamics in superfluids by imprinting disordered phases. [Preview Abstract] |
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E01.00101: Creating solitonic excitations with controllable velocity in Bose-Einstein condensates Amilson R Fritsch, Mingwu Lu, Graham H Reid, Alina M Pi\~{n}eiro, Ian B Spielman Established techniques for deterministically creating dark solitons in repulsively interacting atomic Bose-Einstein condensates (BECs) can only access a narrow range of soliton velocities. Because velocity affects the stability of individual solitons and the properties of soliton-soliton interactions, this technical limitation has stymied experimental progress. Here we create dark solitons in highly anisotropic cigar-shaped BECs with arbitrary position and velocity by simultaneously engineering the amplitude and phase of the condensate wavefunction, improving upon previous techniques which only manipulated the condensate phase. We readily create dark solitons with speeds from zero to half the sound speed. The observed soliton oscillation frequency suggests that we imprinted solitonic vortices, which for our cigar-shaped system are the only stable solitons expected for these velocities. Our numerical simulations of 1D BECs show this technique to be equally effective for creating kink solitons when they are stable. We demonstrate the utility of this technique by deterministically colliding dark solitons with domain walls in two-component spinor BECs. [Preview Abstract] |
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E01.00102: Quantum droplet in a mixture of Rb and Na Bose-Einstein condensates Zhichao GUO, Fan Jia, Lintao Li, Dajun Wang According to the mean-field theory, an atomic Bose-Einstein condensate (BEC) will collapse when the interaction between atoms is attractive. However, the mixture of two BECs with attractive interspecies interaction can be stabilized by the beyond mean-field Lee-Huang-Yang correction in the format of self-bound quantum droplets [1, 2, 3]. In this poster, I will present our progress in studying the heteronuclear quantum droplet with the double BEC of Rb and Na atoms. With the help of an interspecies Feshbach resonance, we have created double BECs with nearly arbitrary interaction strengths and signs. When setting the interspecies scattering length to larger enough negative values, we observe the self-bound behavior as the signature of the Na-Rb droplet during the time of flight expansion upon releasing the mixture from the optical trap. Future plan for studying the phase diagram and formation dynamics will also be discussed. [Preview Abstract] |
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E01.00103: Pattern formation and gauge-induced domains in a driven Bose-Einstein Condensate Kaixuan Yao, Zhendong Zhang, Liangchao Chen, Cheng Chin Floquet engineering, the application of temporal periodic drive to a system, has offered rich opportunities for creating novel quantum dynamics and phases inaccessible in static systems. Here we discuss our recent progress with driven Bose-Einstein condensates based on two examples: pattern formation and quantum phases with density-dependent gauge field. With atomic interactions driven at two frequencies, we observe formation of density patterns with two- (D2), four- (D4) and six-fold (D6) symmetries. The symmetry of the pattern is controlled by the ratio of the frequencies. With simultaneous modulation of lattice phase and atomic interactions, we observe gauge-induced density dependent pseudo-spin domains. Numerical simulations suggest that the two pseudo-spin domains have different densities, similar to a liquid-gas system. [Preview Abstract] |
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E01.00104: Higher-order matter-wave solitons formed by inter- action quenches Y. Jin, D. Luo, J. H. V. Nguyen, R. G. Hulet, B. Malomed, O. Marchukov, V. Yurovsky, V. Dunjko, M. Olshanii Solitons are 1D nonlinear waves that propagate without dispersion. Higher-order solitons, i.e$.$ coherent superpositions of fundamental solitons known as breathers, can be formed using a specific interaction quench. We experimentally produce and characterize higher-order matter-wave solitons. Using a $^7$Li BEC whose interactions are tuned using a Feshbach resonance, an $n$th order breather is created by suddenly increasing the strength of the attractive interactions by a factor of $n^2$, where $n$ is an integer. The breathing frequency is determined by the chemical potential difference between the constituent solitons\footnote{V. E. Zakharov and A. B. Shabat, Soviet Physics JETP, 34, 1 (1972)}$^,$\footnote{J. Satsuma and N. Yajima, Prog. Theor. Phys. Supp. 55, 284 (1974)}. We show that the breathing frequency depends on the aspect ratio of the confinement and the strength of the post-quench non-linearity. The frequency is independent of the axial confinement when it is sufficiently weak. We demonstrate the realization of both the second (n=2) and third (n=3) order breather. [Preview Abstract] |
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E01.00105: Towards a Dual-Species Bose-Einstein Condensate of $^{7}$Li and $^{133}$Cs Yi-Dong Chen, Wei-Xuan Li, Chia-Shan Li, Min-En Chou, Shih-Kuang Tung Quantum degenerate mixtures of atomic gases are the subject of intensive study. Intriguing quantum phenomena flourish because of the extra complexity brought in by a second species. Being able to create a dual-species Bose-Einstein condensate is crucial to study these quantum effects. Here, we present technical progress towards creating a dual-species BEC of $^{7}$Li and $^{133}$Cs. The combination of heavy and light can open up new possibilities to probe and simulate disordered many-body systems. [Preview Abstract] |
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E01.00106: Observations of ultracold atoms in microgravity shell potentials Nathan Lundblad, Ryan Carollo, David Aveline, Courtney Lannert, Karmela Padavic, Brendan Rhyno, Smitha Vishveshwara NASA's Cold Atom Laboratory (CAL) provides investigators the unique capability of producing BECs in orbit, where the perpetual freefall environment enables experiments largely free of gravitational perturbation. We use this environment to study radiofrequency-dressed ultracold samples in an ellipsoidal shell potential, a geometry that is technically difficult to achieve on Earth. We discuss the results of the first-generation science run, focusing on shell thermometry, model characterization, and inflation adiabaticity. We also summarize our understanding of the apparatus-related limitations on shell size, shell coverage and uniformity, and review possibilities for the second-generation instrument now in orbit. [Preview Abstract] |
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E01.00107: Fast Quantum Control of Trapped $^{87}$Rb Bose-Einstein Condensates Denuwan Vithanage, Skyler Wright, E. Carlo Samson We present numerical simulations on manipulating Bose-Einstein condensates (BECs) at a fast rate while maintaining the coherence properties of its initial quantum state. The main problem in transporting a quantum system like a BEC at a fast rate is that the energy we add to the system for transport will change the BEC's initial state or completely destroy the BEC. Two-dimensional (2D) simulations of BEC transport are performed by numerically solving the Gross-Pitaevskii equation (GPE) using a split-step Fourier method. In our simulations, we use trapping potentials in the form of painted potentials because it is possible to achieve arbitrary, dynamic traps with this method. In order to achieve high quantum fidelity, we use shortcuts-to-adiabaticity (STA) for high-speed BEC transport. With these simulations, we compared different time intervals for a particular spatial displacement that a BEC can travel while keeping high quantum fidelity using experimentally feasible parameters. The effects of atomic interactions, and trapping frequencies to the effectiveness of STA will also be discussed. [Preview Abstract] |
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E01.00108: Progress on Measurements of the Time a Tunnelling Bose-Einstein Condensate Spends in the Classically Forbidden Region Joseph McGowan IV, David Spierings, Aephraim Steinberg We report improvements on our initial measurements of the tunnel barrier traversal time for a Bose-Einstein Condensate of rubidium 87. Our experiment measures the Larmor time of Baz' and Rybachenko, wherein the net magnetization of the tunnelling atoms is used to encode a clock. By localizing a pseudo-magnetic field inside an optical barrier, the populations of the hyperfine levels of the tunnelling condensate encode the time spent inside the barrier region. Following technical improvements to the apparatus and measurement techniques, we report notably reduced uncertainties on measured times and velocities as well as comparing times for reflected and transmitted atoms. We also note discrepancies between our results and a simple theory based on weak measurement, and we discuss possible sources of these discrepancies, including the sensitivity to exact details of the shape and symmetry of the barrier. [Preview Abstract] |
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E01.00109: Probing driven quantum systems with ultracold lithium in optical lattices Ethan Simmons, Roshan Sajjad, Alec Cao, Jeremy Tanlimco, David Weld Ultracold lithium atoms in optical lattices provide a flexible playground for the experimental study of driven quantum systems. We describe recent progress on a variety of experiments along these lines, including both topological and polychromatic Floquet-band engineering, continuously-trapped atom interferometry, and the investigation of many-body dynamical localization in an interacting quantum kicked rotor. [Preview Abstract] |
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E01.00110: Mapping imaging transfer functions through holographic field correlations Francisco Salces-Carcoba, C. J. Billington, E. Aluntas, Y. Yue, I. B. Spielman Holographic microscopy recovers both the phase and amplitude of an optical field through a calibrated interferogram. We combine holographic imaging and {\it in-situ} microscopy to image elongated superfluids. By looking at the scattered field density correlations of an otherwise point correlated ensemble, we study an aberrated imaging transfer function. A regularized inversion digitally frees our images from the detected aberrations, improving our imaging performance with optimal signal-to-noise ratio. [Preview Abstract] |
