Bulletin of the American Physical Society
52nd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 66, Number 6
Monday–Friday, May 31–June 4 2021; Virtual; Time Zone: Central Daylight Time, USA
Session V01: Poster Session III 4pm-6pm CDTPoster
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V01.00001: COLLISIONS AND SPECTROSCOPY
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V01.00002: L-dependences in the autoionization of high-n Rydberg states Robert A Brienza A comparative study of the autoionization of high-n, 120 ≤ n ≤ 160, strontium Rydberg atoms with intermediate values of L, 0 ≤ L ≤ 5, following excitation of the 5s 2S1/2 → 5p 2P1/2 transition in the core ion is presented. Measurements of Rydberg atom loss as the core ion-exciting laser frequency is scanned are used to determine the widths, i.e., lifetimes, of the two-electron-excited states together with the shift of the core ion resonance frequency from that of the bare core ion. The data demonstrate that, for a fixed value of L, both the widths of the autoionization loss features and their detunings vary as 1/(n−δ)3, where δ is the quantum defect, i.e., depend on the probability of finding the Rydberg electron in the vicinity of the core ion. For a fixed value of n, however, no simple L-dependence of either of these quantities is seen. The experimental results are discussed from the standpoint of quantum defect theory as well as using a two-active-electron model. |
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V01.00003: Photoionization of C60 at High Energies Aurora Ponzi, Piero Decleva, Steven T Manson Calculations of the photoionization cross sections of C60 including all valence and core subshells have been carried out for photon energies up to 1 keV using density functional theory (DFT) and time-dependent DFT (TDDFT) within the framework of a fully molecular model [1]. The high-energy valence subshell cross sections behave rather differently than the results from model potentials where the cross section falls far too rapidly with energy. This unphysical behavior is traced to smearing out of the carbon nuclei in the model potentials which makes it difficult for momentum to be conserved at the higher energies. In addition, it is found that confinement resonances persist with greater amplitude than in model calculations owing to the difference in much stronger reflection of the photoelectron wave off carbon nuclei as compared to reflection from the walls of a potential well. It was also found that interchannel coupling between valence and core cross sections is quite small except right near the inner-shell thresholds in the 300 eV region. [1] A. Ponzi, S. T. Manson and P. Decleva, J. Phys. Chem. A 124, 108 (2020). |
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V01.00004: Curious behaviour of Cooper minima in relativistic channels of ns subshells in high-Z atoms Saumyashree Baral, Subhasish Saha, Jobin Jose, Pranawa Deshmukh, Ahmad Razavi Cooper minima (CM) in dipole photoionization channels refer to a zero in the matrix element which lead to minima in the cross section [1] and intriguing features in the angular distribution asymmetry parameter β. Furthermore, it is well known that the CM is extremely sensitive to relativistic and correlation effects [2]. A systematic survey of CM in the relativistic channels, with comparisons to nonrelativistic results were studied in earlier [3-5]. The present work highlights and provides explanations for some of the curious behaviours of CM in the ns→εp1/2 and ns→εp3/2 dipole channels such as (1) movement of CM in the relativistic split channels in opposite directions of energy and (2) resurgence of CM in the ns→εp3/2 channel which had moved in the discrete region as a function of Z. To demonstrate these behaviors, we consider the dipole matrix elements of the ns subshells of Hg (Z=80), Rn (Z=86), Ra (Z=88), No (Z=102), Cn (Z=112), and Og (Z=118) and find that these curious behaviours are result from the competition between Coulomb attraction and spin-orbit forces. [1] J. W. Cooper, Phys. Rev. 128, 681 (1962); [2] W. R. Johnson and K. T. Cheng, Phys. Rev. A 20, 978 (1979); [3] R. Y. Yin and R. H. Pratt, Phys. Rev. A 35, 1149 (1987); [4] P. C. Deshmukh, B. R. Tambe, and S. T. Manson, Austral. J. Phys. 39, 679 (1986); [5] S. T. Manson, Phys. Rev. A 31, 3698 (1985). |
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V01.00005: Dramatic relativistic effects on the ns dipole angular distribution asymmetry parameter βns of high-Z atoms Saumyashree Baral, Akanksha Dubey, Subhasish Saha, Jobin Jose, Pranawa Deshmukh, Ahmad Razavi It is well-known that the dipole angular distribution asymmetry parameter βns for photoionization from ns subshells takes a value of 2.0 nonrelativistically for closed shell atoms [1]. However, relativistic effects [2] cause the βns deviate from its nonrelativistic value. One such case is Cooper minimum (CM) [3] region, at which the βns takes a lower value than 2.0, and is energy-dependent, because the minima in the relativistic dipole channels, ns→εp1/2 and ns→εp3/2, do not energetically coincide [4]. In the present work, we address the question: can βns deviate from 2.0 in closed shell atoms due to relativistic effects other than CM? To accomplish the objective, we examine the photoionization parameters of the high-Z elements employing the Dirac-Fock (DF) and relativistic-random-phase approximation (RRPA) methodologies. The photoionization from the 6s subshells of Hg (Z=80), Rn (Z=86), Ra (Z=88), No (Z=102), Cn (Z=112), Og (Z=118) and the 7s subshells of Ra, No, Cn and Og are considered. The present work concludes that βns will asymptotically tend to a value lower than 2.0; the degree of deviation depends upon the phase shift difference of spin-orbit split continuum channels that increases with Z. [1] J. Cooper, and R. N. Zare, J. Chem. Phys. 48, 942 (1968); [2] T. E. H. Walker and J. T. Waber, Phys. Rev. Lett. 30, 307 (1973); [3] J. W. Cooper, Phys. Rev. 128, 681 (1962); [4] S. T. Manson and A. F. Starace, Rev. Mod. Phys. 54, 389 (1982). |
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V01.00006: Photoionization Branching Ratios of Spin-Orbit Doublets Far Above Thresholds C. Rasadi Munasinghe, Pranawa Deshmukh At higher energies far above thresholds where the spin-orbit splitting is comparably insignificant, branching ratios of the photoionization cross sections of spin-orbit (nl) doublets must go to the statistical value of (l+1)/l in the absence of relativistic effects. Therefore, the alteration of branching ratio from its statistical value at higher energies is indicative of relativistic interactions on the radial wave functions as predicted earlier [1] and verified experimentally recently [2]. To understand this relativistic behavior quantitatively, calculations were performed on noble gases using the relativistic-random-phase approximation (RRPA) based on the Dirac equation, which includes relativistic interactions in an ab initio manner along with many-body correlations. The results show that branching ratios well above the threshold are energy-dependent and move further away from the nonrelativistic values with increasing energy. This deviation increases with the increase of atomic number, which enhances the relativistic effects. In addition, significant energy variations of the ratios are found, over broad energy ranges, owing to interchannel coupling with inner-shell photoionization channels, as suggested by earlier studies [3,4]. [1] A. Ron, Y. S. Kim, R. H. Pratt, Phys. Rev. A 24, 1260 (1981); [2] R. Püttner, et al, J. Phys. B (in press). [3] E. W. B. Dias, et al, Phys. Rev. Lett. 78, 4553 (1997); [4] W. Drube, et al, J. Phys. B 46, 245006 (2013). |
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V01.00007: Dipole and Quadrupole Contributions to Photoionization Time Delay in Atoms Rezvan Hosseini, Pranawa Deshmukh The study of Wigner time delay [1] in atomic photoionization provides information of on the dynamics of atomic electrons in transition on the attosecond time scale, the time scale of atomic electron motion [2]. This time delay generally has an angular dependence and calculations have been carried out looking at this angular dependence including only dipole transitions [3,4]. Owing to angular momentum geometry, the amplitude for dipole photoionization vanishes at certain angles. Under such circumstances, the amplitude for quadrupole transitions dominates and can be studied; in particular, at angles where the dipole amplitude vanishes, the time delay exhibited is that of quadrupole photoionization, thereby allowing us to get information on the attosecond dynamics of quadrupole transitions. Fully relativistic calculations have been performed to delineate the circumstances under which the quadrupole channels dominate. In addition, calculations have been carried out using relativistic random phase approximation (RRPA) [5] for noble gas atoms for the angular distribution of time delay including both dipole and quadrupole channels where the transition from dipole-dominance to quadrupole dominance is seen as a function of the angle between the photoelectron momentum and photon polarization. [1] E. P. Wigner, Phys. Rev. 98, 145 (1955); [2] R. Pazourek, S. Nagele and J. Burgdörfer, Rev. Mod. Phys. 87, 765 (2015); [3] J. Wätzel, et al, J. Phys. B 48, 025602 (2015); [4] A. Mandal, et al, Phys. Rev. A 96, 053407 (2017); [5] W. R. Johnson and C. D. Lin, Phys. Rev. A 20, 964 (1979). |
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V01.00008: Studies of excited electron decay in photoionization dynamics of Na20 inside C240 Hari Varma Ravi, Rasheed Shaik, Himadri Chakraborty The photoresponse studies on Na [1,2] clusters and fullerenes [3] has already been reported widely over the past few years. A family of novel endohedral fullerenes [4] can be realised by accommodating small metal clusters inside the hollow space of fullerene cages. In this work, the ground state of such an endohedral system, Na20@C240, is studied using a jellium-based density functional method with a gradient corrected exchange-correlation functional (LB94). Photoionization (PI) dynamics of this system is studied using a linear response framework called time-dependent local density approximation (TDLDA) [3]. The PI results obtained for Na20@C240 , and their comparison with results for isolated Na20 and C240 clusters, facilitate detailed understandings of the plasmon and inter-cluster Coloumbic decay (ICD) [5] resonances in the system. |
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V01.00009: Geometry driven structures in Na20 photoemission time delays Rasheed Shaik, Hari Varma Ravi, Himadri Chakraborty The advent of attosecond laser pulses has enabled the observation of ultrafast electronic dynamics of matter in real-time and initiated a number of studies in this direction over the past several years [1]. The photoemission time delay studies were reported earlier on valence shells of C60 near the cavity minima of emission [2]. The detection of minima in photoemission spectra of metal clusters [3] suggests possibilities of similar studies in cluster systems. In the current work, we study the photoemission quantum phases and Wigner-Smith time delays for Na20 cluster in the high energy region where such minima are seen [4]. Fundamentally, these structures arise due to the diffraction experienced by the outgoing photoelectron from the cluster edge. The ground state of Na20 is modelled using a jellium-based density functional method with a gradient corrected exchange-correlation functional (LB94) and its photoresponse properties are studied using the time-dependent local density approximation (TDLDA) [5]. |
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V01.00010: Molecular Frame Photoelectron Angular Distributions of 1,1-Dichloroethene (C2H2Cl2) Dissociated by 211.9 eV Photons at the Chlorine L-edge Demitri Call, Spenser J Burrows, Vern Davis, Gregor Kastirke, Wael Iskander, Kirk A Larsen, Niklas Melzer, Guglielmo G Panelli, Richard Strom, Travis Severt, Miriam Weller, Oleg Kostko, Itzik Ben-Itzhak, Thorsten Weber, Daniel Slaughter, Allen L Landers, Joshua Williams Photoionization and dissociation of 1,1-Dichloroethene at the Chlorine L-edge was performed with soft X-rays photons from the Advanced Light Source (ALS) on Beamline 9.0.1. The photon energy of 211.9 eV was used, which subsequently results in expected photoelectron energies of 4 and 5.7 eV. Data was collected to examine the correlated momenta of the molecular fragments and the photoelectron in coincidence using the COld-Target-Recoil-Ion Momentum Spectroscopy (COLTRIMS) method. Dissociation channels in the target involving two separate H+ ions contain substantial and unexpected proportion of measured electrons between 0-2 eV. These electrons indicate the possible presence of Post-Collisional Interaction (PCI) streaking effects, which would correlate to a molecular dissociation time in the hundreds of attoseconds. Other potential explanations for these low energy electrons will be examined. Results for channels including H+H+X and H+H+X+ measurements will be discussed. |
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V01.00011: Study on Anisotropic Materials to Enhance the Efficiency of the Photon Absorption in Optical Devices Jongmin Kim, Richard Kyung In this paper, a study of photonics on nano-scaled metal and nonmetal units consisting of layers of different atoms and molecules to form an optical device was presented. The optical strength can be maximized by adjusting material properties and the angle of incident light in the absorption layer, where the light resonantly excites surface plasmon polariton(SPP) in the SPP employed device. The purpose of this research is, through calculations and the use of a computer program, to find new combinations of metal and nonmetal units or metamaterials. The optimal incident angle of the light wave and the effective index were found with the use of Maxwell's equations and by modeling various metamaterials with multi-layers where efficient surface plasmon polariton was created. Their types of materials and size of layers showed propagating waves of light in an unconventional manner, such as Hyperbolic dispersion, which is anisotropic propagation. |
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V01.00012: The Iron Project \& The Opacity Project: 1.Photoionization of Fe XVII-XVIII for solar plasma opacities Sultana N Nahar, Werner Eissner, Anil K Pradhan We report the ongoing research at the Ohio State University for determination |
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V01.00013: PRECISION MEASUREMENTS
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V01.00014: Neutron Impact Ionization of the Carbon Atom James P Colgan, Michael S Pindzola Neutron impact single and double ionization cross sections |
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V01.00015: Magnetic Dichroism in the Two- and Three-Photon Ionization of Polarized Lithium Bishnu P Acharya, Santwana Dubey, A.H.N.C. D Silva, K. L. Romans, K. Foster, O. Russ, N. Douguet, Klaus R Bartschat, Daniel Fischer Symmetry breaks and shifts in the angular distributions of electrons emitted in ionization due to intense femtosecond laser fields have proven to provide detailed insights into the atomic break-up dynamics and timing. Prominent examples are “attoclock” experiments where ionization by elliptically polarized light is studied. Shifts in the photoelectron angular distributions are then interpreted in terms of tunneling time. In this contribution, we report on a similar phenomenon that arises in the few-photon ionization of excited and polarized atoms by linearly polarized light. A lithium target is prepared in the 2p (ml=+1) state and exposed to femtosecond laser pulses with tunable center wavelengths ranging from 665 nm to 800 nm. Depending on the wavelength, the angular distributions feature strong shifts with respect to the laser polarization direction. These observations are interpreted in terms of interfering partial waves with asymmetric m-distributions. |
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V01.00016: Charge Exchange Cross-Sections and Spectroscopy with Highly Charged Ions: Experimental Progress and Simulation Richard H Mattish, Patrick Johnson, Timothy J Burke, Jim Harriss, Steven Bromley, Michael Fogle, Chad E Sosolik, Joan Marler The Clemson University Electron Beam Ion Trap (CUEBIT) Facility allows for the creation and study for highly charged ions (HCIs). Currently, work is underway to combine cold target recoil ion momentum spectroscopy (COLTRIMS) with the EBIT, for the purpose of obtaining momentum-transfer-resolved charge exchange cross section measurements. We plan to study single and double electron capture with low/medium atomic number elements (e.g. Ne, Mg, Si, P, and Fe) from different neutral targets (e.g. H, He, and H2). Additionally, simulations of single electron capture for these ion-target species are being carried out using the flexible atomic code (FAC). These preliminary results are presented and trends that we might expect to see experimentally are discussed. |
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V01.00017: Comparison of elastic scattering of electron, positron and positronium from helium Cody M DeMars, Josiah Claypool, Sandra J Ward Quintanilla, Peter Van Reeth There exists a remarkable degree of similarity between the total cross section for electron and positronium scattering as a function of velocity from a number of targets, including helium \cite{[1]}. We have computed $s$-, $p$-, $d$- and $f$-wave phase shifts for elastic positron-helium scattering using the Kohn and inverse Kohn variational methods \cite{[2],[3]}. Using phase shifts for positron, electron and positronium scattering from helium, we have computed partial-wave, elastic differential, elastic integrated and momentum-transfer cross sections \cite{[4]}. We plan to show a comparison of various cross sections as a function of velocity for the three projectiles. |
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V01.00018: Collisions of excited Ps with antiprotons: Ps break-up and antihydrogen formation Ilya I Fabrikant, Harindranath B Ambalampitiya, Michael Charlton, Dmitry Fursa, Alisher Kadyrov, Igor Bray Low energy antimatter science has reached an important stage: experiment has moved from being technique-limited and has reached |
