Bulletin of the American Physical Society
50th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 64, Number 4
Monday–Friday, May 27–31, 2019; Milwaukee, Wisconsin
Session L01: Poster Session II (4:00pm6:00pm) 
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Room: Wisconsin Center Hall A 

L01.00001: COLLISIONS AND SPECTROSCOPY 

L01.00002: Laser ablation molecular spectroscopy of radium monofluoride Joshua Abney, Matthew Dietrich The diatomic molecule radium monofluoride (RaF) is a promising candidate for a molecular probe of physics beyond the Standard Model. In particular the large nuclear octupole deformation and heavy mass of radium enables electric dipole moment (EDM) measurements that are highly sensitive to CP violation within the nucleus. Additionally, the large effective electric field of the polar molecule at the Ra nucleus further enhances EDM sensitivity. Initial predictions suggest that RaF is susceptible to direct cooling with lasers due to a potentially highly diagonal FrankCondon matrix. In order to determine the feasibility of cooling RaF for future experiments, we have prepared a setup to perform laser ablation molecular spectroscopy (LAMS) to measure for the first time the vibrational structure of RaF and determine the FrankCondon factors for its AX transition near 700 nm. This work is supported by the U.S. DOE, Office of Science, Office of Nuclear Physics, under contract DEAC0206CH11357. [Preview Abstract] 

L01.00003: Undergraduate research for molecular bond measurements Dayton Brown, Joseph Yang, Vola M Andrianarijaona When studying molecules it is useful to calculate the energetics, atomic spatial positions relative in three dimensions, and the vibrational frequency of each bond. Due to the huge number of particles, the sheer number of interconnected bonds, and the complexity in large biological molecules, simplifications and approximations are required for the calculations and estimations of useful data. To calculate ionization energy for a particular geometry of a molecule, we use the free version of ORCA [1], a program based on Density Functional Theory (DFT), and use the results as tools to quantify physical and chemical properties of various biological compounds including basic compounds such as water. The applications of these research tools can be easily extended to the study of large biomolecules such as amino acids. Amino acid interactions cause proteins to fold in specific manners. Basic properties such as ionization energies shed lights on these interactions, thus they are useful for studying diseases where proteins misfold and produce cellular problems. Few examples, including the different steps are shown in this poster. \newline [1] F Neese, ``The ORCA program system''. Wiley Interdisciplinary Reviews: Computational Molecular Science 2 (1), 7378 [Preview Abstract] 

L01.00004: Photoassociation of Fermionic ${}^{87}$Sr via the ${}^{1}$S$_0$  ${}^{1}$P$_1$ Transition Joshua Hill, James Aman, Thomas Killian The fermionic isotope of strontium, ${}^{87}$Sr, is of interest for the development of optical frequency standards and the study of quantum manybody phenomena. In many of these experiments, ${}^{87}$Sr is confined in an optical lattice. Detecting the presence of doubly occupied lattice sites is a valuable tool for studies of atomic gases in optical lattices, and this is typically done with photoassociation, in which two goundstate atoms in a scattering state are photoexcited to a molecular state. No resonance frequencies have been reported for transitions to molecular states of any excited electronic potential for ${}^{87}$Sr. Here we present results for photoassociation of ${}^{87}$Sr atoms via the ${}^{1}$S$_0$  ${}^{1}$P$_1$ transition at 461nm ($\Gamma = (2\pi*30.5) s^{1}$), and measurements of optical lengths for select photoassociation spectra. [Preview Abstract] 

L01.00005: A Cryogenic Testbed for HighQ Thin Films and Optical Coatings Aaron Markowitz, Brittany Kamai, Chris Wipf, Johannes Eichholz, Jordan Kemp, Mariia Matiushechkina, Mandy Cheung, Ching Pin Ooi, Rana Adhikari A limiting source of noise for optomechanical experiments, including nextgeneration gravitational wave detectors, is coupling to the thermal bath of the mechanical system. We present a recently developed cryogenic testbed for measuring the internal friction of thin disk resonators with rapid sample turnover. The apparatus makes use of an amplitudelocked loop to continuously measure the quality factor and eigenfrequencies of several resonances of the system, permitting precise, noncontact temperature control. The testbed has been applied to the development of amorphous silicon coatings on silicon substrates for use in nextgeneration gravitational wave interferometers, and has application for other thin film development. [Preview Abstract] 