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E01.00111: Superfluid phases and excitations in a cold gas of d-wave interacting bosonic atoms and molecules Zehan Li, Jian-song Pan, W. Vincent Liu Motivated by recent advance in orbitally tuned Feshbach resonance experiments, we analyze the ground-state phase diagram and related low-energy excitation spectra of a d-wave interacting Bose gas. A two-channel model with d-wave symmetric interactions and background s-wave interactions is adopted to characterize the gas. The ground state is found to show three interesting phases: atomic, molecular, and atomic-molecular superfluidity. Remarkably different from what was previously known in the p-wave case, the atomic superfluid is found to be momentum-independent in the present d-wave case. Bogoliubov spectra above each superfluid phase are obtained both analytically and numerically. [Preview Abstract] |
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E01.00112: Atom Chip Radio-Frequency Traps for Neutral Atoms Andrew Rotunno, Shuangli Du, Doug Beringer, Seth Aubin We report on theoretical and experimental progress in the development of spin-dependent traps based on radio frequency (RF) atom chip near-field potentials using the AC Zeeman effect. The ability to trap and spatially control atoms based on their internal spin state has applications in atom interferometry, qubit logic gates, novel many-body systems, and sympathetic evaporative cooling. In recent work, we have shown the ability to push or pull individual atomic spin states of rubidium-87 using a single RF current of roughly 10 mA at a few MHz on an atom chip. With the use of two or three RF currents with controlled phase and amplitude, trapping of specific spin states should be possible, and we explore the effectiveness of this trapping scheme experimentally. Simulations show that 2 W of power in each of three parallel chip wires can produce a trap depth of 60-80 $\mu $K, without impedance matching. Other trapping schemes employ a ground plane, multiple RF frequencies, and different combinations of amplitude and phase parameters to alter trap geometry while targeting specific spin states. We also report on equipment development for this trapping method, as well as preliminary tests of state mixing over time. [Preview Abstract] |
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E01.00113: A High Intensity Cold Atom Source William Debenham, Jeremy Glick, Brent Kruzel, Christian Brandt, Daniel Heinzen Continuous, high intensity cold atomic beams are excellent sources for precision measurement experiments and atom optics applications. Laser cooling and buffer gas-based methods are already well developed, but new methods that could potentially provide higher brightness beams are still of interest. We present our work on a new approach based on continuous post-nozzle injection of lithium atoms into a supersonic helium jet. We reduce the jet velocity to 200 m/s by cryogenically cooling the helium nozzle and extract the lithium atoms with magnetic focusing. The focused beam has a peak intensity of 7*10$^{\mathrm{10}}$ cm$^{\mathrm{-2\thinspace }}$s$^{\mathrm{-1}}$ and a temperature of 20 mK in the moving frame. Ongoing efforts to increase the beam brightness will be discussed as well as work towards the development and construction of a magnetic storage ring for the cold atoms.~ [Preview Abstract] |
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E01.00114: Three fermions with high angular momentum in the unitarity limit Yu-Hsin Chen, Chris Greene This study considers the unitary limit of three equal mass fermions having total orbital angular momentum $J^{\Pi}=1^{-}$, specifically consisting of two spin-up and one spin-down fermion ($\downarrow \uparrow \uparrow $). Our results agree with previous work by Castin and by Blume {\it et al.} in the limit where the s-wave scattering length goes to infinity. To explore another type of unitarity limit, we have derived numerical results for the regime where the p-wave scattering volume approaches infinity. This exploration has also considered different interactions between the atoms in different spin states, for example, the case where the two spin-up fermions have a p-wave interaction but where a spin-up atom interacting with a spin-down atom has a strong s-wave interaction. There are universal states that can be derived for both of the above two cases. Time permitting, this work may also analyze the rates for three-body recombination and atom-dimer dissociation in the limit of a large p-wave scattering volume for such systems involving three fermionic atoms. This work was supported in part by NSF. [Preview Abstract] |
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E01.00115: Cooling Rubidium 87 Atoms Using Adiabatic Expansion in Microgravity Adelaide Pollard, Cass Sackett The Cold Atom Lab on the International Space Station produces samples of cold, magnetically-trapped Rb-87 atoms. By slowly reducing the trapping fields using a series of thirty or more linear ramps in the chip and coil currents, we adiabatically expand the magnetic trap to create an ultra-cold and stationary sample of atoms. We have demonstrated the ability to displace atoms from the chip into a trap with 3 Hz frequency, with minimal residual center-of-mass motional excitation. As part of this effort, we are exploring how different trap turn off procedures affect the population of different magnetic states, as well as how stray background fields may limit the length of time-of-flight observations. We will discuss the application of adiabatic expansion in CAL's future atomic interferometry experiments and possible improvements to the technique. [Preview Abstract] |
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E01.00116: Cold dense ion clouds in a cryogenic neutral plasma Nishant Bhatt, Kosuke Kato, Amar Vutha We describe the production of dense clouds of a variety of cold atomic ions, cooled by collisions with cryogenic helium buffer gas. The ion clouds exist within a neutral plasma with a Coulomb coupling parameter $\Gamma_C \approx 0.5$. High optical depths can be achieved for the ion clouds, enabling convenient laser absorption measurements. We also discuss the first precise measurements of isotope shifts of Nd$^+$ ions, and a test of King plot linearity, performed using this system. [Preview Abstract] |
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E01.00117: Inelastic Raman Scattering and Optical Pumping in Cold $^{87}$Rb Brent Jones, Joshua Carter, Stetson J. Roof, Kasie J. Kemp, M. D. Havey, I. M. Sokolov, D. V. Kupriyanov We report investigation of near-resonance light scattering on a three level system of cold $^{87}$Rb atoms. A weak probe laser is tuned near the $F=2\to F'=2$ hyperfine transition to study optical pumping processes resulting in cold atomic ensembles in the $F=1$ hyperfine ground state. This process can be used to count the number of atoms in a sample for low optical depths, independent of detuning from resonance, by measuring the total absorbed light from the probe beam. For greater optical depths, the results depend on optical depth and probe detuning from resonance. This is a consequence of multiple scattering within the sample. We present experimental results for various optical depths, in comparison with simulation data, to study the dependencies of multiple scattering on optical depth. [Preview Abstract] |
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E01.00118: Modeling the Speed and Efficiency of an Optical Conveyor Garrett Hickman, Mark Saffman Fast, high-fidelity transport of cold atoms has been the subject of considerable theoretical and experimental effort. Much theoretical work has focussed on the corresponding 1D problem. These solutions may suffice for experiments in which an atom has been cooled to its 3D motional ground state, so that motion in the transverse plane can be neglected. In other cases however this may not be true. In particular, 3D ground-state cooling is more difficult in systems for which one or more trap frequencies is relatively small, since resolving motional sidebands might not be possible. This is particularly true of many optical conveyor setups. In these and similar cases it has been unclear whether a 1D model will be adequate. Here we present a numerical quantum 1D model that characterizes heating and atom loss in a realistic optical conveyor. The model depends on dephasing in the density matrix formalism to account for effects of motion in the transverse plane. We compare its predictions against measurements of an experimental system in which atoms are transported into an optical fiber cavity, and against a 3D classical Monte Carlo simulation. Comparisons indicate that the addition of dephasing into the model allows it to capture essential features of the 3D motion during transport. [Preview Abstract] |
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E01.00119: An Integrated Portable 2D Magneto-optical Trap System for the Production of a Cold Cesium Beam Jonathan Yang, Kaiyue Wang, Eric Mulero-Flores, Cameron Caligan, Matthew Dittrich, Colin Parker The production of a sample of trapped cold atoms using a magneto-optical trap (MOT) is the basis for a plethora of studies on ultracold atomic systems. In pursuit of a compact system that can provide a continuous cold beam of cesium (Cs) atoms, we designed and constructed a detachable 2D MOT platform. The detachable system allows for a single laser source to be split five ways, with each beam being reflected into both the horizontal and vertical directions with the correct polarization and power ratio. Our design is a single self-contained and orientable apparatus, with all external connections coming from optical fibers and electrical cables. The collimated beam then enters a 3D MOT test chamber where we measured and optimized the loading rate based off multiple 2D MOT parameters including beam intensity, cooling light detuning, and magnetic field etc. Thus, we characterize the effectiveness of the 2D loading rate. The modular design is intended to facilitate moving the source to another chamber where lithium (Li) atoms are also available. In the future we plan to investigate the properties of a combined ultracold system of Li and Cs. [Preview Abstract] |