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V01.00019: Electron and positronium scattering by rare-gas atoms: free electron gas approximations and orthogonality Curtis Michels, Robyn S Wilde, Ilya I Fabrikant Measured total cross sections for scattering of Positronium (Ps) by various atomic and molecular targets are very similar to electron scattering cross sections above the Ps ionization threshold [1]. Below the ionization threshold measurements for rare-gas atoms exhibit small cross sections. Previously we used a Free Electron Gas (FEG) model for the exchange and correlation potentials supplemented by an Orthogonalizing Pseudopotential (OPP) to study Ps scattering with rare-gas atoms [2]. For the heavy rare-gases we obtained good agreement with experiment, although we did not find evidence of a Ramsauer-Townsend minimum. For the lighter rare gases like He and Ne agreement with experiment was worse. Free electron gas approximations do not take into account the effects of orthogonality between target and continuum orbitals. In this work we investigate the effect of enforcing orthogonality in electron and Ps scattering by rare-gas atoms. To enforce orthogonality we use a Lagrange multiplier method and make a comparison to results using the OPP and to experimental results. 1S. J. Brawley et al., Science 330, 789 (2010). 2R. S. Wilde and I. I. Fabrikant, Phys. Rev. A 98, 042703 (2018). |
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V01.00020: Electron, Positron and Positronium scattering by molecules: Free Electron Gas Approximations Robyn S Wilde, Harindranath B Ambalampitiya, Ilya I Fabrikant Free Electron Gas (FEG) approximations to the exchange and correlation interactions have long been used in electron scattering by atoms and molecules [1,2]. More recently we developed a FEG model for the exchange and correlation potentials describing the Positronium (Ps)-atom or molecule interaction [3]. This FEG model was applied to Ps-N2 scattering and successfully reproduced resonant features that were seen experimentally near the Ps-ionization threshold. In this work we apply our FEG model to Ps-O2 and Ps-CO2 scattering. For these targets we also see resonance structures in the elastic cross section near the ionization threshold. Lastly, we apply the correlation potential of [2] to positron scattering by the same molecular targets with the purpose of calculation of Ps break-up in the binary-encounter approximation. |
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V01.00021: Positron binding to chlorinated hydrocarbons: experiment and theory. James R Danielson, Andrew Swann, Gleb Gribakin, Soumen Ghosh, Clifford M Surko Measurement of the low-energy positron annihilation on molecules is dominated by vibrational Feshbach resonances. The downshift of the resonances relative to the known molecular vibrations provides a measure of the positron-molecule binding energy, $\epsilon_b$. Measured and calculated positron binding energies are presented for a range of hydrocarbons and their chlorine-substituted counterparts. The calculations are performed using the model-correlation-potential method.\footnote{\small A. R. Swann and G. F. Gribakin, J. Chem. Phys. 149, 244305 (2018).}$^{,}$\footnote{\small A. R. Swann and G. F. Gribakin, Phys. Rev. Lett 123, 113402 (2019)} Generally good agreement is found between the model predictions and the experiments. Both experiment and theory demonstrate the large effect that the chlorine atoms have on $\epsilon_b$ and the strong sensitivity of $\epsilon_b$ to the position of the Cl atoms. Overall trends with molecular polarizability, dipole moment, and geometry are discussed. Calculated wavefunctions and the electron-positron annihilation rates in the bound state will also be discussed. |
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V01.00022: K-Shell Photoabsorption in Si11+ Including Relativistic Effects Thomas W Gorczyca, M. Fatih Hasoglu, Steven T Manson As part of a complete investigation into the entire Si isonuclear sequence for x-ray spectral diagnostics, we focus on the Li-like Si11+ ion, which is a simpler 3-electron system, is susceptible to stronger relativistic effects due to the large charge, and also features in x-ray astrophysical spectral models. R-matrix calculations are carried out for the photoabsorption cross section of Si11+ including 1) the Auger broadening due to spectator Auger decay of K-shell excited autoionizing resonances, and 2) relativistic contributions via use of a Breit-Pauli R-matrix (BPRM) approach. Computed background cross sections are in good overall agreement with earlier resonanceless photoionization cross sections, indicating that the direct photoabsorption features are taken into account properly. Comparison with earlier BPRM cross sections [M.~C.~Witthoeft, et al., ApJ 192, 7 (2011)] shows good agreement in general but the new calculations now resolve earlier step-like discontinuities and improve relaxation energies. The computed cross sections are important for the detailed analysis of the gaseous component of the atomic and ionic Si K edge by using high resolution Chandra spectra of low-mass X-ray binaries. |
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V01.00023: ULTRAFAST AND STRONG FIELD PHYSICS
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V01.00024: A curious case of hybrid photoionization of (Mg@C60)+ molecular cation Maia Magrakvelidze, Steven T Manson, Himadri Chakraborty The closeness of Mg 3s and C60 HOMO level-energies in Mg@C60 suggests that the total ground state energies of its cation with configurations Mg+@C60 and Mg@C60+ are comparable. This near-degeneracy ensures hybridization between these configurations in the photoionization of singly-charged (Mg@C60)+ cation. We investigate the effect of this hybridization by comparing the photoionization properties of each configuration with that of their hybrid in equal proportion of mixing at the level of photo-amplitudes. The calculation is performed in the framework of linear-response density functional theory (DFT) with the dipole response of the system to the incoming radiation [1]. The Kohn-Sham equations of the delocalized valence electrons are solved to obtain the ground state structures while the cage of 60 C4+ ions is jelliumized [2]. Results of cross sections, emission phases and Wigner time delays will be presented in the conference. |
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V01.00025: Three electron coincidence scheme and momentum maps for Strong-field atomic ionization Dmitry Efimov, Artur Maksymov, Marcelo Ciappina, Jakub Prauzner-Bechcicki, Maciej Lewenstein, Jakub Zakrzewski Kinematically complete measurements of charged particles are a standard tool for strong-field ionization experiments nowadays that allow one for restoring ionization dynamics from the recorded electronic and ionic momenta1,2. Recent studies employ the well-developed two-electron coincidence technique3,4. At the same time the three-electron coincidence schemes are a clear next possible step. We simulate such a prospective experiment with our newly developed computational code that is based on numerical solution of time-dependent Schrödinger equation on a grid5-7. For the first time we obtain quantum-mechanical three-electron momenta distributions. These data are visualized with Dalitz plots and are further analysed. For the regime of femtosecond linearly-polarised near-infrared laser pulses acting on atomic target, we show that such plots are a valuable source of information on electronic rescattering that is sensitive to peak laser intensity and carrier-envelope phase. We pay a special attention to the effect of electronic spin configuration of particular atoms on the ionization process. |
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V01.00026: Study of ionization-induced hole localization of molecules by a strong external field using WFAT Imam S Wahyutama, Kenneth Lopata, Mette B Gaarde, Kenneth J Schafer In this work, we try to answer the question of where a hole is most likely to be created following tunnel ionization by a strong electric field. Using Weak-Field Asymptotic Theory (WFAT), we look at the contribution of the various atom-centered regions of the molecular orbital to be ionized. By comparing the transverse momentum distribution of the ionized electron from the spatial region around each atom making up the molecule, insight can be gained about where an electron has most likely tunneled through the field-induced barrier. The result of this study is expected to be useful for other fields of research where the creation of a localized hole is central, such as the study of charge migration. Here, one desires an initial density exhibiting a localized hole because its subsequent dynamic is more easily tracked. Hence, the knowledge about how to create such a hole is critical. |
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V01.00027: Total and net photon number pathways to optimize molecular orientation by an ultra-short THz pulse Norio Takemoto, Brett Esry Molecules oriented in the laboratory frame offer many benefits for experiments to understand their complex interaction with strong laser light. One method to orient molecules under field-free conditions is to apply a short, impulsive THz pulse. There have been various proposals, such as using a pulse sequence, to enhance the degree of orientation. Yet, basic questions---such as at which time after the pulse is the orientation degree maximized and what is the optimal carrier-envelope phase (CEP)---have been addressed largely by numerical computation so that a general analytical understanding is still lacking. We attempt to address this lack by analyzing the orientation dynamics of a linear rigid molecule in terms of the interference of transition pathways labeled by the total and net numbers of THz photons absorbed and emitted. The amplitudes of these pathways are unambiguously obtained by expanding the rotational state as a perturbation series in the THz field strength and a Fourier series in the CEP. The perturbation order and the Fourier index correspond to the total and net photon numbers, respectively. We derive an expression for the optimal free-propagation time and CEP to maximize the orientation degree at the weak-field limit and predict how this optimal condition changes as the THz intensity is increased. |
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V01.00028: Two-Body Dissociation of Formic Acid Following Double Ionization by Ultrafast Laser Pulses Darwin Daugaard, Tiana A Townsend, Eric Wells, Travis Severt, Farzaneh Ziaee, Kurtis D Borne, Surjendu Bhattacharyya, Bethany C Jochim, Kevin D Carnes, Daniel Rolles, Artem Rudenko, Itzik Ben-Itzhak While formic acid (HCOOH) is a relatively small, planar polyatomic molecule, it contains three atomic species. Formic acid displays complicated dynamics following strong-field ionization, including hydrogen migration and bond rearrangement channels. Deuterium tagging combined with coincidence momentum imaging measurements of all fragment ions allows for the exploration of the two-body dissociation channels resulting from double ionization. The branching ratios, kinetic energy release, and angular distributions for two-body double ionization channels obtained with 25-fs laser pulses centered at 780 nm and a peak intensity of 2×1015 W/cm2 are presented. The role of the hydroxyl and the carbonyl hydrogen atoms is explored. |
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V01.00029: Probing the effect of laser-carrier-envelop phase in frequency-comb high-order harmonic generation of He atoms. Chang-Tong Liang, Peng-Cheng Li We present an ab initio nonperturbative study of the role of carrier envelop phase (CEP) of the laser pulse trains in frequency-comb high-order harmonic generation (HHG). The frequency-comb HHG is obtained by solving three-dimensional time-dependent Schrödinger equation of the He atom driven by the intense laser pulse trains. We find that the structures of frequency-comb HHG in plateau regions are very sensitive to CEP of the laser pulse trains, while the dependence of the low-energy and near-cutoff harmonics on CEP is not observed. In addition, the dynamics of frequency-comb HHG at the plateau regions are clarified. Our results enable us to obtain a clear understanding of the role of CEP of the laser pulse trains in frequency-comb HHG and provide an insight into the field of ultrafast science and technology. |
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V01.00030: Enhanced ionization of counterrotating electrons via doorway states in ultrashort circularly polarized laser pulses. Spencer R Walker, Lucas Kolanz, Joel A Venzke, Andreas Becker Atto- or femtosecond laser pulses potentially provide the opportunity to generate ultrashort spin-polarized electron pulses for probing chiral systems and magnetic properties of materials on ultrafast timescales. A key element in the generation of spin-polarized electrons is a selectivity in ionization to the sense of the electron's rotation in the initial state with respect to the rotation direction of the laser field. Based on numerical solutions of the time-dependent Schrodinger equation we predict a surprisingly large enhancement in the emission of electrons, that are initially counterrotating with respect to the rotation of the applied field, during the interaction of rare gas atoms with ultrashort circular polarized laser pulses in the intermediate few-photon ionization regime. The physical mechanism behind this observation is related to resonant enhanced ionization via states close in energy to the initial states. |
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V01.00031: Circular Dichroism in Atomic Resonance-Enhanced Few-Photon Ionization Taylor Moon, Nicolas Douguet, Haruma Handi Nishanka De Silva, Klaus R Bartschat, Daniel Fischer We investigate few-photon ionization of lithium atoms prepared in the polarized 2p (m = +1) state when subjected to femtosecond light pulses with left- or right-handed circular polarization [1] at wavelengths between 665 nm and 920 nm. We consider whether ionization proceeds more favorably for the electric field co- or counter-rotating with the initial electronic current density. Strong asymmetries are found and quantitatively analyzed in terms of “circular dichroism” (CD). While the intensity dependence of the measured CD values is rather weak throughout the investigated regime, a very strong sensitivity on the center wavelength of the incoming radiation is observed. While the co-rotating situation overall prevails, the counter-rotating geometry is strongly favored around 800 nm due to the 2p-3s resonant transition, which can only be driven by counter-rotating fields. The observed features provide insights into the helicity dependence of light-atom interactions, and on the possible control of electron emission in atomic few-photon ionization by polarization-selective resonance enhancement. |
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V01.00032: Study of attoclock experiments using Bohmian mechanics Taylor Moon, Nicolas Douguet, Klaus R Bartschat We employ Bohmian mechanics to investigate strong-field ionization in attoclock experiments [1,2]. We consider hydrogen and a short-range Yukawa potential to compute streamlines of the probability current. The obtained trajectories can be used to retrieve physical observables and to improve our understanding of the tunneling dynamics with circular light. In particular, we can look at the spatial origin of the Bohmian trajectories associated with a specific asymptotic photoelectron momentum, as well as the correspondong exit position and velocity. This information provides us with new insights to interpret momentum distributions in the attoclock setup. |
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V01.00033: Ultrafast Resonant Rescattering Quantum Interference in Laser-Induced Photoelectron Imaging Nicholas Werby, Andrew S Maxwell, Ruaridh Forbes, Carla Figueira de Morisson Faria, Philip H Bucksbaum In laser-induced strong-field ionization (SFI), ultrafast electron dynamics can be revealed by analyzing the holographic interference structures in photoelectron momentum distributions (PMDs) produced by interfering electron trajectories. Of these interfering trajectories, ones which involve rescattering from the parent ion or molecule probe attosecond dynamics in strongly driven atoms and molecules. In the strong-field approximation (SFA), backwards rescattering trajectories are respectively labeled short or long depending on whether they rescatter before or after the peak of the vector potential of the laser. Rescattering patterns have been extensively studied for the highest rescattering momentum electrons, at which the short and long trajectories are the most similar; however, the lower momentum rescattering regime is largely unexplored. In this regime, we identify rings of enhanced photoelectron yield which appear to be caused by the interference of short and long trajectories with the same final momentum. We simulate coalescing short and long trajectory interference patterns and match them to high fidelity experimental PMDs with reasonable success. We determine that the locations of these rings are independent of laser intensity. Because these trajectories have different launch points in the laser cycle, manipulating the shape of the laser field by adding a second laser frequency will cause these rings to respond, providing attosecond-scale insight into the target. A complete understanding of these interference patterns may prove crucial to our interpretation of SFI dynamics, and allow us to probe attosecond electron-ion interactions after ionization. |