L01.00006: Measurement of the radial matrix elements for the $6s ^2S_{1/2} \rightarrow 7p ^2P_J$ transitions in cesium Amy Damitz, George Toh, Eric Putney, Carol Tanner, Daniel Elliott We report measurements of the dipole matrix elements of the cesium $6s\,^2S_{1/2} \rightarrow 7p\,^2P_{1/2}$ and $6s\,^2S_{1/2} \rightarrow 7p\,^2P_{3/2}$ transitions. Each of these determinations is based on direct, precise comparisons of the absorption coefficients between two absorption lines. For the $\langle 7p\,^2P_{3/2}r 6s\,^2S_{1/2}\rangle $ moment, we measure the ratio of the absorption coefficient on this line with that of the D$_1$ transition. The moment of the D$_1$ line has been determined with high precision previously by many groups. For the $\langle 7p\,^2P_{1/2}r 6s\,^2S_{1/2} \rangle$ moment, we measure the ratio of the absorption coefficient on this line with that of the $6s\,^2S_{1/2} \rightarrow 7p\,^2P_{3/2}$ transition. These measurements have implications on cesium parity nonconservation theory. [Preview Abstract] 

L01.00007: Optical Spectroscopy of High$L$ Rydberg States of Calcium Alina Gearba, Jefferson Sesler, Daniel McIlhenny, Randy Knize, Jerry Sell, Brett DePaola, Stephen Lundeen The Resonant Excitation Stark Ionization Spectroscopy (RESIS) technique has been used to measure the details of the binding energies of a nonpenetrating high$L$ Rydberg electron bound to the Ca$^{+}$ ion. A sample of high$L$ Rydberg calcium atoms is formed by capture of a single electron from an $n = 9$ rubidium Rydberg target by a fast beam of Ca$^{+}$ ions. Individual finestructure levels in the $n = 10$ manifold of Ca are selectively detected using Dopplertuned CO$_{2}$ laser excitation to $n = 26$, followed by Stark ionization of the $n = 26$ products. The Stark ionization rate is proportional to the population of the individual $L$ level which is selectively excited by the CO$_{2}$ laser and the positions of these lines are used to determine initial estimates of the dipole and quadrupole polarizabilities of the Ca$^{+}$ ion. [Preview Abstract] 

L01.00008: Direct search for the thorium229 nuclear isomeric transition with a pulsed VUV laser Ricky Elwell, Justin Jeet, Christian Schneider, Eugene Tkalya, Eric Hudson The nucleus of $^{229}$Th has an exceptionally lowenergy isomeric transition in the vacuumultraviolet (VUV) spectrum around $7.8 \pm 0.5$ eV [1]. While inaccessible to standard nuclear physics techniques, there are various prospects for a laseraccessible nuclear transition. Our direct search for the transition uses thoriumdoped crystals as samples. In a previous experiment [2] at the Advanced Light Source (ALS) synchrotron, LBNL, we were able to exclude a large portion of the transition lifetimevs.frequency regionofinterest (ROI) [3]. Here, we will report on our ongoing efforts of a search using a pulsed VUV laser system as light source, which allows us to enhance our sensitivity up to $10^4\times$ over the ALS and extend the accessible frequency range over the entire ROI [3]. An updated exclusion region will be presented. \newline \newline [1] B. R. Beck et al.: LLNLPROC415170 (2009) \newline[2] J. Jeet et al.: Phys. Rev. Lett. 114, 253001 (2015) \newline[3] E. V. Tkalya et al.: Phys. Rev. C 92, 054324 (2015) [Preview Abstract] 