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E01.00120: Building a magneto-optical trap with millimeter ball lenses Michael Viray, Leo Nofs, Cainan Nichols, Eric Paradis, Georg Raithel Since the development of the first magneto-optical trap (MOT), multiple researchers have successfully created alternative MOT configurations. These MOT configurations (e.g. grating MOTs, pyramidal MOTs) rely on the same physical principles as the original design, but they are also usually designed to achieve a specific goal such as miniaturization or single-beam MOT formation. We report on the development of a MOT that utilizes millimeter ball lenses to expand narrow beams into divergent light cones for atom trapping. We present a computational model of the ball lens MOT, construction details of the Ball Lens Optical Box (BLOB), and experimental and computational results for this MOT. We discuss advantages of this new design and plans for future implementation. [Preview Abstract] |
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E01.00121: Progress towards laser cooling of AlCl John Daniel, Kayla Rodriguez, Taylor Lewis, Shane Kelly, Alexander Teplukhin, Brian Kendrick, Christopher Bardeen, Shan-Wen Tsai, Boerge Hemmerling Cooling atoms to the ultracold regime has allowed for studies of physics, ranging from many-body physics of quantum degenerate gases, quantum computing, precision measurements and tests of fundamental symmetries. Extending these experiments to polar molecules has the prospect of enhancing the sensitivity of such tests and of enabling novel studies, such as cold controlled chemistry. However, applying traditional laser cooling techniques to molecules is rendered difficult due their additional degrees of freedom which result in a limited photon scattering budget. Here we study aluminum monochloride (AlCl) as a promising candidate for laser cooling and trapping. The cooling transition at 261 nm ($A^{1} \Pi - X^{1} \Sigma^{+}$) has an estimated Franck-Condon factor of 0.9988 which allows for scattering ~800 photons with a single laser before the molecule enters an excited vibrational state. We use a frequency-tripled (SHG + SFG) Titanium-Sapphire laser. We plan to generate AlCl via laser ablation of AlCl$_3$ in a cryogenic helium buffer gas beam source and we will discuss initial spectroscopy on AlCl necessary for future laser cooling and trapping. [Preview Abstract] |
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E01.00122: Holographic Generation of Laguerre-Gaussian Beams with Aberration Control Using a Digital Micromirror Device Kaiyue Wang, Colin Parker Inspired by recent application of the digital micromirror device (DMD) for creating arbitrary beam shapes, we developed our own control system to test advanced beam manipulation for future use in versatile optical lattices and tweezers for ultracold atoms. To measure and eliminate aberrations in the light path, we designed a test sequence that, within each run, can analyze the interference pattern by the two patches generated on the DMD, hence acquiring the relative phase and amplitude information in the patch positions. We implemented an algorithm that fits the 2D interference pattern while maintaining tolerance for mechanical instabilities, providing convenient diagnostics compared to a single intensity measurement at a fixed position. The holographic pattern is generated together with compensation for aberrations and can be proved as valid by the shape-maintaining properties at different propagation distances of Laguerre-Gaussian beams. [Preview Abstract] |
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E01.00123: Towards sympathetic rotational cooling of CaH$^+$ in a hybrid atom-ion trap Eric Pretzsch, Jyothi Saraladevi, Lu Qi, Evan Reed, Kenneth Brown A hybrid ion and magneto-optical trap is proposed to be a good environment for achieving the sympathetic cooling of molecular ions. We have previously shown that simultaneous trapping and spatial overlap of laser cooled Ca$^+$ with CaH$^+$ allows for sympathetic cooling of CaH$^+$. Coulomb interactions with calcium ions cool the translational motion of the molecular ion, and we expect the addition of interactions with potassium cool the internal states. We have observed charge exchange interactions between the coolants (Ca$^+$ and K) which can be minimized through state manipulation of the calcium ions. We present results of charge exchange reactions between trapped Ca$^+$ and K and our plans for the sympathetic rotational cooling of CaH$^+$. [Preview Abstract] |
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E01.00124: Continuous BECs and superradiant clocks with strontium Shayne Bennetts, Chun-Chia Chen, Rodrigo Gonzalez-Escudero, Francesca Fama, Sheng Zhou, Benjamin Pasquiou, Florian Schreck We have demonstrated a steady-state Bose-Einstein Condensate (BEC), a BEC for which losses are compensated by stimulated gain from a continuously refilled thermal reservoir surrounding the condensate. By continuously streaming a beam of strontium atoms through a sequence of laser cooling stages [1, 2] we cool the gas to 1$\mu$K while simultaneously increasing its density to reach the quantum regime. After switching the system on, steady-state is reached within 8 seconds after which we always destructively detect a BEC of $\sim$15000 atoms at randomly chosen times up to 5 minutes. This represents a critical step towards developing steady-state atom lasers and interferometers which may offer advantages for some applications like gravitational wave detection. The same concepts used to create a steady-state degenerate gas can also be applied to generate high phase-space density beams [3] and samples opening the door for demonstrating a continuous active optical clock on a clock transition. We will describe our progress towards a superradiant optical clock in strontium. [1] Bennetts et al., PRL 119, 223202 (2017). [2] Stellmer et al., PRL 110, 263003 (2013). [3] Chen et al., Phys. Rev. Applied 12, 044014 (2019). [Preview Abstract] |
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E01.00125: Towards a Magneto-Optical Trap of Potassium Atoms Loaded from a Cold Buffer Gas Beam Maryam Hiradfar, Sridhar Prabhu, Eunice Lee, Zack Lasner, Benjamin Augenbraun, Lawrence Cheuk, John Doyle We report on progress towards a magneto-optical trap (MOT) of potassium (K) atoms loaded from a cryogenic buffer gas beam (CBGB). We are building on our previous work,\footnote{B Hemmerling, et al. New J. Phys. \textbf{16} 063070(2014)} which demonstrated high MOT loading rates. In this work, we intend to refine the approach, characterize the process in more detail, and increase the number of atoms loaded into the MOT. We are using atomic potassium, which is produced by laser ablation of a potassium-rich solid target in the presence of a high-density He buffer gas at 4 Kelvin. Potassium atoms are extracted into the CBGB with pulse length of a few ms. Further laser slowing (either white light or Zeeman) will bring the atoms to below the capture velocity of the MOT and should lead to exceptionally high loading rates and atom number. [Preview Abstract] |
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E01.00126: Sawtooth Wave Adiabatic Passage in a Magneto-Optical Trap Murray Holland, John Bartolotta We investigate theoretically the application of Sawtooth Wave Adiabatic Passage (SWAP) within a 1D magneto-optical trap (MOT). As opposed to related methods that have been previously discussed, our approach utilizes repeated cycles of stimulated absorption and emission processes to achieve both trapping and cooling, thereby reducing the adverse effects that arise from photon scattering. Specifically, we demonstrate this method's ability to cool, slow, and trap particles with fewer spontaneously emitted photons, higher forces and in less time when compared to a traditional MOT scheme that utilizes the same narrow linewidth transition. We calculate the phase space compression that is achievable and characterize the resulting system equilibrium cloud size and temperature. [Preview Abstract] |
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E01.00127: An apparatus for laser-cooling and trapping potassium with reduced magnetic field fluctuations William Tavis, Jonathan Wrubel, Kellan Kremer, Matt Beauchem We describe our apparatus for laser-cooling potassium-39 and potassium-41 at Creighton University, which is a primarily undergraduate institution. We use a two-dimensional magneto-optical trap (2D MOT) with a push beam loading a 3D MOT. The 3D MOT is formed inside of an octagonal glass cell with a high degree of optical access. The ultimate goal of this apparatus is to study spinor dynamics in a potassium-41 BEC. We describe a number of the critical experimental features including an active feedback system for control and cancellation of magnetic field fluctuations. Our homebuilt proportional-integral-derivative circuit reduces the magnetic field noise by up to a factor of 100 from dc through 1 kHz. [Preview Abstract] |
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E01.00128: A magneto-optical trap with octupolar symmetry for sub-Doppler cooling Jonathan Wrubel, William Tavis, Kellan Kremer We present our progress in implementing a 3D magneto-optical trap (MOT) with octupolar symmetry in a laser-cooling experiment for potassium. Because of the reduced symmetry of the trap, simulations suggest the trapping volume will be approximately 1000 times larger than a standard quadrupolar 3D MOT. In addition, we expect sub-Doppler cooling mechanisms to be operative over an enlarged central region because of weak magnetic fields. This sub-Doppler cooling is expected without significant loss of atoms due to the residual field gradient near the edges. We discuss the experimental design we have implemented while preserving optical access, as well as simulations of the cooling process and trap depth of the MOT. [Preview Abstract] |