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V01.00034: Mechanism of below-threshold high-order harmonic generation of Na in the intense elliptically polarized laser field Zhi-Bin Wang, Peng-Cheng Li We explore the mechanism of below-threshold harmonic generation (BTHG) of Na atom subject to intense elliptically polarized laser fields. The Na atom is described by an accurate model potential which reproduces both the bound state energies and the oscillator strengths. An intuitive picture is demonstrated by the analysis of the quantum channels of electron in BTHG. The HHG spectra can be calculated accurately and efficiently by solving three-dimensional time-dependent Schrödinger equation by means of the time-dependent generalized pseudospectral method. The results show that the yields of the BTHG generated by the elliptically polarized laser fields are high when the ellipticity is decreased, and the yields of the BTHG are sensitive to the ellipticity of the laser fields. Our results provide a potential method to control the enhancement of the BTHG by the polarized laser field. |
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V01.00035: Role of carrier-envelope phase on below-threshold high-order harmonic generation of Ar atom. Yang-Yang Chen, Peng-Cheng Li We theoretically study the dependence of carrier-envelope phase (CEP) on high-order harmonic generation (HHG) of Ar atom in the few cycle laser pulses. The HHG spectra can be calculated accurately and efficiently by solving three-dimensional time-dependent Schrödinger equation by means of the time-dependent generalized pseudospectral method. We find that the yields of near- and below-threshold HHG is sensitive to the CEP of the laser pulse. Combining with a wavelet transform of the quantum time-frequency spectrum and an extended semiclassical analysis, the role of CEP on the near- and below-threshold harmonic generation processes is clarified. |
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V01.00036: Strong-field-induced dissociation dynamics of tribromomethane studied using coincident ion momentum imaging Surjendu Bhattacharyya The strong-field-induced dissociation dynamics of tribromomethane (CHBr3) were investigated as a function of time delay between a pair of 28-femtosecond (fs) near-infrared laser pulses at a peak intensity of 6 x 1014 Wcm-2. Hydrogen and bromine migration channels are observed, and the onset of dissociation in the H-migration channel appears to be delayed by 120 fs compared to the direct C-Br bond dissociation. Three- and four-body fragmentation processes are found to occur via both concerted and sequential pathways, with a major contribution from the former. Five-body fragmentation is dominated by concerted bond breakup. The experimental results are compared to Coulomb explosion simulations. |
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V01.00037: Wavelength dependence in strong field ionization of water Mathew Britton, Gregory A McCracken, Andrew J Howard, Nolan Peard, Ruaridh Forbes, Philip H Bucksbaum It has recently been shown that strong field multiple ionization of water depends on the duration and intensity of the laser pulse. While the polarizability of neutral water is isotropic, the polarizability of the molecular ions can be significant and evolve in time. If the molecular ions spend enough time in the field, dynamic alignment can reorient them and modify the yield of dissociating fragments as a function of angle relative to the polarization of the laser. Unbending motion is one way that the polarizability of the molecular ions increases. Here, we study strong field ionization of water in the long pulse regime where dynamic alignment and unbending are known to contribute at 800 nm, and we tune the laser wavelength to modify coupling between the states of the monocation. A resonance between the X and A states at 660 nm should excite the monocation and initiate unbending motion, but our results cannot be explained without considering the dynamics and structure of the dication and trication. To conduct these measurements, we utilize laser pulses with a duration of 40 fs and central wavelengths of 660 nm, 800 nm, and 1330 nm to multiply-ionize an effusive molecular beam of water. The resulting charged fragments are detected using a velocity map imaging apparatus. Our results provide additional clues about the strong field ionization of water. |
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V01.00038: Effective time-independent potentials for Coulomb-laser coupling Soumi Dutta, Ulf Saalmann Since the introduction of the attocklock, there has been intense research to calibrate the clock by determining the angular deflections due to |
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V01.00039: Computing Ionization Rates from Periodic Orbits in Chaotic Rydberg Atoms Ethan T Custodio, Kevin A Mitchell When placed in parallel magnetic and electric fields, the electron trajectories of a classical hydrogenic atom are chaotic. The classical ionization rate of such a system can be computed with brute force Monte Carlo techniques, but these computations require enormous numbers of trajectories, provide little understanding of the dynamical mechanisms involved, and must be completely rerun for any change of system parameter, no matter how small. We demonstrate an alternative technique to classical trajectory Monte Carlo computations, based on classical periodic orbit theory. In this technique, ionization rates are computed from a relatively modest number, perhaps a few thousand, of periodic orbits of the system. One only needs the orbits' periods and stability eigenvalues. A major advantage is that as system parameters are varied, one does not need to repeat the entire analysis from scratch; one can numerically continue the periodic orbits as the parameters are varied. We demonstrate the periodic orbit technique for the ionization of a hydrogen Rydberg atom in applied parallel electric and magnetic fields. Additionally, this technique can be extended to analyze the semi-classical behavior of the system. |
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V01.00040: Optimal Control of the Elliptically Polarized Attosecond Pulse Generated by Two-color Polarization Gating Using Bayesian Optimization Chon-Teng Belmiro Chu, Shih-I Chu We present an efficient high-order-harmonic optimal control scheme for the generation of an for the generation of an isolated ultrashort elliptically polarized attosecond pulse in gases with a two-color polarization-gating. The optimal control scheme is implemented using Bayesian Optimization. For illustration, the high-order-harmonic generation (HHG) of a Helium atom is considered for optimization. It is shown that optimally shaped laser waveforms can greatly enhance the difference between the right circularly polarized component of the HHG and the left one and extend the HHG plateau that can generate an isolated ultrashort elliptically polarized attosecond pulse efficiently. Moreover, by performing a Monte Carlo classical trajectory study and a detailed wavelet time-frequency analysis, the detailed mechanism responsible for the HHG processes is revealed and the optimized harmonics corresponding to the short-trajectory electrons are responsible for an isolated ultrashort 53-as pulse. |
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V01.00041: Interference in nonlinear Compton scattering Akilesh Venkatesh We study the interference between Compton and nonlinear Compton scattering from bound electrons using a two-color field in the x-ray regime theoretically. The underlying phase shifts are analyzed using a perturbative approach in the incoming classical field. A non-perturbative approach in the classical field is used to benchmark the perturbative approach. The interference is examined for different combinations of linear polarization of the two fields when the Compton and the nonlinear Compton scattered waves have the same wave vector and polarization. The interference is found to occur only for two cases. When it does occur, there exists an intrinsic phase difference between the Compton and nonlinear Compton scattered wave function of either 0 or π depending on the scattering angle. |
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V01.00042: QUANTUM INFORMATION AND QUANTUM OPTICS
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V01.00043: GaAs-based photoemission sources of spin-polarized electrons: A composite GaAs-coated W nanotip and plasmonic planar GaAs emitters Sam Keramati, Joon Sue Lee, Ali passian, Herman Batelaan, Timothy J Gay We have recently demonstrated ultrafast multi-photon photoemission of spin-polarized electrons from GaAs shards using a 20 kV Mott gold-target electron polarimeter. Both the yield and polarization of the emitted electron pulses were characterized. Scanning electron microscopy of these photocathodes revealed random nanostructures at the photoemitting surfaces. To achieve well-defined point-like nanotips with significant spatial coherence properties, we are now investigating the deposition of thin layers of GaAs on electrochemically etched W nanotip needles using molecular beam epitaxy. We report progress made on this study as well as on the development of GaAs tips fabricated by focused ion beam milling. Additionally, simulation results of several plasmonic nanostructures in planar film geometry are presented that demonstrate local field enhancement due to surface plasmon excitation. The excited plasmons are expected to increase both the photoemission yield and the order [1], when compared with a flat film at modest fs laser oscillator powers. The structures include arrays of nanoholes [2], and noble metal islands and nanoscale patterns on flat GaAs substrates. |
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V01.00044: Time crystals in a shaken atom-cavity system Jim P Skulte, Phatthamon Kongkhambut, Hans Keßler, Andreas Hemmerich, Jayson Cosme, Ludwig Mathey Periodically driven atoms in a high finesse optical cavity enjoy a very rich phase diagram. By off resonant driving the equilibrium properties of the system can be renormalised in a controlled fashion, while resonant driving allows for new non-equilibrium phases such as time crystalline phases and dynamical density wave orders as recently reported. In this poster, I will discuss the emergence of an incommensurate time crystal by a phase-modulated transverse pump field resulting in a shaken pump lattice. This periodically driven system exhibits macroscopic oscillations in the number of cavity photons and order parameters at noninteger multiples of the driving period, which signals the appearance of an incommensurate time crystal. The subharmonic oscillatory motion corresponds to dynamical switching between symmetry-broken states, which are nonequilibrium bond ordered density wave states. Employing a semiclassical phase-space representation for the driven-dissipative quantum dynamics, we confirm the rigidity and persistence of the time crystalline phase. We identify experimentally relevant parameter regimes for which the time crystal phase is long lived, and map out the dynamical phase diagram. I will further present preliminary experimental results that confi rm our theoretical predictions. |
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V01.00045: Cold molecule synthesis on a nanophotonic microring circuit Ming Zhu, Tzu-Han Chang, Xinchao Zhou, HIKARU TAMURA, Chen-Lung Hung Cold molecules can be synthesized from a pair of cold atoms via photoassociation (PA) followed by spontaneous decay. However, the decay channel is not unique due to complex rovibration energy levels. Through enhancing the radiative coupling between an excited state and a targeted ground state, it is possible to synthesize a cold ground state molecule with near-unity efficiency. Our goal is to achieve strong coupling between a single Rb atom and subsequently a Rb2 excited state molecule with a whispering gallery mode nanophotonic resonator. We aim at achieving large molecule-photon cooperativity that can enhance the decay rate towards a rovibrational ground state. Our experiment will make use of optical tweezers to localize Rb atoms on a high-Q Si3N4 microring resonator, followed by performing resonator-enhanced PA of ground state molecules. We will discuss our experiment setup, and a state-sensitive optical detection scheme that may be realized to achieve near-unity quantum state detection fidelity. |
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V01.00046: Cavity QED with trapped atoms on a nanophotonic microring circuit Xinchao Zhou, Tzu-Han Chang, HIKARU TAMURA, Ming Zhu, Chen-Lung Hung Atoms trapped and interfaced with guided light in nanophotonic circuits form an exciting new platform for fundamental research and applications in quantum optics, quantum many-body physics and quantum networks. The ability to form an organized atom–nanophotonic hybrid lattice, and to induce tunable long-range atom-atom interactions with photons present a novel opportunity to explore collective quantum optics and many-body physics. Our system is based on high quality silicon nitride microring resonators fabricated on a transparent membrane substrate, which is compatible with laser cooling and trapping of cold atoms. This platform holds great promises as a scalable on-chip atom cavity QED system with potentially high cooperativity parameters C ≈ 500. We present our on-going experimental effort for trapping and coupling atoms with a microring, and improvements of the microring platform for future applications as a high-fidelity atom-photon quantum interface. |
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V01.00047: Spin- and atom-interactions in multimode cavity QED Ronen Kroeze, Yudan Guo, Brendan Marsh, Jonathan Keeling, Benjamin L Lev Optical cavity QED provides a versatile platform with which to explore quantum many-body physics in driven-dissipative systems. Multimode cavities are particularly useful for exploring beyond mean-field physics. We highlight experimental progress towards simulation of driven-dissipative spin glasses. This involves demonstrating a strong, tunable-range, photon-mediated atom-atom interaction, a sign-changing interaction due to Gouy phases, and a spin-spin interaction in a spinful Bose-Einstein condensate. The joint spin-spatial degrees of freedom exhibit spinor self-organization as well as dynamical spin-orbit coupling. We highlight near-term experimental studies of few-body interacting systems exploring exotic, strongly correlated phenomena such as driven-dissipative spin glasses and quantum neural networks. |
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V01.00048: A Quantum Network Node Based on a Nanophotonic Interface for Atoms in Optical Tweezers Brandon Grinkemeyer, Polnop Samutpraphoot, Tamara Dordevic, Paloma Ocola, Ivana Dimitrova, Hannes Bernien, Vladan Vuletic, Mikhail Lukin Efficient interfaces between photons and memory qubits constitute fundamental building blocks for quantum networking and large-scale quantum information processing. Our approach utilizes a photonic crystal cavity to realize such optical interfaces for atoms in optical tweezers. With this platform, we observe strong coupling between two atoms mediated by the cavity. Combining this observation with coherent manipulation and non-destructive measurements, we implement a protocol for generating Bell pairs that remain entangled when transported away from the cavity structure. These results present prospects for additional capabilities, such as rapid non-destructive readout and flexible connectivity, to neutral atom quantum information processors with integrated optical interconnects. |
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V01.00049: Toward the implementation of quantum key distribution with cold atomic quantum memories Cesar Muro Cabral, Jesús A Jiménez Arias, J. Mauricio López Romero, Karina Jimenez-Garcia, Neil V Corzo Quantum key distribution (QKD) is a quantum technology designed to encrypt sensitive information in an era where increasing computation power poses a threat on classical encryption methods. As a branch of Quantum Information Science, QKD has had a significant advance toward its practical implementation. At the Quantum Technologies Laboratory of the Center for Research and Advanced Studies (Laboratorio de Tecnologías Cuánticas, CINVESTAV, Unidad Querétaro), we seek to implement a complete quantum communication network based on QKD that includes elements such as quantum memories as repeater nodes, allowing the storage and retrieval of information encoded in quantum states of light. |
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V01.00050: Unraveling the Quantum Nature of Atomic Self-Ordering in a Ring Cavity Stefan Ostermann, Wolfgang Niedenzu, Helmut Ritsch Atomic self-ordering to a crystalline phase in optical resonators is a consequence of the intriguing nonlinear dynamics of strongly coupled atom motion and photons. Generally the resulting phase diagrams and atomic states can be largely understood on a mean-field level. However, close to the phase transition point, quantum fluctuations and atom-field entanglement play a key role and initiate the symmetry breaking. Here we propose a modified ring cavity geometry, in which the asymmetry imposed by a tilted pump beam reveals clear signatures of quantum dynamics even in a larger regime around the phase transition point. Quantum fluctuations become visible both in the dynamic and steady-state properties. Most strikingly we can identify a regime where a mean-field approximation predicts a runaway instability, while in the full quantum model the quantum fluctuations of the light field modes stabilize uniform atomic motion. The proposed geometry thus allows to unveil the "quantumness" of atomic self-ordering via experimentally directly accessible quantities. |
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V01.00051: Novel structures, phase transitions and dissipation induced dynamics in a superradiant crystal Alexander Baumgärtner, Davide Dreon, Xiangliang Li, Simon Hertlein, Tobias Donner, Tilman Esslinger We report on the experimental realization of a superradiant phase transition of a Bose-Einstein Condensate in a high finesse Cavity with a repulsive pump-lattice, in which the destructive interference between pump and cavity elds lowers the total energy of the system. Due to lattice symmetries, the band structure plays a key role in this process, and we show that the atoms self-organize in the second band with observable consequences for the phase diagram and the atomic momentum distributions. |