L01.00009: Photoionization and Structure of the Superheavy Atom Og (Z$=$118): Interchannel Coupling on Steroids Rezvan Khadenhosseini, Ahmad Razavi, David Keating, Steven Manson, Pranawa Deshmukh Calculations of the structure and photoionization of the closedshell superheavy oganesson (Og) atom have been performed using DiracFock (DF) and relativisticrandomphase approximation (RRPA) methods, a study inspired by a recent investigation of the structure of Og [1]. Although Og is in the noble gas column of the periodic, the ordering of nearouter subshells is rather peculiar owing to the strength of relativistic and spinorbit interactions at such high Z, Specifically, the ordering of the levels is hydrogenic from the 1s up to the 6s subshell. But interlopers are found between the levels of spinorbit doublets; the ordering of the nearouter subshells is found to be 6p$_{\mathrm{1/2}}$, 5f$_{\mathrm{5/2}}$, 5f$_{\mathrm{7/2}}$, 6p$_{\mathrm{3/2}}$. Photoionization cross sections and angular distributions have been obtained for each subshell from threshold to almost 2 keV and the results show that interchannel coupling dominates the photoionization process over most of the energy region; the cross sections of the weaker subshells become miniversions of the stronger cross sections owing to the coupling. Work supported partially by the US DOE and SERB (India). [1] P. Jerabek, et al, Phys. Rev. Lett. \textbf{120}, 053001 (2018). [Preview Abstract] 

L01.00010: Varying initial state symmetries in the double photoionization of $p^2$ electrons from atoms Frank L. Yip, Thomas N. Rescigno, C. William McCurdy Recent investigations on double photoionization events from multielectron targets directly probes the electron correlation between the two photoejected electrons and, thus requires an accurate consideration of their correlated dynamics. Recently, we have treated atomic targets with some accounting of the interactions of these outgoing electrons with those electrons that remain bound to the target. In considering the singlephoton double ionization of two $p$orbital electrons, for example, distinct finalstate symmetries exist, depending on the the possible angular momentum couplings of how these electrons are initially coupled (three possibilities:$^3P$, $^1D$, and $^1S$). We consider the full possibilities of removing two valence $p$ electrons from atomic targets and examine the fullydifferential cross sections that result. [Preview Abstract] 

L01.00011: Effects of exchangecorrelation functionals on the structure and the photoionization dynamics of Na$_{\mathrm{40\thinspace }}$cluster Rasheed Shaik, Hari Varma, Himadri Chakraborty Over the years, timedependent density functional theory has emerged as a powerful tool to study photoionization dynamics of manyelectron systems such as atomic clusters [1,2,3]. The accurate prediction of the system's dynamical response to external radiations depends on the accuracy of the form of exchangecorrelation functional (xc) used within a densityfunctional formalism [3]. For spherical Na$_{\mathrm{40}}$ cluster, we apply two well known implementations of xc functional in the framework of timedependent local density approximation (TDLDA), with the GunnarssonLundqvist parametrization [4] for the correlation term. These are: (i) the electron selfinteraction correction (LDASIC) by Perdew and Zunger [5] and (ii) the van Leeuwen and Baerends model potential (LDALB94) [6]. The results obtained by these two schemes will be compared in determining their effects on the ground state structure and the photoionization properties of the system. [1] E. Runge and E. K. U. Gross, \textit{Phys. Rev. Lett.} \textbf{52}, 997 (1984); [2] Choi \textit{et al}., \textit{Phys. Rev. A} \textbf{95}, 023404 (2017); [3] Onida \textit{et al}., \textit{Rev. Mod. Phys.} \textbf{74}, 601 (2002); [4] O. Gunnarsson and B. I. Lundqvist, \textit{Phys. Rev. B} \textbf{13}, 4274 (1976); [5] J.P. Perdew and A. Zunger, \textit{Phys. Rev. B} \textbf{23}, 5048 (1981); [6] R. van Leeuwen and E. J. Baerends, \textit{Phys. Rev. A}\textbf{ 49}, 2421 (1994). [Preview Abstract] 

L01.00012: KAMP: a new photoionphotoelectron coincidence setup for timeresolved XUVIR experiments S. J Robatjazi, S. Pathak, W. L. Pearson, J. Powell, Kanaka Raju P., J. Buerger, D. Rolles, A. Rudenko We describe a newly developed Kansas Atomic and Molecular Physics (KAMP) instrument, which combines a femtosecond pumpprobe setup employing extremeultraviolet (XUV) and nearinfrared (NIR) pulses with a doublesided velocity map imaging (VMI) spectrometer for photoionphotoelectron coincidence measurements. The spectrometer equipped with two time and positionsensitive delayline detectors is attached to a highharmonics generation (HHG) setup based on a commercial KM Labs eXtreme Ultraviolet Ultrafast Source. The latter is capable of delivering HHG radiation of less than 30 fs pulse duration in the photon energy range of \textasciitilde 17  100 eV. We present the results of the instrument's commissioning, including ionelectron coincidence spectra from XUVNIR pumpprobe measurements on valenceshell and innershell ionization of Xe and Kr atoms, as well as ionization and fragmentation of CO2 molecules. Most of the major setup elements such as the interaction chamber, VMI spectrometer, detectors and a gas target arrangement are compatible with the CAMP and LAMP instruments installed at FLASH and LCLS freeelectron laser facilities, respectively, enabling efficient testing of the new equipment components for experiments at these facilities. [Preview Abstract] 