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E01.00129: Progress Towards a Magneto-Optical Trap of Titanium Scott Eustice, Kayleigh Cassella, Diego Peña, Miguel Aguirre, Dan Stamper-Kurn We report on experimental progress towards a magneto-optical trap of bosonic $^{48}$Ti. Unlike previously laser-cooled atoms, Ti's ground state ([Ar]$4s^23d^2$ $a^3F_2$) supports strong anisotropic atom-light interactions with off-resonant light. The $a^3F_2$ state's magnetic moment is on par with an alkali atom ($\sim4/3\mu_B$), suppressing long-range dipolar interactions between Ti atoms and extending spin-mixture lifetimes compared to more magnetic atoms. The $a^3F_2$ state does not have a closed transition amenable to laser cooling. However, the metastable state ([Ar]$4s3d^3$ $a^5F_5$) does posses such a transition at 498 nm with a linewidth of 10.5 MHz ($T_D=250\mu K$). We report on the production of a beam of atomic Ti from an effusive oven, as well as the optical pumping of the atomic beam into the metastable $a^5F_5$ state. Progress towards magneto-optical trapping of Ti is presented, as well as future plans to achieve a quantum degenerate gas of Ti atoms. [Preview Abstract] |
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E01.00130: A generalized phase space approach for solving quantum spin dynamics Bihui Zhu, Ana Maria Rey, Johannes Schachenmayer Numerical techniques to efficiently model nonequilibrium dynamics in quantum many-body systems are crucial for advancing our capability to harness and understand complex quantum matter. Here we propose a new numerical approach based on a discrete semi-classical phase space sampling, which allows to investigate quantum dynamics in lattice spin systems with arbitrary spin S. We refer to this approach as generalized discrete truncated Wigner approximation (GDTWA). We show that the GDTWA can accurately simulate dynamics of large ensembles in arbitrary dimensions, by applying it to study S\textgreater 1/2 spin-models with dipolar long-range interactions, a scenario arising in recent experiments with magnetic atoms. We compute experimentally accessible observables such as spin populations, spin coherence, spin squeezing, and entanglement quantified by single-spin Renyi entropies, and reveal features in large S systems different from conventional S-1/2 systems. We further discuss potential applications of GDTWA for studying other systems with discrete local Hilbert space. Our analysis demonstrates that the GDTWA can be a powerful tool for modeling complex spin dynamics in regimes where other state-of-the art numerical methods fail. [Preview Abstract] |
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E01.00131: Measurement of AC polarizability and photoionization cross section of the Rb $5D_{3/2}$ state in a 1064 nm optical lattice Ryan Cardman, Jamie L. MacLennan, Xiaoxuan Han, Georg Raithel We perform measurements of the AC polarizability and photoionization cross section for the $5D_{3/2}$ state of ultracold $^{85}$Rb in a cavity-enhanced optical lattice. An in-vacuum cavity, with a finesse of 600, enhances the 1064 nm light field and results in $\sim$GHz-deep AC-Stark shifts on the $5S_{1/2}\rightarrow5P_{1/2}$ (795 nm) and $5P_{1/2}\rightarrow5D_{3/2}$ (762 nm) transitions. The two excitation lasers are scanned through the AC-Stark-shifted resonances while phase-locked to lasers stabilized to atomic references. Atoms are photoionized by the 1064 nm field, and the resulting ions are then collected with a micro-channel plate detector (MCP). A two-dimensional map of the ion counts is then analyzed with the known AC polarizabilities of the $5S_{1/2}$ and $5P_{1/2}$ states and with the D1 hyperfine structure. This analysis yields the resulting AC polarizability for $5D_{3/2}$. Measured linewidths of the spectra are used to extract the photoionization cross section. [Preview Abstract] |
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E01.00132: Optical phase dependence and formation time for superlattice density patterns in a 6-beam $\sigma +$-$\sigma $-- optical lattice. Timothy Roach, Wilber Alfaro Castro We have been studying superlattice density variations in a 6-beam $\sigma +$-$\sigma $-- optical lattice (optical molasses). These density patterns, seen also in magneto-optic traps, are caused by slight beam misalignments that produce a gradient in the time phases of the optical lattice across the interaction region. The resulting superlattice has regions with different polarization character and hence different potential wells and damping forces. For example, one region has primarily circular polarization and Sisyphus cooling while another has linear polarization and an induced-orientation friction force. We impose a phase-gradated optical lattice on an initially uniform (Gaussian distributed) atomic cloud and observe the diffusion of atoms into a periodic structure over times $\sim $ 10$^{\mathrm{-2}}$ sec. We also induce gradients of the two independent optical time phases each in a different spatial direction. This creates a mapping of the 2D optical phase space onto real space, where we see a density distribution with atoms localized in islands arranged in a 2D pattern. While this gradient method itself does not allow unambiguous determination of optical phases, there is a particular symmetry and topography in the experimental distribution and in the calculated light field ellipticity that allows us to infer that atoms are accumulating at points of minimum ellipticity, where the optical time phases are equal. The diffusion rate within the superlattice can be explored as a function of intensity and detuning which will be useful for comparison with theoretical models. [Preview Abstract] |
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E01.00133: Towards two dimensional synthetic lattice of momentum states Shraddha Agrawal, Sai Naga Manoj Paladugu, Fangzhao Alex An, Hannah Jean Manetsch, Bryce Gadway We describe progress towards an experimental platform for engineering two dimensional synthetic lattices based on laser coupled atomic momentum states of potassium-39 atoms. This technique allows for the local and time-dependent control over nearly all system parameters, including tunneling phases, which makes it suitable for studying a range of novel transport phenomena in two-dimensional lattices. We describe how an arrangement of three equally separated in-plane Bragg lasers can be used as a versatile setup for realizing triangular lattices, honeycomb lattices, Kagome lattices, and Hofstadter model. The ability to augment these various two-dimensional lattices with disorder or other forms of parameter variation promises to allow for the exploration of a broad range of lattice physics. We additionally describe the experimental progress towards creating Bose-Einstein condensates of potassium-39 atoms, the control of atomic interactions by a Feshbach resonance, and the implementation of two-dimensional momentum state synthetic lattices. [Preview Abstract] |
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E01.00134: Realization of individual addressing on two-dimensional ion crystal using MEMS mirror Zhengyang Cai, Mu Qiao, Chunyang Luan, Pengfei Wang, Kihwan Kim Individual manipulation of qubits is the essential element for universal quantum computation and quantum simulation. The technology of individual quantum operation on qubits can be realized by individually addressing laser beams with the capability of independent control for trapped ion quantum computation. Recently, two-dimensional (2D) crystal of ions has been developed for the quantum computation and simulation [1]. However, the ability of individual and independent control of ion-qubits is still missing. In this work, we present the design and simulation results of an optical setup to generate an arbitrary two-dimensional pattern of laser beams using a MEMS mirror array. We fabricate the MEMS mirror array into a customized ceramic pin grid array (CPGA) base and seal it with rare gas. The flipping angle of the MEMS mirrors are controlled by a high-accuracy digital-analog-convert (DAC). Finally, the aberration and beam pattern are studied with CCD camera. [1] Wang, Ye et al. “Realization of two-dimensional crystal of ions in a monolithic Paul trap.” (2019). [Preview Abstract] |
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E01.00135: Optical rotation of few-ion crystals ARPITA PAL, M Bhattacharya Trapped ion crystals are of immense use in quantum simulation, information processing and metrology. The overwhelming number of investigations in such systems have targeted the linear vibrational motion of ion arrays and their normal modes. Recently, coherent control of a rotating two-ion crystal in a circularly symmetric potential was demonstrated experimentally [1], where angular momentum was imparted to the ions using time-periodic trap voltages. We theoretically consider instead the rotation of few-ion planar crystals using radiation pressure from an asymmetrically placed optical cooling beam. We expect our system to be useful for simulating quantum rotors and time crystals and for rotation sensing. [1] E. Urban et al., Phys . Rev. Lett. 123, 133202 (2019). [Preview Abstract] |
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E01.00136: A surface trap for multi-qubit quantum computing Yue Jiang, Wending Zhao, Zhichao Mao, Weixuan Guo, Gangxi Wang, Li He, Zichao Zhou, Luming Duan A silicon-based surface trap which integrates a shunt-capacitor interposer has been fabricated for quantum computation and simulation experiments. The trap is fabricated through the standard MEMS processes and in a bow-tie shape for high optical access, compatible with cross-chip Raman beams for individual addressing. The RF and inner-DC electrodes are modified for smooth potential to shuttle ions loaded from the back of the chip, and RF loss is minimized as well. The parallel-plate capacitors around 600 pF each on interposer are devised to shunt the pick-up RF signal of DC electrodes to ground. The full package is standardized on a 100-pin CPGA architecture for easy replacement. A Yb$^{\mathrm{+}}$ ion chain with a radial trap frequency over 3 MHz has been successfully trapped on our surface trap. After optimization of trapping parameters, we have measured the dark lifetime and heating rate through Doppler-recooling method. In future, we will implement Raman-sideband cooling and individual addressing in this new type of surface trap. [Preview Abstract] |