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V01.00052: A Single Atom Scanning Microscope for Cavity Field Detection Yuehui Lu We present a novel cavity QED system of a tweezer array of single rubidium atoms trapped in a high finesse near-concentric optical cavity. Individual atom-cavity couplings are controlled by tuning tweezer position, and single atoms are imaged with high fidelity through a high numerical aperture (NA=0.5) objective transverse to the cavity. |
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V01.00053: Simulating Loading Dynamics of Laser-Cooled Atoms into Photonic Crystal Membrane – Capped Hollow-Core Fibers Sreesh V, Michal Bajcsy A dielectric slab perforated with a lattice of wavelength-sized holes can be designed to act as a high-reflectivity mirror. A pair of such photonic crystal (PC) membranes can create a cavity when attached to either side of a piece of a hollow-core optical fiber. Laser-cooled atoms loaded into the few-micron diameter hollow core of the fiber through the PC membranes would form a new type of cavity-based quantum optics platform. Using numerical simulations, we estimate whether laser-cooled atoms can make their way through the holes of the PC membrane and be guided into the hollow fiber core with optical dipole trap. The atoms, released from a MOT (Magneto-Optical Trap) cloud placed vertically above the capped-fiber, will traverse through the scattered fields of the optical dipole trapping laser and also interact with the membrane when sufficiently close. These 3D potential maps are estimated by computational electromagnetics software. The trajectories of atoms are integrated with the help of parallel programs in order to estimate the overall loading efficiencies. We aim to explore different conditions of the system to assess loading feasibility: namely, the position, size and temperature of the MOT cloud, optical dipole trapping beam strength, and also, the geometry of the PC membrane. |
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V01.00054: Echoes in a single quantum Kerr-nonlinear oscillator Ilia Tutunnikov, Viswambharan Rajitha, Ilya Averbukh A quantum Kerr-nonlinear oscillator is a paradigmatic model in cavity and circuit quantum electrodynamics, and quantum optomechanics. We theoretically study the echo phenomenon in a single impulsively excited ("kicked") Kerr-nonlinear oscillator. We reveal two types of echoes, "quantum" and "classical" ones, emerging on the long and short time scales, respectively. The mechanisms of the echoes are discussed, and their sensitivity to dissipation is considered. These echoes may be useful for studying decoherence processes in a number of systems related to quantum information processing. |
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V01.00055: Active control of a diode laser with injection locking Ziting Chen, Bojeong Seo, Mingchen Huang, Mithilesh Parit, Peng Chen, Gyu-boong Jo Injection locking of a diode laser is essential in a majority of fields including laser spectroscopy, laser cooling and trapping and optical communication, and especially critical when the laser power budget is limited. However, the stability of injection locking is a major obstacle, since environmental variations and laser current drifts can frequently cause the injected slave laser out of lock. In this poster, we introduce a novel active stabilization scheme for injection locking by simply using a narrow laser-line filter and a photodiode. Based on characteristic response of the reflected power from the filter versus spectral modes, high spectral mode purity and low intensity noise can be simultaneously maintained by a proper feedback to the laser current. This method is already used in the daily production of Bose-Einstein condensates of erbium atoms in our lab. Besides, our method eliminates the usual need of complicated and bulky devices, such as Fabry-Perot interferometers or wavemeters, to monitor the state of injection locking. Moreover, it favors miniaturized and integrated modules for the active control of injection locking of diode lasers, which would greatly simplify versatile applications of laser injection locking. |
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V01.00056: QUANTUM INFORMATION SCIENCE
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V01.00057: A fast optimal control algorithm for quantum sensing Santiago Hernández Gómez, Giovanni Fasiolo, Paola Cappellaro, Antonello Scardicchio, Nicole Fabbri NV centers in diamond have been established in the last decade as a prime platform for quantum sensing, with applications ranging from nanomaterial characterization to biosensing, and magnetic resonance imaging. With the burgeoning of these applications, more relevant becomes the demand for improving the sensor performance. |
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V01.00058: Enhanced Quantum Sensing with Dual Probing Twin Beams Umang Jain, Mohammadjavad Dowran, Alberto M Marino Quantum metrology with light utilizes the reduced noise properties of quantum states of light for enhancing the sensitivity of measurements beyond the shot noise. The ability to take full advantage of available quantum resources is still an open question and requires customizing the response of the sensing devices. We show that a dual probing approach where both beams of a two-mode squeezed state (twin beams) of light interface with the sensing device can enhance its sensitivity beyond approaches where one beam is used as a probe and the other as a reference for intensity difference measurements. To implement this sensing configuration, we design plasmonic structures that consist of an array of nanoholes that exhibit resonances with relative shift for two orthogonal linearly polarized fields. Our calculations show that if we interface orthogonally polarized twin beams with structures that exhibit a response with opposite slopes for the different polarizations, the sensitivity in detection of local changes in refractive index approaches the sensitivity limit that can be achieved with single mode squeezed light. Although single mode quantum states, in principle, are optimal states for sensing, our approach enables the use of differential detection techniques that cancel technical noise that can limit or prevent a quantum enhancement. Finally, we present our preliminary experimental progress on this sensing approach. |
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V01.00059: High-purity solid parahydrogen for trapping atoms and molecules Ashok Bhandari, Alexandar Rollings, Jonathan D Weinstein Alkali atoms trapped in solid hydrogen matrices have demonstrated ultralong electron spin coherence times and are promising as quantum sensors. Solid hydrogen consists of hydrogen molecules which can exist in two nuclear spin states: I=0 parahydrogen and I=1 orthohydrogen. Prior work has revealed that the spin coherence of atoms (and the nuclear spin coherence of molecules) is limited by magnetic noise from orthohydrogen molecules in the parahydrogen matrix. Through the use of a cryogenic catalyst we purify gaseous parahydrogen prior to deposition and grow solid parahydrogen matrices with lower orthohydrogen impurity fractions than previously reported in the literature. This should lead to greater spin coherence times and improved quantum sensing. |
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V01.00060: Universal Optima of EIT-based quantum sensors for Rydberg RF-field detection David H Meyer, Christopher M O'Brien, Donald P Fahey, Kevin C Cox, Paul Kunz Electric field sensors based on thermal Rydberg atoms hold great potential as wideband RF field sensors, with Standard Quantum Limit (SQL) sensitivities at the pV/cm/√Hz level. Despite significant progress, experiments are still orders of magnitude away from achieving the SQL. We present an analytical and numerical study of one aspect of this shortfall: to find the universal optimum performance, under minimal assumptions, of electromagnetically induced transparency (EIT) based spectroscopy. We determine under what conditions EIT probing approaches the standard quantum limit, deduce the numerical inefficiency of EIT relative to Ramsey spectroscopy, and derive the optimal probing strengths for realistic experimental parameters. Our generalized model is not specific to Rydberg sensors, and is generally applicable to any quantum sensor that relies on EIT spectroscopy readout. As such, these results set a bound to how close such an EIT-probed quantum sensor can get to the SQL and what experimental resources are required to achieve it. |
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V01.00061: Multi-parameter estimation with multi-mode Ramsey interferometry Xinwei Li, Jia-Hao Cao, Qi Liu, Meng Khoon Tey, Li You Estimating multiple parameters simultaneously is of great importance to measurement science and application. For a single parameter, atomic Ramsey interferometry (or equivalently optical Mach–Zehnder interferometry) is capable of providing the precision at the standard quantum limit (SQL) using unentangled probe states as input. In such an interferometer, the first beam splitter represented by unitary transformation generates a quantum phase sensing superposition state, while the second beam splitter recombines the phase encoded paths to realize interferometric sensing in terms of population measurements. We prove that such an interferometric scheme can be directly generalized to estimation of multiple parameters (associated with commuting generators) to the SQL precision using multi-mode unentangled states, if (but not iff) U is orthogonal, i.e. a unitary transformation with only real matrix elements. We show thatsuch a U can always be constructed experimentally in a simple and scalable manner. The effects of particle number fluctuation and detection noise on such multi-mode interferometry are considered. Our findings offer a simple solution for estimating multiple parameters corresponding to mutually commuting generators. |
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V01.00062: Extreme spin squeezing: transforming non-squeezing interaction into squeezing interaction via rotation pulses Long-Gang Huang, Feng Chen, Xinwei Li, Yaohua Li, Rong Lu, Yong-Chun Liu Spin squeezing plays an important role in quantum metrology and quantum information science. In realistic systems, the lack of required squeezing interactions prevents the generation of squeezing. We put forward a general scheme to synthesize extreme spin squeezing in non-squeezing systems. Aided with the periodical rotation pulses, we transform the original non-squeezing interaction into squeezing interaction, with significantly enhanced interaction strength. The sign of the enhanced interaction coefficient can also be altered, which can be applied to the time-reversal readout protocol for nonlinear interferometers. The obtained spin squeezing can ultimately reach the Heisenberg limit with measurement precision ∝ 1/N for N particles. Meanwhile, our scheme is demonstrated to be robust to fluctuations of pulse areas and pulse separations. This work provides the possibility of realizing extreme spin squeezing with Heisenberg-limited precision measurements in a large number of non-squeezing systems. |
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V01.00063: Progress towards realizing a cw superradiant laser Vera M Schäfer, Julia R Cline, Dylan Young, James K Thompson Superradiant lasers are a promising path towards realizing a narrow-linewidth, high-precision and high-bandwidth active frequency reference [1]. They shift the phase memory from the optical cavity, which is subject to technical and thermal vibration noise, to ultra-narrow optical atomic transitions of cold atoms trapped inside the cavity. Our previous demonstration of pulsed superradiance on the mHz transition in 87Sr [2,3] achieved a fractional Allan deviation of 6.7·10-16 at 1s of averaging. Moving towards continuous-wave superradiance shows promise to improve the short-term frequency stability by orders of magnitude. A key challenge in realizing a cw superradiant laser is the continuous supply of cold atoms that act as the laser's gain and phase memory. We will present continuous loading of cold 88Sr atoms into a ring cavity in the strong collective atom-cavity coupling regime, after several stages of laser cooling and slowing. We will further present progress towards transporting the atoms within the ring cavity using a travelling wave optical lattice. |
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V01.00064: Probing Defects and Dynamics in 2D Materials Using Single Nitrogen Vacancy Centers in Diamond Eric Peterson, Aleksandr A Zibrov, Elana K Urbach, Nabeel Aslam, Bo Dwyer, Xiaoling Liu, Hongkun Park, Mikhail Lukin Covalently-bonded defects on graphene have been demonstrated to induce local magnetic moments. However, aspects of this system remain controversial, in part due to the existence of few techniques for probing defect magnetism directly and with nanoscale spatial resolution. Nitrogen vacancy (NV) centers in diamond can be used as sensitive nanoscale magnetometers capable of measuring the magnetic field of an individual electronic spin on or near the surface of diamond. This presents the opportunity to study small clusters of coupled electronic spins in two dimensional materials, and to probe electronic systems in the vicinity of an individual Kondo impurity. Here I describe the photochemical production of covalently-bonded defects in graphene and the characterization of their stability in conditions necessary for NV sensing, as well as proposals to modulate and study their properties using electrical doping and near-surface NV centers in diamond. In addition, I will describe an ongoing effort to use NV centers and a quantum memory-enhanced sensing protocol to study spin dynamics in a layered 2D material on the surface of diamond, which constitutes a variable-dimension system of strongly-interacting dipoles. |
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V01.00065: Toward an Entangled Matterwave Interferometer Graham P Greve, Chengyi Luo, Baochen Wu, James Thompson A current frontier is to apply recent advances in entanglement generation using cavity-QED [1,2,3] to enhance quantum sensors beyond the standard quantum limit (SQL). As part of this effort, we will describe a rubidium matterwave interferometer with atoms guided by a blue-detuned hollow optical dipole trap as they free-fall along the axis of a high-finesse cavity. The hollow guiding potential is created in the cavity by driving a Laguerre-Gauss LG01 mode. Multiple adjacent longitudinal modes of the standing wave cavity are also excited to provide a smooth axial guiding potential. Raman beams are injected through the cavity to realize the interferometer’s beamsplitter operations as well as the necessary velocity selection for state preparation. The interferometer is read out using cavity-enhanced quantum non-demolition (QND) with added readout noise as much as 10 dB below the projection. We will conclude by discussing our efforts to further improve the QND measurements to realize an entangled interferometer with sensitivity surpassing the SQL. |
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V01.00066: Rydberg-Dressed Ising Interactions for Spin Squeezing Jacob A Hines, Ognjen Markovic, Shankari V Rajagopal, Victoria Borish, Monika H Schleier-Smith Rydberg dressing provides a versatile way to create strong coherent interactions between ground-state neutral atoms. These local, optically controlled interactions can theoretically be used to create metrologically useful entanglement, such as spin squeezing in one or more independent atomic ensembles within an array of optical tweezers. Employing one-axis twisting dynamics via single-photon coupling to nP states, we present progress on generating spin squeezing on the clock transition of cesium. Initial observation of spin squeezing with Rydberg dressing will open prospects for optimized squeezing through the addition of a transverse field and implementation of variational algorithms. |
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V01.00067: Semiclassical Lindblad master equation for spin dynamics Jonathan Dubois, Ulf Saalmann, Jan M Rost Open microscopic systems, which interact with an environment, are prevalent in nature and experiments. The contact with the environment leads to energy loss, dissipation and fluctuation. If the relaxation time of the environment is short compared to the typical timescale of the system, a Markovian approximation can be used and quantum dynamics of the open microscopic system is governed by the Lindblad master equation (LME). |
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V01.00068: An optical chip for a single atom single photon source Jin Zhang, Eunji Oh, Zhaoning Yu, Brandon Mehlenbacher, Mikhail Kats, Randall Goldsmith, Mark Saffman We report on progress towards a single atom, single photon source using a fiber connected optical chip. Quantum experiments with cold atoms are burdened by the complexity of the experimental apparatus. Using fiber connectorized optics and a grating MOT suitable for cooling Rb atoms we fabricate a pre-aligned device usable as a single photon source for quantum communication experiments. The device integrates a grating MOT with a single beam dipole trap produced by a fiber and GRIN lens combination. MOT atoms are loaded into the dipole trap and then used as a source of single photons which are collected by the same optical fiber. We will report on details of the fabrication of the optical chip, experimental characterization, and progress towards generating high purity single photons. |
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V01.00069: Single-Spin Magnetomechanics with Levitated Micromagnets John D Schaefer Coupling quantum nonlinearities to mechanical degrees of freedom is an outstanding challenge in the field of quantum science. Realizing such a system would prove useful for applications in quantum metrology and quantum information. We demonstrate a system consisting of micromagnets levitated over a type-II superconductor. The magnet’s center of mass is shown to be trapped in three dimensions, resulting in modes of more than 1 kHz and quality factors of ~106. Additionally, the modes can be tuned by adjusted the conditions of the system before cooldown. We also demonstrate the coupling of the levitated magnet to the spin of a single nitrogen-vacancy center in diamond, ~0.048(2) Hz. This proof-of-principle is the first step towards a spin-mechanics system in coupling regimes relevant for quantum applications. |
