Bulletin of the American Physical Society
47th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 61, Number 8
Monday–Friday, May 23–27, 2016; Providence, Rhode Island
Session Q1: Poster Session III (4:00pm-6:00pm)Poster
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Room: Exhibit Hall C |
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Q1.00001: ATOMIC AND MOLECULAR STRUCTURE AND PROPERTIES |
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Q1.00002: Modification of Schrodinger Equation in Quantum Mechanics by Adding Derivations of Time's Flow (Relative Time) with Respect of the Both Space and Time Based on the "Substantial Motion" Theory of Iranian Philosopher; Mulla Sadra Hassan Gholibeigian, Abdolazim Amirshahkarami, Kazem Gholibeigian "The nature has two magnitudes and two elongations, one is gradual being (wavy-like motion) which belongs to the time and dividable to the former and the next times in mind, and the other one is jerky-like motion which belongs to the space and dividable to the former and the next places " [Asfar, Mulla Sadra, (1571/2-1640)]. These two separated natures of space-time are matched on wave-particle duality. Therefore, the nature of time can be wavy-like and the nature of space can be jerky-like. So, there are two independent variable sources of particle(s)' flow while they are match exactly with each other. These two sources are potential of flow and potential of time (relative time) which vary with respect to both space and time. Here, we propose two additional parts to Schrodinger's equation with respect to relative time: $H\Psi +\nabla {t}'=E\Psi +\partial {t}'/\partial t$, where $t$ is time and ${t}'$ is relative time: ${t}'=t\pm \Delta t$ [Gholibeigian et. al, APS March Meeting 2016], \quad which for each atom becomes: $t_{atom} =\sum {m_{nucleons} +\sum m_{electrons} } $ where $m $is momentum \quad [Gholibeigian, APS March Meeting 2015, abstract {\#}V1.023]. Using time's relativity in Schrodinger equation will give us more precious results. [Preview Abstract] |
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Q1.00003: Calculations of long-range three-body interactions for Li($2S$)-Li($2S$)-Li($2P$) Pei-Gen Yan, Li-Yan Tang, Zong-Chao Yan, James F Babb With the rapid developments in ultracold atomic and molecular physics, accurate determinations of long-range interactions between two and three atoms are important in, for example, analyzing atomic photoassociation. Long-range interactions of two-body systems were extensively studied for $S$ and $P$ state atoms, however, for three-body systems studies are limited to $S$-state atoms. In this work, a general formula for calculating the long-range interactions among three like atoms is presented using perturbation theory up to second order, where two atoms are in identical $S$ states and the other atom is in a $P$ state. Unlike the case where the three atoms are in identical $S$ states, here the first order interaction coefficients already show a dependence on the geometrical configuration of the three atoms, and nonadditive terms start to appear at the second order in energy corrections. For the Li($2\,^2S$)-Li($2\,^2S$)-Li($2\,^{2}P$) system, we perform precision evaluation of various dispersion coefficients using variationally generated atomic lithium wave functions in Hylleraas coordinates. These additive and nonadditive long-range dispersion coefficients may be useful in constructing a precise potential energy surface of this three lithium system. [Preview Abstract] |
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Q1.00004: Transitions between the $4f$-core-excited states in Ir$^{16+}$, Ir$^{17+}$, and Ir$^{18+}$ ions for clock applications U. I. Safronova, V. V. Flambaum, M. S. Safronova Iridium ions near $4f$-$5s$ level crossings are the leading candidates for a new type of atomic clocks with a high projected accuracy and a very high sensitivity to the temporal variation of the fine structure constant $\alpha$. To identify spectra of these ions in experiment accurate calculations of the spectra and electromagnetic transition probabilities should be performed. Properties of the $4f$-core-excited states in Ir$^{16+}$, Ir$^{17+}$, and Ir$^{18+}$ ions are evaluated using relativistic many-body perturbation theory and Hartree-Fock-Relativistic method (COWAN code). We evaluate excitation energies, wavelengths, oscillator strengths, and transition rates. Our large-scale calculations included the following set of configurations: $4f^{14}5s$, $4f^{14}5p$, $4f^{13}5s^2$, $4f^{13}5p^2$, $4f^{13}5s5p$, $4f^{12}5s^25p$, and $4f^{12}5s5p^2$ in Pm-like Ir$^{16+}$ ; $4f^{14}$, $4f^{13}5s$, $4f^{13}5p$, $4f^{12}5s^2$, $4f^{12}5s5p$, and $4f^{12}5p^2$ in Nd-like Ir$^{17+}$; and $4f^{13}$, $4f^{12}5s$, $4f^{12}5p$, $4f^{11}5s^2$, and $4f^{11}5s5p$ in Pr-like Ir$^{18+}$. The $5s-5p$ transitions are illustrated by the synthetic spectra in the 180 - 200~\AA ~range. Large contributions of magnetic-dipole transitions to lifetimes of low-lying states in the region 2.5~Ry [Preview Abstract] |
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Q1.00005: Study of dipolar many-body system in a one-dimensional zig-zag chain Niraj R. Ghimire, Susanne F. Yelin The goal is to understand the many-body properties of a one-dimensional zig-zag chain of a fixed number of classical dipolar spins. This is a system that could potentially be modeled by ultracold polar molecules, and be extended such that topological quantities in triangular or hexagonal lattices can be studied. In order to achieve this, we use the density-matrix renormalization group (DMRG) method and find the ground state of the spin $S=1/2$ model. For this purpose, we will take into account nearest-neighbor (NN) and next-nearest-neighbor (NNN) hopping and interactions which can be expressed as functions of angles between the dipoles. [Preview Abstract] |
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Q1.00006: Relativistic CI+all-order calculations of U III energies, g-factors, transition rates and lifetimes Igor Savukov, Ulyana Safronova, Marianna Safronova Excitation energies, term designations, $g$-factors, transition rates and lifetimes of U$^{2+}$ are determined using a relativistic configuration interaction (CI) + all-order (linearized coupled-cluster, LCC) approach. The all-order energies are compared with CI+many-body-perturbation-theory (MBPT) and available experimental energies. Close agreement has been found with experiment, within hundreds of cm$^{-1}$. In addition, lifetimes of higher levels have been calculated for comparison with three experimentally measured lifetimes, and close agreement was found within t he experimental error. CI-LCC calculations constitute a benchmark test of the CI+all-order method in complex relativistic systems such as actinides and their ions with many valence electrons. The theory yields many energy levels, g-factors, transition rates, and lifetimes of U$^{2+}$ that are not available from experiment. The theory can be applied to other multi-valence atoms and ions, which would be of interest to many applications. [Preview Abstract] |
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Q1.00007: Experimental Studies of the 4$^3\Pi$ Electronic State of NaCs Andrew Steely, Ciara Whipp, Carl Faust, Andrew Kortyna, Kara Richter, John Huennekens We present results from experimental studies of the 4$^3\Pi$ electronic state of the NaCs molecule. This electronic state is interesting in that its potential energy curve likely exhibits a double minimum. As a result, interference effects are observed in the resolved bound-free fluorescence spectra. The optical-optical double resonance method was used to obtain Doppler-free excitation spectra for the 4$^3\Pi$ state. This dataset of measured level energies was expanded largely by observing fluorescence from levels populated by collisions. Simulations of resolved bound-free fluorescence spectra were calculated using the BCONT program (R. J. Le Roy, University of Waterloo). Spectroscopic constants are presented as a preliminary step toward an experimental potential energy curve. [Preview Abstract] |
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Q1.00008: Theoretical Characterization of Visual Signatures and Calculation of Approximate Global Harmonic Frequency Scaling Factors D. O. Kashinski, R. G. Nelson, G. M. Chase, O. E. Di Nallo, E. F. C. Byrd We are investigating the accuracy of theoretical models used to predict the visible, ultraviolet, and infrared spectra, as well as other properties, of product materials ejected from the muzzle of currently fielded systems. Recent advances in solid propellants has made the management of muzzle signature (flash) a principle issue in weapons development across the calibers. \emph{A priori} prediction of the electromagnetic spectra of formulations will allow researchers to tailor blends that yield desired signatures and determine spectrographic detection ranges. Quantum chemistry methods at various levels of sophistication have been employed to optimize molecular geometries, compute unscaled harmonic frequencies, and determine the optical spectra of specific gas-phase species. Electronic excitations are being computed using Time Dependent Density Functional Theory (TD-DFT). Calculation of approximate global harmonic frequency scaling factors for specific DFT functionals is also in progress. A full statistical analysis and reliability assessment of computational results is currently underway. [Preview Abstract] |
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Q1.00009: Observation and Analysis of the 6 $^{\mathrm{1}}\Sigma _{\mathrm{g}}^{\mathrm{+}}$ and 3 $^{\mathrm{1}}\Pi_{\mathrm{g}}$ states of Rubidium Dimer Ergin Ahmed, Xinhua Pan, Marjatta Lyyra Detailed knowledge of the excited electronic states of Rubidium dimer is of significant importance to a number of areas of research such as, the production of ultracold ground state molecules, cold atom-molecule collisions, and the development of new \textit{ab-initio} molecular electronic structure methods. The potential energy curves and transition dipole moments of dozens of electronic states of Rb$_{\mathrm{2}}$ have been calculated. However, only few low-lying electronic states have been experimentally studied and assigned. We report our experimental work and analysis of the 6$^{\mathrm{1}}\Sigma_{\mathrm{g}}^{\mathrm{+}}$ and 3$^{\mathrm{1}}\Pi_{\mathrm{g}}$ electronic states. In the experiment large number of ro-vibrational levels of the two states were observed using narrow band \textit{cw} TiSa and dye laser in double resonance cascade configuration. The intermediate states used in the experiment are from the mutually perturbed A$^{\mathrm{1}}\Sigma_{\mathrm{g}}^{\mathrm{+\thinspace }}$\textasciitilde b$^{\mathrm{3}}\Pi_{\mathrm{u}}$ pair of states. Potential energy curve was generated for each state from the term values of the observed levels. [Preview Abstract] |
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Q1.00010: Ion-Pair States in Triplet Molecular Hydrogen W. Setzer, B. C. Baker, S. Ashman, T. J. Morgan An experimental search is underway to observe the long range triplet ionic states H$^{\mathrm{+}}$ H$^{\mathrm{-}}$ of molecular hydrogen. Resonantly enhanced multi-photon ionization of the metastable c $^{\mathrm{3}}\prod _{\mathrm{u}}^{\mathrm{-\thinspace }}$ 2p$\pi $ state is used access to the R(1)nd1 n$=$21 Rydberg state that serves as an intermediate stepping stone state to probe the energy region above the ionization limit with a second tunable laser photon. The metastable state is prepared by electron capture of 6 keV H$_{\mathrm{2}}^{\mathrm{+}}$ ions in potassium in a molecular beam. Formation of the H$^{\mathrm{+}}$ H$^{\mathrm{-}}$ triplet configuration involves triplet excited states of the H$^{\mathrm{-}}$ ion, especially the 2p$^{\mathrm{2}} \quad^{\mathrm{3}}$P$^{\mathrm{e}}$ state, the second bound state of H$^{\mathrm{-}}$ predicted to exist with a lifetime long compared to typical auto ionization lifetimes but not yet observed experimentally. Details of the experiment and preliminary results to date will be presented at the conference. [Preview Abstract] |
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Q1.00011: Preliminary work on the quantum defect measurements Lindsay Hutcherson, Justin Sanders, Jianing Han Van der Waals interactions are generally studied in physics, chemistry, biology, and other fields of science. In order to fine-tune van der Waals interactions, the atomic energy levels need to be known very accurately. That is, we must accurately determine the quantum defects. Quantum defects of 85Rb have been recently measured, and the quantum defects of 87Rb have also been measured for nS and nD states with the resolution of 1 MHz. this experiment will focus on the P, F, and G states, which are higher angular momentum states and more sensitive to electric fields. These states are crucial for collisions, which may lead to some of the interesting phenomena in ultracold atoms, such as ultracold plasma. In this presentation, a progress report will be given on this project. [Preview Abstract] |
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Q1.00012: ELECTRON-ATOM COLLISIONS |
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Q1.00013: Electron-impact ionization of the K-shells of Heavy Atoms M. S. Pindzola Fully-relativistic subconfiguration-average distorted-wave (SCADW) calculations are made for the electron-impact ionization of the K-shells of heavy atoms. One set of calculations only include the two-body electrostatic interaction, while the other set includes the full two-body retarded electromagnetic interaction. The SCADW retarded electromagnetic calculations are found to be in good agreement with recent measurements made at the Institute for Physics at the University of Sao Paulo, Brazil [J. M. Fernandez-Varea et al., J. Phys. B 47, 155201 (2014)] for Au and Bi atoms. Calculations and measurements will also be presented for the K-shell ionization of the Ta atom. [Preview Abstract] |
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Q1.00014: Electron-impact ionization of the Se$^{2+}$ and Se$^{3+}$ atomic ions S. D. Loch, M. S. Pindzola Semi-relativistic configuration-average distorted-wave (CADW) calculations are made for the electron-impact ionization of the Se$^{2+}$ and Se$^{3+}$ atomic ions. The CADW calculations are found to be in reasonable agreement with recent measurements made at the Multicharged Ion Research Facility at the University of Nevada in Reno [G. A. Alnawashi et al. J. Phys. B 47, 105201 and 135203 (2014)]. The CADW calculations for configurations near ionization thresholds are checked against level to level distorted-wave (LLDW) calculations. [Preview Abstract] |
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Q1.00015: Out-of-plane ($e,2e$) measurements on He autoionizing levels at 80, 150, and 488eV N.L.S Martin, B.N. Kim, C.M. Weaver, B.A. deHarak, K. Bartschat We report out-of-scattering-plane $(e,2e)$ measurements on helium $2\ell2\ell'$ auto\-ionizing levels for 80, 150, and 488eV incident electron energies, and scattering angles 60$^\circ$, 39.2$^\circ$, and 20.5$^\circ$, respectively. The kinematics are the same in all cases: ejected electrons are detected in a plane that contains the momentum transfer direction and is perpendicular to the scattering plane, and the momentum transfer is 2.1~a.u.. The 80eV results complete our sets of measurements at low, intermediate,\footnote{http://meetings.aps.org/link/BAPS.2015.DAMOP.Q1.123} and high,\footnote{B.A. deHarak, K. Bartschat, and N.L.S. Martin, Phys. Rev. Lett. {\bf 100}, 063201 (2008)} incident energies. The results are presented as $(e,2e)$ angular distributions energy-integrated over each level, and are compared with our theory calculated for 488eV incident electron energy. The 150eV and 488eV experiments are characterized by recoil peaks appropriate to each autoionizing level. However, for the 80eV angular distributions, these recoil peaks are largely absent for all levels, including the $^3P$ level observed at this energy. [Preview Abstract] |
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Q1.00016: A proposed multipass laser system for free-free electron scattering experiments B.N. Kim, C.M. Weaver, N.L.S. Martin, B.A. deHarak We propose to use a multipass laser system to increase the data-taking rate of our laser-assited electron scattering experiments.\footnote{N. L. S. Martin and B. A. deHarak, Phys. Rev. A {\bf 93}, 013403 (2016)} The scheme will be similar to that used by other workers.\footnote{T. Mohameda, G. Andler, R. Schuch, Rev. Sci. Instrum. {\bf 86}, 023113 (2015)} The basic idea is that there will be an ``injection mode" where vertically polarized light from the laser passes straight through an appropriately oriented beamsplitter cube, and then passes through an activated Pockels cell (not yet purchased) which rotates the polarization to horizontal. The laser beam passes through the interaction region for the first time, and is reflected by a plane mirror. The laser beam will then be in the ``trapped mode" where the reflected laser beam is then deflected through 90$^\circ$ by the beamsplitter cube. It will be reflected back by a second mirror for the return journey, and will repeat this cycle {\it ad infinitum}. We are carrying out a feasibility study for a round trip of approximately 50 feet. In the absence of a working Pockels cell, $\lambda/4$ plates are used to create 50\% of the beam with the appropriate polarization on each cycle. [Preview Abstract] |
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Q1.00017: Electron Affinity Calculations for Atoms: Sensitive Probe of Many-Body Effects Z. Felfli, A. Z. Msezane Electron--electron correlations and core-polarization interactions are crucial for the existence and stability of most negative ions. Therefore, they can be used as a sensitive probe of many-body effects in the calculation of the electron affinities (EAs) of atoms. The importance of relativistic effects in the calculation of the EAs of atoms has recently been assessed to be insignificant up to Z of 85[1]. Here we use the complex angular momentum (CAM) methodology [2] wherein is embedded fully the electron--electron correlations, to investigate core-polarization interactions in low-energy electron elastic scattering from the atoms In, Sn, Eu, Au and At through the calculation of their EAs. For the core-polarization interaction we use the rational function approximation of the Thomas-Fermi potential, which can be analytically continued into the complex plane. The EAs are extracted from the large resonance peaks in the CAM calculated low-energy electron-atom scattering total cross sections and compared with those from measurements and sophisticated theoretical methods. It is concluded that when the electron-electron correlations and core polarization interactions (both major many-body effects) are accounted for adequately the importance of relativity on the calculation of the EAs of atoms can be assessed. Even for the high Z (85) At atom relativistic effects are estimated to contribute a maximum of 3.6{\%} to its EA calculation. [1] Z. Felfli and A.Z. Msezane, J. Phys. B, Submitted (2015) [2] D. Sokolovski \textit{et al}, Phys. Rev. A \textbf{76,} 026707 (2007) [Preview Abstract] |
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Q1.00018: Two measured completely different electron affinities for atomic Eu? A. Z. Msezane, Z. Felfli Recently, the electron affinity (EA) of atomic Eu was measured to be 0.116?eV [1]. This value is in outstanding agreement with the theoretically calculated values using the Regge pole [2] and MCDF-RCI [3] methods. Previously, the EA of Eu was measured to be 1.053 eV [4]. In an attempt to resolve the discrepancy between the two measured values, we have adopted the complex angular momentum (CAM) method and investigated in the electron energy range 0.11 eV \textless E\textless 4.0 eV the binding energies (BEs) of negative ions formed during the collision of an electron with atomic Eu as Regge resonances following Ref. [5]. We find the value of 2.63 eV as the EA of Eu. This leads us to conclude that neither the claimed measured EA of Eu correspond to the actual EA of Eu. We conclude that the EA in [1] corresponds to the BE of an excited (metastable) state of the Eu\asciimacron anion and that in [4] to a shape resonance. We have also investigated the EA of atomic Nd and found the value of 1.88 eV, consistent with the measurement [6]. These significant EA values of Eu and Nd could be important in the use of their negative ions in catalyzing the oxidation of water to peroxide and of methane to methanol without CO$_{\mathrm{2}}$ emission. These new results call for immediate experimental and theoretical verification. [1] S. -B. Cheng \textit{et al}., Sci. Rep. \textbf{5}, 12414 (2015) [2] Z. Felfli et al, \textit{Phys. Rev. A} \textbf{79, }012714 (2009) [3] S. M. O'Malley et al, \textit{Phys. Rev. A} \textbf{78,} 012510 (2008) [4]V. T. Davis \textit{et al}, J. Phys. B \textbf{37}, 1961 (2004). [5] Z. Felfli \textit{et al}, J. Phys. B, Submitted (2015) [6] V. T. Davis \textit{et al,} NIMB \textbf{241}, 118 (2005) [Preview Abstract] |
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Q1.00019: Operating experience with a zinc oven Nathan Clayburn, Evan Brunkow, Timothy Gay A zinc oven has been constructed and tested. Atomic zinc emitted from this resistively heated oven is subsequently excited by a polarized electron beam in crossed-beam geometry. Light emitted in the decay of the (4s5s)$^{\mathrm{3}}$S$_{\mathrm{1}}$ state to the (4s4p)$^{\mathrm{3}}$P$_{\mathrm{J}}$ final state, where J $=$ 0, 1, 2, is then detected by a photomultiplier tube for polarization analysis. The zinc oven apparatus and operating experience with the oven are described in detail. Measures to assure that the oven produces a stable, localized beam which does not adhere to essential components of the apparatus are addressed. Estimates of the zinc density are made. The importance of magnetic field control in the apparatus will be discussed. [Preview Abstract] |
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Q1.00020: Elastic scattering of electrons and positrons by cadmium atom B. C. Saha, A. K. F. Haque, M. Maaza, M. I. Hossain, M. A. Uddin, M. A. R. Patoary, A. K. Basak Using optical potential the differential, integrated total and momentum transfer cross sections for the elastic scattering of electrons and positrons by cadmium atom are calculated for E$=$6.4 eV to 1.0 keV. In addition to the static and polarization effects this optical potential includes exchange and absorption effects exclusively. Employing Dirac partial wave analysis these elastic cross sections are evaluated. Our results are presented along with a comparison with available experimental and some other theoretical findings. [Preview Abstract] |
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Q1.00021: Electron Impact Excitation and Ionization of Atomic Oxygen Swaraj Tayal, Oleg Zatsarinny The B-spline R-matrix with pseudostates method has been employed to treat electron collisions with atomic oxygen. The excitation, cross sections have been calculated for transitions between all $2s^22p^4$ and $2s^22p^33l$ (l = 0,1,2) states of oxygen in the energy range from threshold to 150 eV. The present calculations differ from numerous previous studies as we included a large number of pseudostates in the close-coupling expansion to represent continuum and excitation-autoionization states. The pseudostates have a major influence on the theoretical predictions, especially at intermediate energies, where many of the excitation cross sections are reduced significantly. Our calculated cross sections are in better agreement with available experimental data. Detailed treatment of ionization cross sections for the ground and metastable states will also be provided. Our calculation is the first non-perturbative calculation of ionization cross sections. We included all important physical effects including short-range correlation in the target states and long-range polarization effects in the scattering system. [Preview Abstract] |
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Q1.00022: Electron-impact excitation and ionization of atomic boron at low and intermediate energies. Kedong Wang, Oleg Zatsarinny, Klaus Bartschat We present a comprehensive study of electron collisions with neutral boron atoms. The calculations were performed with the $B$-Spline $R$-matrix (close-coupling) method [1], by employing a parallelized version of the associated computer code [2]. Elastic, excitation, and ionization cross sections were obtained for all transitions involving the lowest 11 states of boron, for incident electron energies ranging from threshold to 100 eV. A multiconfiguration Hartree-Fock method with nonorthogonal term-dependent orbitals was used to generate accurate wave functions for the target states. Close-coupling expansions including 13, 51, and 999 physical and pseudo states were set up to check the sensitivity of the predictions to variations in the theoretical model. The cross-section dataset generated in this work is expected to be the most accurate one available today and should be sufficiently comprehensive for most modeling applications involving neutral boron. \par\noindent [1] O. Zatsarinny and K. Bartschat, J. Phys. B 46 (2013) 112001. \par\noindent [2] O. Zatsarinny, Comp. Phys. Commun. 174 (2006) 273. [Preview Abstract] |
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Q1.00023: Towards A Miniature EBIT for the Production and Isolation of Highly Charged Ions with Low Ionization Threshold A.S. Naing, S.F. Hoogerheide, J.M. Dreiling, J.N. Tan Multiply-ionized atoms are known to play a key role in the study of many radiative and collisional processes occurring in laboratory and astrophysical plasmas [1]. Recent theoretical studies indicate that certain highly-ionized atoms with special features, e.g., Pr$^{\mathrm{9+}}$, Nd$^{\mathrm{10+}}$, could potentially be useful for the development of next-generation atomic clocks, for quantum information processing, and in the search for variation in the fine-structure constant [2]. Highly charged ions are typically produced in an electron beam ion trap (EBIT) with a strong magnetic field, such as the EBIT at NIST. However, lower fields are more suitable for abundantly producing the proposed candidate ions, as well as other interesting ions with relatively low ionization thresholds (greater than 100 eV and up to 2000 eV). We are developing a room-temperature miniature electron beam ion source/trap (mini-EBIS/T) that is optimized for ions with low ionization. We report on the progress in the design/construction of the mini-EBIS/T and the production/trapping of the above-mentioned ions. [1] H.F. Beyer and V.P. Shevelko, Intro to the Physics of Highly Charged Ions, Inst. of Physics, 2003. [2] M. Safronova, \textit{et al.}, PRL \textbf{113}, 030801 (2014). [Preview Abstract] |
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Q1.00024: Electron impact excitation of the Ne II and Ne III fine structure levels Q. Wang, S.D. Loch, M.S. Pindzola, R. Cumbee, P.C Stancil, C.P. Ballance, B.M. McLaughlin Electron impact excitation cross sections and rate coefficients of the low lying levels of the Ne II and Ne III ions are of great interest in cool molecular environments including young stellar objects, photodissociation regions, active galactic nuclei, and X-ray dominated regions. We have carried out details computations for cross sections and rate coefficients using the Dirac R-matrix codes (DARC), the Breit-Pauli R-matrix codes (BP) and the Intermediate Coupling Frame Transformation (ICFT) codes, for both Ne II and Ne III. We also compare our results with previous calculations. We are primarily interested in rate coefficients in the temperature range below 1000 K, and the focus is on obtaining the most accurate rate coefficients for those temperatures. We present both a recommended set of effective collision strengths and an indication of the uncertainties on these values. [Preview Abstract] |
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Q1.00025: Near-threshold Ps(n=2)-p scattering Ilya Fabrikant, Igor Bray We study the threshold behavior of elastic and inelastic collisions of the excited positronium (Ps) atom with the proton using the theory developed by Gailitis [J. Phys. B {\bf 15}, 3423 (1982)]. We show that partial cross sections for elastic and quasielastic processes exhibit pronounced oscillations above the threshold and diverge as $1/E$ where $E$ is the collision energy. This behavior is limited from below by the energy equal to the relativistic splitting between degenerate Ps states. {\it Ab initio} close coupling calculations are in excellent agreement with the results of the threshold theory. The oscillations almost completely disappear in the total (summed over partial waves) cross sections. However, dipole-supported resonances appear in inelastic processes, in particular in the important process Ps($nl)+p\to$ H$(n'l')+e^+$ below higher-energy thresholds. Above thresholds these cross sections don't exhibit oscillations but have the $1/E$ divergence in an exothermic case. These results are important for current attempts to produce antihydrogen in a similar charge-conjugated reaction Ps($nl)+\bar{p}\to \bar{\rm H}(n'l')+e^-$. [Preview Abstract] |
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Q1.00026: ABSTRACT WITHDRAWN |