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E01.00137: Observations of trapped ions phase transition processes Yuzi Xu, Yunhan Hou, Wending Zhao, Quanxin Mei, Bowen Li, Jianyu Ma, Xiang Zhang, Zichao Zhou, Luming Duan We directly observed laser-cooled $^{174}Yb^{+}$ ions confined in 4-rod Ion trap to study ions crystalline phase, and images of them taken by EM-CCD were used to characterize the structural phase of trapped ions and calculate temperature of each ion. With a variety of perturbations in the beginning, different structural phase transition processes were detected by continuously taking pictures of ions in the experiment. The experiments results are in good agreement with theoretically simulation that show symmetrical and partial temperature-driven structural phase transition for trapped ion crystal and help us understand ions melting phenomenon to increase ions lifetimes in the future. [Preview Abstract] |
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E01.00138: Near-ground state cooling and sensing experiments with 2D arrays of hundreds of trapped ions M. Affolter, K.A. Gilmore, J.E. Jordan, J.J. Bollinger, A. Shankar, R.J. Lewis-Swan, A.M. Rey, M. Holland We summarize recent experimental work with 2D arrays of hundreds of trapped $^{9}$Be$^{+}$ ions stored in a Penning trap. The goal of this work is quantum simulations and sensing with large trapped ion crystals. For improved sensing and simulation fidelity, electromagnetically induced transparency (EIT) cooling has recently been implemented [1], with near ground state cooling observed for all the drumhead modes. In previous simulations of these Doppler and EIT cooled axial mode spectra, ad hoc frequency fluctuations of the modes were required to produce the smooth mode spectra experimentally observed. Recent theoretical work shows that these fluctuations could be caused by the finite temperature of the in-plane modes. We also measure 70Hz fluctuations in the axial COM mode that, with currently available laser power, limit our ability to measure weak excitations of the axial COM mode. Using an rf tickle far from the axial center-of-mass (COM) mode, where these fluctuations can be ignored, a single measurement displacement sensitivity 40x smaller than the ground state wave function was achieved corresponding to an order-of-magnitude enhancement over previous work [2]. [1] J. E. Jordan et al. PRL 122, 053603 (2019). [2] K. A. Gilmore et al. PRL 118, 263602 (2017). [Preview Abstract] |
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E01.00139: $^{138}$Ba$^{+}$ Zeeman qubit operation through Raman transition Liudmila Zhukas, Tomasz Sakrejda, Boris Blinov Barium (Ba) and Ytterbium (Yb) are excellent candidates to perform sympathetic cooling [1] due to the relatively small mass difference between those species. It is possible to reach Doppler cooling limit for the Ba-Yb linear ion chain of multiple ions [2]. Here $^{138}$Ba$^{+}$ is used as an informational qubit. We drive $6S_{1/2}-6P_{1/2}$ Raman transitions with a 532 nm mode-locked laser to perform qubit operations and use the narrow $6S_{1/2}-6D_{5/2}$ quadrupole transition for state detection and initialization. Starting with a linear chain of Ba ions, we discuss the possibility to incorporate $^{174}$Yb$^{+}$ ions to perform sympathetic cooling. [1] D. Kielpinski et al., Phys. Rev. A 61, (2000) [2] T. P. Sakrejda, L. Zhukas, B. B. Blinov arXiv:1809.00240 [physics.atom-ph] [Preview Abstract] |
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E01.00140: A Dual-species Trapped-ion System for Quantum Information Processing with $^{88}$Sr$^+$ and $^{133}$Ba$^+$. Susanna Todaro, Jasmine Sinanan-Singh, Jules Stuart, Colin Bruzewicz, Gabriel Mintzer, Luke Qi, Roberto Gauna, Isaac Chuang, John Chiaverini, Jeremy Sage Dual-species ion trapping is a potentially useful tool for scalable trapped-ion quantum information processing (QIP), since the second ion species can be used as a sympathetic coolant or as an ancilla qubit. $^{88}$Sr$^+$ and $^{133}$Ba$^+$ both have accessible visible laser wavelengths for cooling, state preparation, detection, and gate operations, making them a promising pair for QIP applications. The mass ratio is also appropriate for sympathetic cooling. Further, $^{133}$Ba$^+$ has a spin-1/2 nucleus so the qubit can be encoded in the ground-state hyperfine manifold, which can have long coherence times [1]. We show progress towards dual-species trapping and control of $^{88}$Sr$^+$ and $^{133}$Ba$^+$. [1] D. Hucol \textit{et al.}., PRL {\bf 119} 100501 (2017). [Preview Abstract] |
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E01.00141: Characterization of a Structural Phase Transition in Ultracold Ion Crystals Brendin Chow, Jie Zhang, Paul Haljan We experimentally characterize a structural phase transition, known as the linear-zigzag transition, for arrays of ions confined in a linear radio-frequency Paul trap where the ions are laser-cooled to vibrational energies of a few quanta or less. Enabled by low thermal fluctuations and a stabilized trap potential, we use Raman sideband spectroscopy to investigate effects close to the transition's critical point, including modifications to the nature of the transition, for small arrays of ions. This work builds the foundation for explorations of quantum coherence close to the transition's critical point. [Preview Abstract] |
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E01.00142: The $^{133}\mathrm{Ba}^{+}$ Ion Platform Z. S. Smith, D. Hucul, W. T. Grant, P. Haas, H. J. Rutbeck-Goldman, B. Tabakov, J. A. Williams, C. F. Woodford, K.-A. Brickman-Soderberg Laser cooled and trapped atomic ions are well isolated quantum systems, making them promising platforms for quantum sensing, information processing, and networking. Different ion species bring different advantages: hyperfine qubits in species with nuclear spin $I=1/2$ have long coherence times together with robust qubit manipulation. Other ion species have electronic excited states with a long lifetime, allowing shelving schemes for high-fidelity qubit state measurement. $^{133}\mathrm{Ba}^{+}$ is the only ion species to combine these properties, making it an ideal candidate for trapped ion quantum information science. Additionally, all required laser wavelengths are in the visible, eliminating the need for difficult-to obtain power at ultraviolet wavelengths. We will discuss recent work at AFRL with photoionization, laser cooling, and trapping of this isotope of barium, and discuss milestone experiments including background-free state readout and other future work. Distribution A. Approved for public release Case Number 88ABW-2020-0253 [Preview Abstract] |
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E01.00143: A High Fidelity AC-Stark Shift Gate for Trapped-Ion Clock-State Qubits Daniel Stack, Bryce Bjork, Michael Foss-Feig, John Gaebler, David Hayes, Mark Kokish, Christopher Langer, Jonathon Sedlacek, Grahame Vittorini, Charles Baldwin To date, the highest fidelity quantum logic gates between two qubits have been achieved with variations on the geometric-phase gate in trapped ions, with the two leading variants being the M\o lmer-S\o rensen gate and the light-shift (LS) gate. Both of these approaches have their respective advantages and challenges. For example, the latter is technically simpler and is natively insensitive to optical phases, but it has not been made to work directly on a clock state qubit. We present a new technique for implementing the LS-gate that combines the best features of these two approaches: By detuning relatively close to a narrow (dipole-forbidden) optical transition, we are able to operate an LS-gate directly on hyperfine clock states, achieving gate fidelities of $99.8(1)\%$ using modest laser power at optical wavelengths. Current gate infidelities appear to be dominated by laser phase noise, and theoretical modeling suggests a path towards gate fidelity above $99.99\%$. [Preview Abstract] |
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E01.00144: Ablation Ion Source for Cold Chemistry Timothy Burke, Richard Mattish, Joan Marler Atomic ions isolated in an rf trap and laser-cooled to temperatures in which their internal states can be measured, set, and switched at the individual ion level provide the ideal starting conditions for quantum chemistry experiments. Ablation loading of the rf trap opens up the possibility of a wide range of ion species which could be trapped and sympathetically cooled in the same apparatus without needing to break vacuum. We present a two part loading scheme using ablation to load various target ions and photoionization to load coolant ions into a linear rf trap. At Clemson, near term experiments include first characterizing and refining this loading technique. This system can then be used to study chemistry relevant to astrophysical systems, follow state to state chemical reactions, and perform accurate measurements of carbon containing organic systems. [Preview Abstract] |
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E01.00145: Apparatus for Rb-$^{\mathrm{129}}$Xe/$^{\mathrm{131}}$Xe-N$_{\mathrm{2\thinspace }}$vapor cells. Sin Hyuk Yim, Sangkyung Lee, Tae hyun Kim, Deok Young Lee, Kyu Min Shim We present the experimental setup for the production of atomic vapor cell containing Rb, $^{\mathrm{129}}$Xe, $^{\mathrm{131}}$Xe, N$_{\mathrm{2}}$, and H$_{\mathrm{2}}$ gases. A cell is 12.5 mm cubic with pyrex. Long stem is attached on top of the cell. The cell is cleaned several times with neutral detergent, distilled water, acetone, ethanol, IPA, and methanol respectively. The cell is attached to high vacuum chamber and baked for a week with turbo pump and ion pump. A Rb dispenser is activated after finishing the baking procedure. While the dispenser is activated, the cell is cooled in the cold water to collect Rb atoms into the cell. Mixed gases, then, with $^{\mathrm{129}}$Xe, $^{\mathrm{131}}$Xe, N$_{\mathrm{2}}$, and H$_{\mathrm{2\thinspace }}$are inserted into the Rb cell by monitoring the total pressure. The Rb-$^{\mathrm{129}}$Xe/$^{\mathrm{131}}$Xe-N$_{\mathrm{2\thinspace }}$vapor cells are sealed by glass welding technique. The transverse spin relaxation time of $^{\mathrm{129}}$Xe/$^{\mathrm{131}}$Xe are 10 s and 20 s, respectively, which are measured by using free induction technique. [Preview Abstract] |