L01.00013: Deep minimum in the CoulombBorn TDCS for e$^$H, e$^$He and e$^+$He ionization C. M. DeMars, J. B. Kent, S. J. Ward A deep minimum in the experimental measurements [1] of the triply differential cross section (TDCS) for electronhelium ionization has been attributed to a vortex in the velocity field that is associated with the ionization amplitude [2]. The deep minimum has been theoretically obtained using the timedependent closecoupling and distortedwave methods [3]. We have shown that the CoulombBorn approximation is able to obtain the deep minimum in the TDCS for electronhelium ionization. Furthermore, we have shown that within this approximation a deep minimum is present for electronhydrogen ionization and for positronhelium ionization. These minima are due to vortices in velocity field that is associated with the transition matrix element. Previously, vortices have been shown to exist for positronhydrogen ionization [4]. [1] A. J. Murray and F. H. Read, Phys. Rev. A {\bf 47}, 3724 (1993). [2] J. H. Macek, J. B. Sternberg, S. Y. Ovchinnikov and J. S. Briggs, Phys. Rev. Lett. {\bf 104}, 033201 (2010). [3] J. Colgan, O. AlHagan, D. H. Madison, A. J. Murray and M. S. Pindzola, J.Phys.B {\bf 42} 171001 (2009). [4] F. Navarrete and R. O. Barrachina, J.Phys.B {\bf 48}, 055201 (2015). [Preview Abstract] 

L01.00014: Efficient computation of collisional $\ell$mixing rate coefficients in astrophysical plasmas D. Vrinceanu, R. Onofrio, H. R. Sadeghpour We present analytical expressions for direct evaluation of $\elll$mixing rate coefficients in angular momentumchanging transitions of excited hydrogen atoms colliding with protons and describe a software package for their efficient numerical evaluation. Com parisons between rate coefficients calculated with various levels of approximation are discussed, highlighting their range of validity. These rate coefficients are benchmarked with calculations of level populations in radio recombination of protons and departure coefficients from local thermal equilibrium. [Preview Abstract] 

L01.00015: Collisional EPR Frequency Shifts in CsRbXe Mixtures Sheng Zou, Chamithri Adikarige, Zahra Armanfard, Trevor Foote, David P. Morin, Brian Saam Spinexchange optical pumping (SEOP) generates large nonthermal nuclear polarizations in certain nonzerospin noble gases. The collisionally modulated Fermicontact hyperfine interaction between the alkalimetal valence electron and the noblegas nucleus is crucial to SEOP physics, which is incompletely understood, especially for heavy noble gases like Xe. One current question is whether Rb, Cs, or a mixture of the two is ideal for SEOP of $^{129}$Xe. The magnetization of hyperpolarized $^{129}$Xe generates a frequency shift in the alkalimetal EPR hyperfine spectrum that is directly proportional to the electronwavefunction overlap characterized by the enhancement factor $\kappa_0$ [1]. We performed nearsimultaneous measurements of the $^{87}$Rb and $^{133}$Cs EPR shifts caused by sudden destruction of $^{129}$Xe hyperpolarization in a ``hybrid” RbCs SEOP vapor cell. Our preliminary result for the shift ratio is about 1.5 to 1.6 at 110 $^{\circ}$C, suggesting that $(\kappa_0)_{\rm CsXe}$ is about 25\% to 35\% larger than $(\kappa_0)_{\rm RbXe}$; the latter has been previously measured to be $493\pm 31$ [2]. [1] S.R. Schaefer, et al., Phys Rev. A {\bf 39}, 5613 (1989). [2] Z.L. Ma, et al., Phys. Rev. Lett. {\bf 106}, 193005 (2011). [Preview Abstract] 