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Q1.00027: Hybrid theory of positron-hydrogen scattering and positronium formation Anand Bhatia A variational wave function incorporating short range correlations via Hylleraas type functions plus long-range polarization terms of the polarized orbital type but with smooth cut-off function has been used to calculate S-wave phase shifts for positron scattering from hydrogen. This approach gives the direct r$^{\mathrm{-4}}$potential and a non-local optical potential which is negative definite. The resulting phase shifts have rigorous lower bounds and the convergence is much faster than those obtained without the modification of the target function. The continuum functions obtained have been used to calculate positronum formation. [Preview Abstract] |
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Q1.00028: Experiments Enabled by a New High-Resolution Positron Beam Mike Natisin, James Danielson, Cliff Surko The ability to make state-resolved measurements of positron interactions with atoms and molecules is limited by difficulties encountered in creating beams with narrow energy spreads. Recent experiments and simulations of buffer gas positron cooling and trap-based beam formation\footnote{M. R. Natisin, invited talk at this conference.} have enabled the design and construction of a cryogenic buffer-gas trap with total beam energy spreads as low as 7 meV FWHM and temporal spreads of sub-microsecond duration.\footnote{M. R. Natisin, \emph{et al.}, Appl. Phys. Lett. \textbf{108}, 024102 (2016)} The potential effect of this narrow energy spread on the ability to probe new physics in positron scattering and annihilation experiments will be discussed. For example, beams with such energy spreads are expected to enable the first measurements of state-resolved excitation of molecular rotations by positron impact (i.e., H$_2$). Further, these narrow spreads and resulting enhanced resolving power are expected to permit the study of new features in annihilation energy spectra, such as possible overtone, combination, and IR-inactive vibrational modes in Feshbach-resonant positron annihilation. [Preview Abstract] |
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Q1.00029: Large numbers of cold positronium atoms created in laser-selected Rydberg states using resonant charge exchange . R. McConnell, G. Gabrielse, W. S. Kolthammer, P. Richerme, A. Mullers, J. Walz, D. Grzonka, W. Oelert, M. Zielinski, D. Fitzakerley, M. C. George, E. A. Hessels, C. H. Storry, M. Weel Lasers are used to control the production of highly excited positronium atoms (Ps*). The laser light excites Cs atoms to Rydberg states that have a large cross section for resonant charge-exchange collisions with trapped positrons. For each trial with 30 million trapped positrons, more than 700 000 of the created Ps* have trajectories near the axis of the apparatus, and are detected using Stark ionization. This number of Ps* is 500 times higher than realized in an earlier proof-of-principle demonstration [Phys. Lett. B 597, 257 (2004)]. A second charge exchange of these near-axis Ps* with trapped antiprotons could be used to produce cold antihydrogen, and this antihydrogen production is expected to be increased by a similar factor. [Preview Abstract] |
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Q1.00030: PHOTONIZATION, PHOTODETACHMENT AND PHOTODISSOCIATION |
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Q1.00031: Merging quantum-chemistry with B-splines to describe molecular photoionization L. Argenti, C. Marante, M. Klinker, I. Corral, J. Gonzalez, F. Martin Theoretical description of observables in attosecond pump-probe experiments requires a good representation of the system's ionization continuum. For polyelectronic atoms and molecules, however, this is still a challenge, due to the complicated short-range structure of correlated electronic wavefunctions. Whereas quantum chemistry packages (QCP) implementing sophisticated methods to compute bound electronic molecular states are well established, comparable tools for the continuum are not widely available yet. To tackle this problem, we have developed a new approach that, by means of a hybrid Gaussian-B-spline basis, interfaces existing QCPs with close-coupling scattering methods. To illustrate the viability of this approach, we report results for the multichannel ionization of the helium atom and of the hydrogen molecule that are in excellent agreement with existing accurate benchmarks. These findings, together with the flexibility of QCPs, make of this approach a good candidate for the theoretical study of the ionization of poly-electronic systems. [Preview Abstract] |
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Q1.00032: A semi-classical approach for solving the time-dependent Schr\"{o}dinger equation in inhomogeneous electromagnetic fields Jianxiong Li, Uwe Thumm During the IR-streaked XUV photoemission from nanoparticles, the net IR electric field varies over the spatial extension of the target, an effect that for metallic particles is further enhanced by strong induced plasmonic polarization. This spatial dependence prevents the convenient use of ``Volkov states'' [solutions of the time-dependent Schr\"{o}dinger equation for a free electron in a spatially homogeneous (cw) electromagnetic field] as approximate final states in quantum-mechanical photoemission calculations. To obtain the wave function of a free electron in a spatially inhomogeneous electromagnetic field, we propose a semi-classical approach based on time-dependent WKB theory. Generalizing ordinary Volkov states, this method provides a simple expression for modeling the final photoelectron state. We employ such generalized Volkov states to calculate the streaked photoelectron spectra from gold nanospheres and assess their accurary. [Preview Abstract] |
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Q1.00033: Effects of exchange-correlation potentials in density functional descriptions of ground-state and photoionization of fullerenes Jinwoo Choi, EonHo Chang, Dylan M. Anstine, Himadri Chakraborty We study the ground state properties of C$_{\mathrm{60}}$ and C$_{\mathrm{240}}$ molecules in a spherical frame of local density approximation (LDA). Within this mean-field theory, two different approximations to the exchange-correlation (xc) functional are used: (i) The Gunnerson-Lundqvist parametrization [1] augmented by a treatment to correct for the electron self-interaction [2] and (ii) the van Leeuwen and Baerends (LB94) model potential [3] that inclusively restores electron's asymptotic properties [4]. Results show differences in the ground-state potential, level energies and electron densities between the two xc choices. We then use the ground structure to find the excited and ionized states of the systems and calculate dipole single-photoionization cross sections in a time-dependent LDA method that incorporates linear-response dynamical correlations. Comparative effects of the choices of xc on collective plasmon and single-excitation Auger resonances as well as on geometry driven cavity oscillations are found significant. [1] Gunnersen and Lundqvist, PRB \textbf{13}, 4274 (1976); [2] Madjet \textit{et al}., JPB \textbf{41}, 105101 (2008); [3] van Leeuwen and Baerends, PRA \textbf{49}, 2421 (1994); [4] Magrakvelidze \textit{et al}, PRA \textbf{91}, 053407 (2015). [Preview Abstract] |
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Q1.00034: Near-Threshold, Vibrationally-Resolved Photoionization of Molecular Nitrogen Gaetan VanGyseghem, Thomas Gorczyca, Connor Ballance Photoionization of molecular nitrogen $\left(\textrm{N}_2\right)$ is investigated near the first ionization threshold using an R-matrix, multi-channel quantum defect theory (MQDT) approach. Building on an existing fixed-nuclei R-matrix photoionization model [M.~Tashiro, J.~Chem. Phys. 132, 134306, (2010)], which, in turn, is built on the UKRmol suite of codes, photoionization cross sections, as well as scattering and dipole matrices, are computed in the Born-Oppenheimer approximation. By varying the internuclear separation, potential energy curves have been constructed for the $\textrm{N}_2$ and $\textrm{N}_2^+$ states and compared to quantum chemistry calculations. Using these fixed-nuclei potential energy curves, and corresponding vibronic eigenenergies and eigenfunctions, a frame transformation is enacted on the fixed-nuclei scattering and dipole matrices, allowing for the calculation of vibrationally-resolved photoionization cross sections. The resultant photoionization cross sections are compared to high-resolution experimental data [P.~O'Keeffe et al. J.~Chem.~Phys 136, 104307, (2012)] near threshold, a region complicated by multiple vibrationally-resolved, interacting Rydberg series. [Preview Abstract] |
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Q1.00035: Multiphoton double ionization of the He atom Y. Li, M. S. Pindzola Time-dependent close-coupling (TDCC) calculations are made for the multiphoton double ionization of the He atom under the influence of a fast pulse XUV laser. One set of TDCC calculations employs $l_1 m_1 l_2 m_2$ coupling on a 2D ($r_1,r_2$) numerical lattice, a second set of TDCC calculations employs $m_1 m_2$ coupling on a 4D ($r_1, \theta_1, r_2, \theta_2$) numerical lattice, and a third set of TDCC calculations employs $m_1 m_2$ coupling on a 4D ($\rho_1, z_1, \rho_2, z_2$) numerical lattice. Studies are made to see which TDCC method is the most efficient at explaining measurements as the number of photons absorbed is increased. [Preview Abstract] |
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Q1.00036: Correlation-induced Time Delay in Atomic Photoionization David A. Keating, Steven T. Manson, Pranawa C. Deshmukh, Anatoli S. Kheifets Interchannel coupling has been seen to result in structures in the photoionization cross sections of outer shell electrons in the vicinity of inner-shell thresholds [1], a result which leads us to ask if the same would be true for the time delay of outer shell electrons near inner-shell thresholds. Using the relativistic-random-phase approximation (RRPA) methodology [2], a theoretical study of neon, argon, krypton, and xenon were performed to search for these correlation-induced effects. Calculations were performed both with coupling and without coupling to verify that the structures found in the time delay were in fact due to interchannel coupling. Using this method to study the effects of interchannel coupling reveals how much of an impact the coupling has on the time delay, in some cases over a broad energy range. In cases where the spin-orbit doublets' respective thresholds are far enough apart, effects can be found in the $j=l+$\textit{1/2 }channels due to interchannel coupling with the $j=$\textit{l-1/2} channels. These structures are purely a relativistic effect and are related to spin-obit activated interchannel coupling effects [3]. Work supported by DOE, Office of Chemical Sciences, DST (India), and the Australian Research Council. [1] W. Drube \textit{et al}, J. Phys. B \textbf{46}, 245006-1-6 (2013); [2] W. R. Johnson and C. D. Lin, Phys. Rev. A \textbf{20}, 964 (1979); [3] M. Ya. Amusia, \textit{et al}, Phys. Rev. Lett \textbf{88}, 9 (2002). [Preview Abstract] |
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Q1.00037: High-harmonic generation in aligned water molecules Song Wang, Julien Devin, Matthias Hoffmann, James Cryan, Andreas Kaldun, Philip Bucksbaum In recent years, the use of high harmonic generation (HHG) in aligned molecular vapors has become a powerful tool to study ultrafast dynamics of electronic and nuclear wave packets. In our new experimental setup, we are able to orient H$_{2}$O and D$_{2}$O molecules using a single cycle terahertz (THz) pulse. Aligning water is especially interesting as the highest occupied molecular orbital (HOMO) of water contains a node in the xz plane of the molecular frame, allowing us to perform HHG from second highest occupied molecular orbital (HOMO-1) only, by setting the polarization of the fundamental laser along the z-axis of the aligned water molecules. We are particularly interested in the HOMO-1 state, as there is fast motion of the H-O-H angle leading to sub-wavelength dynamics. On this poster we present our all-optical alignment setup where HHG and single-cycle THz generation take place in high-vacuum, where measurements with arbitrary polarization angles between the two are possible. In addition, we discuss the effects of the molecular orientation on HHG, including symmetry breaking that could produce even harmonics and isotope effects between H$_{2}$O and D$_{2}$O due to different vibrational energies. [Preview Abstract] |
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Q1.00038: High harmonic generation from impulsively aligned SO2 Julien Devin, Song Wang, Andreas Kaldun, Phil Bucksbaum Previous work [1][2] in high harmonics generation (HHG) in aligned molecular gases has mainly focused on rotational dynamics in order to determine the contributions of different orbitals to the ionization step. In our experiment, we focus on the shorter timescale of vibrational dynamics. We generate high harmonics from impulsively aligned SO2 molecules in a gas jet and record the emitted attosecond pulse trains in a home-built high resolution vacuum ultra violet (VUV) spectrometer. Using the high temporal resolution of our setup, we are able to map out the effects of vibrational wavepackets with a sub-femtosecond resolution. The target molecule, SO2 gas, is impulsively aligned by a near-infrared laser pulse and has accessible vibrations on the timescale of the short laser pulse used. We present first experimental results for the response to this excitation in high-harmonics. We observe both fast oscillations in the time domain as well as shifts of the VUV photon energy outside of the pulse overlaps. [1] R. Velotta, N. Hay, M. B. Mason, M. Castillejo, and J. P. Marangos. Phys. Rev. Lett. 87, 183901 [2] L. Spector, M. Artamonov, S. Miyabe, T. Martinez, T. Seidermann, M. Guehr, and P. Bucksbaum. Nature Communications 5, 3190. [Preview Abstract] |
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Q1.00039: Understanding x-ray driven impulsive electronic state redistribution using a three-state model Matthew R. Ware, James Cryan, Philip H. Bucksbaum The natural timescale for electron motion is extremely fast; electrons can move across molecular bonds in less than a femtosecond.~To understand this fast motion and the role of electronic coherence, we are interested~in creating a superposition of valence excited states through excitation with a broad bandwidth~(\textgreater 5eV)~laser pulse.~In the x-ray regime, the molecular ground state can couple to valence-excited states through an intermediate autoionizing resonance in a process known as stimulated x-ray Raman scattering (SXRS). X-rays excite electrons from the highly localized K-shells in a molecule, creating a superposition of valence-excited states initially localized around a target atom in the molecule. Coherences between states in the superposition will subsequently drive charge transfer as the wavepacket spreads out across the molecule. We use an effective 3-state model coupling the ground, auto-ionizing, and valence-excited states in diatomic systems to study the cross-section of SXRS as function of x-ray intensity, central frequency, bandwidth, and chirp. We also make observations on how the x-ray parameters affect the degree of initial localization to an atom of the wavepacket created in SXRS. [Preview Abstract] |
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Q1.00040: TIME RESOLVED MOLECULAR DYNAMICS AND FEMTOCHEMISTRY |
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Q1.00041: Mapping Ultrafast Dynamics of Highly Excited H$_{\mathrm{\mathbf{2}}}$\textbf{ by Attosecond VUV-Radiation} Thorsten Weber, Felix Sturm, Travis Wright, Dipanwita Ray, Niranjan Shivaram, Daniel Slaughter, Irina Bocharova, Predrag Ranitovic, Ali Belkacem We show how attosecond vacuum ultraviolet (VUV) and femtosecond infrared (IR) radiation can be used to excite and map dynamics of a highly excited neutral hydrogen molecule. By using time-delayed, strong laser pulses and ion imaging, we map the dynamics of highly-excited, bound states of hydrogen molecules. Due to the large stretching amplitude of the B electronic state, excited by the 9$^{\mathrm{th}}$ harmonic of the fundamental laser frequency, the effective ionization potential of the hydrogen molecular ion changes substantially as the nuclear wave packet (NWP) vibrates in the bound, B potential energy curve. Therefore, the probability of ionizing the neutrally-excited hydrogen molecule by the IR probe pulse changes as the NWP evolves in the B potential. We probe this dynamics by ionizing the vibrating molecule by means of time-delayed IR radiation, and identify the dissociation channels with 3D-momentum ion imaging. [Preview Abstract] |
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Q1.00042: Attosecond Coherent Control of the Photo-Dissociation of Oxygen Molecules Felix Sturm, Dipanwita Ray, Travis Wright, Niranjan Shivaram, Irina Bocharova, Daniel Slaughter, Predrag Ranitovic, Ali Belkacem, Thorsten Weber Attosecond Coherent Control has emerged in recent years as a technique to manipulate the absorption and ionization in atoms as well as the dissociation of molecules on an attosecond time scale. Single attosecond pulses and attosecond pulse trains (APTs) can coherently excite multiple electronic states. The electronic and nuclear wave packets can then be coupled with a second pulse forming multiple interfering quantum pathways. We have built a high flux extreme ultraviolet (XUV) light source delivering APTs based on HHG that allows to selectively excite neutral and ion states in molecules. Our beamline provides spectral selectivity and attosecond interferometric control of the pulses. In the study presented here, we use APTs, generated by High Harmonic Generation in a high flux extreme ultraviolet light source, to ionize highly excited states of oxygen molecules. We identify the ionization/dissociation pathways revealing vibrational structure with ultra-high resolution ion 3D-momentum imaging spectroscopy. Furthermore, we introduce a delay between IR pulses and XUV/IR pulses to constructively or destructively interfere the ionization and dissociation pathways, thus, enabling the manipulation of both the O$_{\mathrm{2}}^{\mathrm{+}}$ and the O$^{\mathrm{+}}$ ion yields with attosecond precision. [Preview Abstract] |
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Q1.00043: Quantum Dynamics Simulations for Modeling Experimental Pump-Probe Measurements Brett Pearson, Sahil Nayyar, Kyle Liss, Thomas Weinacht Time-resolved studies of quantum dynamics have benefited greatly from developments in ultrafast table-top and free electron lasers. Advances in computer software and hardware have lowered the barrier for performing calculations such that relatively simple simulations allow for direct comparison with experimental results. We describe here a set of quantum dynamics calculations in low-dimensional molecular systems. The calculations incorporate coupled electronic-nuclear dynamics, including two interactions with an applied field and nuclear wave packet propagation. The simulations were written and carried out by undergraduates as part of a senior research project, with the specific goal of allowing for detailed interpretation of experimental pump-probe data (in additional to the pedagogical value). [Preview Abstract] |
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Q1.00044: Toward picosecond time-resolved X-ray absorption studies of interfacial photochemistry Oliver Gessner, Johannes Mahl, Stefan Neppl We report on the progress toward developing a novel picosecond time-resolved transient X-ray absorption spectroscopy (TRXAS) capability for time-domain studies of interfacial photochemistry. The technique is based on the combination of a high repetition rate picosecond laser system with a time-resolved X-ray fluorescent yield setup that may be used for the study of radiation sensitive materials and X-ray spectroscopy compatible photoelectrochemical (PEC) cells. The mobile system is currently deployed at the Advanced Light Source (ALS) and may be used in all operating modes (two-bunch and multi-bunch) of the synchrotron. The use of a time-stamping technique enables the simultaneous recording of TRXAS spectra with delays between the exciting laser pulses and the probing X-ray pulses spanning picosecond to nanosecond temporal scales. First results are discussed that demonstrate the viability of the method to study photoinduced dynamics in transition metal-oxide semiconductor (SC) samples under high vacuum conditions and at SC-liquid electrolyte interfaces during photoelectrochemical water splitting. Opportunities and challenges are outlined to capture crucial short-lived intermediates of photochemical processes with the technique. [Preview Abstract] |
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Q1.00045: Intense-Field Photoionization of Molecules using Ultrashort Radiation Pulses: Carbon Disulfide and Carbon Dioxide Joshua Beck, Cornelis Uiterwaal We experimentally investigate the photoionization and photofragmentation of molecules using intense fields from an 800 nm, femtosecond laser source and an experimental method that eliminates the focal volume effect without the need for data deconvolution [\textit{Phys.\ Rev.\ Lett.\ }\textbf{100,} 023002 (2008)]. Targets include carbon disulfide and carbon dioxide. We show that ionization is insignificant for intensities that maximize alignment of carbon disulfide, which validates ultrafast electron diffraction experiments from aligned carbon disulfide [\textit{Nature Comm.\ }\textbf{6,} 8172 (2015)]. For comparison, we also investigate the analogous molecule carbon dioxide. In this molecule the molecular bonding orbitals include the $n=2$ atomic orbitals of the oxygen atom, while in carbon disulfide the $n=3$ orbitals of the sulfur atom contribute to the bonding. Recent work will be presented. [Preview Abstract] |
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Q1.00046: Fragmentation of negative ions in a strong laser field Ben Berry, Bethany Jochim, T. Severt, Peyman Feizollah, Jyoti Rajput, D. Hayes, K. D. Carnes, B. D. Esry, I. Ben-Itzhak The fragmentation of negative ions in a strong laser field can provide a testing ground for a variety of unique phenomena. For example, anions with a loosely bound electron allow for the study of rescattering phenomena at lower laser intensities than for neutral targets. We study the behavior of keV anion beams in an ultrafast, intense laser field. The use of a fast-beam target facilitates the measurement of neutral fragments. This capability allows us to explore laser-induced dynamics in both ionic and neutral charge states. Using a coincidence 3D momentum imaging technique, we obtain the full 3D momentum of all nuclear fragments. In this preliminary work, we study atomic (H$^-$) and molecular (H$_2^-$, F$_2^-$) systems with the goal of identifying and controlling their fragmentation pathways. [Preview Abstract] |
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Q1.00047: ABSTRACT MOVED TO K1.00195 |
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Q1.00048: Strong-field isomerization dynamics of fast beams of hydrocarbon ions Bethany Jochim, Jyoti Rajput, Ben Berry, T. Severt, M. Zohrabi, Peyman Feizollah, K. D. Carnes, B. D. Esry, I. Ben-Itzhak Bond rearrangement and fragmentation of hydrocarbons in intense laser fields has been a topic of considerable interest in the strong-field community in recent years. We study the interactions of keV hydrocarbon ion beams with ultrafast, intense laser pulses, employing coincidence 3D momentum imaging to elucidate the fragmentation dynamics and identify laser parameters that might be used for controlling outcomes such as the branching ratios. We focus on dissociation to ensure that isomerization occurs on the particular electronic channels of the molecular ion investigated. In C$_2$H$_2$$^+$, for example, we measure the intensity-dependent branching ratios of the acetylene (CH$^+$+CH) and vinylidene ($\emph{e.g.}$, C$^+$+CH$_2$) channels. The relative fragmentation rates between the acetylene and vinylidene channels change by a factor of $\sim$2 over the range of experimental intensities (10$^{13}$--10$^{15}$ W/cm$^2$). Other hydrocarbons of interest include not only cations but also anions, such as C$_2$H$_2^-$. [Preview Abstract] |
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Q1.00049: Using hyperspherical coordinates to analyze many-particle fragmentation experiments Peyman Feizollah, Jyoti Rajput, Ben Berry, Bethany Jochim, T. Severt, Kanaka Raju P., K. D. Carnes, I. Ben-Itzhak, B.D. Esry Analyzing and plotting the distribution of momenta for processes producing more than two fragments has long been a challenge for two reasons: lack of an appropriate representation and our inability to effectively plot and visualize more than two or three dimensions. While there is little that can be done about the latter, we propose using hyperspherical coordinates to address the former. Existing methods such as Newton and Dalitz plots give us information about the fragmentation process for three or four bodies, but neither can be easily generalized to fragmentation with an arbitrary number of particles. We will show that hyperspherical coordinates provide a systematic framework for doing exactly this. We will compare the suggested method with Newton and Dalitz plots for three-body breakup and discuss the similarities and differences between them. [Preview Abstract] |
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Q1.00050: Strong-Field Ionization of Laser Cooled Li Atoms. Sachin Sharma, Kevin Romans, Daniel Fischer Recently, our understanding of few-body effects has been substantially boosted by the development of intense femto- and attosecond laser sources. Observing the momenta of the fragments of atoms and molecules ionized in these strong fields provided new and before inconceivable insights in molecular and electronic dynamics. Here, we report on a new experiment, where the target atoms ($^{6}$Li) are laser cooled and trapped using a magneto optical trap (MOT). Momentum vectors of the target fragments will be measured using a reaction microscope (ReMi). The exclusivity of this setup is a combination of MOT and ReMi, thus dubbed as MOTReMi. Here, the advantages over standard COLTRIMS systems are multifold: Firstly, an unprecedented recoil ion momentum resolution can be achieved, as the target can be prepared at significantly lower temperatures. Second, the atoms can be optically prepared in the ground or in polarized excited states. In a first experimental campaign, studies on single ionization of laser excited and polarized Lithium atoms will be performed with circularly polarized light. This experiment can provide insight into the helicity-dependence of the ionization dynamics as the differences among co- and counter rotating electron and laser field, if any, can be investigated. [Preview Abstract] |
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Q1.00051: Adiabatic Approximation for Atomic Ionization Youliang Yu, Brett Esry Strong-field processes involving long wavelengths (longer than $800$ nm) have attracted particular attention in recent years due to the highly nonlinear nature of its interaction with atoms and molecules. Although numerically solving the time-dependent Schr\"odinger equation (TDSE) is the only way to describe these interactions in a fully quantitative manner, it usually requires intensive computational resources. For example, the usual single active electron calculation for single set of laser parameters under typical laboratory conditions can take several hours to several days to compute. In this work, we take advantage of the fact that the Hamiltonian varies slowly in the long-wavelength limit compared to the intrinsic time scales of the system to derive an approximate solution. Specifically, we expand the solution of the TDSE on the adiabatic basis calculated from the instantaneous Hamiltonian. The field strength is thus treated as the slowly varying parameter; and the non-adiabatic couplings, as a time-dependent perturbation. Results from this static field perturbation theory are compared with direct TDSE calculations for a model potential. [Preview Abstract] |
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Q1.00052: Cold atom quantum emulation of ultrafast processes Shankari Rajagopal, Zachary Geiger, Kurt Fujiwara, Kevin Singh, Ruwan Senaratne, David Weld Pulsed lasers are an invaluable probe of fast electron dynamics in condensed matter systems. However, despite tremendous progress, physical limitations on lasers and a lack of exact theoretical models still limit the exploration~of ultrafast processes in solids. ~We discuss a possible complementary approach, in which lattice-trapped cold neutral atoms driven far from equilibrium are used as a quantum emulator of ultrafast physics at sub-cycle timescales. The cold atom context is in many ways a natural choice for such experiments: equilibration timescales are more than ten orders of magnitude slower than those in solids, and strong driving forces are easily produced and manipulated. Our experimental approach uses ultracold strontium in optical traps. ~Multiple stable isotopes and a~long-lived metastable state provide control over interaction strengths, while a narrow-linewidth transition expands the typical cold-atom toolbox of readout techniques. We discuss initial efforts in quantum emulation of tunnel ionization and development of a platform for more complicated endeavors, including the study of multiple-pulse sequences and recollision processes. [Preview Abstract] |