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V01.00070: Towards a Quantum Spin Transducer with Mechanical Resonators Frankie Fung Hybrid quantum systems that couple spins to mechanical degrees of freedom allow for a variety of applications in quantum metrology and quantum information processing. For example, one can use such a system to deterministically entangle spins over long distances through their coherent coupling with the dynamics of the resonator. Working towards this goal, we have constructed a system consisting of magnetically functionalized, doubly-clamped silicon nitride beam resonators positioned close to diamond nanopillars. We report on experimental progress towards achieving coherent coupling between the electronic spin states of individual NV centers and the resonator motion. |
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V01.00071: Response of quantum spin networks to attacks Bhuvanesh Sundar, Mattia Walschaers, Valentina Parigi, Lincoln D Carr We numerically investigate ground states of spin models defined on random and complex networks, specifically Erdos-Renyi, Watts-Strogatz, and Barabasi-Albert networks, and their response to decohering processes which we model with network attacks. We quantify the complexity of these ground states, and their response to the attacks, by calculating distributions of network measures of an emergent network whose link weights are the pairwise mutual information between spins. We focus on attacks which projectively measure spins. We find that the emergent networks in the ground state do not satisfy the usual criteria for complexity, and their average properties are captured well by mean-field theory. Counter-intuitive to classical complex networks, we find that the ground states of our spin models respond similarly to attacks, and the resulting properties of the emergent mutual information network are again captured by mean-field theory. Understanding the response of spin networks to decoherence and attacks will have applications in understanding the physics of open quantum systems and in designing robust complex quantum systems - possibly even a robust quantum Internet in the long run - that is maximally resistant to decoherence. |
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V01.00072: A hybrid apparatus for coupling single mm-wave and optical photons using Rydberg atoms Lavanya Taneja, Aishwarya Kumar, Mark J Stone, Aziza Suleymanzade, David I Schuster, Jon Simon We present a hybrid experiment which employs Rydberg atoms to couple single optical and mm-wave photons. The centerpiece of the setup is a superconducting mm-wave cavity that intersects with an optical resonator while providing optical access to cool and trap atoms. Strong electric dipole coupling between Rydberg states, along with high cavity quality factors of up to 107 at 100 GHz and 1 K, enables exceptionally high single-atom cooperativity values in the system. Here, we share our observation of Rydberg electromagnetically induced transparency (EIT) in the hybrid cavity with a mm-wave quality factor of 200,000 at 5 K. We further demonstrate the platform’s capabilities by tuning an atomic resonance to a mm-wave cavity mode using an auxiliary mm-wave field, and showing Autler-Townes splitting of the EIT by the resonant mm-wave mode. We also describe our efforts to increase the coherence times of Rydberg states to enable operation in the strong coupling limit. Finally, we discuss our progress towards realizing a high-efficiency and high-bandwidth mm-wave-optical quantum transducer using this platform. |
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V01.00073: DEGENERATE GASES AND MANY-BODY PHYSICS
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V01.00074: Observation of scale invariance and universal quench dynamics of Townes soliton formation in two-dimensional Bose gases Cheng-An Chen, Sambit Banerjee, Chen-Lung Hung We experimentally study universal non-equilibrium dynamics of two-dimensional (2D) Bose gases quenched from repulsive to attractive interactions. We observe the manifestation of a modulational instability which fragments a 2D sample into multiple wave packets universally around a threshold atom number necessary for the formation of a scale-invariant stationary state -- the Townes solitons. Our measurements reveal the early coherent dynamics of modulational instability, the formation of Townes solitons, and the subsequent collision and collapse dynamics, demonstrating multiple universal behaviors. Furthermore, we test the scale invariance in 2D solitons by observing the collapse of soliton density profiles of different sizes and peak densities onto a single curve in a rescaled, dimensionless coordinate. We confirm that the scale-invariant profiles measured at different atomic interactions can further collapse onto the universal profile of Townes solitons. Our experiment demonstrates remarkable manifestation of 2D scale invariance and universal quench dynamics in the formation of a many-body quasi-stationary state. |
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V01.00075: Tunable coherent and dissipative superradiant dynamics in a spinor quantum gas Fabian Finger, Francesco Ferri, Rodrigo Rosa-Medina, Nishant Dogra, Matteo Soriente, Oded Zilberberg, Tobias Donner, Tilman Esslinger Dissipative and coherent processes are at the core of the evolution of many-body systems. Their competition and interplay can lead to new phases of matter, instabilities, and complex non-equilibrium dynamics. However, probing these phenomena at a microscopic level in a setting of well-defined, controllable coherent and dissipative couplings often proves challenging. In our setup, we realize such a quantum many-body system using a 87Rb spinor Bose-Einstein condensate (BEC) strongly coupled to a single optical mode of a lossy cavity. Two transverse laser fields incident on the BEC allow for cavity-assisted Raman transitions between different motional states of two neighboring spin levels. |
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V01.00076: Nonlinear readout of entangled non-Gaussian state without time reversal Qi Liu, Ling Na Wu, Tian Wei Mao, Xin Wei Li, Meng Khoon Tey, Li You Nonlinear readout has been proposed recently to facilitate the characterization of entangled non-Gaussian states (ENGSs). To achieve efficient detection, nonlinear readout protocols usually take advantage of time-reversed dynamics, which disentangle ENGSs by evolving them unitarily back towards the classical-like states before measurements. However, time reversal typically requires a sign-flip of Hamiltonian, which is challenging to realize in a many-body interacting system. Here we show such challenge can be circumvented if the system takes on cyclic interaction dynamics. By adopting two consecutive time-forward evolutions complementary to each other, ENGSs generated by the first one can be driven back to the initial state after the second one in the absence of phase encoding in between. The second evolution therefore behaves as an effective time reversal of the first. We find for rigorous cyclic dynamics, such a looped-evolution readout scheme is as efficient as with the time reversal and can saturate the quantum Cramer-Rao bound (QCRB) through the measurement of Loschmidt echo. Even for the case of approximate quasi-cyclic dynamics where the system does not completely return to the initial state, our scheme can still provide high phase sensitivity of the same order of QCRB. In addition to the spin-1 87Rb atomic BEC, this scheme can also be directly applied to other spin systems with interactions such as twist-and-turn, one-axis twisting, and two-axis counter-twisting squeezing ones. For the latter two cases, we find the total time durations required can be shortened even to half of that required before, at the instant when the system evolves into a coherent spin state orthogonal to the initial one. |
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V01.00077: Implosions in quenched Bose-Einstein condensates Eli J Halperin, Michael J Van de Graaff, John L Bohn, Jun Ye, Eric A Cornell Fluctuations in a Bose-Einstein condensate remain difficult to probe directly. We consider a series of experiments in which a Bose-Einstein condensate is quenched from a positive to negative scattering length via moving across a Feshbach resonance. Following such a quench, initial fluctuations in the gas, whether seeded by a certain potential, thermal fluctuations, or quantum fluctuations, may be amplified on a time-scale which is fast compared to the collapse of the bulk. We first consider a harmonically trapped gas with a weak perturbing lattice potential, looking at implosions at each lattice site when the gas becomes attractive. We report the latest progress on the comparison between analytic formulae and simulations to laboratory results. This understanding of implosions may then be used to explore intrinsically seeded fluctuations. |
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V01.00078: Microscopic evolution of doped Mott insulators from polaronic to Fermi liquid regime Dominik Bourgund, Joannis Koepsell, Sarah Hirthe, Thomas Chalopin, Petar Bojović, Pimonpan Sompet, Annabelle Bohrdt, Yao Wang, Fabian Grusdt, Eugene Demler, Guillaume Salomon, Christian Groß, Timon Hilker, Immanuel Bloch The competition between antiferromagnetism and hole motion in two-dimensional Mott insulators lies at the heart of a doping-dependent transition from an anomalous metal to a conventional Fermi liquid. Condensed matter experiments suggest that charge carriers change their nature within this crossover, but a full understanding remains elusive. We study this regime by preparing a cold fermionic gas in an optical lattice at a temperature around the superexchange energy. It is imaged using a quantum gas microscope with full spin and density resolution allowing the extraction of a wide range of correlators. Crucial to deeper understanding is the capability to calculate higher order correlators as well as common observables from solid states systems such as the spin susceptibility, all of which are studied as a function of doping level. While at low doping the system exhibits magnetic polarons, i.e. holes with a dressed cloud of spins, higher doping leads to the metallic Fermi liquid regime characterised by incommensurate magnetic fluctuations and altered correlations. The crossover is completed for hole dopings around 30%. Several theoretical models are benchmarked and their agreement with the experiment in different doping regimes discussed. |
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V01.00079: A fermionic triangular-lattice quantum gas microscope Jirayu Mongkolkiattichai, Liyu Liu, Davis A Garwood, Jin Yang, Peter Schauss Ultracold atoms in triangular optical lattices provide a versatile platform to study the phase diagram of the triangular-lattice Hubbard model due to the tunability of all relevant parameters. Recently, numerical calculation showed indications for a chiral spin-liquid phase in the transition region between the metallic and ordered magnetic phase which was found to break time-reversal symmetry [1, 2]. Here, we report on the implementation of a projected triangular lattice for ultracold lithium-6 atoms and demonstrate single-atom-resolved imaging via Raman sideband cooling, yielding an imaging fidelity of 98 % [3]. We measure temperatures below one-fifth of the Fermi temperature for Fermi gases before loading into the lattice. For guidance of the experiment, we implemented a numerical linked cluster expansion to calculate finite-temperature correlations in the triangular lattice Hubbard model. Our next plan is to employ our platform to perform theory-experiment comparisons of spin-spin correlations in the Mott-insulating regime and investigate time-reversal symmetry breaking via three-point correlations. [1] A. Szasz, et al., Phys. Rev. X 10, 021042 (2020). [2] B.-B. Chen et. al. arXiv:2102.05560 (2021). [3] J. Yang, et al., arXiv:2102.11862 (2021). |
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V01.00080: Experimental realization of the symmetry-protected Haldane phase in Fermi-Hubbard ladders Thomas Chalopin, Pimonpan Sompet, Sarah Hirthe, Dominik Bourgund, Joannis Koepsell, Petar Bojović, Guillaume Salomon, Julian Bibo, Ruben Verresen, Frank Pollmann, Timon Hilker, Christian Gross, Immanuel F Bloch The Haldane antiferromagnetic spin-1 chain constitutes a paradigmatic model of a quantum system which holds a symmetry protected topological phase. Here, we experimentally realize the Haldane phase using Fermi-Hubbard ladders in an ultracold quantum gas microscope. Site-resolved potential shaping allows us to create tailored spin-1/2 geometries which permit the exploration of such a topological chain and its comparison to a trivial configuration. We use spin- and density-resolved measurements to probe edge and bulk properties of the system, revealing a clear dinstinction between the trivial and topological cases. The measurement of a non-local string order parameter, in particular, allows to directly capture the underlying protecting symmetry of the topological phase. We furthermore investigate the robustness of the topological phase upon the onset of density fluctuations by tuning the Hubbard interaction. |
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V01.00081: Transport properties of a SU(Ν) Fermi-Hubbard system Qinyuan Zheng, Kaden R Hazzard, Eduardo Ibarra-García-Padilla Transport properties of strongly correlated matter offer some of the most profound insights into its nature, as well as some of its greatest mysteries, such as strange metallicity and pseudogap behaviors. New settings to explore unconventional transport properties offer a chance to unravel many of the mysteries surrounding strongly correlated materials. One such new form of strongly correlated ultracold quantum matter has recently been realized with alkaline-earth atoms in optical lattices. These realize an SU(Ν) symmetric Hubbard model, and techniques such as quantum gas microscopy or Bragg spectroscopy can probe its transport properties. We calculate the optical conductivity of the SU(Ν) Hubbard model with exact diagonalization and linear response theory both in the ground state and in finite-temperature systems in experimentally relevant regions. We will discuss to what extent phenomena such as pseudogap and strange metallicity appear in the experimentally accessible observables. |
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V01.00082: Interaction-Enhanced Group Velocity of Bosons in the Flat Band of an Optical Kagome Lattice Malte Nils Schwarz In the non-interacting limit the kagome lattice exhibits a nearly dispersionless/flat excited band that predicts vanishing group velocity. We place a Bose-Einstein condensate into this s-orbital band and extract its group velocity by analyzing the atomic diffraction pattern. We observe a significant enhancement of the group velocity in the flat band which can be explained by band structure renormalization due to interaction effects. Incorporating interactions via the Gross-Pitaesvkii equation, our calculations indicate that the band structure renormalization is caused by a distortion of the real space atomic distribution away from the kagome geometry. |
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V01.00083: A momentum dependent 1D optical lattice potential induced by a periodically driven Raman process Zekai Chen, Elisha B Haber, Nicholas P Bigelow We propose an experiment to create a one-dimensional optical lattice potential in an ultracold Bose gas system where the lattice potential depends on the transverse momentum of the Bose gas. The transverse momentum dependence of the optical lattice can be induced using an artificial gauge potential generated by a periodically driven, multi-laser Raman process. The momentum dependence of the lattice potential is caused by spin Hall effect. We construct a quasi-1D Bose--Hubbard model of the system by introducing a strong confinement potential in the transverse plane. Using the Gutzwiller mean-field theory, we explore the phase diagram and show that the superfluid-Mott-insulator transition in such a system can be driven by tuning the average transverse momentum of the Bose gas. |
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V01.00084: Cavity QED in a Synthetic Gauge Field Margaret G Panetta, Clai Owens, Andrei Vrajitoarea, Srivatsan Chakram, Brendan Saxberg, Gabrielle Roberts, Ruichao Ma, David I Schuster, Jon Simon Recent advances in the ability to fabricate and manipulate superconducting quantum circuits have opened up exciting opportunities to construct from the ground up synthetic quantum materials hosting rich interactions. We have designed a cavity QED system which harnesses strong interactions between a highly nonlinear transmon qubit and a quarter-flux Hofstadter lattice realized for microwave photons. In this system, a single transmon qubit couples to a 2D lattice of high-Q microwave resonators which interact strongly with magnetic-field-biased ferrimagnets, producing a synthetic magnetic field for photons and giving rise to a topological bandstructure that hosts chiral edge channels. We demonstrate chiral, time-reversal-symmetry-broken edge transport in this lattice with excitation lifetimes exceeding ~1000 times the site-to-site tunneling rate. We also demonstrate strong interactions between the chiral lattice and transmon qubit, measuring Rabi swapping of excitations from the transmon qubit to a range of lattice eigenmodes on timescales ~10 times faster than lattice excitation decay times. We non-destructively measure photon occupation of lattice eigenmodes by characterizing number splitting of dispersive shifts in the qubit transition. Finally, we describe work towards coupling multiple transmon qubits to the chiral lattice edge, enabling quantum communication via edge channels, supporting exploration of photon-photon interactions in a topological bandstructure, and opening avenues towards investigating many-body physics in this synthetic material. |