L01.00016: Dicarbon formation in collisions of two carbon atoms James Babb, Ryan Smyth, Brendan McLaughlin Radiative association cross sections and rates are computed, using a quantum approach, for the formation of C$_2$ molecules (dicarbon) during the collision of two ground state C($^3$P) atoms. We find that transitions originating in the C$\;^1\Pi_g$, d$\;^3\Pi_g$, and 1$\;^5\Pi_u$ states are the main contributors to the process. The results are compared and contrasted with previous results obtained from a semiclassical approximation. New ab initio potential curves and transition dipole moment functions have been obtained for the present work using the multireference configuration interaction approach with the Davidson correction (MRCI+Q) and augccpCV5Z basis sets. Applications of the current computations to various astrophysical environments and laboratory studies are briefly discussed focusing on these rates. We discuss recent calculations on collisions of a carbon atom and a carbon ion. [Preview Abstract] 

L01.00017: Progress toward a coldatom based vacuum standard and pressure gauge Daniel Barker, Eric Norrgard, Julia Scherschligt, James Fedchak, Nikolai Klimov, Stephen Eckel Preparation and evaluation of ultrahighvacuum (UHV) and extremehighvacuum (XHV) environments is critical for highquality semiconductor fabrication and emerging quantum technologies. Vacuum sensors for these pressure ranges, such as iongauges, are not primary (i.e., they require calibration themselves) and have large, poorlyunderstood uncertainties. We present our progress towards a primary standard for vacuum measurement in the XHV using cold Li atoms confined in a magnetic trap. Our apparatus will allow highaccuracy measurements of atommolecule collision crosssections that are necessary to extract the vacuum pressure from the observed backgroundgaslimited lifetime of the trapped atoms. We have also developed chipbased techniques to slow and trap Li atoms with a single laser beam. This nanofabricated atomtrapping platform forms the basis for a deployable, primary vacuum sensor with embedded traceability that can replace an ion gauge. [Preview Abstract] 

L01.00018: Fulldimensional quantum rovibrational scattering of SO with H$_2$ Benhui Yang, Peng Zhang, Chen Qu, Phillip Stancil, Joel Bowman, N. Balakrishnan, Robert Forrey Molecular collisional rate coefficients are required to predict the abundance of molecular gas in the interstellar medium. SO has been widely observed in a variety interstellar regions and its collisional rate coefficients with the dominant collision partner H$_2$ are of astrophysical importance. We present a quantum closecoupling study of rovibrationally inelastic scattering of SO with H$_2$. A sixdimensional (6D) potential energy surface (PES) was constructed with highlevel ab initio calculations and an invariant polynomial fitting. The scattering calculations were carried out for both rotational and rovibrational transitions of SO induced by H$_2$. Cross sections for rotational transitions from $j_1$=010 of SO in the ground vibrational state were computed for collision energies ranging from 1 to 3000 cm$^{1}$. The rotational rate coefficients are compared with previous theoretical results obtained within a rigidrotor approximation. For rovibrational transitions, statetostate quenching cross sections and rate coefficients were calculated for the vibrational quenching of SO from ($v_1=1, j_1$), $j_1$=05. Cross sections for collision energies in the range 1 to 3000 cm$^{1}$ and rate coefficients ranging from 5 to 600 K are presented. [Preview Abstract] 

L01.00019: Freefree experiments: dressedatom effects during inelastic electron scattering B.N. Kim, C.M. Weaver, N.L.S. Martin, B.A. deHarak Freefree experiments investigate the absorption or emission of radiation during the collision of charged particles with atoms and molecules. The first experimental observation of dressedatom effects  due to the electric field of the laser  during the elastic scattering of electrons by Xe were reported by Morimoto {\em et al}.\footnote{Y. Morimoto, R. Kanya, and K. Yamanouchi, Phys.\ Rev.\ Lett.\ {\bf 115}, 123201 (2015)} Their results were compared with an analytical expression by Zon that contains the electric dipole polarizability $\alpha$ of the target.\footnote{B. A. Zon, Sov. Phys. JETP 46(1), 65 (1977)} We are investigating dressing effects for {\em inelastic} electron scattering in the presence of a Nd:YAG laser; specifically we are investigating electronimpact excitation of the lowest excited states of He and Ar. Zon's expression is not valid for {inelastic} scattering so we have developed an equivalent inelastic expression. We will give the results of a simple calculation for dressing effects for the excited states of He, and will give a progress report on our experiments. [Preview Abstract] 