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Q1.00053: SCIENCE WITH XUV AND X RAY FREE-ELECTRON LASERS |
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Q1.00054: Probing Ultrafast Nuclear Dynamics in Halomethanes by Time-Resolved Electron and Ion Imaging F. Ziaee, A. Rudenko, D. Rolles, E. Savelyev, C. Bomme, R. Boll, B. Manschwetus, B. Erk, S. Trippel, J. Wiese, J. Kuepper, K. Amini, J. Lee, M. Brouard, F. Brausse, A. Rouzee, P. Olshin, A. Mereshchenko, J. Lahl, P. Johnsson, M. Simon, T. Marchenko, D. Holland, J. Underwood Femtosecond pump-probe experiments provide opportunities to investigate photochemical reaction dynamics and the resulting changes in molecular structure in detail. Here, we present a study of the UV-induced photodissociation of gas-phase halomethane molecules (CH$_{\mathrm{3}}$I, CH$_{\mathrm{2}}$IBr, \textellipsis ) in a pump-probe arrangement using two complementary probe schemes, either using a femtosecond near-infrared laser or the FLASH free-electron laser. We measured electrons and ions produced during the interaction using a double-sided velocity map imaging spectrometer equipped with a CCD camera for electron detection and with the Pixel Imaging Mass Spectrometry (PImMS) camera for ions, which can record the arrival time for up to four ions per pixel. [Preview Abstract] |
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Q1.00055: Multiphoton ionization and fragmentation of iodine-containing molecules by femtosecond ultraintense hard X-rays S.J. Robatjazi, X. Li, D. Rolles, A. Rudenko, B. Erk, R. Boll, C. Bomme, E. Savelyev, B. Rudek, L. Foucar, Ch. Bostedt, S. Southworth, C.S. Lehmann, B. Kraessig, L. Young, T. Marchenko, M. Simon, K. Ueda, K.R. Ferguson, M. Bucher, T. Gorkhover, S. Carron, R. Alonso-Mori, G. Williams, S. Boutet We present ion charge state distributions and kinetic energy spectra resulting from the breakup of CH$_{3}$I and C$_{6}$H$_{5}$I molecules induced by femtosecond X-ray pulses from the Linac Coherent Light Source (LCLS) at 8.3 keV photon energy. Using a few-hundred nm focus of the LCLS CXI beamline, we reach peak intensities of up to 10$^{20}$ W/cm$^{2}$, resulting in stripping of more than 50 electrons per molecule within few tens of fs. We find that in this regime the interplay between multiphoton absorption and subsequent charge rearrangement considerably differs from earlier observations for soft X-rays [1] or for weaker hard X-rays [2]. We discuss the pulse duration dependence of the data, and compare the results for seeded and unseeded LCLS pulses. [1] B. Erk \textit{et al}., Phys. Rev. Lett. \textbf{110}, 053003 (2013). [2] K. Motomura \textit{et al}., J. Phys. Chem. Lett. \textbf{6}, 2994 (2015). [Preview Abstract] |
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Q1.00056: Channel-resolved photo- and Auger-electron spectroscopy of halogenated hydrocarbons Utuq Ablikim, B. Kaderiya, V. Kumarapan, R. Kushawaha, A. Rudenko, D. Rolles, H. Xiong, N. Berrah, C. Bomme, E. Savelyev, D. Kilcoyne Inner-shell photoelectron and Auger electron spectra of polyatomic molecules such as halogenated hydrocarbons are typically hard to interpret and assign due to many overlapping states that form broad bands even in high-resolution measurements [1]. With the help of electron-ion-ion coincidence measurements performed using the velocity map imaging technique, we are able to detect high-energy ($\le $ 150 eV) photo- and Auger electrons in coincidence with two- or many-body ionic fragmentation channels. Such channel-resolved measurements allow disentangling the overlapping electronic structures and help assigning individual components of the electron spectra to specific potential surfaces and final states. In this work, we present measurements on CH$_{\mathrm{3}}$I, CH$_{\mathrm{2}}$IBr, and CH$_{\mathrm{2}}$ICl molecules in the gas-phase using soft x-ray light provided by the Advanced Light Source at LBNL. [1] D.M.P. Holland \textit{et al}. Chem. Phys. \textbf{326}: 535--550 (2006). [Preview Abstract] |
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Q1.00057: MOLECULAR CONTROL AND IMAGING |
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Q1.00058: Dissociation dynamics of the CO$_{\mathrm{2}}$ molecule studied with XUV pump and near-infrared probe experiments Kanaka Raju Pandiri, Yu Malakar, Xiang Li, Balram Kaderiya, Wright Pearson, Wei Cao, Itzik Ben-Itzhak, Daniel Rolles, Artem Rudenko, Philip Trapp, Daniel Trabert, Florian Wilhelm Ultrafast dynamics of ionic states of the CO$_{\mathrm{2}}$ molecule have recently been studied by employing a pump-probe technique using broadband ultrashort XUV-pump pulses containing the 11$^{\mathrm{th}}$ to 17$^{\mathrm{th}}$ harmonics of a near-infrared laser (NIR) [1]. Here, we present the results of a complimentary experiment employing longer (\textasciitilde 100 fs) but narrowband, single harmonic (11$^{\mathrm{th}}$ or 13$^{\mathrm{th}})$ pulses to excite molecular wave packets to specific states of CO$_{\mathrm{2}}^{\mathrm{+}}$, which are probed by NIR-induced dissociation. We employ a reaction microscope to measure energy- and angle-resolved yields of all charged reaction fragments as a function of XUV-NIR delay. In particular, the delay dependence of O$^{\mathrm{+}}$ and CO$^{\mathrm{+}}$ ion production for parallel and perpendicular NIR and XUV polarizations are contrasted with the data obtained by Timmers \textit{et al.} [1] using ultrashort broadband train of harmonics. [1] H. Timmers \textit{et al.}, Phys. Rev. Lett. \textbf{113}, 113003 (2004). [Preview Abstract] |
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Q1.00059: ULTRAFAST X-RAY PROCESSES |
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Q1.00060: Single and double core-hole ion emission spectroscopy of transient neon plasmas produced by ultraintense x-ray laser pulses Cheng Gao, Jiaolong Zeng, Jianmin Yuan Single core-hole (SCH) and double core-hole (DCH) spectroscopy is investigated systematically for neon gas in the interaction with ultraintense x-ray pulses with photon energy from 937 eV to 2000 eV. A time-dependent rate equation, implemented in the detailed level accounting approximation, is utilized to study the dynamical evolution of the level population and emission properties of the laser-produced highly transient plasmas. The plasma density effects on level populations are demonstrated with an x-ray photon energy of 2000 eV. For laser photon energy in the range of 937 - 1360 eV, resonant absorptions (RA) of 1s-np (n\textgreater $=$2) transitions play important roles in time evolution of the population and DCH emission spectroscopy. For x-ray photon energy larger than 1360 eV, no RA exist and transient plasmas show different features in the DCH spectroscopy. [Preview Abstract] |
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Q1.00061: QUANTUM OPTICS |
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Q1.00062: Large conditional single-photon cross-phase modulation Kristin Beck, Mahdi Hosseini, Yiheng Duan, Vladan Vuletic Deterministic optical quantum logic requires a nonlinear quantum process that alters the phase of a quantum optical state by $\pi$ through interaction with only one photon. Here, we demonstrate a large conditional cross-phase modulation between a signal field, stored inside an atomic quantum memory, and a control photon that traverses a high-finesse optical cavity containing the atomic memory. This approach avoids fundamental limitations associated with multimode effects for traveling optical photons. We measure a conditional cross-phase shift of up to $\pi/3$ between the retrieved signal and control photons, and confirm deterministic entanglement between the signal and control modes by extracting a positive concurrence. With a moderate improvement in cavity finesse, our system can reach a coherent phase shift of p at low loss, enabling deterministic and universal photonic quantum logic. Preprint: arXiv:1512.02166 [quant-ph] [Preview Abstract] |
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Q1.00063: Squeezed light spin noise spectroscopy Vito Giovanni Lucivero, Ricardo Jiménez-Martínez, Jia Kong, Morgan Mitchell Spin noise spectroscopy (SNS) has recently emerged as a powerful technique for determining physical properties of an unperturbed spin system from its power noise spectrum both in atomic and solid state physics. In the presence of a transverse magnetic field, we detect spontaneous spin fluctuations of a dense Rb vapor via Faraday rotation of an off-resonance probe beam, resulting in the excess of spectral noise at the Larmor frequency over a white photon shot-noise background. We report quantum enhancement of the signal-to-noise ratio via polarization squeezing of the probe beam up to 3dB over the full density range up to n$=$10$^{\mathrm{13}}$ atoms cm$^{\mathrm{-3}}$, covering practical conditions used in optimized SNS experiments. Furthermore, we show that squeezing improves the trade-off between statistical sensitivity and systematic errors due to line broadening, a previously unobserved quantum advantage. Reference: Lucivero, et al. arXiv:1509.05653 (2015) [Preview Abstract] |
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Q1.00064: Coherent Forward Broadening in Cold Atom Clouds R.T. Sutherland, Francis Robicheaux It is shown that homogeneous line-broadening in a diffuse cold atom cloud is proportional to the resonant optical depth of the cloud. Further, it is demonstrated how the strong directionality of the coherent interactions causes the cloud's spectra to depend strongly on its shape, even when the cloud is held at constant densities. These two numerical observations can be predicted analytically by extending the single photon wavefunction model. Lastly, elongating a cloud along the line of laser propagation causes the excitation probability distribution to deviate from the exponential decay predicted by the Beer-Lambert law to the extent where the atoms in the back of the cloud are more excited than the atoms in the front. These calculations are conducted at low densities relevant to recent experiments. [Preview Abstract] |
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Q1.00065: Two-channel emission model for collective quantum jumps in Rydberg atoms Lyndon Cayayan, James Clemens We consider a system of driven, damped Rydberg atoms with dipole-dipole energy shifts which can give rise to a Rydberg blockade when the atoms are driven on resonance and collective quantum jumps when the atoms are driven off resonance. For the damping we consider a two-channel emission model with competition between fully independent and fully collective spontaneous emission. For independent emission a quasiclassical model predicts a bistable steady state and quantum fluctuations drive collective jumps between the two bistable branches. We show that the collective emission is enhanced, relative to the independent emission, which shifts the total effective spontaneous emission rate and impacts the presence or absence of bistability predicted by the quasiclassical model. [Preview Abstract] |
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Q1.00066: Measurement of the topological charge of mixed OAM states Mariia Shutova, Alexandra Zhdanova, Alexei Sokolov In the current work, we investigate how the technique of measuring the topological charge of an optical vortex by using a tilted convex lens (tilted lens technique) works for optical vortices in mixed orbital angular momentum (OAM) states (i.e. the case when one beam contains several components with different values of topological charge). A mixed OAM state may occur, for example, because of perturbations in the optical devices used to generate the state, such as spatial light modulators or spiral phase plates. Hence, we present experimental results and theoretical simulations for the measurement of the topological charge of mixed states with variable amounts of each component contributing to the total beam intensity. We also investigate two different cases: first, when interference between components is present (coherent addition of component OAM states), and second, when interference is absent (incoherent addition). We conclude that in both cases the results of the tilted lens technique are valid for that component of light which is dominant (i.e. the component that contributes to more than 50{\%} of the beam's total intensity). [Preview Abstract] |
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Q1.00067: Power and polarization dependences of ultra-narrow electromagnetically induced absorption (EIA) spectra of $^{\mathrm{85}}$Rb atoms in degenerate two-level system Muhammad Mohsin Qureshi, Hafeez Ur Rehman, Heung-Ryoul Noh, Jin-Tae Kim We have investigated ultra-narrow EIA spectral features with respect to variations of polarizations and powers of pump laser beam in a degenerate two-level system of the transition of $^{\mathrm{85}}$Rb D$_{\mathrm{2}}$ transition line. Polarizations of the probe laser beam in two separate experiments were fixed at right circular and horizontal linear polarizations, respectively while the polarizations of the pump lasers were varied from initial polarizations same as the probe laser beams to orthogonal to probe polarizations. One homemade laser combined with AOMs was used to the pump and probe laser beams instead of two different lasers to overcome broad linewidths of the homemade lasers. Theoretically, probe absorption coefficients have been calculated from optical Bloch equations of the degenerate two level system prepared by a pump laser beam. In the case of the circular polarization, EIA signal was obtained as expected theoretically although both pump and probe beams have same polarization. The EIA signal become smaller as power increases and polarizations of the pump and probe beams were same. When the polarization of the pump beam was linear polarization, maximum EIA signal was obtained theoretically and experimentally. Experimental EIA spectral shapes with respect to variations of the pump beam polarization shows similar trends as the theoretical results. [Preview Abstract] |
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Q1.00068: Modelling Spatial Modes of Squeezed Vacuum R. Nicholas Lanning, Zhihao Xiao, Mi Zhang, Irina Novikova, Eugeniy Mikhailov, Jonathan P. Dowling We develop a fully quantum model to describe the spatial mode properties of squeezed light generated as a laser beam propagates through a Rb vapor cell. Our results show that a Gaussian pump beam can generate a collection of higher order Laguerre-Gaussian squeezed vacuum modes, each carrying a particular squeeze parameter and squeeze angle. We show that a proper sorting of modes could lead to improved noise suppression and thus make this method of squeezed light generation very useful for precision metrology and quantum memory applications. Additionally, we model a multi-pass beam configuration and show that this can lead to a further improvement of vacuum squeezing. [Preview Abstract] |
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Q1.00069: Toward perfect homodyne detection of twin vacuum beams Tian Li, Travis Horrom, Brian Anderson, Paul Lett We demonstrate the use of an optical phase-sensitive amplifier to recover the quantum correlations in twin light beams after degradation due to optical loss and detector efficiency. We use four-wave mixing in hot $^{85}$Rb vapor cell to generate correlated twin beams in a two-mode squeezed vacuum state. We then use a second four-wave mixing cell as our optical phase-sensitive amplifier to amplify one half of the two-mode state, which can compensate for downstream optical loss and restore the nonclassical correlations of the state. [Preview Abstract] |
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Q1.00070: Optimized geometric configuration of active ring laser gyroscopes John Gormley, Tony Salloum We present a thorough derivation of the Sagnac effect for a ring laser gyroscope of any arbitrary polygonal configuration. We determine optimized alternative geometric configurations for the mirrors. The simulations incur the implementation of a lasing medium with the standard square system, triangular, pentagonal, and oblongated square configuration (diamond). Simulations of possible new geometric configurations are considered, as well as the possibility of adjusting the concavity of the mirrors. [Preview Abstract] |
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Q1.00071: Three-body physics of Rydberg polaritons Yidan Wang, Alexey Gorshkov, Ran Qi, Michael Gullans, Mohammad Maghrebi Under the conditions electromagnetically induced transparency in Rydberg media, slow-light polaritons interact strongly via Rydberg states. While two such polaritons can interact attractively and form two-body bound states, three polariton physics remains largely unexplored. We show that while exact three-polariton bound states do not exist, metastable ones do. The understanding of three-polariton physics will allow for the construction of more precise low energy many-body theories of Rydberg polaritons and may enable the realization of novel exotic equilibrium and out-of equilibrium phenomena with interacting light. [Preview Abstract] |
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Q1.00072: Nonlinear optical SU(1,1) interferometer using four-wave mixing in Rb Prasoon Gupta, Brian Anderson, Travis Horrom, Paul Lett Quantum-enhanced precision measurements have emerged as one of the most useful applications of quantum optics. By replacing the beamsplitters in a traditional Mach-Zender interferometer with parametric amplifiers, one can create a nonlinear SU(1,1) interferometer. Nonclassical correlations in the interior state of the interferometer allow for Heisenberg-limited sensitivity of this device, an improvement over classical interferometers. The optical SU(1,1) interferometer can be experimentally realized using four-wave mixing in hot rubidium vapor to generate twin beams, and then recombining these beams in a second four-wave mixing process after a phase shift. We investigate the properties of this interferometer both theoretically and experimentally and examine how the sensitivity depends on detection method. [Preview Abstract] |
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Q1.00073: Three-photon interactions and spin exchange in a quantum nonlinear medium Sergio Cantu, Qi-Yu Liang, Jeff Thompson, Travis Nicholson, Aditya Venkatramani, Michael Gullans, Alexey Gorshkov, Soonwon Choi, Mikhail Lukin, Vladan Vuletic Robust quantum gates for photonic qubits are a longstanding goal of quantum information science. One promising approach to achieve this goal requires strong nonlinear interactions between single photons, which is impossible with conventional optical media. We realize these interactions with electromagnetically induced transparency (EIT), and strongly interacting Rydberg states to mediate strong interactions between photons [1]. Operating in the dispersive regime of EIT, we have recently shown that two photons propagating in our system can bind into a photonic molecule [2]. Extending these two-photon experiments to many-body physics would lead to exotic phenomena like photon crystallization. To that end, we have scaled up our two-photon measurements to three-photon experiments. We are now able to discern signatures of three-photon molecules from a variety of two- and three-photon interactions. Three-photon bound states manifest as an increase in photon bunching in $g^{(3)}$ correlation measurements. We also present a recent observation of coherent spin exchange interactions in Rydberg EIT. [1] Peyronel, et al Nature \textbf{488}, 5760 (2012) [2] Firstenberg, et al Nature \textbf{502}, 71-75 (2013) [Preview Abstract] |
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Q1.00074: Probing an NV Center's Nuclear Spin Environment with Coherent Population Trapping David Levonian, Michael Goldman, Swati Singh, Matthew Markham, Daniel Twitchen, Mikhail Lukin Nitrogen-vacancy (NV) centers in diamond have emerged as a versatile atom-like system, finding diverse applications in metrology and quantum information science, but interaction between the NV center’s electronic spin and its nuclear spin environment represent a major source of decoherence. We use optical techniques to monitor and control the nuclear bath surrounding an NV center. Specifically, we create an optical $\Lambda$-system using the $|\pm1\rangle$ components of the NV center’s spin-triplet ground state. When the Zeeman splitting between the two states is equal to the two-photon detuning between the lasers, population is trapped in the resulting dark state. Measuring the rate at which the NV center escapes from the dark state therefore gives information on how spin bath dynamics change the effective magnetic field experienced by the NV center. By monitoring statistics of the emitted photons, we plan to probe non-equilibrium dynamics of the bath. [Preview Abstract] |
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Q1.00075: Studies of Four Wave Mixing in a Cold Atomic Ensemble for Efficient Generation of Photon Pairs Andrew Richard Ferdinand, Xijie Luo, Francisco Elohim Becerra Photon pairs generated by spontaneous four-wave mixing (FWM) in atomic ensembles provide a natural path toward quantum light-matter interfaces due to their intrinsic compatibility with atomic quantum memories. We study the generation of light from a semi-classical FWM process in an elongated ensemble of cold cesium (Cs) atoms. We investigate the generation efficiency as a function of power, detuning, and polarization of the pump fields in the process. This study will allow us to determine the pump-field parameters in our system for the efficient generation of correlated photon pairs from a spontaneous FWM process. [Preview Abstract] |
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Q1.00076: QUANTUM INFORMATION THEORY |
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Q1.00077: Probing Collins conjecture with correlation energies and entanglement entropies for the ground state of the helium isoelectronic sequence Yew Kam Ho, Yen-Chang Lin Correlation energy of a quantum system is defined as the difference between its exact energy $E_{\mathrm{ex}}$, and its Hartree-Fock energy $E_{\mathrm{HF}}$. In a recent related development, entanglement measures can be quantified with von Neumann entropy $S_{vN} (\rho )=-Tr(\rho \log_{2} \rho )$ or linear entropy $S_{L} (\rho )=1-Tr(\rho^{2})$, where $\rho $ is the one-particle reduced density matrix, and $Tr(\rho^{2})$ is defined as the purity of state. In the present work we calculate $S_{L}$ and $S_{vN}$ for the ground 1$s^{\mathrm{2\thinspace 1}}S$ states in helium-like ions for $Z=$ 2 to 15, using configuration interaction (CI) with $B$-Spline basis up to about 6000 terms to construct the wave functions, and with which density matrix, linear and von Neumann entropies are calculated [1]. We have found close relationship between the reduced correlation energy, defined as $E_{\mathrm{corr}}=$ ($E_{\mathrm{CI\thinspace }}$-- $E_{\mathrm{HF}})$/$E_{\mathrm{CI}}$ (with $E_{\mathrm{CI}}$ being our calculated energy), and $S_{L}$ or $S_{vN}$. Our results support Collins conjecture [2] that there is a linear relationship between correlation energy and entanglement entropy, i.e., $E_{\mathrm{corr}}=$ \textit{CS}, where $C$ is called Collins constant. Using the calculated ground state energies for $Z=$ 2 to $Z=$ 15, and the entanglement measured with linear entropy $S_{L}$ for such states, $C$ is determined as 0.90716. At the meeting, we will present result for Collins constant determined from von Neumann entropy, and details of our calculations. [1] Y.-C. Lin, C.-Y. Lin, and Y. K. Ho, \textit{Phys. Rev. A} \textbf{87}, 022316 (2013); \textit{Can. J. Phys}. \textbf{93}, 646 (2015). [2] D. M. Collins, \textit{Z. Naturforsch}, \textbf{48, }68 (1993). [Preview Abstract] |
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Q1.00078: Experimental realization of quantum teleportation from a photon to the vibration modes of a millimeter-sized diamond Yuanyuan Huang, Panyu Hou, XinXing Yuan, Xiuying Chang, Chong Zu, Li He, LuMing Duan Quantum teleportation is of great importance to various quantum technologies, and has been realized between light beams, trapped atoms, superconducting qubits, and defect spins in solids. Here we report an experimental demonstration of quantum teleportation from light beams to vibrational states of a macroscopic diamond under ambient conditions. In our experiment, the ultrafast laser technology provides the key tool for fast processing and detection of quantum states within its short life time in macroscopic objects consisting of many strongly interacting atoms that are coupled to the environment, and finally we demonstrate an average teleportation fidelity $(90.6\pm 1.0)\% $, clearly exceeding the classical limit of 2/3. Quantum control of the optomechanical coupling may provide efficient ways for realization of transduction of quantum signals, processing of quantum information, and sensing of small mechanical vibrations. [Preview Abstract] |
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Q1.00079: Quantum Otto engine using a single ion and a single thermal bath Asoka Biswas, Suman Chand Quantum heat engines employ a quantum system as the working fluid, that gives rise to large work efficiency, beyond the limit for classical heat engines. Existing proposals for implementing quantum heat engines require that the system interacts with the hot bath and the cold bath (both modelled as a classical system) in an alternative fashion and therefore assumes ability to switch off the interaction with the bath during a certain stage of the heat-cycle. However, it is not possible to decouple a quantum system from its always-on interaction with the bath without use of complex pulse sequences. It is also hard to identify two different baths at two different temperatures in quantum domain, that sequentially interact with the system. Here, we show how to implement a quantum Otto engine without requiring to decouple the bath in a sequential manner. This is done by considering a single thermal bath, coupled to a single trapped ion. The electronic degree of freedom of the ion is chosen as a two-level working fluid while the vibrational degree of freedom plays the role of the cold bath. Measuring the electronic state mimics the release of heat into the cold bath. Thus, our model is fully quantum and exhibits very large work efficiency, asymptotically close to unity. [Preview Abstract] |
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Q1.00080: Generation of entangled macroscopic light fields with a coupled gain-loss waveguide Saeid Vashahri-Ghamsari, Bing He, Min Xiao We explore a Parity-Time (PT)-symmetric optical system of two coupled single-mode waveguides. One of the waveguides contains a gain medium, while the second one is with a loss medium. The magnitude of the gain can be adjusted to be equal to that of the loss, so that the PT-symmetric condition will be achieved. Moreover, we add a squeezing element to one of the waveguides. The squeezing can be generated in a parametric down conversion process. Moreover, we have included both amplifying and decaying noises in the process. It is shown that the squeezing intensifies the noise-induced photon emission and leads to the entanglement of the output light fields. Under certain conditions, the noises tend to eliminate the entanglement. If the input beam is strong, the entanglement due to the squeezing can become strong enough to overcome the noise effects, resulting in macroscopic entangled output fields. [Preview Abstract] |
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Q1.00081: HYBRID QUANTUM SYSTEMS |
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Q1.00082: Engineered Rydberg Atom-Surface Interactions Using Metamaterials Yuanxi Chao, Jiteng Sheng, Jonathan Sedlacek, James Shaffer We report on studies of Rydberg atom-surface interactions aimed at engineering Rydberg atom coupling to metamaterials. Rydberg atoms posses large electric dipole moments that can be strongly coupled to the tightly confined electromagnetic fields of surface phonon polariton (SPhP) modes of a properly constructed piezoelectric superlattice (PSL). Coupling of Rb87 Rydberg atoms, typically in microwave range, to real SPhP resonances on a periodically poled lithium niobate surface is studied theoretically for different periodic domain and surface orientations. Coupling constants, much larger than the dissipation of the atom-surface system, are calculated for atom-surface separations in the near field. This remarkable result opens up a simple way to design and conduct experiments to study the atom-surface interactions in the strong coupling regime which is usually hard to reach in other systems. The light-matter interaction described can be used for a quantum hybrid system that has potential applications for quantum photonic devices. Experimental studies of surfaces showing the efficacy of our calculations are also presented. [Preview Abstract] |