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V01.00085: Preparation of the 1/2-Laughlin state with atoms in a rotating trap Bárbara Andrade dos Santos, Valentin Kasper, Maciej A Lewenstein, Tobias Grass, Christof Weitenberg The fast progress in ultracold atom experiments allows for studying strongly correlated quantum many-body states with unprecedented precision. Here we explore the quantum simulation of fractional quantum Hall states by a numerical study of four bosonic atoms in a quasi-two-dimensional rotating trap, which will act as a bosonic analog of electrons in a magnetic field. For rotation frequencies close to the in-plane trapping frequency, the ground state is predicted to be a bosonic Laughlin state at half filling. In particular, we illustrate how a thorough control of the rotation frequency and the ellipticity of the trapping potential enable us to prepare the Laughlin state. By accessing regions of large ellipticity and high angular momentum, we significantly improve the preparation time of the Laughlin state with high fidelity. Finally, we conclude that the present improvements of the adiabatic protocol allows to prepare the Laughlin state with current experimental technology. |
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V01.00086: Toward a spin-tensor-momentum coupled Bose-Einstein condensate Benjamin D Smith, Arina Taschilina, Logan W Cooke, Joseph Lindon, Tian Ooi, Lindsay J LeBlanc
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V01.00087: COLD ATOMS, IONS, MOLECULES, AND PLASMAS
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V01.00088: Microwave-Optical Stark-Sisyphus Deceleration Benjamin Augenbraun, John M Doyle We propose a general method to decelerate beams of polyatomic molecules. The technique uses inhomogeneous static electric fields, microwave adiabatic passage, and optical pumping to remove kinetic energy. It is applicable to any polyatomic molecule possessing an electric dipole moment and reasonably diagonal Franck-Condon factors. We identify over a dozen laser-coolable molecules for which this method is predicted to remove between 1 and 2 K of energy per deceleration stage, thus requiring about 10 photon scatters to slow to rest an optimized cryogenic buffer-gas beam. By way of example, we theoretically evaluate the decelerator's performance for two specific molecules, YbOH and CaOCH$_3$. |
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V01.00089: Direct Laser Cooling of Metal Monohydride Molecules Qi Sun, Sebastian Vazquez-Carson, Tanya Zelevinsky Preparation of ultracold dilute hydrogen gas can significantly improve the precision of hydrogen spectroscopy. Fragmentation of laser coolable alkaline-earth metal monohydrides (e.g., BaH and CaH) provides a feasible scheme for this purpose. We have experimentally demonstrated optical cycling in BaH, and observed radiation-pressure force beam deflection as well as direct laser cooling. Here we present our latest data with CaH. A shorter lifetime and a larger optical cross section enable CaH to experience stronger light pressure with less laser power. We observed clear 1D Doppler and Sisyphus cooling profiles, and magnetic-field assisted dark state remixing. We used two different electronic excited states as the upper states, ΑΠ and ΒΣ, and acquired similar cooling profiles. Measurement of Franck-Condon factors (f00, f01, f02) for both electronic excited states was also performed. Combined with calculated FCFs, it indicates that we can achieve more than 7×104 photon scatters by adding a second vibrational repump laser, potentially enabling the loading and trapping of CaH in a radio-frequency MOT. |
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V01.00090: A Next generation Molecular Tweezer Apparatus for Quantum Simulation Yicheng Bao, Seejia Yu, Loic Anderegg, Sean Burchesky, Eunmi Chae, Kang-Kuen Ni, Wolfgang Ketterle, John M Doyle Optical tweezer arrays of ultracold molecules provide a promising platform for precisely manipulating molecular internal states of individual molecules and inducing strong dipolar interaction between them. Trapping, rearranging, and merging molecular tweezers have been demonstrated and successfully applied to molecular collision measurements with CaF at ultracold temperature. Here we report ongoing progress on a new CaF molecular optical tweezer apparatus designed for quantum simulation. With an upgraded cryogenic beam source and a high magnetic field gradient RF MOT design, we achieve a significantly improved MOT of CaF molecules. A glass cell allows for large numerical apertures for increased detection fidelity and is compatible with future cryogenic operation to improve the vibrational black body limited lifetime. We plan to further cool the molecules to the motional ground state of the tweezers and polarize them with high voltage electrodes and microwave fields, and, finally, coupling them through their intrinsic dipole moments. |
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V01.00091: Construction of a Superconducting Zeeman-Sisyphus Decelerator Alexander J Frenett, Hiromitsu Sawaoka, Benjamin Augenbraun, Zack Lasner, Abdullah Nasir, John M Doyle We describe the construction of a superconducting Zeeman-Sisyphus decelerator, designed to slow to rest beams of magnetic species using approximately three photon scatters. The decelerator relies on large energy shifts in the magnetic field and optical pumping between magnetic sublevels to remove energy. This apparatus comprises two sets of 3 T superconducting solenoid magnets, capable of removing 2-3 Kelvin per stage for molecules with a 2Σ ground state. We discuss in detail the design of the magnets, the cryogenic system that supports them, and the expected performance of the decelerator. We discuss the application of this scheme to slowing beams of YbOH molecules to the capture velocity of a magneto-optical trap. |
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V01.00092: Sticky collisions of ultracold molecules in the dark Roman Bause, Andreas Schindewolf, Renhao Tao, Marcel Duda, Xingyan Chen, Goulven Quéméner, Tijs Karman, Arthur Christianen, Immanuel F Bloch, Xinyu Luo The influence of transient complexes on collisions between ultracold molecules in their absolute ground state has recently been a topic of intense investigation. One particularly important reason for this is the experimentally observed loss of nonreactive ground-state molecules from optical dipole traps. A recent theoretical model attempted to explain this loss via photo-excitation of transient sticky complexes. By trapping fermionic NaK molecules with blue-detuned light near a narrow molecular transition, we are able to to test this hypothesis with light intensities three orders of magnitude lower than what is typical in red-detuned dipole traps. Our results disagree by at least two orders of magnitude with the theoretical predictions, showing that crucial aspects of molecular collisions are not yet understood, and provide a benchmark for the development of new theories. |
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V01.00093: Spectroscopy of AlCl at 261nm for Laser Cooling and Trapping Chen Wang, John R Daniel, Taylor Lewis, Alexander Teplukhin, Brian K Kendrick, Chris Bardeen, Shan-Wen Tsai, Boerge Hemmerling Ultra-cold dipolar molecules offer platforms for precision measurements of fundamental constants, quantum computation, study of ultracold chemistry and other novel physics. Aluminum mono-chloride (AlCl) has been proposed as a promising candidate for laser cooling and trapping. We use a frequency-tripled CW Titanium-Sapphire laser to do spectroscopy on AlCl generated via laser ablation of AlCl3 and other precursors in a cryogenic helium buffer-gas beam source. The spectroscopy light is produced by first frequency-doubling 784nm to 392nm. The 392nm light is then combined with the fundamental in a sum-frequency process to create light at 261nm. Here, we discuss details of our molecular beam source and our laser system for generating UV light and we present our spectroscopy results for the X1Σ+ → A1Π transition in AlCl and our estimated Frank-Condon factors for the ν=0 →ν′ =0 and ν=1→ν′ =1 transitions. Furthermore, we present our results on investigating various precursors for producing AlCl. |
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V01.00094: Controlled Collisions between Ultracold Polar Molecules William G Tobias, Jun-Ru Li, Kyle Y Matsuda, Calder Miller, Giacomo Valtolina, Jun Ye A degenerate gas of polar molecules, which interacts via long-range, anisotropic potentials, allows access to rich many-body physics. One challenge of realizing many-body interacting systems is the short molecular lifetime relative to the interaction timescale, which is limited by two-body loss. |
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V01.00095: Vibrational repumping of thallium fluoride Nathan Clayburn, Michael Cullen, David P DeMille, Larry R Hunter We investigate the B3Π1(νe = 0) ← Χ1Σ+(νg = 0) transition in thallium fluoride by imaging the UV fluorescence from the laser excitation of a cryogenic molecular beam. The investigation is motivated by the promise TlF holds for a measurement of the nuclear electric-dipole moment. If cycling losses can be limited to only vibrational losses, our branching fraction measurements suggest that we should be able to scatter about 100 photons from each molecule with a single laser at 271.7 nm [1]. According to these branching ratio measurements, the addition of this single 278.8 nm (νg = 2) repump laser could allow cycling of up to 1000 photons if other loss mechanisms can be suppressed. Investigations of this vibrational repumping are reported. |
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V01.00096: Van der Waals molecules of a zinc or cadmium atom interacting with an alkali-metal or alkaline-earth metal atom Klaudia Zaremba-Kopczyk, Michal Tomza Alkaline-earth-like transition-metal atoms such as Zn and Cd are promising candidates for precision measurements and quantum many-body physics experiments. Here, we theoretically investigate the properties of diatomic molecules containing these 1S-state atoms. We calculate potential energy curves, permanent electric dipole moments, and spectroscopic constants for molecules consisting of either a Zn or Cd atom interacting with an alkali-metal (Li, Na, K, Rb, Cs, Fr) or alkaline-earth-metal (Be, Mg, Ca, Sr, Ba, Ra) atom. We use the ab initio electronic-structure coupled cluster method with single, double, and triple excitations combined with large Gaussian basis sets and small-core relativistic energy-consistent pseudopotentials for heavier atoms. We predict that the studied molecules in the ground electronic state are weakly bound van der Waals complexes with rather small permanent electric dipole moments. The present results may be useful for spectroscopy and application of the studied molecules in modern ultracold physics and chemistry experiments. |
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V01.00097: Towards the Dipolar Ground State of 6Li40K Anbang Yang, Sofia Botsi, Sunil Kumar, Ieva Cepaite, Sambit Pal, Mark Lam, Andrew Laugharn, Kai Dieckmann We demonstrate a two-photon pathway to the ground state of 6Li40K molecules that involves only singlet-to-singlet optical transitions. We start from a molecular state which contains a significant admixture from the singlet ground state potential by selecting the Feshbach resonance for molecule association. With the only contributing singlet state to the molecular state being fully stretched and with control over the lasers polarization we address a sole hyperfine component of the excited A1Σ+ potential without resolving its hyperfine structure. We perform dark resonance spectroscopy to precisely determine the transition frequencies of the states involved. The strong dipolar nature of 6Li40K is revealed by Stark spectroscopy, as it is necessary for the study of dipolar interactions in an optical lattice. The two Raman lasers utilized for the Stimulated Raman Adiabatic Passage (STIRAP) are locked to a high finesse cavity using the Pound-Drever-Hall lock. The finesse of the cavity is measured at 665nm and 1119nm via the cavity ring-down method. The linewidths of the two Raman lasers are determined by recording their beat frequencies to an ultralow-noise frequency comb in the neighboring group. We perform the phase noise measurement of the Raman lasers. We estimate the contributions from different STIRAP loss mechanisms and propose several improvements to the current Raman laser system towards a successful transfer to the dipolar ground state. |
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V01.00098: Angular momentum dependence of three fermions near unitarity Yu-Hsin Chen This study considers the unitary limit of three equal mass fermions interacting via Lennard-Jones potentials having various total orbital angular momenta and parity, $J^{\Pi}=0^{+}, 1^{+}, 1^{-}$ and $2^{-}$, specifically consisting of three spin-polarized fermions ($\uparrow \uparrow \uparrow $), or of two spin-up and one spin-down fermion ($\downarrow \uparrow \uparrow $). To explore alternative unitarity scenarios, we obtain numerical results for the regime where the p-wave scattering volume approaches infinity. Our study also considers different interactions between the atoms in different spin states, such as the case where the two spin-up fermions have a p-wave interaction and where a spin-up atom interacting with a spin-down atom has a strong s-wave interaction as well. Another case treated involves the different spin state fermions with strong p-wave interaction, while the two identical spin state fermions have a weak p-wave interaction. We also consider three spin-up fermions at the p-wave unitarity limit in different overall symmetries. Universal three-body channel properties are derived for the above cases. This study confirms that the p-wave Efimov effect does not occur for the two-component fermionic system with three equal mass particles, nor for three fermions in a single spin state at the p-wave unitary limit with total angular momentum $J^{\Pi}=1^{-}$. |
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V01.00099: LiK B1Π potential: combining short and long range data Sofia Botsi, Anbang Yang, Sunil Kumar, Sambit B Pal, Mark Lam, Kai Dieckmann We present spectroscopic measurements of the long range states of the 6Li40K molecule near its Li(42S1/2) + K(42P3/2) asymptote which in combination with existing data in the short range lead to the full characterization of the B1Π potential with high spectroscopic resolution. Starting from weakly bound ultracold Feshbach molecules, we performed one-photon loss spectroscopy of the high-lying levels of the B1Π potential. A total of twenty-five vibrational lines were observed close to the asymptote which were combined with existing data from photo association spectroscopy [1]. Extrapolation of the latter led to the assignment of our observed lines to vibrational levels in the spin-orbit coupled potentials near the dissociation threshold. For our Hund’s case (c) molecules, a complete set of data is presented for the Ω=1up state, by combining the long range measurements with data from the short range states of the B1Π from heat-pipe spectroscopy of the 7Li39K molecule [2]. Using mass scaling, we modelled the short range and the long range part of the potential simultaneously and produced the Rydberg-Klein-Rees (RKR) curve for the complete potential. The vibrational energies and the rotational constants were defined in terms of Dunham representation and compared with a mixed near-dissociation / Dunham expansion. We present the improved empirical curve for the long range part of the Ω=1up state. [1] A. Ridinger, et. al., EPL, 96, 33001, (2011); [2] A. Pashov, et. al., Chem. Phys. Lett. 292, 615-620 (1998) |
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V01.00100: New Molecular Species for Quantum Science and Precision Measurements Zack Lasner, Benjamin Augenbraun, Debayan Mitra, Nathaniel Vilas, John M Doyle Following recent advances in the quantum control of molecules, it now appears feasible to laser cool species of increasingly low symmetry. While this entails some additional experimental challenges, it also introduces new physical features and structural complexity that can be exploited for improved control of molecular interactions or sensitivity of precision measurements. For example, many laser-coolable asymmetric top molecules have large dipole moments (>5 Debye) for improved molecule-molecule coupling, permanent dipole moments along orthogonal axes, and vast rovibrational structures for information storage. For precision measurements, the numerous rovibrational modes in larger molecules, such as torsional modes, show promise for enhanced sensitivity to measurements of fundamental constant variation. We present measurements of vibrational branching ratios for asymmetric molecules CaSH and CaNH2, showing a favorable pathway for laser cooling. We also present studies of laser-coolable organic molecules, such as benzene or cresol, decorated with CaO optical cycling centers. |
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V01.00101: Design and construction of a versatile experiment for the production of ultracold gases Cesar J Ruiz Loredo, Gerardo Ortíz Ugalde, J. Mauricio López Romero, Neil V Corzo, Karina Jimenez-Garcia Ultracold atom experiments around the world have significantly advanced our understanding of quantum phenomena, including Bose-Einstein condensation, fundamentals of magnetic phenomena, quantum phase transitions, and the study of topological phenomena, to name a few. The Quantum Technologies Laboratory of the Center for Research and Advanced Studies (Laboratorio de Tecnologías Cuánticas, CINVESTAV, Unidad Querétaro), aims to contribute to this field of research with a versatile and compact experiment for the production of ultracold gases. |