L01.00020: Electronimpact excitation of forbidden and allowed transitions in Cr II Swaraj Tayal, Oleg Zatsarinny Electron excitation collision rates and transitions probabilities for ironpeak Cr II ions are needed for the determination of electron temperatures and densities, ionization equilibria, and abundances in the astrophysical plasmas. The collision strengths have been calculated using the Bspline BreitPauli Rmatrix method. The multiconfiguration HartreeFock method in connection with adjustable configuration expansions and semiempirical fineturning procedure is employed for an accurate representation of the target wave functions. The closecoupling expansion contains 512 finestructure levels of Cr II of the $3d^44s$, $3d^34s^2$, $3d^5$, $3d^44p$, and $3d^44s4p$ configurations. The collision rates are obtained by averaging the electron collision strengths over a Maxwellian distribution of velocities at electron temperatures in the range from $10^2$ to $10^5$ K for the 130816 transitions between these finestructure levels. The present results considerably expand the existing data sets for Cr II, allowing a more detailed treatment of the available measured spectra from different space observatories. Comparison with other calculations for collision rates and available experimental radiative rates is used to assess the likely uncertainties in in the existing data sets. [Preview Abstract] 

L01.00021: Interference in ElectronMolecule Elastic Scattering. Arkadiy Baltenkov, Steven Manson, Alfred Msezane General formulas describing the multiple elastic scattering of electron by polyatomic molecules have been derived within the framework of the model of nonoverlapping atomic potentials [1]. In this model the molecular continuum wave functions have been represented as a plane wave plus a linear combination of the Green's functions for free motion and the derivatives of these functions. Built in such a way, the wave functions far from the target have a form of $N$ spherical waves emitted by $N$ atomic spheres. These waves interfere as in the case of the Young's double slits experiment. The interference of spherical waves manifests itself as diffraction oscillations in the differential and total cross sections for elastic electron scattering. The amplitude of electron scattering by a molecule is defined by the phase shifts for each of the atoms forming the target and its geometry. The numerical calculation of the scattering amplitude in closed form (rather than in the form of $S$matrix expansion) is reduced to solving a system of algebraic equations. The derived general formulas have been applied to different carbon molecules, both for fixedinspace and randomly oriented molecules. The work of [1], which included only $s$ and $p$waves, has been extended to include partial wave of any angular momentum. This work was supported by the Uzbek Foundation Award OT$\Phi $246 (ASB) and U.S. DOE, Basic Energy Sciences, Office of Energy Research (AZM and STM). [1] A.S. Baltenkov, S.T. Manson and A.Z. Msezane, J. Phys. B \textbf{51}, 205101 (2018). [Preview Abstract] 

L01.00022: Simplified model to treat the electron attachment of complex molecules Chi Hong Yuen, Nicolas Douguet, Samantha Fonseca dos Santos, Ann Orel, Viatcheslav Kokoouline We present a theoretical approach to evaluate cross sections for dissociative electron attachment to polyatomic molecules. Starting from the BardsleyO'Malley theory developed for diatomic targets, we extend the formalism of resonant scattering to polyatomic molecules. By inspecting the variation of resonance energies with respect to normal coordinates, a generalized dissociation coordinate is introduced for polyatomic molecules. Using the local complex potential model, the present \textit{ab inito} model gives a reasonable estimate for dissociative attachment cross sections with modest computational efforts. The model is applied to the H$_2$CN molecule, which is considered as a precursor in the formation of the CN$^$ anion observed in the IRC~+10216 carbon star. The computed rate coefficient suggests that the dissociative electron attachment of H$_2$CN may not be an efficient reaction to form CN$^$ in the circumstellar envelope of IRC +10216. [Preview Abstract] 

L01.00023: Metastable Fragment Production in ElectronMethanol Collisions. J William McConkey, Jeffrey Dech, Wladek Kedzierski A unique detector which is selectively sensitive to low energy metastable atoms and molecules, is used to study the production of ground configuration O(1S) atoms and CO(a 3π) molecules following collisions of low energy (0300 eV) electrons with methanol molecules. Timeofflight detection has allowed identification of likely dissociation channels. Excitation probability measurements will be presented as a function of incident electron energy and nearthreshold data will be used to help identify possible excitation channels. [Preview Abstract] 