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Q1.00083: Atomic vapor spectroscopy in integrated photonic structures Tilman Pfau, Robert Löw, Ralf Ritter, Harald Kübler, Nico Gruhler, Wolfram Pernice We investigate an integrated optical chip immersed in atomic vapor providing several waveguide geometries for spectroscopy applications. This includes integrated ring resonators, Mach Zehnder interferometers, slot waveguides and counterpropagating coupling schemes. The narrow-band transmission through a silicon nitride waveguide and interferometer is altered when the guided light is coupled to a vapor of rubidium atoms via the evanescent tail of the waveguide mode. We use grating couplers to couple between the waveguide mode and the radiating wave, which allow for addressing arbitrary coupling positions on the chip surface. The evanescent atom-light interaction can be numerically simulated and shows excellent agreement with our experimental data. This work demonstrates a next step towards miniaturization and integration of alkali atom spectroscopy and provides a platform for further fundamental studies of strong atom light coupling. Cooperativities on the order of 1 are within reach. [Preview Abstract] |
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Q1.00084: Hybrid quantum systems with ultracold spins and optomechanics Airlia Shaffer, Yogesh Sharad Patil, Hil F. H. Cheung, Ke Wang, Aditya Date, Keith Schwab, Pierre Meystre, Mukund Vengalattore Linear cavity optomechanics has enabled radiation pressure cooling and sensing of mechanical resonators at the quantum limits. However, exciting and unrealized avenues such as generating massive macroscopic nonclassical states, quantum signal transduction, and phonon-based manybody physics each require strong, nonlinear interactions. In our group, we are exploring three approaches to realizing strong optomechanical nonlinearities -- i. using atomically thin graphene membranes, ii. coupling optomechanical systems with ultracold atomic spins, and iii. using microtoroidal optomechanical resonators strongly coupled to atoms trapped in their evanescent fields. We describe our progress in each of these efforts and discuss ongoing studies on various aspects of quantum enhanced metrology, nonequilibrium dynamics of open quantum systems and quantum transduction using these novel hybrid quantum systems. [Preview Abstract] |
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Q1.00085: Sympathetic cooling of nanospheres with cold atoms Cris Montoya, Apryl Witherspoon, Gambhir Ranjit, kirsten Casey, John Kitching, Andrew Geraci Ground state cooling of mesoscopic mechanical structures could enable new hybrid quantum systems where mechanical oscillators act as transducers. Such systems could provide coupling between photons, spins and charges via phonons. It has recently been shown theoretically that optically trapped dielectric nanospheres could reach the ground state via sympathetic cooling with trapped cold atoms [1]. This technique can be beneficial in cases where cryogenic operation of the oscillator is not practical. We describe experimental advances towards coupling an optically levitated dielectric nanosphere to a gas of cold Rubidium atoms. The sphere and the cold atoms are in separate vacuum chambers and are coupled using a one-dimensional optical lattice. [1] G. Ranjit, C. Montoya, A. A. Geraci, Phys Rev. A 91, 013416 (2015). [Preview Abstract] |
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Q1.00086: Magnetic-field-mediated hybridization of ultracold atoms and a nanostring Andrei Tretiakov, Erhan Saglamyurek, Lindsay LeBlanc Through nanofabrication, mechanical elements can be engineered with vibration frequencies near the hyperfine and Zeeman resonances in an atomic system. By including magnetic elements as part of this mechanical object, we can couple the vibrational modes of the oscillator to the spin states of the atoms. The nanostring design offers new options for creating magnetic fields using dc and ac currents. Here, we consider and compare different ways to provide magnetic coupling between this mechanical motion and the spin states of an ultracold $^{87}$Rb gas, and discuss methods of manipulating the quantum state of a mechanical oscillator using cold atoms, such as mechanical cooling. Finally, we discuss our progress towards the experimental realization of this system, including a system for optically transferring at cold $^{87}$Rb gas from a remote 3D MOT, and constructing a versatile load-lock type UHV system for rapidly prototyping new devices. [Preview Abstract] |
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Q1.00087: Nanophotonic cavity QED with multiple trapped atoms Tamara Dordevic, Polnop Samutpraphoot, Crystal Senko, Sylvain Schwartz, Vladan Vuletic, Mikhail Lukin Realization of coherent atom interactions mediated by photons in optical cavity QED has been a long-standing goal in AMO physics.~We present a new method for trapping and cooling two atoms near a nanophotonic cavity [1], and describe our progress towards preparing an entangled state of two atoms mediated by the cavity photons. Our approach can be extended to realizing an efficient quantum state transfer and quantum gates [2], with applications to integrated quantum networks. [1] J. D. Thompson, T. G. Tiecke, N. P. de Leon, J. Feist, A. V. Akimov, M. Gullans, A. S. Zibrov, V. Vuletic, and M. D. Lukin, Science 340, 1202 (2013) [2] T. G. Tiecke, J. D. Thompson, N. P. de Leon, L. R. Liu, V. Vuletic and M. D. Lukin, Nature 508, 241 (2014) [Preview Abstract] |
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Q1.00088: Observation of Diamond Nitrogen-Vacancy Center Photoluminescence under High Vacuum in a Magneto-Gravitational Trap Peng Ji, Jen-Feng Hsu, Charles W. Lewandowski, M. V. Gurudev Dutt, Brian D’Urso We report the observation of photoluminescence from nitrogen-vacancy (NV) centers in diamond nanocrystals levitated in a magneto-gravitational trap. The trap utilizes a combination of strong magnetic field gradients and gravity to confine diamagnetic particles in three dimensions. The well-characterized NV centers in trapped diamond nanocrystals provide an ideal built-in sensor to measure the trap magnetic field and the temperature of the trapped diamond nanocrystal. In the future, the NV center spin state could be coupled to the mechanical motion through magnetic field gradients, enabling in an ideal quantum interface between NV center spin and the mechanical motion. [Preview Abstract] |
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Q1.00089: Charge state dynamics of the nitrogen vacancy center in diamond under near-infrared excitation Peng Ji, M. V. Gurudev Dutt The negatively charged NV defect center (NV-) in diamond has become prominent for applications in quantum information, nanoscale magnetic and electric field sensing, and fluorescent biological markers. Switching between NV- and neutral charge states (NV0) have been extensively studied and modeled using exciting laser wavelengths that are shorter than the NV- zero-phonon line (ZPL), and typically result in decreased fluorescence from the NV- state. In this work, we report on the experimental observation that NV0 converts to NV- under excitation with near-infrared (1064 nm) light, resulting in increased fluorescence from the NV- state. We have observed this effect in both ensembles of NVs in bulk diamond, and in diamond nanocrystals, and find that it is robust both at room and low temperature. We carried out microwave and two-color excitation combined with spectral and time-resolved experimental studies. We used rate-equation modeling and find evidence for competition between one-photon and two-photon processes for hole and electron ionization. This finding may help elucidate the study of the NV energy level structure, and impact recently emerging research in single-shot measurement of the NV- spin state via spin-to-charge conversion. [Preview Abstract] |
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Q1.00090: Superresolution measurement of nanofiber diameter by modes beating E. F. Fenton, P. Solano, J. E. Hoffman, L. A. Orozco, S. L. Rolston, F. K. Fatemi Nanofibers are becoming an important tool in quantum information technologies for coupling photonics systems to atomic systems. Nondestructive techniques for characterizing these nanofibers prior to integration into an apparatus are desirable. In this work, we probe the light propagating in a fused silica optical nanofiber (750-nm-diameter) by coupling it evanescently to a 6-$\mu$m-diameter microfiber that is scanned along the nanofiber length. This technique is capable of observing all possible beat lengths among different propagating modes. The beat lengths are strongly dependent on the nanofiber diameter and refractive index of the fiber. The steep dependence has enabled measurements of the fiber diameter with sub-Angstrom sensitivity. The diameter extracted from the beat length measurements agrees with a measurement made using scanning electron microscopy. [Preview Abstract] |
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Q1.00091: Engineering Strong Interactions Between mm-wave and Optical Photons Aziza Suleymanzade, Mark Stone, Jeremy Estes, Scott Eustice, Jonathan Simon, David Schuster We propose an atomic interface of Rydberg atoms as a means of engineering effective strong interactions between single mm-wave and optical photons. The atomic sample resides at the intersection of a high-finesse optical cavity and a superconducting mm-wave cavity, where it can coherently interact with photons of both regimes. The use of mm-wave (100 GHz) frequencies allows strong coupling at higher temperatures and with less sensitivity to stray electric fields. A hybrid cryogenic vacuum chamber at 4 Kelvin enables access to superconductivity as well as a UHV environment with optical access necessary for cold atom experiments. Strong interactions between these separate quantum degrees of freedom has important applications in quantum computing as well as simulation of many-body interacting systems. [Preview Abstract] |
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Q1.00092: Observing spin optodynamical analog of cavity optomechanics Justin Gerber, Jonathan Kohler, Nicolas Spethmann, Sydney Schreppler, Dan Stamper-Kurn Cavity Optomechanics has been realized in many diverse systems and led to many interesting results such as ponderomotive squeezing of light, beyond-SQL measurement sensitivity, and squeezing of mechanical oscillators.~Optical cavities also allow sensitive measurements of the spin of an atomic ensemble. It has been proposed to utilize this sensitivity to realize an analog of optomechanics by measuring the precession of small excitations of a spin-oscillator around a transverse magnetic field. I will present our recent work in which we realize optomechanical analogs in our system such as cavity-assisted cooling and amplification and optical spring shifts. In addition, the presence of a high-energy `ground state' of the spin oscillator allows the realization of an effective negative mass oscillator which is demonstrated by an inverted sideband asymmetry. In our ongoing work we attempt to realize coherent quantum noise cancelation by coupling spin oscillation with mechanical oscillation. [Preview Abstract] |
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Q1.00093: NONLINEAR DYNAMICS AND OUT-OF-EQUILIBRIUM TRAPPED GASES |
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Q1.00094: Computing Rydberg Electron Transport Rates via Classical Periodic Orbits Sulimon Sattari, Kevin Mitchell Electron transport properties of chaotic atomic systems may be computable from classical periodic orbits. This technique allows for replacing a Monte Carlo simulation launching millions of orbits with a sum over tens or hundreds of properly chosen periodic orbits. A firm grasp of the structure of the periodic orbits is required to obtain accurate transport rates. We apply a technique called homotopic lobe dynamics (HLD) to understand the structure of periodic orbits to compute the ionization rate of a hydrogen atom in strong parallel electric and magnetic fields. HLD uses information encoded in the intersections of stable and unstable manifolds of a few orbits to compute all relevant periodic orbits in the system. The ionization rate computed from periodic orbits using HLD converges exponentially to the true value as a function of the highest period used. We then use periodic orbit continuation to accurately compute the ionization rate when the field strengths are varied. The ability to use periodic orbits in a mixed phase space could allow for studying transport in even more complex few body systems. [Preview Abstract] |
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Q1.00095: Nonequilibrium quantum dynamics in optomechanical systems Yogesh Sharad Patil, Hil F. H. Cheung, Airlia Shaffer, Ke Wang, Mukund Vengalattore The thermalization dynamics of isolated quantum systems has so far been explored in the context of cold atomic systems containing a large number of particles and modes. Quantum optomechanical systems offer prospects of studying such dynamics in a qualitatively different regime -- with few individually addressable modes amenable to continuous quantum measurement and thermalization times that vastly exceed those observed in cold atomic systems. We have experimentally realized a dynamical continuous phase transition in a quantum compatible nondegenerate mechanical parametric oscillator. This system is formally equivalent to the optical parametric amplifiers whose dynamics have been a subject of intense theoretical study [1]. We experimentally verify its phase diagram and observe nonequilibrium behavior that was only theorized, but never directly observed, in the context of optical parametric amplifiers. We discuss prospects of using nonequilibrium protocols such as quenches in optomechanical systems to amplify weak nonclassical correlations and to realize macroscopic nonclassical states. \\[4pt] [1] H. F. H. Cheung \em et al. \em\ arXiv:1601.02324 (2016) [Preview Abstract] |
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Q1.00096: Two regimes in the decay behavior of ions from a linear r.f. Paul trap Jonathan Kwolek, James Wells, Douglas Goodman, Reinhold Bl\"umel, Winthrop Smith A linear Paul trap (LPT) enables ions to be trapped for use in a variety of experiments. In many of these experiments, such as those measuring charge exchange or sympathetic cooling, the decay of ions from the trap is used to measure some quantity of interest. This decay is typically modeled as a single exponential. We have found that in cases where the trap is loaded to high numbers of ions, the ion decay is better described by a double exponential decay function [1]. We have experimentally examined the decay of ions from an LPT loaded by photoionization from a magneto-optical trap as a function of the $q$ stability parameter of the Paul trap. The LPT is loaded to steady-state, then the loading is stopped and the number of trapped ions as a function of time is monitored to determine the decay. We present numerical simulations and experimental results that demonstrate two distinct regions in the decay. For high steady-state values, the trap exhibits a double-exponential behavior. However, if the trap is filled to a steady-state value below a threshold, the decay recovers the typical single-exponential behavior. This behavior should be universal to any Paul trap regardless of the geometry or species trapped.\\ \\ \noindent [1] Goodman, et al. PRA {\bf 91}, 012709 (2015) [Preview Abstract] |
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Q1.00097: Dynamics of interacting fermions in spin-dependent potentials Andrew Koller, Michael Wall, Josh Mundinger, Ana Maria Rey Recent experiments with dilute trapped Fermi gases observed that weak interactions can drastically modify spin transport dynamics and give rise to robust collective effects including global demagnetization, macroscopic spin waves, spin segregation, and spin self-rephasing. We present a framework for analyzing the dynamics of weakly interacting fermionic gases following a spin-dependent change of the trapping potential. The dynamics are projected onto a set of lattice spin models defined on the single-particle mode space. Collective phenomena, including the global spreading of quantum correlations in real space, arise as a consequence of the long-ranged character of the spin model couplings. The spin model formulation provides a simple picture of the experimental observations and illuminates the interplay between spin, motion, Fermi statistics, and interactions. This technique opens a route for investigations of generic interacting spin-motion coupled systems in regimes that are not accessible with current numerical capabilities. [Preview Abstract] |
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Q1.00098: Bistability and domain formation in driven-dissipative photon cavity arrays Michael Foss-Feig, Ryan Wilson, Alexey Gorshkov Atomic, molecular, and optical systems afford exciting opportunities to engineer simple, driven-dissipative quantum systems. Even when these systems reach a steady state, they generally remain far from thermal equilibrium, creating many difficulties in describing them theoretically. We confront some of these difficulties in a simple context by studying coupled arrays of non-linear optical cavities [1]. In the limit of strong photon-photon interactions, and making a mean-field approximation, this system exhibits collective bistability between bright and dark states, in close analogy to single-mode quantum optical systems studied decades ago [2]. While this mean-field picture hints at the existence of a first-order phase transition in the true steady state, we are unaware of any general arguments for whether, and if so in what spatial dimensions, such a transition actually exists; the answer depends upon the detailed dynamics of domains in the presence of both quantum and dissipative fluctuations. We study the effects of such fluctuations at various levels of approximation, and develop some simple qualitative pictures of what is going on in the true quantum steady state. [1] R. Wilson et al., arXiv:1601.06857 (2016) [2] P. D. Drummond and D. F. Walls, J. of Phys. A 13, 725 (1980) [Preview Abstract] |
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Q1.00099: Probing Kibble-Zurek Mechanism in Quenched Elongated Bose Gases I-Kang Liu, Shih-Chuan Gou, Giacomo Lamporesi, Simone Donadello, Franco Dalfovo, Gabriele Ferrari, Nikolaos Proukakis We report our numerical findings on the statistics and dynamics of spontaneous formation of defects during a gradual quench of an initially thermal atomic gas to below the critical temperature. Our study focuses on the Trento experiments [Nat.~Phys.~9,~656~(2013) and Phys.~Rev.~Lett.~113,~065302~(2014)], which showed the appearance of a few long-lived solitonic vortices [Phys.~Rev.~A~65,~043612~(2002)], as measured sometime after the system crossed the transition temperature. Our simulations access both the initial quench-driven turbulent regime where a large number of randomly-distributed defects emerge during the condensation, and the subsequent relaxation of such defects towards a few long-lived solitonic vortices, similar to those observed experimentally. We analyze our findings in the context of the Kibble-Zurek scaling law [J.~Phys.~A~9,~1387~(1976) and Nature~317,~505~(1985)], highlighting various subtle issues associated with this dynamical process, and characterize the transition through the critical region, by studying the corresponding first-order spatial correlation functions. Our simulations are based on the 3D stochastic projected Gross-Pitaevskii equation subjected to a linear temperature and chemical potential quench~[arXiv:1408.08 (Phys.~Rev.~A in press)]. [Preview Abstract] |
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Q1.00100: Adiabatic and Non-adiabatic quenches in a Spin-1 Bose Einstein Condensate Matthew Boguslawski, Bharath Hebbe Madhusudhana, Martin Anquez, Bryce Robbins, Maryrose Barrios, Thai Hoang, Michael Chapman A quantum phase transition (QPT) is observed in a wide range of phenomena. We have studied the dynamics of a spin-1 ferromagnetic Bose-Einstein condensate for both adiabatic and non-adiabatic quenches through a QPT. At the quantum critical point (QCP), finite size effects lead to a non-zero gap, which makes an adiabatic quench possible through the QPT. We experimentally demonstrate such a quench, which is forbidden at the mean field level. For faster quenches through the QCP, the vanishing energy gap causes the reaction timescale of the system to diverge, preventing the system from adiabatically following the ground state. We measure the temporal evolution of the spin populations for different quench speeds and determine the exponents characterizing the scaling of the onset of excitations, which are in good agreement with the predictions of Kibble-Zurek mechanism [1]. \\ $^1$ M. Anquez et al, arXiv:1512.06914 [Preview Abstract] |
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Q1.00101: Dynamical gauge effects in an open quantum network Jianshi Zhao, Craig Price, Qi Liu, Nathan Gemelke We describe new experimental techniques for simulation of high-energy field theories based on an analogy between open thermodynamic systems and effective dynamical gauge-fields following $SU(2)\times U(1)$ Yang-Mills models. By coupling near-resonant laser-modes to atoms moving in a disordered optical environment, we create an open system which exhibits a non-equilibrium phase transition between two steady-state behaviors, exhibiting scale-invariant behavior near the transition. By measuring transport of atoms through the disordered network, we observe two distinct scaling behaviors, corresponding to the classical and quantum limits for the dynamical gauge field. This behavior is loosely analogous to dynamical gauge effects in quantum chromodynamics, and can mapped onto generalized open problems in theoretical understanding of quantized non-Abelian gauge theories. Additional, the scaling behavior can be understood from the geometric structure of the gauge potential and linked to the measure of information in the local disordered potential, reflecting an underlying holographic principle. [Preview Abstract] |
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Q1.00102: Cooling and Non-equilibrium Motion of an Ultracold Atomic Gas using Synthetic Thermal Bodies Craig Price, Qi Liu, Jianshi Zhao, Nathan Gemelke We describe the non-equilibrium behavior of atomic gases immersed in synthetic thermal environments created by engineered statistical reservoirs of spatio-temporally disordered light. By dynamically modulating the modal distribution of an optical fiber carrying far off-resonant light, optical dipole potentials are created for $^{87}$Rb atoms with specified spatial and temporal spectra. Additional coupling to thermal reserviors defined by time-dependent radio-frequency-induced hyperfine spin-couplings offers a wide range of control over thermal excitations. By controlling the statistical properties of the baths, diffusive motion can be tailored in real-time, and transport can be controlled even at ultra-cold temperatures below the photon recoil. The use of an effectively statistical classical body opens new avenues for quantum simulation, and offers opportunities for study of systems governed by effective hamiltonians which are \emp{themselves} poised near critical points, and the simulation of effectively many-body systems through the non-equilibrium motion of single atoms. [Preview Abstract] |
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Q1.00103: DYNAMICS OF COLD ATOMS IN OPTICAL LATTICES |
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Q1.00104: Regions of tunneling dynamics for few bosons in an optical lattice subjected to a quench of the imposed harmonic trap Simeon Mistakidis, Georgios Koutentakis, Peter Schmelcher Recent experimental advances have introduced an interplay in the trapping length scales of the lattice and the harmonic confinement. This fact motivates the investigation to prepare atomic gases at certain quantum states by utilizing a composite atomic trap consisting of a lattice potential that is embedded inside an overlying harmonic trap. In the present work, we examine how frequency modulations of the overlying harmonic trap stimulate the dynamics of an 1D few-boson gas. The gas is initially prepared at a highly confined state, and the subsequent dynamics induced by a quench of the harmonic trap frequency to a lower value is examined. It is shown that a non-interacting gas always diffuses to the outer sites. In contrast the response of the interacting system is more involved and is dominated by a resonance, which is induced by the bifurcation of the low-lying eigenstates. Our study reveals that the position of the resonance depends both on the atom number and the interaction coupling, manifesting its many body nature. The corresponding mean field treatment as well as the single-band approximation have been found to be inadequate for the description of the tunneling dynamics in the interacting case. [Preview Abstract] |
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Q1.00105: Control dynamics of interaction quenched ultracold bosons in periodically driven lattices Simeon Mistakidis, Peter Schmelcher The out-of-equilibrium dynamics of ultracold bosons following an interaction quench upon a periodically driven optical lattice is investigated. It is shown that an interaction quench triggers the inter-well tunneling dynamics, while for the intra-well dynamics breathing and cradle-like processes can be generated. In particular, the occurrence of a resonance between the cradle and tunneling modes is revealed. On the other hand, the employed periodic driving enforces the bosons in the mirror wells to oscillate out-of-phase and to exhibit a dipole mode, while in the central well the cloud experiences a breathing mode. The dynamical behaviour of the system is investigated with respect to the driving frequency revealing a resonant behaviour of the intra-well dynamics. To drive the system in a highly non-equilibrium state an interaction quench upon the driving is performed giving rise to admixtures of excitations in the outer wells, an enhanced breathing in the center and an amplification of the tunneling dynamics. As a result of the quench the system experiences multiple resonances between the inter- and intra-well dynamics at different quench amplitudes. [Preview Abstract] |
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Q1.00106: Lattice gas dynamics under continuous measurement Yogesh Sharad Patil, Hil F. H. Cheung, Ivaylo S. Madjarov, Huiyao Y. Chen, Mukund Vengalattore The act of measurement has a profound consequences quantum systems. While this backaction has so far been discussed as being a limitation on the precision of measurements, it is increasingly being appreciated that measurement backaction is a powerful and versatile means of quantum control. We have previously demonstrated that backaction from position measurement can modify the coherent tunneling rate of a lattice gas through the Quantum Zeno effect [1]. Here, we show how spatially designed measurement landscapes can be used to realize entropy segregation in lattice gases. This presents an alternate path to the longstanding challenge of realizing lattice gases with sufficiently low entropy to access regimes of correlated quantum behavior such as N\'{e}el ordered states. \\[4pt] [1] Y. S. Patil, S. Chakram and M. Vengalattore, Phys. Rev. Lett. 115, 140402 (2015) [Preview Abstract] |
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Q1.00107: Visualization of 3D optical lattices Hoseong Lee, James Clemens We describe the visualization of 3D optical lattices based on Sisyphus cooling implemented with open source software. We plot the adiabatic light shift potentials found by diagonalizing the effective Hamiltonian for the light shift operator. Our program incorporates a variety of atomic ground state configurations with total angular momentum ranging from $j=1/2$ to $j=4$ and a variety of laser beam configurations including the two-beam lin$\perp$lin configuration, the four-beam umbrella configuration, and four beams propagating in two orthogonal planes. In addition to visualizing the lattice the program also evaluates lattice parameters such as the oscillation frequency for atoms trapped deep in the wells. The program is intended to help guide experimental implementations of optical lattices. [Preview Abstract] |
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Q1.00108: A Cold-Strontium Laser in the Superradiant Crossover Regime Matthew Norcia, James Thompson We demonstrate and study a laser based on the 7.5 kHz linewidth dipole forbidden $^3 $P$_1$ to $^1 $S$_0$ transition in laser-cooled and tightly confined $^{88}$Sr. We can operate this laser in the bad-cavity or superradiant regime, where coherence is primarily stored in the atoms, or continuously tune to the more conventional good-cavity regime, where coherence is primarily stored in the light field. We show that the cold-atom gain medium can be repumped to achieve quasi steady-state lasing. We also demonstrate up to an order of magnitude suppression in the sensitivity of laser frequency to changes in cavity length, verifying a key feature of proposed narrow linewidth lasers based on dipole-forbidden transitions in alkaline earth atoms. [Preview Abstract] |
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Q1.00109: Atom optics simulator of lattice transport phenomena Fangzhao An, Eric Meier, Bryce Gadway We report on a novel scheme for studying lattice transport phenomena, based on the controlled momentum-space dynamics of ultracold atomic matter waves. In the effective tight binding models that can be simulated, we demonstrate that this technique allows for a local and time-dependent control over all system parameters, and additionally allows for single-site resolved detection of atomic populations. We demonstrate full control over site-to-site off-diagonal tunneling elements (amplitude and phase) and diagonal site-energies, through the observation of continuous time quantum walks, Bloch oscillations, and negative tunneling. These capabilities open up new prospects in the experimental study of disordered and topological systems. [Preview Abstract] |