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E01.00146: Noise reduction in $^{\mathrm{87}}$Rb-$^{\mathrm{129}}$Xe/$^{\mathrm{131}}$Xe atom spin gyroscopes based on parametric modulation Sangkyung Lee, Sin Hyuk Yim, Deok Young Lee, Tae Hyun Kim, Kyumin Shim We analyze an $^{\mathrm{87}}$Rb-$^{\mathrm{129}}$Xe/$^{\mathrm{131}}$Xe atom spin gyroscope based on parametric modulation. The parametric modulation enables either B$_{\mathrm{x}}$ sensitive mode or B$_{\mathrm{y\thinspace }}$sensitive mode, depending on the demodulation phase. The white noise is analyzed as a function of demodulation phases in parametric modulation. We achieve an angular random walk of 0.08 deg/hr$^{\mathrm{1/2\thinspace }}$and a bias instability of 0.75 deg/hr in the B$_{\mathrm{x}}$ sensitive mode. The noise minimum mode reduces the angular random walk but it sometimes degrades the bias instability. We discuss how to reach the minimum angular random walk without degradation of the bias instability. Finally, we introduce our recent progress on development of $^{\mathrm{87}}$Rb-$^{\mathrm{129}}$Xe/$^{\mathrm{131}}$Xe Atom Spin gyroscopes. [Preview Abstract] |
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E01.00147: Quantum-enabled spectroscopy of trapped highly charged ions for tests of fundamental physics Alessandro L. Banducci, Samuel M. Brewer The standard model (SM) of particle physics provides a description of nature that has been well-tested and confirmed at the high-energy scale. With the recent discovery of the Higgs boson, all known particles in the SM have been observed experimentally. However, despite the success of the SM several major problems remain unsolved. These include such phenomena as baryon asymmetry and the existence of dark matter. 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 tests of fundamental physics including tests of quantum electrodynamics (QED) and searches for time-variation of the fundamental constants (e. g. $\dot{\alpha} / \alpha$). Here, we present the status of an experimental program aimed at performing high-precision, quantum-enabled laser spectroscopy of trapped HCIs to search for physics beyond the standard model. [Preview Abstract] |
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E01.00148: Ultrasensitive Force sensing with optically levitated nanoparticles Evan Weisman, Chethn Galla, Ghambir Ranjit, Cris Montoya Optically levitated and cooled dielectric particles in high vacuum are a promising tool for use in precision experiments. Since they are decoupled mechanically from the environment optically levitated particles can have very high-quality factors enabling ultrasensitive force detection. We describe progress on an experiment using silica nanospheres trapped in an optical lattice to search for deviations from Newton's inverse square law at the micron scale where we have achieved zeptonewton force sensitivity. Recent modifications to the experiment include a fiber-based dipole trap and solid invar cavity. [Preview Abstract] |
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E01.00149: Towards a Precise Test of King's Linearity in Ca$^+$ Paige Robichaud, Jacob Lezberg, S. Charles Doret We report progress towards a precise measurement of the isotope shifts in the 4$^2$S$_{1/2}\rightarrow$3$^2$D$_{3/2}$ 732 nm electric quadrupole transition in Ca$^+$. We co-trap two isotopes and simultaneously excite both ions using frequency sidebands on a single laser, dramatically reducing systematic uncertainties from many sources such as laser frequency drift and magnetic field instabilities. Such measurements have the potential to reach Hz-level precision or better, as with our recent ppb measurement of the parallel 4$^2$S$_{1/2}\rightarrow$3$^2$D$_{5/2}$ transition. When combined into a King Plot, these two measurements will test King's linearity with heretofore unprecedented precision, offering a path toward probing new physics beyond the Standard Model and also providing benchmarks for ever-improving theory of atomic and nuclear structure. [Preview Abstract] |
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E01.00150: Calculation of the $3C/3D$ line intensity ratio in Fe XVII Charles Cheung, Mikhail Kozlov, Sergey Porsev, Marianna Safronova Some of the brightest X-ray lines in the spectra of many hot astrophysical objects arise from Fe XVII spectra around 15 \AA: the resonance line $3C$ ($[(2p^5)_{1/2} 3d_{3/2}]_{J=1} \rightarrow$ $ [2p^6]_{J=0}$) and the intercombination line 3D ($[(2p^5)_{3/2} 3d_{5/2}]_{J=1} \rightarrow$ $[2p^6]_{J=0}$). These lines are crucial for plasma diagnostics of electron temperatures, elemental abundances, ionization conditions, velocity turbulences, and opacities [1]. However, for the past four decades, their observed intensity ratios persistently disagree with advanced plasma models. We have carried out very large-scale relativistic configuration interaction (CI) calculations of the $3C/3D$ line intensity ratio, correlating all ten electrons, including Breit and quantum electrodynamical (QED) corrections, for Fe XVII [1]. Using a new parallel version of our CI code, we were able to increase the number of configurations to over 230,000, saturating the computation for all possible numerical parameters. Our theoretical 3C-3D energy difference of 13.44 eV is in agreement with the experiment [1] to 0.3\%. The computational advances highlighted in this work are widely applicable and can be used on most elements in the periodic table.\\ [1] Steffen K\"{u}hn et al., arXiv:1911.09707. [Preview Abstract] |
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E01.00151: High-Precision Transition Amplitude and Polarizability Measurements in Atomic Lead using Faraday Rotation Spectroscopy John Lacy, Abdullah Nasir, Gabriel Patenotte, Protik Majumder We recently completed a direct measurement of the very weak $(6s^2 6p^2) {^3}P_0 \rightarrow {^3}P_2$ 939 nm electric quadrupole (E2) transition in atomic lead using an optical polarimeter with microradian resolution.\footnote{Maser \textit{et al.}, Phys. Rev. \textbf{A} 100, 052506 (2019)} A Faraday rotation spectroscopy technique was used to compare the transition strengths of the E2 transition to the ${^3}P_0 \rightarrow {^3}P_1$ 1279 nm M1 transition in a lead vapor cell heated to between 800 and 950 $^{\circ}$C. We found excellent agreement with new {\em ab initio} theoretical calculations of relevance to parity nonconservation in lead.\footnote{Porsev \textit{et al.}, Phys. Rev. \textbf{A} 93, 012501 (2016)} Using this highly-sensitive technique we are now studying optical rotation signals in an atomic beam apparatus where we will measure the $(6s^2 6p^2) \rightarrow (6s^2 6p7s)$ 368 nm (E1) transition using transverse (Doppler-narrowed) Faraday spectroscopy. In recent years, we have completed a series of atomic-beam polarizability measurements in thallium and indium, and we now plan to extend these measurements to excited states of lead which will serve as new, sensitive tests of atomic theory. Current experimental results will be presented. [Preview Abstract] |
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E01.00152: Upgrades for an Improved Measurement of the Permanent EDM of Radium Tenzin Rabga, Kevin Bailey, Michael Bishof, Donald Booth, Mathew Dietrich, John Greene, Peter Mueller, Thomas O'Connor, Roy Ready, Jaideep Singh A non-zero Electric Dipole Moment (EDM) in a non-degenerate system violates time-reversal (T) symmetry and consequently also charge-parity (\textit{CP}) symmetry. EDM measurements are therefore sensitive searches for new CP violating interactions. The octupole deformation and nearly degenerate nuclear parity doublet in radium (Ra) make it an attractive candidate for probing \textit{CP} violations in the hadronic sector. Experimental upgrades are being implemented to enhance the current EDM sensitivity for Ra-225. These include more than a factor of three enhancement in the electric field from our electrode upgrade, a STIRAP-based electron shelving for improved state detection efficiency, and an improved atom slowing scheme. With these upgrades, the increased EDM sensitivity will substantially improve constraints on certain \textit{CP} violating processes within the nucleus. This work is supported by the U.S. DOE, Office of Science, Office of Nuclear Physics, under contract DE-AC02-06CH11357 and the Michigan State University. [Preview Abstract] |
On Demand |
E01.00153: Effects of Gravitational Waves on a Highly Excited Hydrogen-like Atom Nontapat Wanwieng, Apimook Watcharangkool, Nithiwadee Thaicharoen, Narupon Chattrapiban Effects of gravitational waves on a highly excited hydrogen-like atom near ionization threshold are investigated. The plane gravitational waves are described on the basis of Linearized General Relativity. The quantum mechanical description of electron coupled to the field of gravitational waves and electromagnetic is governed by the generalized Dirac equation to curved spacetime. To obtained systematically the physical interpretation of interaction terms in non-relativistic limit, the Exact Foldy-Wouthuysen (EFW) transformation has been performed. Then the calculation of energy correction and deviation of Rabi oscillation are carried out on the perturbation theory approach. The discussion of sensitivity to the gravitational waves generated from the compact astronomical sources are also presented. [Preview Abstract] |
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E01.00154: Material magnetism characterization for particle trap design Samuel Fayer, Gerald Gabrielse The magnetic properties of electrode and electronics used in particle and ion traps are important for high precision measurements, such as the electron magnetic moment that was able to test the standard model to 0.9 ppt [1]. At low temperatures and high magnetic fields, the magnetism of the trap materials can cause a significant perturbation to the background field. These perturbations can be temperature, position, and background field dependent. Impurities in even high purity sample materials have been identified to cause additional unwanted magnetism. The potentially detrimental effect of these materials on trapped particles will presented in the context of the electron and positron magnetic moment measurement [1] (where nuclear paramagnetism was a considerable challenge in the previous determination) and high resolution NMR magnetometry [2]. 1. G. Gabrielse, S. E. Fayer, T.G. Myers, X. Fan, Atoms 7 (2019) 45.~~ 2. X. Fan$,~$S.E. Fayer$,~$G. Gabrielse,~Review of Scientific Instruments 90 (2019) 083107 [Preview Abstract] |