L01.00024: Experimental and Theoretical Studies of the Isotope Exchange Reaction: \boldmath{${\rm D+H_3^+ \to H_2D^++H}$} Daniel Wolf Savin, Kyle P. Bowen, PierreMichel Hillenbrand, Jacques Li\'evin, Xavier Urbain H$_{\mathrm{2}}$D$^{\mathrm{+}}$ is an important chemical tracer of the evolution of protostellar cores. Accurate thermal rate coefficients for the reactions that generate this ion are critical for reliably understanding the star formation process. Here we present laboratory measurements of the titular reaction. Astrochemical models currently rely on rate coefficients from classical (Langevin) or semiclassical methods for this reaction. Fully quantummechanical calculations are beyond current computational capabilities. Laboratory studies are the most tractable means of providing the needed data. For our studies we used our novel dualsource, merged fastbeams apparatus, which enables us to study reactions of neutral atoms and molecular ions. Copropagating beams allow us to measure cross sections as a function of collision energy. We then convolve these results with a MaxwellBoltzmann distribution to generate thermal rate coefficients. High level quantum \textit{ab initio} calculations have been used to model the reaction energy profile and the shape of the potential energy barrier, allowing an evaluation of the tunneling effects. Here we present our experimental and theoretical results for this reaction and discuss some of the astrochemical implications. [Preview Abstract] 

L01.00025: ABSTRACT WITHDRAWN 

L01.00026: Grazing scattering of anions to explore electronic subbands of nanostructured surfaces Himadri Chakraborty, John Shaw, David Monismith, Yixiao Zhang, Danielle Doerr We study the electron dynamics at a monocrystalline prototype surface of Pd(111) with stepped vicinal nanostructures [1]. The unoccupied bands of the surface are resonantly excited \textit{via} the charge transfer interaction of the surface with a hydrogen anion reflected at grazing angles. The dynamics is simulated in a quantum mechanical wave packet propagation approach [2] using parallel computing. Evolution of the wave packet suggests that the electron transfers from the ion to the surface and image subband states of the metal as it evolves through the superlattice. But the electron returns to the ion only from the image subbands. The ion survival probability exhibits modulations as a function of the vicinalterrace size and shows peaks at energies that access the image subband dispersions [3]. A square well model producing standing waves between the steps on the surface suggests the application of such ion scattering at shallow angles to map electronic substructures in vicinal surfaces. The work serves as proofofprinciple in the utility of our computational method to address surfaces with nanometric patterns. [1] Mugarza and Ortega, \textit{J. Phys. Cond. Matt.} \textbf{15}, S3281 (2003); [2] Schmitz \textit{et al.}, \textit{Phys. Rev. A} \textbf{81} 042901 (2010); [3] Shaw \textit{et al.}, \textit{Phys. Rev. A} \textbf{98}, 052705 (2018). [Preview Abstract] 

L01.00027: PRECISION MEASUREMENTS 

L01.00028: A microwave measurement of the $n$=2 Lamb shift in hydrogen using the FOSOF technique N. Bezginov, T. Valdez, M. Horbatsch, A. Marsman, A.C. Vutha, E.A. Hessels We present the details of a recently completed measurement of the $n$=2 Lamb shift in atomic hydrogen. The measurement uses a fast beam of hydrogen atoms that interact with two separated oscillatory fields. The two fields are slightly offset in frequency to employ the new frequencyoffset separated oscillatory field (FOSOF) technique[1]. The uncertainty in our measurement is 3.2 kHz, which allows for a precise determination of the rms charge radius of the proton. This charge radius can be compared to that obtained from the measurements of the Lamb shift of muonic hydrogen[2] and helps to resolve the nineyearlong discrepancy between proton size measurements that use electrons and those that use muons. [1] A Vutha, EA Hessels, PRA 92, 052505 (2015). [2] R Pohl, et al Nature 466, 213 (2010); A Antognini, et al Science 339 417 (2013). [Preview Abstract] 