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Q1.00110: Dynamical Quasicondensation of Hard-Core Bosons at Finite Momenta: A Non-equilibrium Condensation Effect Fabian Heidrich-Meisner, L. Vidmar, J.P. Ronzheimer, S. Hodgman, M. Schreiber, S. Braun, S. Langer, I. Bloch, U. Schneider Long-range order in quantum many-body systems is usually associated with equilibrium situations. Here, we experimentally investigate the quasicondensation of strongly interacting bosons at finite momenta in a far-from-equilibrium case [1]. We prepare an inhomogeneous initial state consisting of one-dimensional Mott insulators in the center of otherwise empty one-dimensional chains in an optical lattice with a lattice constant $d$. After suddenly quenching the trapping potential to zero, we observe the onset of coherence in spontaneously forming quasicondensates in the lattice. Remarkably, the emerging phase order differs from the ground-state order and is characterized by peaks at finite momenta $\pm(\pi/2)(\hbar/d)$ in the momentum distribution function. [1] Vidmar et al., Phys. Rev. Lett. 115, 175301 (2015) [Preview Abstract] |
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Q1.00111: Collective non-equilibrium spin exchange in cold alkaline-earth atomic clocks Oscar Leonardo Acevedo, Ana Maria Rey Alkaline-earth atomic (AEA) clocks have recently been shown to be reliable simulators of two-orbital $SU(N)$ quantum magnetism. In this work, we study the non-equilibrium spin exchange dynamics during the clock interrogation of AEAs confined in a deep one-dimensional optical lattice and prepared in two nuclear levels. The two clock states act as an orbital degree of freedom. Every site in the lattice can be thought as populated by a frozen set of vibrational modes collectively interacting via predominantly $p$-wave collisions. Due to the exchange coupling, orbital state transfer between atoms with different nuclear states is expected to happen. At the mean field level, we observe that in addition to the expected suppression of population transfer in the presence of a large magnetic field, that makes the single particle levels off-resonance, there is also an interaction induced suppression for initial orbital population imbalance. This suppression resembles the macroscopic self-trapping mechanism seen in bosonic systems. However, by performing exact numerical solutions and also by using the so-called Truncated Wigner Approximation, we show that quantum correlations can significantly modify the mean field suppression. Our predictions should be testable in optical clock experiments. [Preview Abstract] |
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Q1.00112: Defect-free atom arrays on demand Harry Levine, Hannes Bernien, Alex Keesling, Eric Anschuetz, Crystal Senko, Vladan Vuletic, Markus Greiner, Manuel Endres, Mikhail Lukin Arrays of neutral, trapped atoms have proven to be an extraordinary platform for studying quantum many-body physics and implementing quantum information protocols. Conventional approaches to generate such arrays rely on loading atoms into optical lattices and require elaborate experimental control. An alternative, simpler approach is to load atoms into individual optical tweezers. However, the probabilistic nature of the loading process limits the size of the arrays to small numbers of atoms. Here we present a new method for assembling defect-free arrays of large numbers of atoms. Our technique makes use of an array of tightly focused optical tweezers generated by an acousto-optic deflector. The positions of the traps can be dynamically reconfigured on a sub-millisecond timescale. With single-site resolved fluorescence imaging, we can identify defects in the atom array caused by the probabilistic loading process and rearrange the trap positions in response. This will enable us to generate defect-free atom arrays on demand. We discuss our latest results towards reaching this goal along with schemes to implement long-range interactions between atoms in the array. [Preview Abstract] |
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Q1.00113: Exploring the Hubbard model: the interplay of geometry and interactions R\'emi Desbuquois, Michael Messer, Thomas Uehlinger, Gregor Jotzu, Frederik G\"org, Daniel Greif, Sebastian Huber, Tilman Esslinger The nature of the ground state of many-body systems not only depends on the relative strength of kinetic and interaction energies, but also on the geometry imposed by the Hamiltonian. We show here two different experiments performed with ultracold fermions, where the geometry of the optical lattice strongly influences the many-body state. In the Ionic Hubbard model, a new energy scale associated with the breaking of the inversion symmetry of the lattice can be tuned to shift from a Mott insulating to a band insulating state. In the spin sector as well, the geometry of the lattice also plays an important role. Even above the transition temperature, the influence of the lattice geometry is revealed by nearest-neighbour (NN) magnetic correlations, and provides key insights on their formation. [Preview Abstract] |
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Q1.00114: Probing Fermi-Hubbard physics with local spin excitations W. Morong, W. Xu, B. DeMarco The Fermi-Hubbard model is a minimal model for a strongly correlated material. Despite decades of studies, there are many outstanding questions relating to transport properties of this model, which ultracold Fermi gases in optical lattices are well suited to address. We propose a new approach to transport measurements in this system that utilizes tightly focused Raman beams to create a spatially localized spin imbalance. Monitoring the reequilibration of this imbalance in real time and real space will make it possible to directly measure spin diffusion and relaxation rates, providing a flexible tool to study transport in a variety of phases. This will open up a new avenue of investigation into strongly correlated ultracold gases that complements existing measurement techniques in momentum space. We describe our proposal for this method and current progress towards its implementation. We acknowledge funding from NSF grant PHY 15-05468 and ARO grant W911NF-12-1-0462. [Preview Abstract] |
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Q1.00115: Cooling fermions in optical lattices by faster entropy redistribution Rafael P Teles, Tsung-Lin Yang, Thereza Paiva, Richard T. Scalettar, Stefan S. Natu, Randall G. Hulet, Kaden R. A. Hazzard Lower entropy for fermions in optical lattices would unlock new quantum phases, including antiferromagnetism and potentially superconductivity. We propose a method to cool these systems at temperatures where conventional methods fail: slowly turning on a tightly focused optical potential transports entropy from the Mott insulator to a metallic entropy reservoir formed along the beam. Our scheme places the entropy reservoir close to the targeted cooling region, which allows entropy redistribution to be effective at lower temperatures than in prior proposals. Furthermore we require only a straightforwardly-applied Gaussian potential. We compute the temperatures achieved with this scheme using an analytic $T\gg t$ approximation and, for low $T$, determinantal quantum Monte Carlo. We optimize the waist and depth of the focused beam, and we find that repulsive potentials cool better than attractive ones. We estimate that the time required for entropy transport under nearly adiabatic conditions at these low temperatures is compatible with the system lifetime. Finally, we explore further improvements to cooling enabled by sophisticated potential engineering, e.g. using a spatial light modulator. [Preview Abstract] |
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Q1.00116: Diffusion dynamics in the disordered Bose Hubbard model Laura Wadleigh, Philip Russ, Brian DeMarco We explore the dynamics of diffusion for out-of-equilibrium superfluid, Mott insulator, and Bose glass states using an atomic realization of the disordered Bose Hubbard (DBH) model. Dynamics in strongly correlated systems, especially far from equilibrium, are not well understood. The introduction of disorder further complicates these systems. We realize the DBH model---which has been central to our understanding of quantum phase transitions in disordered systems---using ultracold Rubidium-87 atoms trapped in a cubic disordered optical lattice. By tightly focusing a beam into the center of the gas, we create a hole in the atomic density profile. We achieve Mott insulator, superfluid, or Bose glass states by varying the interaction and disorder strength, and measure the time evolution of the density profile after removing the central barrier. This allows us to infer diffusion rates from the velocities at the edge of the hole and to look for signatures of superfluid puddles in the Bose glass state. [Preview Abstract] |
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Q1.00117: Relaxation Dynamics Of Bose-Fermi Doublons In Optical Lattices Arghavan Safavi-Naini, Martin G\"arttner, Johannes Schachenmayer, Michael L. Wall, Jacob P. Covey, Steven A. Moses, Matthew T. Miecnikowski, Zhengkun Fu, Ana Maria Rey, Deborah S. Jin, Jun Ye Motivated by a recent experiment at JILA [1] we investigate the out-of-equilibrium dynamics of a dilute Fermi-Bose mixture, starting from a well-defined initial state, where each lattice site is either empty or occupied by a Bose-Fermi doublon. Utilizing analytical techniques and numerical simulations using the t-DRMG method, we identify the leading relaxation mechanisms of the doublons. At short times strong interactions tend to hold the doublons together, as previously reported in similar type of experiments made with identical bosons or two component fermions. Since the fermions feel a much shallower lattice than the bosons, the bosons can be visualized as random localization centers for the fermions. However, at longer times the boson tunneling cannot be ignored and additional decay channels unique to Bose-Fermi mixtures become relevant. While cluster expansion allows us to characterize the short time dynamics for dilute arrays, the long time relaxation dynamics at higher densities is strongly correlated. In this regime exact numerical techniques are employed.\\ [1] J. P. Covey, {\it et. al.}, arXiv:1511.02225. [Preview Abstract] |
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Q1.00118: Resolved Sideband Spectroscopy and Cooling of Strontium in a 532-nm Optical Lattice James Aman, Joshua Hill, T. C. Killian Resolved sideband cooling is a powerful and well established technique for driving ultracold atoms in optical lattices to the motional ground state of individual lattice sites. Here we present spectroscopy of the narrow $5s^2\;^1\mathrm{S}_0\rightarrow5s5p\;^3\mathrm{P}_1$ transition for neutral strontium-84 in a 532nm optical lattice. Resolved red- and blue-detuned sidebands are observed corresponding to changes in the motional state in the lattice sites. Driving the red sideband, we demonstrate cooling into the ground state, which increases the initial phase-space density before forced evaporative cooling. This is a promising technique for improving the production of strontium quantum degenerate gases. [Preview Abstract] |
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Q1.00119: Characterization of dilute optical lattices using pump-probe spectroscopy and photon correlation measurements Ethan Clements, Preston Ross, Anthony Rapp, Hong Cai, Alex Reigle, Eli Schlonsky, Hoseong Lee, James Clemens, Samir Bali We experimentally investigate optical lattices using three different methods: pump-probe spectroscopy of vibrational energy levels, photon correlation of light scattered by cold atoms, and fluorescence imaging. Photon correlations of the scattered light can be used to measure lattice dwell times and crossover times between lattice sites [C. Jurczak~et al.,~\textit{Phys. Rev. Lett.}~\textbf{77}, 1727 (1996)]. From this information we can derive the diffusion constant which can then be compared to direct measurement via fluorescence imaging. Furthermore, by Fourier transforming the time delayed photon correlations we can obtain the intensity spectrum which can be compared directly to pump-probe spectroscopy of the vibrational energy levels. We plan to carefully study situations in which the atomic transport properties deviate from Boltzman Gibbs statistics. [Preview Abstract] |
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Q1.00120: Thermalization dynamics in a quenched many-body state Adam Kaufman, Philipp Preiss, Eric Tai, Alex Lukin, Matthew Rispoli, Robert Schittko, Markus Greiner Quantum and classical many-body systems appear to have disparate behavior due to the different mechanisms that govern their evolution. The dynamics of a classical many-body system equilibrate to maximally entropic states and quickly re-thermalize when perturbed. The assumptions of ergodicity and unbiased configurations lead to a successful framework of describing classical systems by a sampling of thermal ensembles that are blind to the system's microscopic details. By contrast, an isolated quantum many-body system is governed by unitary evolution: the system retains memory of past dynamics and constant global entropy. However, even with differing characteristics, the long-term behavior for local observables in quenched, non-integrable quantum systems are often well described by the same thermal framework. We explore the onset of this convergence in a many-body system of bosonic atoms in an optical lattice. Our system's finite size allows us to verify full state purity and measure local observables. We observe rapid growth and saturation of the entanglement entropy with constant global purity. The combination of global purity and thermalized local observables agree with the Eigenstate Thermalization Hypothesis in the presence of a near-volume law in the entanglement entropy. [Preview Abstract] |
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Q1.00121: Cold atom quantum emulation with ultracold lithium and strontium Shankari Rajagopal, Ruwan Senaratne, Zachary Geiger, Kurt Fujiwara, Kevin Singh, David Weld We discuss progress towards cold atom quantum emulation of nonequilibrium dynamics in optical lattices, focusing on quasiperiodic and strongly-driven systems using lithium and strontium.~Tunable interactions in lithium grant access to an added dimension of parameter space to explore in such systems, which could uncover rich physics.~The high nuclear spin of fermionic strontium presents opportunities to study interactions in spin-dependent lattices and~develop novel cooling techniques.~We also describe construction of a single-site resolution imaging chamber for strontium, including a novel bio-inspired imaging scheme that makes use of a dark metastable state. [Preview Abstract] |
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Q1.00122: QUANTUM PHASES AND ATOMS IN OPTICAL LATTICES |
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Q1.00123: Observation of a superradiant Mott insulator in the Dicke-Hubbard model Jens Klinder, Hans Ke{\ss}ler, Christoph Georges, Jose Vargas, Andreas Hemmerich It is well known that the bosonic Hubbard model possesses a Mott insulator phase. Likewise, it is known that the Dicke model exhibits a self-organized superradiant phase. By implementing an optical lattice inside of a high-finesse optical cavity, both models are merged such that an extended Hubbard model with cavity-mediated infinite range interactions arises. In addition to a normal superfluid phase, two superradiant phases are found, one of them coherent and hence superfluid and one incoherent Mott insulating [1]. \\ [1] J. Klinder et al., Physical Review Letters 115, 230403 (2015) [Preview Abstract] |
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Q1.00124: Measurement-induced control with a nondestructive quantum gas microscope Minwoo Jung, Ivaylo S. Madjarov, Jacob Rabinowitz, Zoe Wellner, Huiyao Y. Chen, Hil F. H. Cheung, Yogesh Sharad Patil, Mukund Vengalattore The physics of ultracold lattice gases has expanded from understanding Hubbard models to a much broader set of questions of nonequilibrium quantum dynamics, quantum thermodynamics, manybody entanglement, etc. These studies are increasingly being enabled by the advent of quantum gas microscopy, i.e. acquiring in-situ real space information, that is gaining prominence as a very powerful technique to study lattice gases. Nonetheless, the realization of fascinating correlated manybody states requires prohibitively low temperatures and entropies, far below what can be accessed through conventional evaporative cooling. The combination of quantum gas microscopy and measurement based quantum control offers an alternate route to state preparation of lattice gases in regimes of strong correlations. In this poster, we present our ongoing work on using site resolved imaging for the preparation of correlated manybody phases. [Preview Abstract] |
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Q1.00125: Signatures of a first-order phase transition from competing short- and infinite-range interactions Lorenz Hruby, Renate Landig, Nishant Dogra, Manuele Landini, Rafael Mottl, Tobias Donner, Tilman Esslinger We experimentally realize a two dimensional bosonic lattice model with competing short- and infinite-range interactions. We map out the phase diagram consisting of a superfluid, a supersolid, a Mott insulator and a charge density wave phase. When probing the phase transition between the Mott insulator and the charge density wave in real-time, we discover a behavior characteristic of a first order phase transition. Short-range interactions in our system are controlled via an optical square lattice, while the infinite-range interaction potential stems from the coupling of the external degree of freedom of the atoms to the single mode of an optical cavity. [Preview Abstract] |
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Q1.00126: Detection of the many-body topological invariant in a driven, dissipative spin model Michael Fleischhauer, Dominik Linzner Systems with topological order have attracted a growing interest in recent years as they have been associated with exotic, strongly correlated quantum states and can possess protected edge states. Engineering dissipative driven quantum systems with a topologically ordered stationary state could circumvent the problem of preparing topological states as encountered in weakly gapped closed systems. Moreover, the stationary state of an open system is an attractor of the dynamics which ensures additional robustness against fluctuations, decoherence and even particle losses. While topological states in closed systems are by now reasonably well understood, at least if non-interacting systems are considered, the concept of topology in open systems is still in its infancy. We here propose and discuss a conceptual detection scheme for topological properties of a one-dimensional dissipative spin chain by coupling it to a well understood closed system. The presence of topological order of the non-gaussian steady state in the dissipative spin chain induces a non-trivial topology in the closed system resulting in a quantized charge pump. Using this we are able to introduce a topological invariant with a clear physical meaning. [Preview Abstract] |
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Q1.00127: An ytterbium quantum gas microscope with narrow-line laser cooling Ryuta Yamamoto, Jun Kobayashi, Kohei Kato, Takuma Kuno, Yuto Sakura, Yoshiro Takahashi Single-site resolved imaging of alkali metal in a two-dimensional optical lattice (Quantum Gas Microscope, QGM) is realized [1] and enables us to directly observe the in-trap atom distribution and study quantum dynamics with single-site resolution [2]. It is important to extend the applicability of a QGM technique to two-electron atoms such as alkaline-earth metal and ytterbium (Yb) atoms because it opens up many unique possibilities for the quantum simulation and quantum information research. Differently from the first report on single-site resolved imaging of Yb atoms with a long lattice constant 544 nm and a short lifetime of 62 $\mu$s without cooling [3], we successfully realize the QGM of Yb atoms with a short lattice constant 266 nm, in which we achieve a high-resolution imaging with a low temperature of 7.4 $\mu$K and a long lifetime of 7 s by narrow-line laser cooling [4]. The high detection fidelity of 87(2)$\%$ is achieved in our method. In addition, we are developing a different mode of QGM for Yb atoms. [1] W. S. Bakr et al., Nature 455, 204 (2009), J. F. Sherson et al., Nature 467, 68 (2010) [2] T. Fukuhara et al., Nat. Phys. 9, 235 (2013) [3] M. Miranda et al., PRA 91, 063414 (2015) [4] R. Yamamoto et al., arXiv:1509.03233 (to appear in NJP) [Preview Abstract] |
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Q1.00128: Reservoir-induced phase transitions in bosonic lattice systems Matthias Moos, Michael Fleischhauer We discuss bosonic lattice systems that are coupled to local reservoirs and driven to non-equilibrium steady states. By engineering the reservoirs we can tailor different phases of steady states that are separated by critical points, where the criticality is defined as a divergence of the correlation length. Free bosonic lattice systems with a linear coupling to reservoirs always show a dynamical instability accompanying the criticality. We investigate interacting many-body systems as well as nonlinear coupling to reservoirs, as, for instance, by saturated gain processes. To this end we employ mean-field approximations as well as numerical methods to derive correlations and critical exponents of the reservoir-induced phase transitions. [Preview Abstract] |
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Q1.00129: Robust Supersolidity in the V$_{\mathrm{1}}$-V$_{\mathrm{2}}$ Extended Bose-Hubbard Model Nicole Greene, Jedediah Pixley Motivated by ultra-cold atomic gases with long-range interactions in an optical lattice we study the effects of the next-nearest neighbor interaction on the extended Bose-Hubbard model on a square lattice. Using the variational Gutzwiller approach with a four-site unit cell we determine the ground state phase diagrams as a function of the model parameters. We focus on the interplay of each interaction between the nearest neighbor (V$_{\mathrm{1}})$, the next-nearest neighbor (V$_{\mathrm{2}})$, and the onsite repulsion (U). We find various super-solid phases that can be described by one of the ordering wave-vectors ($\pi $, 0), (0, $\pi )$, and ($\pi $, $\pi )$. In the limits V$_{\mathrm{1,\thinspace }}$V$_{\mathrm{2}}$ \textless U and V$_{\mathrm{1,\thinspace }}$V$_{\mathrm{2}}$ \textgreater U we find phases reminiscent of the limit V$_{\mathrm{2\thinspace }}=$ 0 but with a richer super solid structure. For V$_{\mathrm{1}}$ \textless U \textless V$_{\mathrm{2}}$ we find a qualitatively new super solid phase that is quite stable and occupies a large region of the phase diagram. For sufficiently strong interactions we find various Mott and charge density wave (CDW) insulating phases that can be understood in the classical limit (i.e. no inter-site tunneling). We characterize the nature of each quantum phase transition between Mott/CDW to super-solid to superfluid at the mean field level. [Preview Abstract] |
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Q1.00130: Quantum phases and dynamics of bosonic atoms trapped in a single-mode optical cavity Bhuvanesh Sundar, Erich Mueller Motivated by experiments performed by R. Landig et al (arXiv:1511.00007), we theoretically explore the behavior of bosonic atoms trapped in a single-mode cavity in the presence of a two-dimensional optical lattice. As explained by arXiv:1511.00007, Rayleigh scattering of light from the lattice-inducing beams into the cavity produces infinite-range cavity-mediated interactions between the atoms, leading to competition between superfluid, supersolid, Mott insulating and charge density wave phases. We calculate the phase diagram for a uniform trap using a variation of the Gutzwiller Ansatz. We also calculate the spatial distribution of the different phases in the gas in the presence of a harmonic trap. We explore hysteretic behavior when parameters of the system are changed. [Preview Abstract] |
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Q1.00131: Fermionic Many-Body States Under the Microscope Anton Mazurenko, Daniel Greif, Maxwell F. Parsons, Christie S. Chiu, Sebastian Blatt, Florian Huber, Geoffrey Ji, Markus Greiner We demonstrate the site-resolved observation of two component, fermionic Mott insulators, band insulators and metals of ultracold $^6$Li in a single layer of a three-dimensional optical lattice. Site-resolved imaging enables measurements of local observables, including the local occupation variance. A comparison with predictions of the high temperature series expansion of the Fermi-Hubbard model is consistent with thermally equilibrated samples, with local entropies as low as $0.7k_{\mathrm{B}}$ per particle in the Mott insulator, and $0.5k_{\mathrm{B}}$ per particle in the band insulator. The phase diagram in the Mott regime is studied, exploiting the fact that the underlying harmonic potential enables measurements across a wide range of chemical potentials in a single experimental shot. Our experiments provide a starting point for implementing entropy redistribution based cooling schemes. Furthermore, we report on our recent progress towards measuring site-resolved spin correlations for low temperature samples, opening the door for studying many-body systems in theoretically intractable regimes. [Preview Abstract] |
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Q1.00132: Measuring entanglement entropy in a quantum many-body system Matthew Rispoli, Philipp Preiss, Eric Tai, Alex Lukin, Robert Schittko, Adam Kaufman, Ruichao Ma, Rajibul Islam, Markus Greiner The presence of large-scale entanglement is a defining characteristic of exotic quantum phases of matter. It describes non-local correlations between quantum objects, and is at the heart of quantum information sciences. However, measuring entanglement remains a challenge. This is especially true in systems of interacting delocalized particles, for which a direct experimental measurement of spatial entanglement has been elusive. Here we measure entanglement in such a system of itinerant particles using quantum interference of many-body twins. We demonstrate a novel approach to the measurement of entanglement entropy of any bosonic system, using a quantum gas microscope with tailored potential landscapes. This protocol enables us to directly measure quantum purity, R\'{e}nyi entanglement entropy, and mutual information. In general, these experiments exemplify a method enabling the measurement and characterization of quantum phase transitions and in particular would be apt for studying systems such as magnetic ordering within the quantum Ising model. [Preview Abstract] |
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Q1.00133: Implementation of a Quantum Gas Microscope for Fermions Rhys Anderson, Vijin Venu, Peihang Xu, Graham Edge, Dylan Jervis, Dave McKay, Ryan Day, Stefan Trotzky, Joseph Thywissen We discuss the technical development of a quantum gas microscope for $^{40}$K. We load a degenerate Fermi gas into a cubic optical lattice of period 527\,nm, which is capable of simulating the Fermi-Hubbard model. The sample is prepared in UHV below a 200\,$\mu$m-thick sapphire window, at the focus of a 5\,mm focal length objective located outside the chamber. To isolate a single plane for imaging, we perform spectroscopic selection in a 210\,G/cm gradient, which separates the hyperfine transition frequencies of adjacent vertical planes by 28\,kHz. We actively suppress variations in the transition frequency due to fluctuations in the ambient magnetic field to less than 3\,kHz via a feed-forward stabilization system. EIT cooling on the 770.1\,nm D$_1$ transition facilitates fluorescence imaging of our atoms with long exposures. Atoms remain pinned in a 200\,$\mu$K-deep lattice, with a $1/e$ lifetime of $67(9)\,\rm{s}$, while scattering $\sim 10^3$ photons per second. Collection of fluorescence photons onto an EMCCD via a 0.8\,NA objective results in a PSF of FHWM 600\,nm, and 94(2)\% of atoms identified in the first frame remain pinned in successive frames, enabling reconstruction of the lattice-site occupancy. We present ongoing progress in obtaining lower entropy samples. [Preview Abstract] |