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E01.00155: Search for a variation of the fine-structure constant around the supermassive Black Hole in our Galactic Center Benjamin Roberts, A. Hees, T. Do, A. M. Ghez, S. Nishiyama, R. Bentley, A. K. Gautam, S. Jia, T. Kara, J. R. Lu, H. Saida, S. Sakai, M. Takahashi, Y. Takamori Searching for space-time variations of the constants of Nature is a promising way to search for new physics beyond General Relativity and the standard model motivated by unification theories and models of dark matter and dark energy. We propose a new way to search for a variation of the fine-structure constant using measurements of late-type evolved giant stars from the S-star cluster orbiting the supermassive black hole in our Galactic Center. A measurement of the difference between distinct absorption lines (with different sensitivity to the fine structure constant) from a star leads to a direct estimate of a variation of the fine structure constant between the star's location and Earth. Using spectroscopic measurements of 5 stars, we obtain a constraint on the relative variation of the fine structure constant below 1e-5. This is the first time a varying constant of Nature is searched for around a black hole and in a high gravitational potential. This analysis shows new ways the monitoring of stars in the Galactic Center can be used to probe fundamental physics. [Preview Abstract] |
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E01.00156: Deuteron to Proton Mass Ratio from Precision Measurement of the Cyclotron Frequencies of H$_2^+$ and D$^+$ with H$_2^+$ in a Resolved Ro-vibrational State David Fink, Edmund Myers Determination of the deuteron-to-proton mass ratio ($m_{d}/m_{p}$) from precision measurement of the CFR (cyclotron frequency ratio) H$_2^+/$D$^+$ benefits from a reduction in systematic error due to the use of ions of similar $m/q$. However, additional uncertainty results from lack of knowledge of the H$_2^+$ ro-vibrational state. Following a previous measurement using alternating measurements of cyclotron frequency with ions in large and small cyclotron orbits [1], we are implementing a two-ion simultaneous measurement technique, originally developed at MIT for ions with $m/q \sim 30$, to increase the precision of our measurement of the H$_2^+/$D$^+$ CFR. By measuring the cyclotron frequency of the H$_2^+$ and D$^+$ ions simultaneously, statistical uncertainty due to magnetic field variation is minimized. With feedback cooling to reduce statistical noise on the cyclotron frequency (due to thermal fluctuations in the cyclotron radius combined with special relativity) this technique may enable us to identify specific ro-vibrational decays, and hence obtain a sub-$10^{-11}$ measurement of $m_d/m_p$. \break \break [1] D. J. Fink and E. G. Myers, Phys. Rev. Lett. 124, 013001 (2020). [Preview Abstract] |
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E01.00157: Continued Work on Improving the Precision of Helium Laser Spectroscopy Garnet Cameron, Jonathan Cuevas, Ali Khademian, David Shiner Precision measurements of the fine structure of the helium 2P state provide a proving ground for various experimental techniques as well as a test of the bound state quantum electrodynamics of the electron-electron interaction. Additional applications are to nuclear few-body physics and possible input to the fine structure constant determination. In our experimental approach, the first order Doppler shifts in the laser excitation of an atomic beam can be conveniently reduced by laser beam retro-reflection, but at the cost of a standing wave laser interaction. This interaction causes ``power'' dependent shifts arising from laser cooling effects. The experimental implementation of a straight forward approach that circumvents this effect while maintaining Doppler insensitivity will be discussed. Additional improvements to the atomic beam preparation and optical techniques include a compact, collimated, kG NdFeB magnet assembly optimized with 3-D COMSOL simulation, picomotors, and a 20 ms variable retarder LC. Data collection to further identify sources of uncertainty which limit precision will be examined. [Preview Abstract] |
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E01.00158: Time-reversal test in radiative beta decay: progress J.A. Behr, A. Gorelov, J.C. McNeil, D. Melconian, M. Anholm, G. Gwinner, T. Valencict, A. Afanassieva We are developing a time-reversal breaking test in radiative beta decay, using just the momenta of three outgoing particles. This type of time reversal is independent of nuclear spin, so explores time reversal-breaking physics unrelated to electric dipole moments, though there are model-dependent constraints at 1-loop order from null measurements of EDM's. The scalar triple product of three momenta provides a unique time-reversal odd observable, but trivially vanishes in ordinary beta decay when the three momenta sum to zero. So we need the fourth outgoing particle in radiative beta decay, considering the correlation between beta, neutrino, and gamma. We add gamma-ray detectors to TRIUMF's MOT for beta decay, which includes a COLTRIMS-like electrostatic field for recoil ion detection. Explicit models produce this observable with an antisymmetric Chern-Simons term from QCD-like new interactions, combined with the vector electroweak interactions within the nucleon [S. Gardner and D. He, Phys. Rev. D 87 116012 (2013)], and among the predicted features are a quite different gamma-ray spectrum than normal bremsstrahlung. We will show initial data from the decay of $^{92}$Rb, a case without vector interactions not yet testing the explicit models. [Preview Abstract] |
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E01.00159: Towards multiplexed and continuous trapped-ion spectroscopy for the JILA Gen. III eEDM experiment Sun Yool Park, Kia Boon Ng, Noah Schlossberger, Yan Zhou, Tanya Roussy, Tanner Grogan, Yuval Shagam, Antonio Vigil, Madeline Pettine, Eric Cornell, Jun Ye The third-generation (Gen. III) measurement of the electron's electric dipole moment (eEDM) at JILA utilizes ThF$+$, rather than HfF$+$, because: (i) the eEDM sensitive state of ThF$+$ promises a longer coherence time (\textasciitilde 20 seconds) [1,2], and (ii) its 50{\%} larger effective electric field increases eEDM sensitivity [3]. To take full advantage of the long coherence time, we are designing a ``conveyor belt'' of 100 ion traps called the Bucket Brigade (B.B.). The B.B. continuously loads and reads out ThF$+$, allowing for a 10,000{\%} duty cycle that leads to more precise measurements. The Gen. III experiment will also include cryogenics to eliminate blackbody radiation effects that are detrimental to the coherence time. Here, we present the progress on the design of the Gen. III eEDM experiment including the geometry of the B.B. and cryogenics schemes. [1] Gresh, Daniel N., et al. \textit{Journal of Molecular Spectroscopy} 319 (2016): 1-9. [2] Zhou, Yan et al. J. Mol. Spec. 358, (2019) 1-16 [3] Skripnikov, L. V., and A. V. Titov. \textit{Physical Review A} 91.4 (2015): 042504. [Preview Abstract] |
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E01.00160: Development of a silicon photomultiplier module for ACME III Takahiko Masuda, Daniel Ang, James Chow, David DeMille, John Doyle, Gerald Gabrielse, Zhen Han, Bingjie Hao, Peiran Hu, Nicholas Hutzler, Daniel Lascar, Siyuan Liu, Cole Meisenhelder, Cristian Panda, Noboru Sasao, Satoshi Uetake, Xing Wu, Koji Yoshimura A search for the eEDM is one of the powerful ways to probe for the existence of physics beyond the standard model. The current upper limit of $1.1\times10^{-29}\,e\cdot$cm has been achieved by the ACME experiment II which used cold ThO polar molecules. One of the upgrade plans for the next generation ACME experiment is a new fluorescence detection system based on a silicon photomultiplier (SiPM). SiPMs have higher quantum efficiency, $\sim 50\%$ at 512 nm, than the normal PMTs used in ACME II. To use SiPMs for ACME III, we are designing a cooling system to reduce the dark count rate and a preamplifier and shaper to overcome the relatively slow bandwidth of SiPMs. We developed a prototype module and characterized its performance. We will present the current status of SiPM development including prototype tests. [Preview Abstract] |
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E01.00161: Progress towards an electron EDM measurement using Cesium atoms Zhenyu Wei, Teng Zhang, David Weiss Observation of a permanent electron electric dipole moment (eEDM) would imply time reversal symmetry violating effects not contained in the Standard Model. We have constructed an apparatus designed to measure the EDM of laser-cooled Cesium (Cs) atoms trapped in optical lattices. We will describe our measurement scheme and discuss preliminary results for a related measurement on the ground state tensor polarizability (GSTP) of Cs. The GSTP measurement, which will represent more than an order of magnitude increase in precision over current experiments, provides a challenge to atomic theory, some aspects of which relate to atomic parity violation measurements. It also shares many systematic effects in common with the eEDM measurement. We anticipate an ultimate shot noise limit of 4x10$^{\mathrm{-28}} \quad e·$cm of the atomic Cs EDM, which would correspond to a limit on the eEDM of 3x10$^{\mathrm{-30}} \quad e·$cm. [Preview Abstract] |
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E01.00162: High-precision ultracold-molecule spectroscopy for metrology and new physics Emily Tiberi, Hendrik Bekker, Kon H Leung, Chih-Hsi Lee, Iwona Majewska, Robert Moszynski, Tanya Zelevinsky Ultracold molecules offer a rich platform for precision measurements of fundamental interactions, metrology, and quantum chemistry. We employ an optical lattice to trap ultracold $^{\mathrm{88}}$Sr$_{\mathrm{2}}$ molecules with the goal of probing fundamental molecular structure and studying new, beyond-the-Standard-Model physics, including enhanced constraints on nanometer-scale gravity. Improvements to \textit{ab-initio} theory models are crucial in order to select optimal clock states and to develop predictive models to guide the experiment. In the most recent experimental work, we measured the binding energies and transition strengths for both deeply and weakly bound vibrational levels in the ground and first excited states via light shifts and Autler-Townes spectroscopy. These measurements inform theory and improve our current predictive models and understanding of the underlying molecular structure, enabling us to design a molecular clock with longer quantum-state coherence. [Preview Abstract] |
Not Participating |