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V01.00102: High Phase Space Density for Laser Cooled YO Molecules in an Optical Lattice Kameron Mehling We report the highest phase space density of molecules by direct laser cooling. Our experiment begins with a dual-frequency magneto optical trap of yttrium monoxide (YO) loaded from a cryogenic buffer gas beam. Next, our molecules are further cooled via gray molasse and compressed via a compression sequence tailored for the special structure of YO, achieving a density of 5.4 x 10 cm-3 and temperature of 4 µK. Molecules are then loaded and cooled into a 1 dimensional optical lattice. Utilizing effective sub-Doppler cooling inside the lattice, we create a molecular sample with a peak phase space density of 3 x 10-6. With a long lattice lifetime of 850(70) ms, we are poised to explore molecular interaction effects. |
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V01.00103: Studying chemical reactions below one micro-Kelvin Yi-Xiang Liu, Matthew A Nichols, Yu Liu, Ming-Guang Hu, Lingbang Zhu, Kang-Kuen Ni Chemical reactions at ultralow temperatures provide an ideal platform for studying quantum effects in chemistry. Our goal is to understand how the various quantum degrees of freedom of reactant atoms and molecules govern the behavior of molecule-molecule and atom-molecule collisions. To do this, we create ultracold KRb molecules in well-controlled quantum states within the rovibronic ground state at temperatures below one micro-Kelvin, and detect both reaction intermediates and products using quantum-state-selective ionization and coincidence ion imaging. In this poster, we discuss our measurements which map out the full product state distribution for the reaction 2KRb-> K2+Rb2, and which show that the quantum states of reaction outcomes can be controlled via the reactant nuclear spins. We also present recent results which examine KRb+Rb collisions. |
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V01.00104: Progress towards achieving higher phase space density of trapped SrF molecules Varun Jorapur, Thomas K Langin, Yuqi Zhu, Qian Wang, David P DeMille Recently, there has been tremendous progress in laser cooling of molecules with temperatures as low as 5µK being reported. The next natural step to increasing the phase space density is to load the molecules in a conservative trap. Here we report on our progress towards optical dipole trapping (ODT) of SrF molecules along with plans for future improvements to the apparatus. By optimizing both the polarization of the ODT light and the relative intensity imbalance of the counter-propagating beams that we use for Λ-enhanced gray molasses, we are able to load molecules with temperatures as low as 10µK in a 420µK deep trap. We also detail further improvements to the apparatus including plans for switching to a Sr + SF6 source and a better slowing scheme. With these improvements, along with the already demonstrated capability to achieve cold temperatures in deep traps, studying SrF-SrF molecule collisions should be within reach. |
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V01.00105: Towards site-resolved microscopy of NaRb molecules in an optical lattice Lysander Christakis, Jason S Rosenberg, Zoe Yan, Waseem S Bakr Ultracold molecules are a promising platform for quantum simulation of many-body physics due to their long-range interactions and rich set of quantum states. However, their complex internal structure and fast two-body loss rates also pose experimental challenges for quantum simulation. Here, we describe our approach to create and detect individual bosonic NaRb molecules in a 2D optical lattice. Starting from a mixture of sodium and rubidium atoms, we prepare quasi-2D condensates of each species using a light sheet optical potential combined with a tightly focused, bichromatic "dimple" trap. We load the degenerate mixture into a 2D optical lattice, where the atoms can be bound into Feshbach molecules. Each molecule can then be detected by dissociating the molecule and performing site-resolved fluorescence imaging of the constituent rubidium atoms. In the future, we will coherently transfer the molecules into their absolute ground state, setting the stage for studying quantum magnetism with interacting dipolar molecules at the single-particle level. |
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V01.00106: Towards a Quantum Gas Microscope for Laser-Cooled Molecules Yukai Lu, Connor Holland, Lawrence W Cheuk Ultracold molecules, with their rich internal structure and long-range dipolar interactions, could be a powerful new quantum platform for many applications ranging from quantum simulation to quantum information processing. Here we present our progress towards building a quantum gas microscope for laser-cooled CaF molecules, including work on molecular beam-slowing, magneto-optical trapping and deep laser cooling of CaF molecules. Our apparatus will combine a rearrangeable optical tweezer array along with an optical lattice, which will enable single-molecule readout and control as well as provide clean optical trapping potentials. The rearrangeable tweezers will allow us to initialize large 2D arrays of molecules in arbitrary spatial configurations, while the optical lattice will provide disorder-free trapping potentials that could permit highly coherent interactions. Together, they could provide a pristine platform to study interacting lattice spin Hamiltonians and to explore quantum information processing with molecular qubits. |
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V01.00107: Modelling laser cooling in barium monofluoride molecules Felix Kogel Cold molecular gases are promising candidates for studies of cold chemistry, precision tests of fundamental symmetries and quantum simulation. However, while there has recently been significant progress in the direct cooling of molecules, the preparation of a new molecular species in the cold temperature regime still requires a careful optimization of the available cooling techniques. Motivated by our experiments on barium monofluoride (BaF), we report here on the simulation of laser cooling for this species, using multi-level rate equations and optical Bloch equations. This allows us to identify optimized strategies and parameter regimes for the realization of a cold molecular gas of BaF. |
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V01.00108: Towards Strongly Correlated 2D Systems of Dipolar NaCs Molecules Weijun Yuan, Niccolò Bigagli, Aden Z Lam, Claire Warner, Ian C Stevenson, Sebastian Will We report on progress towards the creation of ultracold sodium-cesium molecules in their absolute ground state. NaCs molecules feature a large dipole moment of 4.6 Debye and are ideally suited for the creation of strongly interacting dipolar many-body quantum systems. We have made advances towards this goal on several frontiers: (1) We have created the first ultracold mixtures of sodium and cesium, including overlapping BECs of Na and Cs. (2) We have located and characterized Feshbach resonances between Na and Cs. (3) Using a Feshbach resonance at 864 G, we have created near-degenerate ensembles of NaCs Feshbach molecules at temperatures as low as 100 nK. (4) Finally, we have taken steps towards identification of a STIRAP pathway to the absolute ground state, including bound-bound precision spectroscopy of electronically excited molecular states and the construction of a phase-coherent STIRAP laser system. The goal of this project is the creation of strongly interacting dipolar 2D systems, for which a myriad of interesting phases is predicted, including the formation of supersolid phases and dipolar quantum crystals. |
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V01.00109: Cold, slow CH radicals for laser cooling and trapping experiments Joseph Schnaubelt, Jamie Shaw, Daniel McCarron Techniques to directly laser cool and trap molecules at ultracold temperatures have revealed a new route towards the full quantum control of a diverse range of molecules with a variety of internal structures. This experiment aims to capitalize on this generality by laser cooling and trapping CH radicals for tests of ultracold organic chemistry. The low mass and blue optical transitions in this species lead to high recoil velocities which can significantly reduce the required photon budget to slow, cool and trap a molecular beam from our cryogenic source [1]. We will present our proposed optical cycling schemes alongside recent experimental work characterizing cold, slow CH radicals within our apparatus. |
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V01.00110: An optical tweezer array of ultracold rovibrational ground state dipolar molecules Lewis R Picard, William B Cairncross, Jessie Zhang, Kenneth Wang, Yichao Yu, Kang-Kuen Ni Ultracold molecules with large electric dipoles possess a range of properties which make them attractive for a new generation of quantum information and simulation experiments. Using microwave or electric fields, the long-range electric dipole interactions between molecules can be precisely controlled, and the hyperfine manifold of molecules prepared in their rovibrational ground state can encode quantum information with long coherence times. We present here an optical tweezer array of rovibrational ground state NaCs molecules, prepared by association of laser cooled Na and Cs atoms. Using the tight confinement of optical tweezers combined with motional ground state cooling of the constituent atoms, we are able to achieve full motional and internal state control of the molecules. With this level of control in hand, we can go about engineering coherent dipolar interactions between spatially separated molecules across the array. |
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V01.00111: Advances in molecule production and detection techniques for laser cooling experiments Jamie Shaw, Daniel McCarron Molecular laser cooling and trapping has the potential to bring a variety of diatomic and polyatomic species into the ultracold regime for applications in quantum science and ultracold chemistry. Many of these applications demand molecule-molecule interactions, and trapped samples at higher density, alongside the introduction of surfaces, such as superconducting circuits or microtrap arrays, near the molecules that will scatter laser light and make standard fluorescence imaging challenging. Here we will present several advances to tackle these challenges including a new cryogenic source design capable of making bright continuous beams of free radicals as the first step towards longer magneto-optical trap loading times [1]. We will also present a novel and sensitive fluorescence imaging technique that is immune to scattered laser light and combines optical cycling with Raman scattering. These general advances are applicable to a wide variety of molecules amenable to laser cooling. |
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V01.00112: A pulsed ion microscope to probe quantum gases. Viraatt Sai Vishwakarma Anasuri, Christian Veit, Nicolas Zuber, Óscar-Andrey Herrera-Sancho, Thomas Schmid, Florian Meinert, Robert Loew, Tilman Pfau A pulsed ion microscope to probe quantum gases |
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V01.00113: Wave-packet dynamics of ultra-long-range Rydberg molecules Frederic Hummel, Kevin Keiler, Peter Schmelcher We investigate the quantum dynamics of ultra-long-range trilobite molecules exposed to homogeneous electric fields. A trilobite molecule consists of a Rydberg atom and a ground-state atom, which is trapped at large internuclear distances in an oscillatory potential due to scattering of the Rydberg electron off the ground-state atom. Within the Born-Oppenheimer approximation, we derive an analytic expression for the two-dimensional adiabatic electronic potential energy surface in weak electric fields. This is used to unravel the molecular quantum dynamics employing the Multi-Configurational Time-Dependent Hartree method. Opportunities to control the molecular configuration are identified, a specific example being the possibility to superimpose different molecular bond lengths by a series of periodic quenches of the electric field. |
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V01.00114: Polyatomic Cs-NO Rydberg Molecules Including Short-Range, Non-Dipolar Interactions Samantha E Orie, Seth Rittenhouse A Rydberg molecule forms when an electron orbit of a highly excited atom encompasses a ground state perturber such as another atom or molecule. This interaction between the electron and the perturber can weakly bind the two objects together. In this work we examine the Rydberg molecules formed when the ground state perturber is a diatomic molecule, specifically nitrogen oxide. Unlike an atom, a diatomic molecule has different states that respond differently to the electric fields of the Rydberg system. Earlier studies of similar systems have treated the electron-molecule interaction as a pure charge-dipole potential. In this work we include an additional contact interaction to simulate the non dipolar, short-range component of the interaction. We examine how this additional term affects the structure of Born-Oppenheimer potentials of the Rydberg molecule. |
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V01.00115: Modeling the Effects of State-Mixing Interactions near Förster Resonance Tomohisa Yoda, Milo Eder, Andrew Lesak, Abigail E Plone, Aaron Reinhard State-mixing interactions can compromise the effectiveness of the Rydberg excitation blockade near Förster resonance. Up to ∼ 50% of the detected Rydberg atoms can be found in dipole coupled product states within tens of ns of excitation. We use state-selective field ionization spectroscopy to measure, on a shot-by-shot basis, the distribution of states populated during narrowband laser excitation of ultracold rubidium atoms. Our method allows us to quantify both the number of additional excitations added by each mixing event, and the extent to which state-mixing “breaks” the blockade. We use a Monte Carlo method to model the effect of experimental noise sources on our data. We find good agreement with a three-body model for state-mixing, except near exact Förster resonance. |
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V01.00116: Towards Rydberg Excitation of Sodium Spinor Bose-Einstein Condensates Hio Giap Ooi, Qimin Zhang, Shan Zhong, Chase Heinen, Michael Osisanya, John Moore-Furneaux, Arne Schwettmann We present our progress towards Rydberg excitation of our sodium spinor BEC to study the effect of impurities on coherent spin-mixing dynamics. Spin-mixing dynamics convert pairs of atoms with magnetic quantum numbers m_F=0 to entangled pairs with m_F=+1 and m_F=-1, useful for quantum-enhanced sensing. To study the effect of Rydberg impurities on the spin dynamics, we designed a blue laser locking system for Rydberg excitation, as well as a custom pulsed-field ionization spectrometer for Rydberg atom detection. Our system will generate Rydberg impurities by exciting the valance electron of Na BEC atoms far away from the nucleus with a two-photon process from 3s to nd states, where n will range between 40 and 90 in our case. In this poster, we present the design progress of our Rydberg atom excitation and detection systems. |
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V01.00117: Hybrid ion-atom systems: exploring ion-molecule collisions and prospects for getting colder Miss Eleanor Trimby, Henrik Hirzler, Rianne S Lous, Rene Gerritsma Both trapped ions and ultracold atoms are excellent systems for studying quantum many-body physics and quantum information applications. Combining the two opens up a new field with rich physics [1], giving us the possibility to study impurity-bath interactions, quantum chemistry, and buffer gas cooling. In our experiment [2] we have an Yb+ ion in an ultracold bath of fermionic Li atoms, with collision energies reaching the s-wave regime [3]. In this poster we present the prospects and approaches for new experiments in such a system. We theoretically explore the dynamics of a charged impurity in a bath of Feshbach dimers [4] and find a crossover from dimer dissociation to molecular ion formation. This could provide a new approach for creating molecular ions. Further, we explore buffer gas cooling of a trapped ion by ultracold atoms. Here we present the theoretical optimal parameters for reaching deeper into the quantum regime in our system, as well as comparing the suitability of different time-dependent ion traps. Obtaining lower atom-ion collision energies will put our experiment in a regime where we could expect to observe atom-ion Feshbach resonances. |
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V01.00118: Stable trapping of K, Ca+, and CaH+: Towards ground state CaH+ molecules in an ion-atom trap Swapnil Patel, Jyothi Saraladevi, Eric Pretzsch, Evan C Reed, Lu Qi, Kenneth R Brown Molecular ions are good candidates for probing the time variation of fundamental constants, precision spectroscopy, and quantum information processing. For these exciting applications, the molecular ions need to be in their ground internal state and translationally cold. Laser cooling molecular ions is hindered by their rich energy level structure. We are developing an alternative and general approach to cool molecular ions using an ion-atom hybrid trap [1], where the molecular ions are trapped with laser-cooled neutral atoms and atomic ions. Coulomb interactions with calcium ions cool the translational motion of the molecular ion, and we expect collisions with cold atoms cools their internal states. We present results of charge exchange reaction between trapped Ca+ and K [2] and our progress in sympathetic rotational cooling of CaH+ ions. |