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Q1.00134: Geometrically representing spin correlations Ian G. White, Anthony Mirasola, Jacob Hollingsworth, Rick Mukherjee, Kaden R. A. Hazzard We develop a general method to visualize spin correlations, and we demonstrate its usefulness in ultracold matter from fermions in lattices to trapped ions and ultracold molecules. Correlations are of fundamental interest in many-body physics: they characterize phases in condensed matter and AMO, and are required for quantum sensing and computing. However, it is often difficult to understand even the simplest correlations -- for example between two spin-1/2's -- directly from the components $C^{ab}=\langle S_1^a S_2^b\rangle - \langle S_1^a \rangle \langle S_2^b \rangle $ for $\{a,b\}\in \{x,y,z\}$. Not only are the nine independent $C^{ab}$ unwieldy, but considering the components also obscures the natural geometric structure. For example, simple spin rotations lead to complex transformations among the nine $C^{ab}$. We provide a one-to-one map between the spin correlations and certain three-dimensional objects, analogous to the map between single spins and Bloch vectors. This object makes the geometric structure of the correlations manifest. Moreover, much as one can reason geometrically about dynamics using a Bloch vector -- e.g. a magnetic field causes it to precess and dephasing causes it to shrink -- we show that analogous reasoning holds for our visualization method. [Preview Abstract] |
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Q1.00135: Manipulation, control and characterization of a bichromatic lattice Tsz-Him Leung, Claire Thomas, Thomas Barter, Masayuki Okano, Dan Stamper-Kurn Ultracold atoms in optical lattices provide a clean and highly controllable platform to study many-body physics. Different optical lattices have been realized to study models in condensed matter physics. Kagame lattice has the feature of geometric frustration in both the orbital and spin degree of freedom, giving rise to possible exotic phases of matter and dynamics in flat band that have not been well studied. For the purpose of creating and stabilizing the optical Kagame lattice. We have developed experimental schemes to manipulate and characterize a bichromatic lattice. The relevant schemes, as well as recent works done with such a lattice, will be presented. [Preview Abstract] |
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Q1.00136: Quantum Gas Microscope for Fermionic Atoms Melih Okan, Lawrence Cheuk, Matthew Nichols, Katherine Lawrence, Hao Zhang, Martin Zwierlein Strongly interacting fermions define the properties of complex matter throughout nature, from atomic nuclei and modern solid state materials to neutron stars. Ultracold atomic Fermi gases have emerged as a pristine platform for the study of many-fermion systems. In this poster we demonstrate the realization of a quantum gas microscope for fermionic $^{\mathrm{40}}$K atoms trapped in an optical lattice and the recent experiments which allows one to probe strongly correlated fermions at the single atom level. We combine 3D Raman sideband cooling with high- resolution optics to simultaneously cool and image individual atoms with single lattice site resolution at a detection fidelity above 95{\%}. The imaging process leaves the atoms predominantly in the 3D motional ground state of their respective lattice sites, inviting the implementation of a Maxwell's demon to assemble low-entropy many-body states. Single-site resolved imaging of fermions enables the direct observation of magnetic order, time resolved measurements of the spread of particle correlations, and the detection of many-fermion entanglement. [Preview Abstract] |
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Q1.00137: SYNTHETIC GUAGE FIELDS AND SPIN-ORBIT COUPLING IN COLD GASES Abstract APS TBD [Preview Abstract] |
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Q1.00138: Harmonically Trapped Atoms with Spin-Orbit Coupling Chuanzhou Zhu, Lin Dong, Han Pu We study harmonically trapped atoms subjected to an equal combination of Rashba and Dresselhaus spin-orbit coupling induced by Raman transition. We first examine the wave function and the degeneracy of the single-particle ground state, followed by a study of two weakly interacting bosons or fermions. For the two-particle ground state, we focus on the effects of the interaction on the degeneracy, the spin density profiles, and the density-density correlation functions. Finally we show how these studies help us to understand the many-body properties of the system. [Preview Abstract] |
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Q1.00139: Cavity-Induced Spin-Orbit Coupling in Cold Atoms Chuanzhou Zhu, Lin Dong, Han Pu We consider a single ultracold atom trapped inside a single-mode optical cavity, where a two-photon Raman process induces an effective coupling between atom's pseudo-spin and external center-of-mass (COM) motion. Without the COM motion, this system is described by the Jaynes-Cummings (JC) model. We show how the atomic COM motion dramatically modifies the predictions based on the JC model, and how the cavity photon field affects the properties of spin-orbit coupled system. We take a quantum Master equation approach to investigate the situation when the cavity pumping and decay are taken into account. [Preview Abstract] |
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Q1.00140: Explicitly correlated Gaussian basis set expansion approach for few-body systems with spin-orbit coupling Qingze Guan, Doerte Blume The explicit correlated Gaussian (ECG) basis set expansion approach is a variational approach that has been used in various areas, including molecular, nuclear, atomic, and chemical physics. In the world of cold atoms, e.g., the ECG approach has been used to calculate the eigenenergies and eigenstates of few-body systems governed by Efimov physics. Since the first experimental realization of synthesized gauge fields, few-body systems with spin-orbit coupling have attracted a great deal of attention. Here, the ECG approach is customized to few-body systems with both short-range interactions and spin-orbit couplings. Benchmark tests and a performance analysis will be presented. [Preview Abstract] |
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Q1.00141: Photonic Landau levels on cones Nathan Schine, Albert Ryou, Andrey Gromov, Ariel Sommer, Jonathan Simon We present the first experimental realization of a bulk magnetic field for optical photons. By using a non-planar ring resonator, we induce an image rotation on each round trip through the resonator. This results in a Coriolis/Lorentz force and a centrifugal anticonfining force, the latter of which is cancelled by mirror curvature. Using a digital micromirror device to control both amplitude and phase, we inject arbitrary optical modes into our resonator. Spatial- and energy- resolved spectroscopy tracks photonic eigenstates as residual trapping is reduced, and we observe photonic Landau levels as the eigenstates become degenerate. We show that there is a conical geometry of the resulting manifold for photon dynamics and present a measurement of the local density of states that is consistent with Landau levels on a cone. While our work already demonstrates an integer quantum Hall material composed of photons, we have ensured compatibility with strong photon-photon interactions, which will allow quantum optical studies of entanglement and correlation in manybody systems including fractional quantum Hall fluids. [Preview Abstract] |
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Q1.00142: A long-lived spin-orbit-coupled dipolar Fermi gas Yijun Tang, Nathaniel Burdick, Wil Kao, Benjamin Lev We report on the demonstration of spin-orbit coupling in a quantum degenerate dipolar Fermi gas of dysprosium. The $T/T_F = 0.4$ gas has a lifetime as large as 0.4 s under Raman dressing at densities exceeding $10^{13}$ cm$^{-3}$. The lifetime is limited not by spontaneous emission but by dipolar relaxation loss, and the effect of the dipolar interaction is also observed in the dephasing of Rabi oscillations. This spin-orbit-coupled dipolar gas will allow future studies of fermionic systems in the presence of synthetic gauge fields wherein long lifetimes are essential to observing collective effects. [Preview Abstract] |
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Q1.00143: Floquet-engineering topological and spin-dependent bands with interacting ultracold fermions Gregor Jotzu, Michael Messer, Frederik G\"{o}rg, Daniel Greif, Martin Lebrat, Thomas Uehlinger, R\'{e}mi Desbuquois, Tilman Esslinger Periodically driven quantum systems, when observed on time-scales longer than one modulation period, can be described by effective Floquet Hamiltonians that show qualitatively new features. Using a magnetic field gradient, we apply an oscillating force to ultracold fermions in an optical lattice. The resulting effective energy bands then become spin dependent, allowing for a tunable ratio of the effective mass for each internal state, also giving access to the regime where one spin is completely localized whilst the other remains itinerant. In a honeycomb lattice, circular modulation leads to the appearance of complex next-nearest neighbour tunnelling. This corresponds to a staggered magnetic flux in the lattice, allowing for the realisation of Haldane's model of a topological Chern insulator. When spin dependence is included, time-reversal symmetry can be restored giving rise to the Kane-Mele model. A crucial question is whether Floquet engineering can be extended to interacting systems, how the resulting Hamiltonians are modified, and whether the system thermalizes to a steady state. In particular, we study how heating in the system depends on the modulation and interaction parameters and identify regimes where it becomes negligible. [Preview Abstract] |
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Q1.00144: Physics with Ring Lattices Jacob Christ, Joshua Garner, Kunal Das Toroidal or ring-shaped lattices can be used to study a broad range of physical phenomena often with novel features due to the combination of two different kinds of periodicities - the lattice and the boundary condition. Such phenomena include, rotation sensing, nonlienear criticality and spin-squeezing and various topological and synthetic gauge structures. We examine several of these in the context of possible implementation in experiments with ultracold atoms. [Preview Abstract] |
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Q1.00145: Fourier Spectroscopy of a Spin-Orbit Coupled Bose Gas Ana Valdes-Curiel, Dimitris Trypogeorgos, Erin Marshall, Ian Spielman We generate spin-orbit coupling in a spin-1 Bose-Einstein condensate using Raman transitions. We are able to measure the system's spin and momentum dependent energy spectrum by looking at the time evolution of the three spin states. We drive transitions at different detunings from Raman resonance and extract the Fourier components of the time dependent evolution to reconstruct the spectrum. We also add a periodic modulation to one Raman field which allows us to have a fully tunable spin-orbit coupling dispersion that we can directly measure using our spectroscopy technique. [Preview Abstract] |
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Q1.00146: Topological quantum states of light in coupled microwave cavities John Owens, Aman LaChapelle, Ruichao Ma, Jonathan Simon, David Schuster We present a unique photonic platform to explore quantum many-body phenomena in coupled cavity arrays. We create tight binding lattices with arrays of evanescently coupled three-dimensional coaxial microwave cavities. Topologically non-trivial band structures are engineered by utilizing the chiral coupling of the cavity modes to ferrite spheres in a magnetic field. We develop robust, minimal methods to completely characterize the tight-binding Hamiltonian, including all onsite disorder, tunnel coupling, local dissipation and effective flux, using only spectroscopic measurement on specific sites. These efforts pave the way to realize low-disorder, long-coherence, topological tight binding models, where the many-body states can be spectroscopically driven and probed in temporally- and spatially- resolved measurements. Using techniques from circuit QED, effective onsite photon-photon interactions may be introduced by coupling to superconducting qubits. This will allow us to explore the interplay between topology and coherent interaction in these artificial strongly-correlated photonic quantum materials. [Preview Abstract] |
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Q1.00147: QUANTUM GASES WITH DIPOLAR INTERACTIONS |
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Q1.00148: Shielding ultracold dipolar molecular collisions with electric fields Goulven Qu{\'e}m{\'e}ner, John Bohn The prospect for shielding ultracold dipolar molecules from inelastic and reactive collisions is investigated [1]. Molecules placed in their first rotationally excited states are found to exhibit effective long-range repulsion for applied electric fields above a certain critical value. This repulsion can safely allow the molecules to scatter while reducing the risk of inelastic or chemically reactive collisions. Several molecular species of molecules of experimental interest such as NaRb, NaK, RbSr, SrF, BaF, and YO, are considered and all are shown to exhibit orders of magnitude suppression in quenching rates in a sufficiently strong laboratory electric field. [1] G. Qu{\'e}m{\'e}ner, J. L. Bohn, Phys. Rev. A 93, 012704 (2016). [Preview Abstract] |
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Q1.00149: An Erbium Quantum Gas Microscope with a Reflective Objective Aaron Krahn, Gregory Phelps, Anne Hebert, Susannah Dickerson, Markus Greiner Dipolar atoms present an exciting opportunity to extend previous quantum gas microscope (QGM) experiments to more complex systems influenced by long range, anisotropic interactions. We present on current progress toward the construction of a QGM for ultracold Erbium atoms in an optical lattice, including the development of a novel imaging system for single-site resolution. While most QGMs until now have typically utilized a high numerical aperture microscope objective, we discuss a reflective mirror alternative that offers an equally high NA (.9-.95), a comparable field of view (34 micrometers radial), and a larger working distance (25 millimeters) that keeps the atoms far from any surfaces. By operating in a Schmidt telescope configuration, this imaging system is well-suited both for collecting 401 nm imaging fluorescence and for the creation of an expandable lattice with a variety of associated lattice geometries. [Preview Abstract] |
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Q1.00150: Dipolar Physics in an Erbium Quantum Gas Microscope Anne Hebert, Aaron Krahn, Gregory Phelps, Susannah Dickerson, Markus Greiner Erbium offers exciting possibilities for extending the single-site imaging work of current quantum gas microscopes. With a magnetic dipole moment of 7$\mu_B$, the dipole-dipole interaction of erbium is 50 times that of alkali atoms. The long-range and anisotropic nature of the dipole interaction adds richness to the short-range interactions that dominate the physics of the ground-state alkali atoms commonly used in ultracold experiments today. Erbium has several abundant isotopes, giving the added flexibility of studying both bosonic and fermionic systems. We present proposed avenues of research for the dipolar microscope being developed, including studies of magnetism, the Einstein-de Haas effect, and quantum phase transitions with fractional filling factors. [Preview Abstract] |
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Q1.00151: COLD AND ULTRACOLD MOLECULES |
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Q1.00152: Trapping cold molecules and atoms: Simultaneous magnetic deceleration and trapping of cold molecular Oxygen with Lithium atoms Nitzan Akerman, Michael Karpov, Yair Segev, Natan Bibelink, Julia Narevicius, Edvardas Narevicius Cooling molecules to the ultra-cold regime remains a major challenge in the growing field of cold molecules. The molecular internal degrees of freedom complicate the effort of direct application of laser cooling. An alternative and general path towards ultra-cold molecules relies on sympathetic cooling via collisions with laser-cooled atoms. Here, we demonstrate the first step towards application of sympathetic cooling by co-trapping of molecular Oxygen with Lithium atoms in a magnetic trap at a temperature of ~300 mK. Our experiment begins with a pulsed supersonic beam which is a general source for cold high-flux atomic and molecular beams. Although the supersonic expansion efficiently cools the beam to temperatures below 1K, it also accelerates the beam to high mean velocities. We decelerate a beam of O$_2$ in a moving magnetic trap decelerator from 375 m/s to a stop. We entrained the molecular beam with Li atoms by laser ablation prior to deceleration. The deceleration ends with loading the molecules and atoms into a static quadrupole trap, which is generated by two permanent magnets. We estimate $10^9$ trapped molecules with background limited lifetime of 0.6 Sec. Our achievement enables application of laser cooling on the Li atoms in order to sympathetically cool the O$_2$. [Preview Abstract] |
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Q1.00153: The determination of potential energy curve and dipole moment of the (5)0$^{\mathrm{+}}$ electronic state of $^{\mathrm{85}}$Rb$^{\mathrm{133}}$Cs molecule by high resolution photoassociation spectroscopy Jinpeng Yuan, Yanting Zhao, Zhonghua Ji, Zhonghao Li, Jin-Tae Kim, Liantuan Xiao, Suotang Jia The creation and manipulation of ultracold polar molecules have attracted intensive attentions due to their permanent electric dipole moments interacting strongly with an external electric field and with long-range dipole-dipole force, which facilitate applications such as precision measurement, quantum control of cold chemical reactions, and quantum computation. The (5)0$^{\mathrm{+}}$ state is a good candidate to produce ultracold ground state RbCs molecule through a short-range photoassociation (PA). We present the formation of ultracold $^{\mathrm{85}}$Rb$^{\mathrm{133}}$Cs molecules in the (5)0$^{\mathrm{+}}$ electronic state by PA and their detection via resonance-enhanced two-photon ionization. Up to v $=$ 47 vibrational levels including the lowest v $=$ 0 and lowest J $=$ 0 levels are identified with high resolution. Precise Dunham coefficients and the Rydberg-Klein-Rees potential energy curve of the (5)0$^{\mathrm{+}}$ state are determined The electric dipole moments with respect to the vibrational numbers of the (5)0$^{\mathrm{+}}$ electronic state are also measured in the range between 1.9 and 4.8 D. These comprehensive studies on previously unobserved rovibrational levels of the (5)0$^{\mathrm{+}}$ state are helpful to understand the molecular structure and discover suitable transition pathways for transferring to the lowest rovibrational level of the ground state. [Preview Abstract] |
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Q1.00154: Slowing techniques for loading a magneto-optical trap of CaF molecules Stefan Truppe, Noah Fitch, Hannah Williams, Moritz Hambach, Ben Sauer, Ed Hinds, Mike Tarbutt Ultracold molecules in a magneto-optical trap (MOT) are useful for testing fundamental physics and studying strongly-interacting quantum systems. With experiments starting with a relatively fast (50-200 m/s) buffer-gas beam, a primary concern is decelerating molecules to below the MOT capture velocity, typically 10 m/s. Direct laser cooling, where the molecules are slowed via momentum transfer from a chirped counter-propagating narrowband laser, is a natural choice. However, chirping the cooling and repump lasers requires precise control of multiple laser frequencies simultaneously. Another approach, called “white-light slowing” uses a broadband laser such that all fast molecules in the beam are decelerated. By addressing numerous velocities no chirping is needed. Unfortunately, both techniques have significant losses as molecules are transversely heated during the optical cycling. Ideally, the slowing method would provide simultaneous deceleration and transverse guiding. A newly developed technique, called Zeeman-Sisyphus deceleration, is potentially capable of both. Using permanent magnets and optical pumping, the number of scattered photons is reduced, lessening transverse heating and relaxing the repump requirements. Here we compare all three options for CaF. [Preview Abstract] |
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Q1.00155: An updated apparatus for generating a sample of ultracold polar NaCs molecules Marek Haruza, Nicholas P. Bigelow We present an updated design of our apparatus for generating an ultracold sample of trapped NaCs molecules through photoassociation of laser cooled atoms. The implemented changes resulted in a more stable experimental platform. [Preview Abstract] |
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Q1.00156: LONG RANGE INTERACTIONS |
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Q1.00157: Long--Range Atom--Wall Mixing Terms for Excited States Ulrich D. Jentschura Long-range interactions between an atom and a perfectly conducting surface have been studied for a number of decades. Based on the work of G. Barton [J. Phys. B 7 (1974) 2134], we know that the treatment of these interactions for excited reference states can be highly problematic, requires the careful regularization of infinities, and additional renormalizations. Here, the treatment is extended to higher-order corrections, namely, mixing terms which are generated by the spatial symmetry breaking due to the presence of the conducting surface. These terms are evaluated, with full account of retardation, for metastable hydrogen [see Phys. Rev. A 91 (2015) 010502(R)]. Very-long-range admixture ``tails'' due to neighboring $2P_{3/2}$ states which are removed from the reference $2S$ state only by the fine structure, have a characteristic and surprising oscillatory $1/Z$ form in the vicinity of a surface, where $Z$ is the atom-surface distance. The transition from the long-range regime to the nonretarded close-range interactions and admixture terms is studied. [Preview Abstract] |
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Q1.00158: Slow Relaxation in Anderson Critical Systems Soonwon Choi, Norman Yao, Joonhee Choi, Georg Kucsko, Mikhail Lukin We study the single particle dynamics in disordered systems with long range hopping, focusing on the critical cases, i.e., the hopping amplitude decays as $1/r^d$ in $d$-dimension. We show that with strong on-site potential disorder, the return probability of the particle decays as power-law in time. As on-site potential disorder decreases, the temporal profile smoothly changes from a simple power-law to the sum of multiple power-laws with exponents ranged from $0$ to $\nu_\textrm{max}$. We analytically compute the decay exponents using a simple resonance counting argument, which quantitatively agrees with exact numerical results. Our result implies that the dynamics in Anderson Critical systems are dominated by resonances. [Preview Abstract] |
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Q1.00159: Slow thermalization in disordered dipolar spin systems Joonhee Choi, Georg Kucsko, Soonwon Choi, Peter Maurer, Nathalie de Leon, Norman Yao, Fedor Jelezko, Junichi Isoya, Mikhail Lukin Ensembles of strongly interacting spins offer an attractive platform for the study of many-body quantum dynamics. We present a detailed study of the electronic spin dynamics within a diamond sample with high nitrogen vacancy (NV) concentration (\textasciitilde 40 ppm). Due to the small distance between neighboring NV centers (\textasciitilde 5 nm), the spin-spin interactions dominate over decoherence. In particular, we investigate the interplay between interactions and disorder in such a system. By utilizing coherent resonance phenomena under a spin-locking pulse sequence, we observe and study slow thermalization corresponding to the critical regime of interacting many-body system at various disorder strengths. [Preview Abstract] |
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Q1.00160: ATOM INTERFEROMETERS |
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Q1.00161: Scale Factor Measurements for a Gyroscope Based on an Expanding Cloud of Atoms Gregory Hoth, Bruno Pelle, Stefan Riedl, John Kitching, Elizabeth Donley We present an atom interferometer that can simultaneously measure two-axis rotations and one-axis accelerations with a single cloud of atoms in an active evacuated volume of about 1 cm$^3$. This is accomplished by extending the point-source interferometry technique (Dickerson et al. PRL, 111, 083001, 2013) to a compact regime. In this technique, the cloud of atoms is imaged after the interferometer sequence. Rotations cause spatial fringes to appear across the cloud. To realize a gyroscope with this method, it is necessary to know how the wave-vector of the spatial fringes, $k$, is related to the rotation rate, $\Omega$. If the cloud is initially infinitesimally small, it can be shown that $k=F\Omega$ with a scale factor $F$ determined by the time between interferometer pulses, the total free expansion time, and the wavelength of the interrogating laser. However, the point-source approximation is not appropriate in our case because the final size of the cloud in our experiment is between 1.4 and 5 times its initial size. We show experimentally that in this finite expansion regime the phase gradient is still well described by $k=F \Omega$, but the scale factor $F$ depends on the initial distribution of the atoms. We also present modeling that explains this dependence. [Preview Abstract] |
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Q1.00162: Highly birefringent crystal for Raman transitions with phase modulators Nieves Arias, Vahide Abediyeh, Saeed Hamzeloui, Yasser Jeronimo-Moreno, Eduardo Gomez We present a system to excite Raman transitions with minimum phase noise. The system uses a phase modulator to generate the phase locked beams required for the transition. We use a long calcite crystal to filter out one of the sidebands, avoiding the cancellation that appears at high detunings for phase modulation. The measured phase noise is limited by the quality of the microwave synthesizer. We use the calcite crystal a second time to produce a co-propagating Raman pair with perpendicular polarizations to drive velocity insensitive Raman transitions. [Preview Abstract] |
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Q1.00163: Atom-interferometric measurement of Stark level splittings Jianming Zhao, Georg Raithel Rydberg atoms are highly sensitive to external electric fields due to their large polarizability, scaling as n$^{\mathrm{7}}$ (n is the principal quantum number). In cesium, nS Rydberg levels mix with nearby (n-4) high-$l$ states, forming sequences of avoided crossings. Mixed adiabatic/diabatic passages through these crossings [1] are employed as beam splitters and recombiners in an atom-interferometric measurement of energy level splittings [2]. We subject cold cesium atoms to laser-excitation, electric-field and detection sequences that constitute an (internal-state) atom interferometer. For the read-out of the interferometer we utilize state-dependent collisions, which selectively remove atoms of one kind from the detected signal. We investigate the dependence of the interferometric signal on timing and field parameters, and find good agreement with quantum simulations of the interferometer. Fourier analysis of the interferometric signals yield coherence frequencies that agree with corresponding energy-level differences in calculated Stark maps. [1] L. Wang, et al, New J. Phys. \textbf{17} 063011 (2015). [2] L. Wang, et al, Phys. Rev. A \textbf{92} 033619 (2015). [Preview Abstract] |
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Q1.00164: A Fast Ramsey-Bord\'{e} Interferometer with Cold Lithium Eric Copenhaver, Kayleigh Cassella, Holger Mueller We demonstrate light-pulse interferometry with bosonic lithium in both Mach-Zehnder and Ramsey-Bord\'{e} geometries. We capture 12 million Li-7 atoms at 200 $\mu$K and build a fast interferometer with ($\sim$ 100 ns) stimulated Raman pulses and short interrogation times (tens to hundreds of microseconds). We achieve approximately 20$\%$ of the maximum fringe contrast, which is limited to 25$\%$ by non-interfering atomic trajectories. The contrast decays at a rate consistent with the limit set by thermal expansion out of the Raman beam. The signal in a Ramsey-Bord\'{e} interferometer scales inversely with mass and highlights the advantage of interferometry with light atoms like lithium. This allows for a measurement of the fine structure constant with shorter interrogation times than interferometers based on heavier atoms. Additionally, fast interferometers may have applications in the detection of high frequency signals resulting from exotic physics. [Preview Abstract] |
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Q1.00165: Measuring $h/m_{Cs}$ and the Fine Structure Constant with Bragg Diffraction and Bloch Oscillations Richard Parker We have demonstrated a new scheme for atom interferometry based on large-momentum-transfer Bragg beam splitters and Bloch oscillations [1]. In this new scheme, we have achieved a resolution of $\delta\alpha/\alpha$=0.25ppb in the fine structure constant measurement, which gives up to 4.4 million radians of phase difference between freely evolving matter waves. We suppress many systematic effects, e.g., Zeeman shifts and effects from Earth’s gravity and vibrations, use Bloch oscillations to increase the signal and reduce the diffraction phase, simulate multi-atom Bragg diffraction to understand sub-ppb systematic effects, and implement spatial filtering to further suppress systematic effects. We present our recent progress toward a measurement of the fine structure constant, which will provide a stringent test of the standard model of particle physics. [1] Estey et al., PRL 115, 083002 (2015). [Preview Abstract] |