E01.00163: First-Principles Molecular Spectra of Air Mark Zammit, Jeffery Leiding, Julie Jung, James Colgan, Eddy Timmermans Comprehensive and highly accurate rovibronic spectral measurements of air molecules are critical to the modeling of low-temperature plasmas and air in extreme conditions. However, with the lack of experimental data, first-principles approaches are key to generating complete molecular line lists. For the last five decades approximate approaches have been utilized to calculate comprehensive line lists of air molecules. Here we put these approximations to the test, comparing these results with our first principles state-of-the-art calculations for OH and NO, which form in significant abundance in air under extreme conditions. We will discuss the methods employed to calculate molecular rovibronic states, present emission spectra and equation of state results. By exploring the implications of emission spectra produced from approximate and state-of-the-art calculations we devise a ground-truth-oriented quantification of the line-list differences. [Preview Abstract] |
Not Participating |
E01.00164: Production of antimatter molecular ions Mark Zammit, Michael Charlton, Svante Jonsell, James Colgan, Dmitry Fursa, Alisher Kadyrov, Igor Bray, Robert Forrey, Christopher Fontes, Jeffery Leiding, David Kilcrease, Peter Hakel, Eddy Timmermans Recent years have seen marked progress in the production of, and experimentation with, atomic antimatter in the form of antihydrogen, $\overline{{\rm H}}$. Now we investigate the feasibility of producing the anti-molecular hydrogen anion, $\overline{{\rm H}}_2^-$ (analogue of ${\rm H}_2^+$, consisting of two antiprotons and a positron), in the laboratory [1]. Recently Myers [2,3] argued that spectroscopic investigations of the anti-anion can offer very sensitive tests of the CPT theorem, which is one of the primary motivations for undertaking experiments with antimatter systems. Taking into account the present day ALPHA $\overline{{\rm H}}$ trap [4], utilizing reaction rates calculated here, from the literature, and via detailed balance, key processes are identified that could lead to the anion production. The feasibility of these reactions are discussed in the context of present day and near future experimental capabilities. [1] M. C. Zammit et al. Phys. Rev. A {\bf 100}, 042709 (2019). [2] E. G. Myers Phys. Rev. A {\bf 98}, 010101(R) (2018). [3] E. G. Myers Hyperfine Interact. {\bf239}, 43 (2018). [4] C. Amole et al. Nuc. Inst. Meth. In Phys. Research A {\bf735}, 319 (2014). [Preview Abstract] |
Not Participating |
E01.00165: All-optical characterization of a topological phase transition via circular dichroism in HHG. Alvaro Jimenez-Galan, Rui Silva, Bruno Amorim, Olga Smirnova, Misha Ivanov Quantum materials encompass a rich variety of systems with fascinating features. One of them is the topological phase transition, upon which an insulator becomes conducting, supporting robust currents around the insulator's edges. So far, the ultrafast dynamics of non-equilibrium electronic response to intense optical fields in these materials has remained virtually unexplored. Yet, understanding these dynamics is not only fundamentally interesting, it is also crucial for light-wave electronics in topological materials. Attosecond science has made major progress in understanding ultrafast electron dynamics in solids. Yet, the role of properties such as the Berry curvature and topological invariants on the attosecond dynamics of electronic response has been hardly explored. Does the highly non-equilibrium electron dynamics in the bulk, driven by a strong laser field, encode topological information on the sub-laser cycle time-scale? In this talk, I will answer this question using the paradigmatic example of the topological insulator, the Haldane system. I will demonstrate how the topological phase transition can be tracked all-optically by a linearly polarized field using polarization-resolved HHG, or by two circularly-polarized fields from the HHG spectrum, and I will illustrate how the ellipticity of the pulses influences this detection. I will further show that the highly nonlinear optical response to strong fields, the high harmonic emission, displays topologically-dependent attosecond delays. [Preview Abstract] |
Not Participating |
E01.00166: Numerical studies of efficient macroscopic calculations for high-order harmonic generation. Spencer Walker, Ran Reiff, Andreas Becker, Agnieszka Jaron-Becker High-order harmonic generation occurs when an intense laser pulse illuminates a target. Since the laser interacts with many atoms one must not only consider the microscopic response of individual atoms but solve Maxwell's wave equation in order to describe how radiation propagates through the non-linear medium. We explore various models for both microscopic response and macroscopic propagation. [Preview Abstract] |
Not Participating |
E01.00167: DC Magnetometry Using 15N-enriched Nitrogen-Vacancy Center Ensembles Jner Tzern Oon, Connor Hart, Matthew Turner, Jennifer Schloss, Ronald Walsworth Nitrogen-vacancy ensembles in diamond offer promising applications in magnetometry, including navigation, object detection, and imaging. The recent development of high-purity $^{15}$N-doped CVD diamond ($I=1/2$) offers advantages over the naturally occurring $^{14}$N isotope ($I=1$) for magnetometry. However, the lack of a quadrupole moment leads to pronounced envelope modulation effects in the presence of misaligned fields, and hinder magnetic sensitivity. While such effects in spin echo experiments (ESEEM) have been well studied, discussion of analogous effects in Ramsey measurements and the implications for magnetometry remain under-explored. Double-quantum (DQ) coherences that utilize the full 3-level ground state electronic system can be used to suppress these effects, while additionally proving resilient to effects from local strain and temperature shifts. In this work, we analytically describe the expected Ramsey response for $^{15}$N ensembles in the presence of misaligned bias magnetic fields and compare with results of simulations and experiments, for both single- and double-quantum experiments. We also introduce conditions unique to $^{15}$N-vacancies which enable robust preparation of DQ superposition states without the need for high microwave power. [Preview Abstract] |
Not Participating |
E01.00168: Characterization of ultracold 88Sr atoms for the dipolar interaction of the 3P0-3D1 transition Shengnan Zhang, Preetam Ramchurn, Yeshpal Singh, Kai Bongs Recently, a novel idea on the long-range dipolar interactions on the 3P0 - 3D1 transition at 2.6 µm for bosonic strontium (Sr) atoms has been proposed. The challenge for experimentally achieving the dipolar interaction is the preparation of dense and ultracold samples. In this paper we demonstrate the experimental facility of preparing dense and ultracold 88Sr atoms and characterize them. The unique points of the facility are self - assembled Zeeman slower based on the permanent magnets and the repumping mechanism with 3P0 - 3D1. The combination of the high slowing efficiency slower and the 707 nm/2.6 µm repumping enables to prepare 1 billion cold 88Sr atoms in the blue MOT. The high vacuum < $1*10^-11 mBar$ makes the lifetime of blue MOT more than 1 s. In the single frequency red MOT, the atom number can reach more than 100 million. The magnetic trap of 3P2 has a lifetime of 1.1 s and loading time of 0.3 s. The facility can be applied to other isotopes. The atoms will be loaded from the single frequency red MOT to 3D optical lattice at the magic wavelength of 412.8 nm. Once the atoms are trapped in the lattice, the experiment of dipolar interactions will be implemented. [Preview Abstract] |
Not Participating |
E01.00169: Progress towards \textit{in situ} observation of Yb Bloch oscillations in an optical lattice searching for ultra-light dark matter Chandler Schlupf, Robert Niederriter, Paul Hamilton We present progress towards an atomic force sensor for measuring linear and oscillating forces on atoms via observation of Bloch oscillations. The experiment consists of ytterbium atoms suspended in an optical lattice formed by an in-vacuum optical cavity. We expect the coupling of the atoms and the cavity light will cause the transmission of the cavity to be modulated at the Bloch frequency [1], providing a way to measure the frequency \textit{in situ}. Ultra-light dark matter, for example, would produce an oscillating force which could be detected through oscillations in the Bloch frequency [2]. We have shown the sensitivity of the atom-cavity coupling to changes in the atom spatial distribution by performing a fast ($<10~\mu s$) single-shot temperature measurement of our trapped atom sample. We continue to develop techniques to cool $^{171}$Yb atoms to the ground band of the optical lattice which will enable optimal Bloch oscillation measurements. [1] B. Prasanna Venkatesh, M. Trupke, E. A. Hinds, and D. H. J. O'Dell, “Atomic Bloch-Zener oscillations for sensitive force measurements in a cavity", Physical Review A 80, 063834 (2009). [2] A. Arvanitaki, J. Huang, and K. Van Tilburg, ``Searching for dilaton dark matter with atomic clocks", Physical Review D 91, 015015 (2015). [Preview Abstract] |
Not Participating |
E01.00170: Progress toward a cold-atom based vacuum standard and pressure gauge Stephen Eckel, Daniel Barker, James Fedchak, Nikolai Klimov, Eric Norrgard, Julia Scherschligt Preparation and evaluation of ultra-high-vacuum (UHV) and extreme-high-vacuum (XHV) environments is critical for high-quality semiconductor fabrication and emerging quantum technologies. Vacuum sensors for these pressure ranges, such as ion-gauges, are not primary (i.e., they require calibration themselves) and have large, poorly-understood uncertainties. We present our progress towards a primary standard for vacuum measurement in the XHV using cold Li atoms confined in a magnetic trap. Our apparatus will allow high-accuracy measurements of atom-molecule collision cross-sections that are necessary to extract the vacuum pressure from the observed background-gas-limited lifetime of the trapped atoms. We have also developed chip-based techniques to slow and trap Li atoms with a single laser beam. This nano-fabricated atom-trapping platform forms the basis for a deployable, primary vacuum sensor with embedded traceability that can replace an ion gauge. [Preview Abstract] |
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