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V01.00119: Exploring new frontiers for the interaction of trapped anions with photons and atoms. Saba Zia Hassan, Jonas Tauch, Milaim D Kas, Markus Noetzold, Eric Endres, Roland Wester, Matthias Weidemuller The study of ion-molecule reactions plays a vital role in cold chemistry, thus implying the need of well-controlled ion ensembles in a cold environment. Ions trapped in multipole radio frequency ion traps, can be cooled via collisions with neutral atoms. Usually the coolant undergoes collisions with a thermal shield mounted on a cryostat attaining temperatures of about 4 K. This lower temperature limit can be overcome, using a laser-cooled buffer-gas localized at the center of the ion cloud or via laser-assisted evaporative cooling. In our hybrid atom-ion trap, the anions O- and OH-, are stored in an octupole radio frequency wire trap and a dense cloud of ultracold buffer-gas (Rubidium) confined in a dark spontaneous-force optical trap (Dark-SPOT). The ions can be overlapped with atoms or a far-threshold photodetachment laser altering the energy distribution of the trapped ions. The ab initio calculations also predict reactive collisions between the ions and atoms, which can be used to probe the effective core potentials used in theoretical studies. By varying the ratio of excited to ground state atoms, the quantum state dependent reactive collisions can be studied. In this contribution, the latest results will be presented. |
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V01.00120: GENERAL PRECISION MEASUREMENTS
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V01.00121: Measurement of the ratio of scalar to vector transition polarizabilities for the 6s → 7s transition in atomic cesium Jonah Quirk, Amy Damitz, Carol E Tanner, Daniel Elliott We report progress on an on-going measurement of the ratio of the scalar (α) to vector (β) transition polarizabilities in atomic cesium (133Cs) for the 6s2S1/2 → 7s2S1/2 transition. This measurement is part of an effort in our laboratory to resolve the discrepancy between two determinations of the vector polarizability β for this transition [PhysRevLett.123.073002]. For the two-pathway coherent control technique used for this measurement, we drive a two-photon interaction and a Stark-induced electric dipole interaction concurrently. By varying the phase difference between the interactions and the direction of the applied electric field, we will be able to precisely measure the transition strength for each field orientation, and determine the ratio α/β. |
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V01.00122: Microwave Atom Chip Design William Miyahira, Andrew P Rotunno, Shuangli Du, Seth Aubin We present work towards the design of a microwave atom chip. Such a chip can produce spin-specific traps using microwave near-field potentials based on the AC Zeeman effect. These potentials are able to trap any spin state and offer suppressed roughness when compared to traditional micro-magnetic chip traps. An atom chip with the ability to spatially control atoms based on their internal spin has applications in trapped atom interferometry and 1D many-body physics. We propose a design based on microstrip transmission lines, which generate traps by overlapping the near-fields of two or three nearby microstrip traces. In such configurations we are able to show the existence of co-located circular traps outside the plane of the chip. Axial confinement of the atoms can be realized through the use of a microwave lattice. The AC Zeeman trap offers unique experimental variables for controlling atoms not found in conventional DC magnetic chip traps: detuning, phase, and the use of circularly polarized magnetic fields. For the three-microstrip geometry, adjusting the phase of the center trace relative to the two outer traces results in the splitting of the trap in two horizontally, providing a potential mechanism for spatially splitting a collection of atoms. Simulations show that due to the proximity of multiple traces to one another, coupling between traces leads to altered power and phase causing the behavior of the trap to differ from simple predictions based on independent traces. |
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V01.00123: Thermodynamic Stability of Stereoisomeric Lactam and benzo[a]pyrene Derivatives in a DNA Mutation Younsu Kim, Richard Kyung The progression of oxidation which occurs during the enzymatic metabolism from benzo[a]pyrene to BPDE causes the alteration of the structure and the abnormal replication proceeds to gene mutation. Density-functional theory and quantum mechanical modelling techniques were used to study electronic structure of stereoisomeric lactam and benzo[a]pyrene(BP) derivatives in a DNA Mutation. In the process of intercalation which results in the formation of an adduct through binding with guanine bases in the DNA, thermodynamic changes were observed while the lactam and BP intercalates to form an adduct. We performed a computational analysis to uncover the structural and thermodynamic changes during the intercalation using molecular dynamics simulation. The free energy differences and the differences in thermodynamic stability between the stereoisomeric adducts were observed during the reaction. |
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V01.00124: Simulation of Magnetic Chip Traps in NASA's Cold Atom Laboratory for Extreme Adiabatic Expansion Leah Phillips, David Aveline, Robert Thompson NASA's Cold Atom Lab facility (CAL) provides an exceptional microgravity environment ideal for experiments with quantum gases that will advance understandings of fundamental physics constants and quantum phenomena [1]. To take advantage of this microgravity environment for atom interrogation and precision measurements, atoms must first be brought to rest without strong, confining magnetic fields. CAL currently applies two strategies to release atoms such that they are brought to rest: delta-kick collimation and adiabatic expansion. The simulation discussed in this poster addresses adiabatic expansion because of the important consequences of its invulnerability to trap anharmonicities [2]. CAL's microgravity climate permits the time required for such expansion without significantly detracting time from the following atom interrogations. This simulation implements the adiabatic expansion using CAL's atom chip and trapping fields aiming to achieve sub-Hz trapping fields and gases of rubidium atoms cooled to temperatures below 100 pK. |
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V01.00125: Search Efforts for the Thorium-229 Nuclear Isomeric Transition Ricky Elwell, Christian Schneider, Justin Jeet, Galen O'Neil, Varun Verma, Dileep Reddy, Sae W Nam, Lars von der Wense, Alina Heihoff, Raphael Haas, Dennis Renisch, Christoph Duellmann, Benedict Seiferle, Florian Zacherl, Peter G Thirolf, Eugene Tkalya, Eric R Hudson Unique among all known nuclei, 229Th has an exceptionally low-energy isomeric transition in the vacuum-ultraviolet (VUV) spectrum around 8 eV [1,2]. The prospect of a laser accessible nuclear system has inspired proposals for a "nuclear clock" based on the $^{229}$Th nuclear transition [3]. However, these applications can only be realized if the transition energy is known more precisely. |
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V01.00126: Tracking the ro-vibrational decay of single H2+ ions using precision measurements of the H2+/D+ cyclotron frequency ratio. David J Fink, Edmund G Myers By re-developing the technique of simultaneous cyclotron frequency measurement of two ions in a Penning trap [1] with H2+ and D+ we have achieved enough mass resolution to differentiate (using the mass-energy relation) between vibrational states of the H2+ ion in a few hours of data taking. By repeated measurements over several weeks we have tracked the ro-vibrational decays of single H2+ ions to the vibrational ground state and, in some cases, identified specific rotational levels. We hence aim to precisely correct the measured H2+/D+ mass ratios for H2+ rotational energy, which was a limitation in our previous measurement of the deuteron to proton mass ratio [2]. Details of the measurement and analysis will be presented. |
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V01.00127: Update on Improving the Precision of Helium Laser Spectroscopy Garnet Cameron Precision measurements of the fine structure of the helium 2P state provides a proving ground for various experimental techniques as well as a test of the bound state quantum electrodynamics of the electron-electron interaction. Additional applications are to nuclear few-body physics and possible input to the fine structure constant determination. We report on the performance of previously presented concepts. (1) Circular polarized atomic beam preparation pumping, accomplished with a custom, miniature, annular, NdFeB magnet assembly and a variable retardance liquid crystal. (2) 10x increased data collection rate via LabVIEW timing optimization. (3) An alternative first-order Doppler shift minimization using picomotor-driven, sub-microradian “active” precision laser alignment, tailored optical mounts, and optical fiber switching. In addition, we describe our in-house fiber laser developments for spectroscopy and atom-state preparation [1]. There was an unexpected discrepancy between the theoretical model and experiment. Further modeling, revised physical parameters, and possible resolution to this discrepancy will be discussed. Data collection to further identify sources of uncertainty which limit precision will be examined also. |
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V01.00128: Measurement of the 2S-8D Transition in Atomic Hydrogen Adam Brandt, Samuel F Cooper, Cory Rasor, Dylan C Yost High-precision laser spectroscopy of hydrogen provides important input data for determinations of the proton radius and Rydberg constant. At Colorado State University, we are currently measuring the hydrogen 2S-8D5/2 transition, which was previously measured in 1997 [Beauvoir et al., Phys. Rev. Lett. 78, 440 (1997)]. In our measurement, a cryogenic beam of metastable hydrogen is formed with a cold nozzle and optically excited to the 2S metastable state. The 2S-8D5/2 two-photon transition is driven in a power enhancement cavity and the remaining metastable atoms are detected to provide a spectroscopic signal. We will carefully describe that status of our measurement, and the characterization of our two main systematic effects – the light shift, and the DC Stark shift. |
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V01.00129: Ultrasensitive Force Sensing with Optically Levitated Nanoparticles Evan Weisman, Chethn Krishna Galla, Cris Montoya Optically levitated and cooled dielectric particles in high vacuum are a promising tool for use in precision experiments. Optically levitated particles have large quality factors by virtue of their mechanical decoupling from the environment enabling ultrasensitive force detection. We report on the trap stability at high vacuum and high intensity of as-grown and heat-treated nanospheres trapped in a new fiber-based counterpropagating trap mounted on 3D moveable piezo stages. The new trap design allows improved maneuverability of the nanoparticle, and will be used to search for deviations from Newton’s inverse square law at the micron scale with comparable sensitivity to the previous free-space version of the experiment which achieved zeptonewton sensitivity. |
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V01.00130: Design and Construction of the first Portable Quantum Gravimeter in México Cristian J López-Monjaraz, Hellmunt Peña Vega, Diego Alegria Meza, Josue G Carmona Moreno, Neil V Corzo, Eduardo De Carlos Lopez, Jesus Flores Mijangos, John A Franco, Eduardo Gomez, Saeed Hamzeloui, Lina M Hoyos, Karina Jimenez-Garcia, Jose Jimenez-Mier, José L López-González, Dai López Jacinto, J. Mauricio López Romero, Alejandra López Vazquez, Ricardo Mendes-Fragoso, Georgina Olivares Rentería, Carlos A Ortiz Cardona, Joaquín G Raboño Borbolla, Fernando Ramirez Martinez, Victor M Valenzuela Jimenez The world is moving forward to its second quantum revolution: a stage in technological history where new devices, including sensors based on quantum systems, with unprecedented degree of sensitivity are being developed. Physicists all over the world are working toward practical implementations on new generation quantum sensors, and with the present project Mexico joins this important international effort through the “Grávico” collaboration. |
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V01.00131: Development of a spin-squeezed strontium optical lattice clock Maya Miklos*, Yee Ming Tso*, John M Robinson, Josephine Meyer, Colin J Kennedy, Tobias Bothwell, James K Thompson, Jun Ye In optical atomic clocks made up of uncorrelated atoms, the fundamental limit of frequency instability is set by quantum projection noise (QPN). By leveraging non-classical spin correlations of the atomic ensemble, entangled atomic clocks can advance past the QPN limit towards the ultimate bound set by the Heisenberg uncertainty principle. As state-of-the-art optical atomic clocks approach QPN-limited operation [1], spin-squeezed clocks offer potential metrological gains. A spin-squeezed optical lattice clock has been demonstrated with stability levels of 10-13 [2]. We report on progress towards the development of a one-dimensional strontium optical lattice clock in a high-finesse cavity to pursue a spin-squeezed clock with a stability of 10-16 or better. By combining the exquisite sensitivity of state-of-the-art optical atomic clocks with long-range cavity-mediated interactions, this system will also offer rich and varied applications to quantum information science, from probing extended Hubbard model physics to studying the scrambling of quantum information. |
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V01.00132: Suppressing a light shift with light in a single-ion 171Yb+ clock Melina Filzinger, Richard Lange, Martin Steinel, Nils Huntemann, Ekkehard Peik Excitation of an optical transition is accompanied by electromagnetic radiation leading to an ac Stark shift. For the electric octupole (E3) transition in 171Yb+, its small oscillator strength leads to the need for high intensities of MW/m2 to drive the transition. Consequently, the resonant frequency is shifted by about 100 Hz during the interrogation pulses, while the unperturbed transition is determined with an accuracy of a few mHz. This is currently achieved using interrogation schemes with nested servo loops, allowing to measure and correct the light shift in real time. However, an uncertainty resulting from intensity variations during the interrogation pulses and slow drifts of the light shift remains. In a new and complementary approach, we utilize the changing sign of the differential polarizability to suppress the light shift directly by combining the 467 nm light used to drive the E3 transition with 976 nm infrared light. Applying both wavelengths from a single photonic crystal fiber, leading to similar intensity profiles at the ion position, makes this method inherently insensitive to pointing instabilities. Controlling the intensity of the infrared light in a nested servo loop during clock operation combines active and passive suppression of the light shift and can reduce the corresponding uncertainty contribution. This approach is particularly promising for multi-ion clocks, where applying equal intensities to all ions is challenging. |
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V01.00133: Measuring Gravitational Redshift at the Centimeter Scale with a Multiplexed Strontium Optical Lattice Clock Xin Zheng, Jonathan C Dolde, Varun Lochab, Brett N Merriman, Haoran Li, Shimon Kolkowitz Optical lattice clocks are amongst the most accurate and precise devices ever built. Their remarkable performance is giving rise to a number of novel applications. In this poster, we will present a "multiplexed" strontium optical lattice clock we have contructed that enables high precision differential measurements between ensembles of ultracold strontium atoms confined in spatially resolved regions of an optical lattice. We will discuss our use of synchronized Ramsey interrogation between multiple ensembles. By making use of a clock transition with reduced magnetic sensitivity, we observe atom-atom coherence times exceeding 10 seconds and measure differential stabilities below 3×10−17/√τ . We will also present preliminary results in which we measure gravitational redshifts between ensembles separated by height difference of 1 cm or less, and will discuss our evaluation of the systematic uncertainty in these measurements. Finally, we will discuss some exciting future prospects for the "multiplexed" clock, such as utilizing Rydberg-dressed spin-squeezing to further enhanced the differential stability, isotope-shift measurements, and tests of relativity with accelerated clocks. |
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V01.00134: Towards a continuous superradiant laser on the strontium 1S0-3P0 transition Camila Beli Silva, Francesca Famà, Sheng Zhou, Stefan Alaric Schäffer, Georgy A. Kazakov, Benjamin Pasquiou, Shayne Bennetts, Florian Schreck Optical atomic clocks have achieved extraordinary precision, which makes them ideal for metrology, quantum sensing, and the exploration of new physics [1]. Superradiant lasers on the strontium 1S0-3P0 clock transition are promising frequency reference candidate for the next-generation of active optical atomic clocks [2]. |
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V01.00135: Towards Record High Stability and Accuracy In A 1D Strontium Optical Lattice Clock Alexander G Aeppli With recent demonstrations of record stability [1] and excellent accuracy [2], strontium is a promising candidate for a broad range of applications including the redefinition of the SI second. We report on the progress of our recently rebuilt 1D strontium optical lattice clock. Our new clock incorporates an in-vacuum build-up cavity for a vertically oriented lattice allowing loading of millimeter sized samples at very low lattice depths. Self-synchronous imaging permits rapid frequency comparison between different regions of the elongated sample, probing frequency homogeneity and atomic coherence. We demonstrate improved stability surpassing that of Ref. [1] and atom-atom coherence times comparable with recent work in optical tweezers [3]. Our room-temperature design has excellent thermal homogeneity and stability, passive and active suppression of DC Stark shifts, and highly reproducible trapping potentials. This system is well positioned for characterization of systematic frequency shifts at the 19th digit corresponding to geodesy at the mm level. |
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