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Q1.00166: Scaling up the precision in a ytterbium Bose-Einstein condensate interferometer Katherine McAlpine, Benjamin Plotkin-Swing, Daniel Gochnauer, Brendan Saxberg, Subhadeep Gupta We report on progress toward a high-precision ytterbium (Yb) Bose-Einstein condensate (BEC) interferometer, with the goal of measuring h/m and thus the fine structure constant $\alpha$. Here h is Planck's constant and m is the mass of a Yb atom. The use of the non-magnetic Yb atom makes our experiment insensitive to magnetic field noise. Our chosen symmetric 3-path interferometer geometry [1] suppresses errors from vibration, rotation, and acceleration. The precision scales with the phase accrued due to the kinetic energy difference between the interferometer arms, resulting in a quadratic sensitivity to the momentum difference. We are installing and testing the laser pulses for large momentum transfer via Bloch oscillations. We will report on Yb BEC production in a new apparatus and progress toward realizing the atom optical elements for high precision measurements. We will also discuss approaches to mitigate two important systematics: (i) atom interaction effects can be suppressed by creating the BEC in a dynamically shaped optical trap to reduce the density; (ii) diffraction phase effects from the various atom-optical elements can be accounted for through an analysis of the light-atom interaction for each pulse. [1] A.Jamison, B.Plotkin-Swing, S.Gupta, PRA 90, 063606 (2014). [Preview Abstract] |
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Q1.00167: Generation of squeezing in a driven many-body system Bharath Hebbe Madhusudhana, Matthew Boguslawski, Martin Anquez, Bryce Robbins, Maryrose Barrios, Thai Hoang, Michael Chapman In a spin-1 Bose-Einstein condensate, the non-linear spin-dependent collisional interactions can create entanglement and squeezing. Typically, the condensate is initialized at an unstable fixed point of the phase space, and subsequent free evolution under a time-independent Hamiltonian creates the squeezed state. Alternatively, it is possible to generate squeezing by driving the system localized at a stable fixed point. Here, we demonstrate that periodic modulation of the Hamiltonian can generate highly squeezed states. Our measurements show -5 dB of squeezing, limited by the detection, but calculations indicate that a theoretical potential of -20 dB of squeezing [1]. We discuss the advantages of this method compared with the typical techniques. \\ $^1$ Hoang, T. M. et al, arXiv:1512.05645 [Preview Abstract] |
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Q1.00168: PRECISION MEASUREMENTS |
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Q1.00169: Precision Wavelength Measurements And Identifications Of EUV Lines From Highly Charged L-Shell yttrium Ions Roshani Silwal, Joan Dreiling, John Gillaspy, Endre Takacs, Yuri Ralchenko We present the measurements of extreme-ultraviolet spectra of the L-shell ions of highly charged yttrium (Y$^{\mathrm{29+}}$-Y$^{\mathrm{36+}})$ created and trapped in the electron beam ion trap (EBIT) of the National Institute of Standards and Technology. Few Na-like, Mg-like and Al-like yttrium lines (Y$^{\mathrm{26+}}$-Y$^{\mathrm{28+}})$ are reported as well. In order to reach the desired ionization stages, the beam energy was systematically varied from 2.3 keV to 6 keV during the experiment. A flat-field grazing-incidence spectrometer was used to record the spectra in the wavelength range of 4.022 nm to 19.957 nm. The wavelength calibration was provided by the previously measured lines of neon, xenon, oxygen and iron. A total of 63 new spectral lines (allowed and forbidden) corresponding to the $\Delta $n$=$0 transitions within n$=$2 and 3 have been identified using collisional-radiative simulations of the non-Maxwellian EBIT plasma. The total uncertainties assigned to the measured wavelengths vary between 0.001 nm to 0.003 nm and include contributions from calibration uncertainties, statistical uncertainties from the line fits, and estimated systematic uncertainties. [Preview Abstract] |
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Q1.00170: Searching for Axion Dark Matter with Atoms and Ultracold Neutrons Yevgeny Stadnik, Vladimir Dzuba, Victor Flambaum, Benjamin Roberts, Michal Rawlik We propose new schemes to directly search for axion dark matter with atoms and ultracold neutrons. Axions are an excellent candidate for the observed cold dark matter; their low mass and weak-strength interactions with ordinary matter mean that axions can readily form an oscillating classical field that survives to reside in the observed galactic dark matter haloes. The oscillating nature of the axion field gives rise to a number of oscillating effects in atoms and neutrons [Stadnik and Flambaum, PRD 89, 043522 (2014); EPJC 75, 110 (2015); Roberts et al., PRL 113, 081601 (2014); PRD 90, 096005 (2014); Graham and Rajendran, PRD 84, 055013 (2011); PRD 88, 035023 (2013)], which include oscillating electric dipole moments, and the precession of polarised spins about Earth's direction of motion through galactic axions. Importantly, these effects scale as the first power of the underlying interaction constant (whereas traditionally-sought effects of dark matter scale as the second or fourth power). First-power effects may thus provide a very strong advantage, since the interaction constant is extremely small. We present an overview of ongoing efforts of the nEDM collaboration at PSI to search for axion dark matter via these effects using a dual neutron/Hg-199 co-magnetometer. [Preview Abstract] |
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Q1.00171: Precise measurements of $^{203}$Tl and $^{205}$Tl excited state hyperfine splittings and isotope shifts using two-step vapor cell spectroscopy P.K. Majumder, Sau Man Cheng, P.M. Rupasinghe We have undertaken a series of high-precision atomic structure measurement in thallium to test ongoing \emph{ab initio} atomic structure calculations of relevance to symmetry violation tests in this element. We are currently completing two-step spectroscopy measurements of the $8P_{1/2}$ and $8P_{3/2}$ hyperfine structure and isotope shift using a heated thallium vapor cell and two external cavity semiconductor diode lasers. One laser, locked to the thallium $6P_{1/2}\rightarrow7S_{1/2}$ 378 nm transition excites one or both naturally-occurring isotopes to an intermediate state. A second red laser overlaps the UV beam within the thallium vapor cell in both a co-propagating and counter-propagating configuration. Analysis of subsequent Doppler-free absorption spectra of the $7S_{1/2}\rightarrow 8P_{1/2, 3/2}$ visible transitions allows us to extract both hyperfine and isotope shift information for these excited states with uncertainties below 1 MHz. Frequency modulation of the red laser provides convenient \emph{in situ} frequency calibration. Recent measurements in our group have shown significant discrepancies from older hyperfine structure measurements in thallium excited states. Current results will be presented. [Preview Abstract] |
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Q1.00172: High-precision Stark shift measurements in excited states of indium using an atomic beam P.K. Majumder, A.L. Carter, B.L. Augenbraun, P.M. Rupasinghe, N.B. Vilas A recent precision measurement in our group of the indium scalar polarizability within the 410 nm $5p_{1/2} \rightarrow 6s_{1/2}$ transition showed excellent agreement with {\em ab initio} atomic theory. We are now completing a measurement of the polarizability within the $6s_{1/2} \rightarrow 6p_{1/2}$ excited-state transition. In our experiment, two external cavity semiconductor diode lasers interact transversely with a collimated indium atomic beam. We tune the 410 nm laser to the $5p_{1/2} \rightarrow 6s_{1/2}$ transition, keeping the laser locked to the exact Stark-shifted resonance frequency. We overlap a 1343 nm infrared laser to reach the $6p_{1/2}$ state. The very small infrared absorption in our atomic beam is detected using two-tone FM spectroscopy. Monitoring the two-step excitation signal in a field-free supplemental vapor cell provides frequency reference and calibration. Precisely calibrated electric fields of 5 - 15 kV/cm produce Stark shifts of order 100 MHz for this excited state. Experimental details, latest results, and comparison to theory will be discussed. In the near future, The same infrared laser will be tuned to 1291 nm to study the scalar and tensor polarizability of the $6p_{3/2}$ excited state providing a distinct test of atomic theory. [Preview Abstract] |
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Q1.00173: Ultra-sensitive force sensing with optically levitated nanospheres Kirsten Casey, Gambhir Ranjit, Mark Cunningham, Andrew Geraci According to many theories beyond the Standard Model, Yukawa-type corrections to Newtonian gravity may be present at short length scales. I will discuss our experiment dedicated to searching for these forces at the micron length scale using laser-cooled silica nanospheres in an optical standing-wave trap. The nanospheres have achieved sub-attonewton force sensitivity in high vacuum, and can act as a sensor for short-range Yukawa-forces when levitated near a microfabricated source mass. [Preview Abstract] |
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Q1.00174: GPS.DM Observatory: Search for Dark Matter and Exotic Physics with Atomic Clocks and GPS Constellation Benjamin Roberts, Geoffrey Blewitt, Andrei Derevianko, Nathan Lundholm, Maxim Pospelov, Alex Rollings, Jeff Sherman Despite the overwhelming cosmological evidence for the existence of dark matter, and the considerable effort of the scientific community over decades, there is no evidence for dark matter in terrestrial experiments. The GPS.DM observatory uses the existing GPS constellation as a 50,000 km-aperture sensor array, analyzing the satellite and terrestrial atomic clock data for exotic physics signatures. In particular, the collaboration searches for evidence of transient variations of fundamental constants correlated with the Earth’s galactic motion through the dark matter halo. This type of search is particularly sensitive to exotic forms of dark matter, such as topological defects.\\ We will present an update on the search.\\ ~\\ A.~Derevianko and M.~Pospelov, Nat.~Phys.~{\bf10}, 933 (2014) [Preview Abstract] |
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Q1.00175: Progress toward measuring the $^{85}$Rb $ng$-series quantum defect using $\Delta l = 0$ microwave spectroscopy Kaitlin Moore, Georg Raithel We describe progress toward a new measurement of the $^{85}$Rb $ng$-series quantum defect via two-photon microwave spectroscopy of a $\Delta l = 0$ transition using cold Rydberg atoms. Past efforts have used resonant energy transfer\footnote{K.Afrousheh, P.Bohlouli-Zanjani, J.A.Petrus, J.D.D.Martin, PRA, 74, 062712 (2006)} and preliminary microwave spectroscopy of a $\Delta l = 2$ transition\footnote{J.Han, Y.Jamil, D.V.L.Norum, P.J.Tanner, T.F.Gallagher, PRA, 74, 054502 (2006)}, yielding $\delta_g(n=30)=0.00405(6)$ and $\delta_g=0.00400(9)$, respectively. By performing a $\Delta l = 0$ measurement, we hope to eliminate uncertainties due to lower-$l$-state quantum defects and differing Land\'{e}-$g$ factors and thereby achieve an improved precision. Preliminary measurements will be presented, including efforts at resolving fine structure in the spectrum. Applications of this high-$l$ measurement method toward experimentally determining the dipole and quadrupole core polarizabilities of $^{85}$Rb will be discussed, including comparisons with calculated values\footnote{J.Heinrichs, J. Chem. Phys. 52, 6316 (1970)},\footnote{R.M.Sternheimer, PRA 1, 321 (1970)} and preliminary experimental limits$^3$, which yield inconsistent results for the dipole polarizability value. [Preview Abstract] |
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Q1.00176: Progress Towards Measurement of the Anapole Moment of $^{\mathrm{137}}$Ba$^{\mathrm{19}}$F Sidney Cahn, Emine Altuntas, David DeMille, Mikhail Kozlov Weak interactions inside the nucleus produce a toroidal current distribution around the axis of nuclear spin. This current distribution, known as the nuclear anapole moment is the dominant source of nuclear spin-dependent parity violation (NSD-PV) effects for nuclei with nucleon number $A\ge $\textit{20. }We propose to measure the anapole moment of $^{\mathrm{137}}$Ba$^{\mathrm{19}}$F. To diagnose systematics and establish a measurement sequence we use $^{\mathrm{138}}$Ba$^{\mathrm{19}}$F, which has negligible NSD-PV effects. $^{\mathrm{138}}$Ba$^{\mathrm{19}}$F has a larger isotopic abundance and fewer hyperfine levels compared to those of $^{\mathrm{137}}$Ba$^{\mathrm{19}}$F. Therefore fluorescence signals from $^{\mathrm{138}}$Ba$^{\mathrm{19}}$F are approximately \textit{26} times larger than those from $^{\mathrm{137}}$Ba$^{\mathrm{19}}$F. Here we present \quad planned improvements to our apparatus, including a magnetic hexapole lens to improve the molecular beam flux and preliminary spectroscopy measurements with $^{\mathrm{137}}$Ba$^{\mathrm{19}}$F. [Preview Abstract] |
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Q1.00177: Rate-coefficients and polarization results for the electron-impact excitation of Ar$^{+}$ ion Rajesh Srivastava, Dipti Dipti A fully relativistic distorted wave theory has been employed to study the electron impact excitation in Ar$^{+}$ ion. Results have been obtained for the excitation cross-sections and rate-coefficients for the transitions from the ground state 3$p^{5}$ ($J=$3/2) to fine-structure levels of excited states 3$p^{4}$4$s$, 3$p^{4}$4$p, $3$p^{4}$5$s$, 3$p^{4}$5$p$, 3$p^{4}$3$d$ and 3$p^{4}$4$d$. Polarization of the radiation following the excitation has been calculated using the obtained magnetic sub-level cross-sections. Comparison of the present rate-coefficients is also done with the previously reported theoretical results for some unresolved fine structure transitions. [Preview Abstract] |
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Q1.00178: Optical excitation and quenching of photocurrent in single-crystal diamond Jeson Chen, Sean Lourette, Kristine Rezai, Pauli Kehayias, Michael Lake, Andrey Jarmola, Milos Nesladek, Louis Bouchard, Philip Hemmer, Dmitry Budker Diamond has found important applications in optoelectronics including electron emitters, windows for high power devices, and x-ray photon detectors, thanks to its unique properties, such as a wide bandgap, high thermal conductance and broadband optical transmittance. It is thus of paramount importance to investigate the photoelectric properties of diamond in greater details. Here we report the observation of optical quenching of photocurrent in diamond using simultaneous illumination of pulsed and continuous wave lasers at the same wavelength and different wavelengths. The quenched photocurrent shows a recovery related to the external bias voltage, pulsed optical power and wavelength. The recovery of the quenched photocurrent provides information on the nature of the electron trap states in diamond. [Preview Abstract] |
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Q1.00179: Inhibition of ground-state superradiance and light-matter decoupling in circuit QED Zeliang Xiang, Tuomas Jaako, Juan José Garcia-Ripoll, Peter Rabl We study effective light-matter interactions in a circuit QED system consisting of a single LC resonator, which is coupled symmetrically to multiple superconducting qubits. Starting from a minimal circuit model, we demonstrate that in addition to the usual collective qubit-photon coupling the resulting Hamiltonian contains direct qubit-qubit interactions, which prevent the otherwise expected superradiant phase transition in the ground state of this system. Moreover, these qubit-qubit interactions are responsible for an opposite mechanism, which at very strong couplings completely decouples the photon mode and projects the qubits into a highly entangled ground state. These finfings shed new light on the controversy over the existence of superradiant phase transitions in cavity and circuit QED systems, and show that the physics of ultrastrong light-matter interactions in two- or multi-qubit settings differ drastically from the more familiar one qubit case. [Preview Abstract] |
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Q1.00180: Stability of a Bose-Einstein condensate in a driven optical lattice: Crossover between weak and tight transverse confinement Sayan Choudhury, Erich Mueller We explore the effect of transverse confinement on the stability of a Bose-Einstein condensate (BEC) loaded in a shaken one-dimensional or two-dimensional square lattice. We calculate the decay rate from two-particle collisions. We predict that if the transverse confinement exceeds a critical value, then, for appropriate shaking frequencies, the condensate is stable against scattering into transverse directions. We explore the confinement dependence of the loss rate, explaining the rich structure in terms of resonances. [Preview Abstract] |
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Q1.00181: Van der Waals Interactions and Dipole Blockade in a Cold Rydberg Gas Probed by Microwave Spectroscopy Thanh Long Nguyen, Raul Celistrino Teixeira, Carla Hermann Avigliano, Tigrane Cantat Moltrecht, Jean Michel Raimond, Serge Haroche, Sebastiens Gleyzes, Michel Brune Dipole-dipole interactions between Rydberg atoms are a flourishing tool for quantum information processing and for quantum simulation of complex many-body problems. Microwave spectroscopy of a dense Rydberg gas trapped close to a superconducting atom chip in the strong dipole blockade regime reveals directly the many-body atomic interaction spectrum. We present here a direct measurement of the interaction energy distribution in the strong dipole blockade regime, based on microwave spectroscopy. We first apply this method to the observation of the excitation dynamics of the Rydberg gas, conditioned by dipole-dipole interactions, in either the strong blockade regime or the so-called facilitation regime. We also observe with this method the atomic cloud expansion driven by the repulsive Van der Waals interaction after excitation. This measurement, in good agreement with Monte Carlo simulations of the excitation process and of the cloud dynamics, reveals the limits of the frozen gas approximation. This method can help investigate self-organization and dynamical phase transitions in Rydberg-atom based quantum simulators. This study thus opens a promising route for quantum simulation of many-body systems and quantum information transport in chains of strongly interacting Rydberg atom [Preview Abstract] |
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Q1.00182: Cooling without contact in bilayer dipolar Fermi gases} Bilal Tanatar, Basak Renklioglu, M. Ozgur Oktel We consider two parallel layers of dipolar ultracold Fermi gases at different temperatures and calculate the heat transfer between them. The effective interactions describing screening and correlation effects between the dipoles in a single layer are modelled within the Euler-Lagrange Fermi-hypernetted chain approximation. The random-phase approximation is employed for the interactions across the layers. We investigate the amount of transferred power between the layers as a function of the temperature difference. Energy transfer proceeds via the long-range dipole-dipole interactions. A simple thermal model is developed to investigate the feasibility of using the contactless sympathetic cooling of the ultracold polar atoms/molecules. Our calculations indicate that dipolar heat transfer is effective for typical polar molecule experiments and may be utilized as a cooling process. [Preview Abstract] |
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Q1.00183: DNA Nucleotides Detection via capacitance properties of Graphene nahid khadempar, Masoud Berahman, Arash Yazdanpanah In the present paper a new method is suggested to detect the DNA nucleotides on a first-principles calculation of the electronic features of DNA bases which chemisorbed to a graphene sheet placed between two gold electrodes in a contact-channel-contact system. The capacitance properties of graphene in the channel are surveyed using non-equilibrium Green's function coupled with the Density Functional Theory. Thus, the capacitance properties of graphene are theoretically investigated in a biological environment, and, using a novel method, the effect of the chemisorbed DNA nucleotides on electrical charges on the surface of graphene is deciphered. Several parameters in this method are also extracted including Electrostatic energy, Induced density, induced electrostatic potential, Electron difference potential and Electron difference density. The qualitative and quantitative differences among these parameters can be used to identify DNA nucleotides. Some of the advantages of this approach include its ease and high accuracy. What distinguishes the current research is that it is the first experiment to investigate the capacitance properties of gaphene changes in the biological environment and the effect of chemisorbed DNA nucleotides on the surface of graphene on the charge. [Preview Abstract] |
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Q1.00184: Steering of hydrogen migration in hydrocarbons using intense few-cycle laser fields Hui Li, Matthias Kuebel, Christian Burger, Nora Kling, Benjamin Foerg, Sergey Zherebtsov, Matthias Kling, Spyros Kaziannis, Robert Siemering, Regina de Vivie-Riedle, Johannes Stierle, Alexander Kessel, Kelsie Betsch, Boris Bergues, Sergei Trushin, Ali Alnaser, Abdallah Azzeer, Itzik Ben-Itzhak, Robert Moshammer Structural rearrangements in hydrocarbons, namely acetylene, allene and toluene, are initiated by phase- and intensity-controlled few-cycle laser pulses. The momentum distributions of several ionic fragments are monitored using single-shot VMI and COLTRIMS. The results show that the hydrogen migration in these hydrocarbons can be steered by changing the CEP and the intensity of the few-cycle pulses. Quantum dynamical calculations performed on acetylene and allene show that a superposition of vibrational modes can be created by wave-form controlled few-cycle laser fields, which will result in a directionality of the hydrogen migration [1]. This mechanism, which appears to be of general importance for such complex molecules, should also be able to explain the molecular dynamics observed in toluene [2]. [1] M. K\"{u}bel, \textit{et al}., arXiv:1508.04018. [2] H. Li, \textit{et al}., \textit{Struct. Dyn}. \textbf{3}, 043206(2016). [Preview Abstract] |
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Q1.00185: Analysis of dark matter and dark energy Han Yongquan As the law of unity of opposites of the Philosophy tells us, the bright material exists, the dark matter also exists. Dark matter and dark energy should allow the law of unity of opposites. The Common attributes of the matter is radiation, then common attributes of dark matter must be absorb radiation. Only the rotation speed is lower than the speed of light radiation, can the matter radiate, since the speed of the matter is lower than the speed of light, so the matter is radiate; The rotate speed of the dark matter is faster than the light , so the dark matter doesn't radiate, it absorbs radiation. The energy that the dark matter absorb radiation produced (affect the measurement of time and space distribution of variations) is dark energy, so the dark matter produce dark energy only when it absorbs radiation. Dark matter does not radiate, two dark matters does not exist inevitably forces, and also no dark energy. Called the space-time ripples, the gravitational wave is bent radiation, radiation particles should be graviton, graviton is mainly refers to the radiation particles whose wavelength is small. Dark matter, dark energy also confirms the existence of the law of symmetry. [Preview Abstract] |
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Q1.00186: Raman sideband cooling of $^{138}$Ba$^+$ on a Zeeman transition Christopher Seck, Mark Kokish, Matthew Dietrich, Brian Odom Here, we report motional ground state preparation of a single $^{138}$Ba$^+$ ion using Raman sideband cooling with the two S$_{1/2}$ Zeeman sublevels. Owing to the small Zeeman splitting, Raman sideband cooling of $^{138}$Ba$^+$ requires only two AOMs and the Doppler cooling lasers. Additionally, we demonstrate coherent operations using a second, far-off-resonant laser driving Raman $\pi$-pulses between the two Zeeman sublevels to characterize our mean motional occupation number, Raman sideband cooling frequency resonance, Raman sideband cooling rate, and ion trap motional heating rate. Motional ground state cooling and molecular internal state preparation, both realized in our group\footnote{C.-Y. Lien, C. M. Seck, Y.-W. Lin, J. H. V. Nguyen, D. A. Tabor, and B. C. Odom, \textit{Nature Communications} \textbf{5}, 4783 (2014)}, are important elements for molecular quantum logic spectroscopy (mQLS). We are now working towards motional ground state preparation of a $^{138}$Ba$^+$ and AlH$^+$ ion pair for mQLS. [Preview Abstract] |
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Q1.00187: Narrow linewidth spectroscopy in quantum degenerate metastable helium Remy Notermans, Robert Rengelink, Wim Vassen Combined with high-precision spectroscopy, QED theory allows extraction of the nuclear charge radius from spectroscopy in simple atomic systems. This recently lead to a significant discrepancy in the proton charge radius determined from hydrogen and muonic hydrogen spectroscopy, now known as the `proton size puzzle'. Spectroscopy in helium can provide additional insight in this conundrum. Our group previously measured the very weak $2\ ^3S \to 2\ ^1S$ transition ($\lambda=1557$ nm, $\Gamma=2\pi \times 8$ Hz) to $10^{-11}$ relative accuracy in quantum degenerate ($T=0.2\ \mu$K) metastable $^4$He and $^3$He, allowing a 1\% accurate determination of the charge radius difference of the $\alpha$ particle and the helion. Recent measurements in muonic He$^+$ aim for a precision of $3\times 10^{-4}$. In order to provide a similar precision, we aim to remeasure the transition to sub-kHz precision by reducing the linewidth of the spectroscopy laser by over an order of magnitude to the kHz level and by implementing a magic wavelength ($\lambda=320$ nm) dipole trap operating at 2 W CW power. First measurements in a helium BEC have shown a 10 kHz asymmetric line profile due to mean-field effects. This allows for the first determination of the unknown $2\ ^3S-2\ ^1S$ scattering length. [Preview Abstract] |
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Q1.00188: Observing the average momentum flow lines of particles in a double slit interferometer Joel Morley, Peter Edmunds, Peter Barker, Basil Hiley, Rob Flack, Vincenzo Monachello The 1988 work on weak values by Aharonov et al, introduced a new kind of quantum variable [1]. This created new perspectives when it came to the limits of quantum uncertainty. More recently, Kocsis et al [2] had used these techniques experimentally, claiming to have reconstructed the trajectories of photons after passing through an interferometer. This was done without destroying the interference pattern, an act apparently forbidden by standard quantum mechanics. We aim to replicate Kocsis’ experiment using atoms. A ready made magneto-optical trap can routinely cool and trap, metastable argon atoms to the mK range[3]. The ultra-cold temperatures offers particles with a large De Broglie wavelength. Here we present our intended method of reconstructing the atom’s trajectories, while maintaining the interference pattern, as they fall below the slits. \begin{thebibliography}{1} \bibitem{Ahar} Y. Aharonov, D.~Z. Albert, L. Vaidman, \emph{Phys. Rev. Lett.} \textbf{60}, 1351-4 (1988) \bibitem{Kocsis} S. Kocsis et al., \emph{Science}, \textbf{332}, 1170-73 (2011) \bibitem{Edmunds} P. Edmunds, P. Barker, \emph{Phys. Rev. Lett.} \textbf{113}, 183001 (2014) \end{thebibliography} [Preview Abstract] |
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Q1.00189: Radiation Damages in Aluminum Alloy SAV-1 under Neutron Irradiation Umar Salikhbaev, Farkhad Akhmedzhanov, Sherali Alikulov, Sapar Baytelesov, Azizbek Boltabaev The aim of this work was to study the effect of neutron irradiation on the kinetics of radiation damages in the SAV-1 alloy, which belongs to the group of aluminum alloys of the ternary system Al-Mg-Si. For fast-neutron irradiation by different doses up to fluence 10$^{\mathrm{19}}$ cm$^{\mathrm{-2}}$ the SAV-1 samples were placed in one of the vertical channels of the research WWR type reactor (Tashkent). The temperature dependence of the electrical resistance of the alloy samples was investigated in the range 290 - 490 K by the four-compensation method with an error about 0.1{\%}. The experimental results were shown that at all the temperatures the dependence of the SAV-1 alloy resistivity on neutron fluence was nonlinear. With increasing neutron fluence the deviation from linearity and the growth rate of resistivity with temperature becomes more appreciable. The observed dependences are explained by means of martensitic transformations and the radiation damages in the studied alloy under neutron irradiation. The mechanisms of radiation modification of the SAV-1 alloy structure are discussed. [Preview Abstract] |
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Q1.00190: Machine learning for molecular scattering dynamics: Gaussian Process models for improved predictions of molecular collision observables Roman Krems, Jie Cui, Zhiying Li We show how statistical learning techniques based on kriging (Gaussian Process regression) can be used for improving the predictions of classical and/or quantum scattering theory. In particular, we show how Gaussian Process models can be used for: (i) efficient non-parametric fitting of multi-dimensional potential energy surfaces without the need to fit ab initio data with analytical functions; (ii) obtaining scattering observables as functions of individual PES parameters; (iii) using classical trajectories to interpolate quantum results; (iv) extrapolation of scattering observables from one molecule to another; (v) obtaining scattering observables with error bars reflecting the inherent inaccuracy of the underlying potential energy surfaces. We argue that the application of Gaussian Process models to quantum scattering calculations may potentially elevate the theoretical predictions to the same level of certainty as the experimental measurements and can be used to identify the role of individual atoms in determining the outcome of collisions of complex molecules. We will show examples and discuss the applications of Gaussian Process models to improving the predictions of scattering theory relevant for the cold molecules research field. More details: PRL 115, 073202 (2015). [Preview Abstract] |
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Q1.00191: Wear Characteristics of Oleophobic Coatings in Aerospace Applications Hamza Shams, Kanza Basit This paper investigates the wear characteristics of oleophobic coatings when applied over Inconel 718, which has widespread applications in the aerospace industry. Coatings once applied were selectively exposed to controlled uni-and then multi-directional stand storm conditions. Size and speed of sand particles colliding with the work surface were carefully moderated to simulate sand storm conditions. Study of friction was performed using Lateral Force Microscopy (LFM) coupled with standard optical microscopy. The analysis has been used to devise a coefficient of friction value and in turn suggest wear behavior of the coated surface including the time associated with exposure of the base substrate. The analysis after validation aims to suggest methods for safe usage of these coatings for aerospace applications. [Preview Abstract] |
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Q1.00192: Observation of Broadband Ultraviolet Emission From Hg$_{3}^{*}$ Wenting Chen, Thomas Glavin, James Eden A previously-unobserved emission continuum, peaking at $\sim$ 380 nm, has been observed when Hg vapor is photoexcited at 248 nm (KrF laser). Attributed to the mercury trimer, Hg$_{3}$, this emission continuum has a spectral breadth (FWHM) which increases from $\sim$ 65 nm to $\sim$ 90 nm when the Hg number density rises from $\sim 10^{16}$ cm$^{-3}$ to $\sim 2 \times 10^{19}$ cm$^{-3}$. Over the same interval in [Hg], the emission decay rate increases only slightly ($\sim 6 \times 10^3$ s$^{-1}$ to $\sim 7 \times 10^3$ s$^{-1}$). Comparisons of the observed spectrum with theory [1] suggest that the observed continuum is the result of transitions between pairs of electronic states having a linear or equilateral triangular configuration. [1] Kitamura, Hikaru. "Theoretical potential energy surfaces for excited mercury trimers." Chemical Physics, 325(2), 207 (2006) [Preview Abstract] |
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Q1.00193: Expanding General Relativity's Space by S-Denying Dmitri Rabounski, Florentins Smarandache, Larissa Borissova Applying the S-denying procedure to signature conditions in a four-dimensional pseudo-Riemannian space - i.e. changing one (or even all) of the conditions to be partially true and partially false. Obtaining five kinds of expanded space-time for General Relativity. Kind I permits the space-time to be in collapse. Kind II permits the space-time to change its own signature. Kind III has peculiarities, linked to the third signature condition. Kind IV permits regions where the metric fully degenerates: there may be non-quantum teleportation, and a home for virtual photons. Kind V is common for kinds I, II, III, and IV. [Preview Abstract] |
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Q1.00194: Correction of walk-off induced wavefront distortion for continuous-variable applications Hongxin Zou, Yong Shen, Hong Guo We theoretically and experimentally investigate wave front distortion in critically phase matched continuous-wave (CW) second harmonic generation (SHG). Due to the walk-off effect in the nonlinear crystal, the generated second harmonic is extremely elliptical and quite non-Gaussian, which causes a very low matching and coupling efficiency in experiment. Cylindrical lenses and walk-off compensating crystals are adopted to correct distorted wave fronts, and obtain a good TEM$_{\mathrm{00}}$ mode efficiency. Theoretically we simulate the correction effect of 266nm laser generated with SHG. The experiment results accord well with theoretical simulation and above 80 percent TEM$_{\mathrm{00}}$ component is obtained for 266nm continuous wave laser with 4.8 degree walk-off angle in BBO crystal. After that, an optical mode cleaner is used to obtain an ideal Gaussian mode. With these treatments, the generated second harmonic can be utilized in continuous-variable regime, where almost perfect mode matching is demanded. [Preview Abstract] |
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Q1.00195: ABSTRACT WITHDRAWN |
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Q1.00196: Decoherence Spectroscopy Theory and Application with an Atom Interferometer Raisa Trubko, Alexander Cronin We developed decoherence spectroscopy as a method~to improve the accuracy of a tune-out wavelength ($\lambda $zero) measurement made with atom interferometry. Specifically, we used atom interference fringe contrast loss~as a function of laser frequency in order~to monitor Doppler shifts.~ This was particularly~helpful since we used a multi-pass cavity to recycle laser light in this experiment.~ The resulting decoherence spectra have non-intuitive features. Therefore~we present a theoretical model for decoherence spectroscopy and compare this model to several empirical examples. [Preview Abstract] |
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Q1.00197: (t, i, f)-Physical Laws and (t, i, f)-Physical Constants Florentin Smarandache In our reality, we do not have perfect spaces and perfect systems. Therefore many \textit{physical laws} function approximatively. Also, the \textit{physical constants} are not universal too. Variations of their values depend from a space to another, from a system to another, from a time to another, and so on depending on many parameters. The physical laws and similarly the physical constants are t{\%} true, i{\%} indeterminate, and f{\%} false in a given space with a certain composition, and it has a different neutrosophical truth value \textless t', i', f'\textgreater in another space with another composition. That's why, instead of universal (1, 0, 0)-physical laws and universal (1, 0, 0)-physical constants, we have (t, i, f)-physical laws and respectively (t, i, f)-physical constants, meaning partially true, partially indeterminate, and partially false in each space. Therefore, one uses the \textit{neutrosophic logic}, which is a general framework for unification of many existing logics, and its components t (truth), i (indeterminacy), f (falsehood) are standard or non-standard real subsets of ]$^{\mathrm{-}}$0, 1$^{\mathrm{+}}$[ with not necessarily any connection between them. It has many applications in physics. Reference: Florentin Smarandache, \textit{Introduction to Neutrosophic Measure, Neutrosophic Integral, and Neutrosophic Probability}, by Sitech {\&} Educational, Craiova, 140 p., 2013. [Preview Abstract] |
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Q1.00198: Theoretical analysis of an atomic spin self-oscillator Zhiguo Wang We present the analytic solutions for atomic spin self-oscillator with and without rotating wave approximation. The spin ensemble is driven by a linear magnetic field which is produced by its output amplitude multiplied by k and phase shifted by $\varphi $. In appropriate condition, the spin will precess self-sustainably. We obtained analytic solutions for amplitude and frequency of the spin self-oscillator with slow-varying amplitude and phase approximation. Some interesting results are found. First, the setup time of the spin self-oscillator has a characteristic time of 2T$_{\mathrm{1}}$, and T$_{\mathrm{1\thinspace }}$is the longitudinal relaxation time. Second, the oscillating frequency is a complicated function of parameters, including $\varphi $, transverse relaxation time T$_{\mathrm{2}}$, k, oscillating frequency $\omega $ and longitudinal component of magnetic moment Mz. When $\varphi $ is optimized, the oscillating frequency has nothing to do with T$_{\mathrm{2}}$, k, Mz at both transient and equilibrium state. On the other hand, the frequency shift is reverse proportional to T$_{\mathrm{2}}$ if $\varphi $ is not optimized. [Preview Abstract] |
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Q1.00199: Toward laser cooling of negative lanthanum Elena Jordan, Giovanni Cerchiari, Stefan Erlewein, Alban Kellerbauer Anion laser cooling holds the potential to allow the production of ultracold ensembles of any negatively charged species by sympathetic cooling. It is a promising technique for cooling of antiprotons to a few mK and could clear the way for precision measurements on cold antihydrogen. Laser cooling of negative ions has never been achieved, since most species have no bound--bound electric dipole transitions. Negative lanthanum (La${}^-$) is one of the few anions with multiple electric dipole transitions. The bound--bound transition from the ${}^3F^e_2$ ground state to the ${}^3D^o_1$ excited state in La${}^-$ has been proposed theoretically as a candidate for laser cooling. The potential laser cooling transition was identified using laser photodetachment spectroscopy and its excitation energy was measured. We have studied the aforementioned transition in a beam of La anions by high-resolution laser photodetachment spectroscopy. Seven of the nine expected hyperfine structure transitions have been resolved and the transition cross sections have been estimated from experimental observations. It was found that presently La$^-$ is the most promising candidate among the atomic anions. We plan to demonstrate the first direct laser cooling of negative ions in a linear radio frequency trap. [Preview Abstract] |
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Q1.00200: Quantum simulation of spin models and the discrete Truncated Wigner Approximation: from Rydberg atoms to trapped ions Asier Pineiro Orioli, Juergen Berges, Adrien Signoles, Hanna Schempp, Shannon Whitlock, Matthias Weidemueller, Arghavan Safavi-Naini, Michael Wall, Johannes Schachenmayer, Ana Maria Rey Accurate description of the dynamics of quantum spin models is a theoretically challenging problem with widespread applications ranging from condensed matter to high-energy physics. Furthermore recent experimental progress in AMO experiments allows for the physical realization of these models in a variety of setups, such as Rydberg systems and trapped ion experiments, with an unprecedented degree of control and flexibility. Therefore, it is vital to develop efficient theoretical methods capable of simulating the many-body dynamics of such systems. In this work, we employ and extend the recently developed discrete Truncated Wigner Approximation (dTWA), an approximation based on the phase space description of quantum mechanics, to compute the dynamics of two types of spin models: the long-range XY model, which can be realized with Rydberg atoms, and a coupled spin-boson model, which is relevant to trapped ion experiments. Comparisons to experimental results and to available exact solutions to benchmark the method show that the dTWA is capable of capturing important features of the spin evolution and can also help uncovering some underlying non-equilibrium processes. [Preview Abstract] |
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Q1.00201: Investigation Into the Utilization of 3D Printing in Laser Cooling Experiments Eric Hazlett, Brandon Nelson, Sam Diaz de Leon, Jonah Shaw With the advancement of 3D printing new opportunities are abound in many different fields, but with the balance between the precisions of atomic physics experiments and the material properties of current 3D printers the benefit of 3D printing technology needs to be investigated. We report on the progress of two investigations of 3D printing of benefit to atomic physics experiments: laser feedback module and the other being an optical chopper. The first investigation looks into creation of a 3D printed laser diode feedback module. This 3D printed module would allow for the quick realization of an external cavity diode laser that would have an adjustable cavity distance. We will report on the first tests of this system, by looking at Rb spectroscopy and mode-hop free tuning range as well as possibilities of using these lasers for MOT generation. We will also discuss our investigation into a 3D-printed optical chopper that utilizes an Arduino and a computer hard drive motor. By implementing an additional Arduino we create a low cost way to quickly measure laser beam waists. [Preview Abstract] |
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Q1.00202: Current Status of Atomic Spectroscopy Databases at NIST Alexander Kramida, Yuri Ralchenko, Joseph Reader NIST's Atomic Spectroscopy Data Center maintains several online databases on atomic spectroscopy. These databases can be accessed via the \underline {http://physics.nist.gov/PhysRefData} web page. Our main database, Atomic Spectra Database (ASD), recently upgraded to v. 5.3, now contains critically evaluated data for about 250,000 spectral lines and 109,000 energy levels of almost all elements in the periodic table. This new version has added several thousand spectral lines and energy levels of Sn II, Mo V, W VIII, and Th I-III. Most of these additions contain critically evaluated transition probabilities important for astrophysics, technology, and fusion research. A new feature of ASD is providing line-ratio data for diagnostics of electron temperature and density in plasmas. Saha-Boltzmann plots have been modified by adding an experimental feature allowing the user to specify a multi-element mixture. We continue regularly updating our bibliography databases, ensuring comprehensive coverage of current literature on atomic spectra for energy levels, spectral lines, transition rates, hyperfine structure, isotope shifts, Zeeman and Stark effects. Our other popular databases, such as the Handbook of Basic Atomic Spectroscopy Data, searchable atlases of spectra of Pt-Ne and Th-Ne lamps, and non-LTE plasma-kinetics code comparisons, continue to be maintained. [Preview Abstract] |
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Q1.00203: Multiple electron processes of He and Ne by proton impact Pavel Nikolaevich Terekhin, Pablo Montenegro, Michele Quinto, Juan Monti, Omar Fojon, Roberto Rivarola A detailed investigation of multiple electron processes (single and multiple ionization, single capture, transfer-ionization) of He and Ne is presented for proton impact at intermediate and high collision energies. Exclusive absolute cross sections for these processes have been obtained by calculation of transition probabilities in the independent electron and independent event models as a function of impact parameter in the framework of the continuum distorted wave-eikonal initial state theory. A binomial analysis is employed to calculate exclusive probabilities. The comparison with available theoretical and experimental results shows that exclusive probabilities are needed for a reliable description of the experimental data. The developed approach can be used for obtaining the input database for modeling multiple electron processes of charged particles passing through the matter. [Preview Abstract] |
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Q1.00204: Ghost Imaging with Matter Waves Roman Khakimov, Bryce Henson, David Shin, Sean Hodgman, Robert Dall, Kenneth Baldwin, Andrew Truscott We demonstrate, for the first time, high resolution ghost imaging of a macroscopic object using atoms. Ghost imaging is a novel technique in which the image emerges from cross-correlation of particles (usually photons)in two separate beams. One beam is detected with a single-pixel (bucket detector) after passing through the object, while the other beam does not interact with the object and is registered with high spatial resolution. Neither detector can reconstruct the image independently. In our experiment, the two beams are formed by correlated pairs of ultracold metastable helium atoms originating from thecollision of two Bose-Einstein Condensates. After s-wave scattering the atoms form a spherical shell of strongly correlated pairs with opposite momenta. We extend this technique with more than a10-foldincrease in the number of correlated pairs available for eachsingle experiment run, by using higher-order Bragg scattering in the Kapitza-Dirac regime, with multiple shells generated from different diffraction orders. Using single-atom detection, we create ghost images of a target maskwith a resolution given by the width of the cross-corrrelation function of atomic momenta. Future extensions could include ghost interference and EPR tests. [Preview Abstract] |
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Q1.00205: Experimental observation of Anderson localization in laser-kicked molecular rotors. Martin Bitter, Valery Milner For the first time, the phenomenon of Anderson localization is observed and studied in a system of true quantum kicked rotors. Nitrogen molecules in a supersonic molecular jet are cooled down to 27 K and are rotationally excited by a periodic train of 24 high-intensity femtosecond pulses. Exponential distribution of the molecular angular momentum - the most unambiguous signature of Anderson localization - is measured directly by means of coherent Raman scattering. We demonstrate the suppressed growth of the molecular rotational energy with the number of laser kicks and study the dependence of the localization length on the kick strength. Both timing and amplitude noise in the pulse train is shown to destroy the localization and revive the diffusive growth of angular momentum. [Preview Abstract] |
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Q1.00206: Kicking atoms with finite duration pulses Julia Fekete, Shijie Chai, Boris Daszuta, Mikkel F. Andersen The atom optics delta-kicked particle is a paradigmatic system for experimental studies of quantum chaos and classical-quantum correspondence. It consists of a cloud of laser cooled atoms exposed to a periodically pulsed standing wave of far off-resonant laser light. A purely quantum phenomena in such systems are quantum resonances which transfers the atoms into a coherent superposition of largely separated momentum states. Using such large momentum transfer ``beamsplitters'' in atom interferometers may have applications in high precision metrology. The growth in momentum separation cannot be maintained indefinitely due to finite laser power. The largest momentum transfer is achieved by violating the usual delta-kick assumption. Therefore we explore the behavior of the atom optics kicked particle with finite pulse duration. We have developed a semi-classical model which shows good agreement with the full quantum description as well as our experiments. Furthermore we have found a simple scaling law that helps to identify optimal parameters for an atom interferometer. We verify this by measurements of the ``Talbot time'' (a measurement of h/m) which together with other well-known constants constitute a measurement of the fine structure constant. [Preview Abstract] |
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Q1.00207: Individual Atoms In Their Quantum Ground State Eyal Schwartz, Pimonpan Sompet, Yin Hsien Fung, Mikkel F. Andersen An ultimate control of pure quantum states is an excellent platform for various quantum science and engineering. In this work, we perform quantum manipulation of individual Rubidium atoms in a tightly focus optical tweezer in order to cool them into their vibrational ground state via Raman sideband cooling. Our experimental scheme involves a combination of Raman sideband transitions and optical pumping of the atoms that couples two magnetic field sublevels indifferent to magnetic noise thus providing a much longer atomic coherence time compared to previous cooling schemes. By installing most of the atoms in their ground state, we managed to achieve two-dimensional cooling on the way to create a full nil entropy quantum state of single atoms and single molecules. [Preview Abstract] |
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Q1.00208: Cavity Cooling of Nanoparticles: Towards Matter-Wave experiments James Millen, Stefan Kuhn, Markus Arndt Levitated systems are a fascinating addition to the world of optically-controlled mechanical resonators. It is predicted that nanoparticles can be cooled to their c.o.m. ground state via the interaction with an optical cavity. By freeing the oscillator from clamping forces dissipation and decoherence is greatly reduced, leading to the potential to produce long-lived, macroscopically spread, mechanical quantum states, allowing tests of collapse models and any mass limit of quantum physics. Reaching the low pressures required to cavity-cool to the ground state has proved challenging. Our approach is to cavity cool a beam of nanoparticles in high vacuum. We can cool the c.o.m. motion of nanospheres a few hundred nanometers in size. Looking forward, we will utilize novel microcavities to enhance optomechanical cooling, preparing particles in a coherent beam ideally suited to ultra-high mass interferometry at {\$}10\textasciicircum 7{\$} a.m.u. [Preview Abstract] |
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Q1.00209: Experimental realization of a strongly interacting quantum memory Lin Li, Alex Kuzmich A quantum memory is a device which enables the storage and retrieval of quantum states of light. Ground atomic states interact only weakly with the environment and with each other, enabling memories with long storage times. However, for scalable generation and distillation of entanglement within distributed quantum information systems, it is desirable to controllably switch on and off interactions between the individual atoms. We realize a strongly interacting quantum memory by coupling the ground state of an ultra-cold atomic gas to a highly excited Rydberg state. The memory is subsequently retrieved into a propagating light field which is measured using the Hanbury Brown-Twiss photo-electric detection. The results reveal memory transformation from an initially prepared coherent state into the state of single excitation. [Preview Abstract] |
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Q1.00210: ConnesFusionTensorProduct/Photon GluonFusion in Mitochondria WH- Maksoed,SSi As in AJ Wassermann distinguished of classical invariant theory {\&} quantum invariant theory subfactor, in S. Palcoux:\textbf{''From Neveu-Schwarz Subfactors {\&} Connes Fusion'' }described the subfactor theory {\&} Witt-algebra whereas Andreas Thom's explanation about ConnesFusionTensorProduct/CFTP related Connes fusion to composition of homomorphism (i). classical tensor product O-X adds the changes,(ii). Relative tensor product H-X preserve the changes. For photonGluonFusion/PGF defined:''photon is the gauge boson of QED, the simplest of all boson'' devotes to CFT as ``quantum field theory which are invariant under conformal transformation {\&} in 2D there are infinite dimensional algebra. Alain Connes states theirselves Connes fusion as ``associative tensor operation'' to be in coincidences with ``their dynamic behavior driven by the balance in mitochondrial fusion {\&} fission (Carveney, 2007 ) from Peter Alexander Williams: \textbf{``Retinal neuronal remodeling in a model of Optic Atrophy'', D}ec, 2011. [Preview Abstract] |
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Q1.00211: Similar Hamiltonian Between Avalanche-effect {\&} Sociophysics WH- Maksoed,SSi Of similar Hamiltonian concerned in ``sociophysics'', there were RandomFieldIsingModel/RFIM in external field retrieved in S. Sabhapandit:''\textbf{Hysteresis {\&} Avalanche in RandomFieldIsingModel'', }2002:'' ..in earthquake, it is an energy release and in case of ferromagnet, it is the size of the domain flips''. Following the extremes {\&} compromises curve in Serge Galam: \textbf{``Sociophysics: a Review of Galam Model'', }2008 fig. 12, h 9 whereas it seems similar with ``heating curve''-Prof. Ir. Abdul Kadir: \textbf{``Mesin Arus Searah'', } h 192 when the heat sources are continuous denote continuous opinion dynamics. Further, hysteresis as duties in ``Kajian Analisis Model Mikromagnetik dari Struktur Magnet Nanokomposit'', 2007 [ UI file no. S29286 ] also sought :''calculate the probability that `one more site became unstable' causes an avalanche of the spin flips\textellipsis '' usually found in Per Bak sand-pile fractal characters experiment exhibits. [Preview Abstract] |
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Q1.00212: High Speed Video Measurements of a Magneto-optical Trap Luke Horstman, Curtis Graber, Seth Erickson, Anna Slattery, Chad Hoyt We present a video method to observe the mechanical properties of a lithium magneto-optical trap. A sinusoidally amplitude-modulated laser beam perturbed a collection of trapped $\ce{^7Li}$ atoms and the oscillatory response was recorded with a NAC Memrecam GX-8 high speed camera at 10,000 frames per second. We characterized the trap by modeling the oscillating cold atoms as a damped, driven, harmonic oscillator. Matlab scripts tracked the atomic cloud movement and relative phase directly from the captured high speed video frames. The trap spring constant, with magnetic field gradient $b_{z} = 36$ G/cm, was measured to be $4.5 \pm .5\times10^{-19}$ N/m, which implies a trap resonant frequency of $988\pm55$ Hz. Additionally, at $b_{z} = 27$ G/cm the spring constant was measured to be $2.3 \pm .2\times10^{-19}$ N/m, which corresponds to a resonant frequency of $707\pm30$ Hz. These properties at $b_{z} = 18$ G/cm were found to be $8.8 \pm .5\times10^{-20}$ N/m, and $438\pm13$ Hz. [Preview Abstract] |
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Q1.00213: Semiclassical Green's function for electron motion in combined Coulomb and electric fields Harindranath Ambalampitiya, Ilya Fabrikant We are developing an extension of the Green-function approach$^1$ to the theory of ionization of a multielectron atom in a strong laser field by using the semiclassical Van Vleck-Gutzwiller propagator. For a static field the exact quantum mechanical Green's function can be calculated with an arbitrary accuracy. Therefore, as a first step towards solution of the problem, we apply the semiclassical method to the static field case for the energies above the ionization threshold where all classical trajectories contributing to the Green's function are real. Required trajectories are determined by solving the problem of finding initial velocity and traveling time corresponding to two position points. For the pure electric field case of two trajectories the semiclassical Green's function agrees very well with the exact Green's function. With the inclusion of the Coulomb field, the number of classical trajectories between two points grows rapidly and here we observe that the agreement between the semiclassical and exact Green's functions increases when more trajectories are included in the computation. $^1$I. I. Fabrikant and L. B. Zhao, Phys. Rev. A {\bf 91}, 053412 (2015). [Preview Abstract] |
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Q1.00214: Uranium doped LiSAF as a precursor for a ${}^{229}$Th nuclear clock experiment Edmund Meyer, Markus Hehlen, Beau Barker, Lee Collins, Xinxin Zhao We experimentally and numerically study the simple idea of growing ${}^{233}$U doped LiSAF crystals. The micro-pulling-down technique is used to grow U:LiSAF single crystals with a high number density of U ions. The crystals are in the shape of rods that are geometrically well matched for imaging onto the spectrophotometer input slit. Growth is performed in an RF-heated chamber under argon inert atmosphere at elevated pressure. This reduces the evaporation of LiF and AlF3 from the melt and crystal surface during growth which otherwise tends to degrade the crystal quality. Through physical arguments and robust numerical calculation we determine the oxidation state of the U ion to likely be trivalent and occupying the Sr site. Charge compensation is numerically studied through F interstitials and Li vacancies. We determine the energetically most favorable state for U:LiSAF and investigate the effects upon $\alpha$-decay of ${}^{233}$U to ${}^{229}$Th, which $\approx$2\% of the time is in the excited isomeric state. Additional charge compensation mechanisms are needed to accommodate the Th$^{4+}$ ground oxidation state and we investigate F interstitial as well as Li vacancy. The band structure is calculated and analyzed for select cases. [Preview Abstract] |
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