L01.00029: A Robust Green AstroComb for EarthLike Exoplanet Searches Aakash Ravi, David Phillips, Nicholas Langellier, Timothy Milbourne, Maya Miklos, Ronald Walsworth One technique for detecting exoplanets (i.e. planets outside our solar system) is the radial velocity method. This technique works by observing, in a starexoplanet system, the periodic shifts in the star’s spectral lines caused by the gravitational influence of an orbiting planet. Detecting Earthsized planets around Sunlike stars is very challenging as it requires extremely precise calibration and characterization the of astrophysical spectrographs used to make such measurements. To address this challenge, we employ a visible wavelength laser frequency comb as a wavelength calibration source. Our frequency comb calibrator, known as an astrocomb, is realized by spectrally broadening and shifting the output of a 1 GHz repetition rate modelocked Ti:sapphire laser using a photonic crystal fiber and then filtering the comb lines to create a coarsetoothed comb with 16 GHz line spacing. Our astrocomb system has been deployed at the TNG telescope on La Palma, Spain to calibrate the HARPSN spectrograph. Here, we present improved spectral broadening techniques, a wider combspacing implementation for instrument profile characterization, and ongoing combcalibrated astrophysical measurements, including measurements of solar radial velocities. [Preview Abstract] 

L01.00030: Precise Measurements of transition amplitudes, polarizabilities, and isotope shifts in lead, thallium, and tin using Faraday rotation spectroscopy Protik Majumder, Daniel Maser, Gabriel Patenotte, Sameer Khanbhai We have undertaken a series of atomic structure, optical polarimetry measurements in group III and IV elements to test ongoing atomic theory and aid in tests of fundamental physics. A highprecision polarimeter consisting of crossed calcite polarizers and a modulation/lockin detection scheme yields optical rotation resolution at the 1 $\mu$Radian/$\sqrt{Hz}$ level. By applying small longitudinal magnetic fields to atomic samples in both heated vapor cells and an atomic beam, we obtain wellresolved Faraday rotation lineshapes even for ‘forbidden’ transitions and atomic samples with very low population density. Using this technique we have detected for the first time the groundstate $(6s^26p^2) ^3P_0  ^3P_2$ 939 nm electric quadrupole (E2) transition in lead, and are completing a precise measurement of its amplitude that can be compared to recent {\em ab initio} atomic theory in lead. We plan to study E1 transitions originating from thermallyexcited atomic samples and measure hyperfine structure and isotope shifts in both the lead and tin atomic systems. Using our atomic beam apparatus and the Faraday polarimetry technique, we will also measure excitedstate polarizabilities and transition amplitudes in these atomic systems. [Preview Abstract] 

L01.00031: Atombased optical RFpower/voltage transducer and sensor Rachel Sapiro, Georg Raithel, David Anderson New technologies for atomic vapor cells enable experiments and applications that require a small footprint. We introduce a detector comprising an atomic vapor cell with integrated electrodes embedded in an RF circuit to serve as a RFtooptical transducer. In our present demonstration, an RF electrical signal collected by an antenna is converted into intracell electric fields, which are then optically read out via spectroscopy of fieldsensitive atomic states. By direct conversion of RF electrical signals to an atommediated optical readout, the atombased transducer provides ultrahigh bandwidth from DC to THz, absolute (atomic) measurement of RF power or voltage in a compact unit. Here, we demonstrate such a detector consisting of a cesium vapor cell with integrated electrodes connected directly to a microwave horn antenna via an SMA cable. Optical readout is facilitated by EIT spectroscopy of the cesium vapor. The acquired EIT spectra exhibit AutlerTownes line splittings that yield the powerequivalent field of the microwaves collected by the horn. [Preview Abstract] 

L01.00032: Optomechanical force sensors Jonathan Cripe, Gordon Shaw The radiation pressure force produced by reflecting light off a surface provides a useful tool in force metrology for measuring and calibrating forces across a large dynamic range. Current implementations, however, rely on transducing the optical power used to create the force into a optical power measurement with a readout using a power meter. This method introduces uncertainty on the order of 1 \% at the point of the power meter. An alternative approach is to conduct a force measurement by monitoring the displacement of the force sensor using cavity optomechanics. Measuring the displacement of a calibrated optomechanical sensor presents an opportunity to reduce the uncertainty in the force measurement. We report on the concept and development of two radiation pressurebased force sensors, one for laser powers on the order of 1 W and the other for measuring the small forces produced by quantum radiation pressure noise. [Preview Abstract] 

L01.00033: Precision Measurement of Isotope Shifts in the $^2S_{1/2} \, \rightarrow \, ^2D_{5/2}$ 729 nm E2 transition in Ca$^+$ S. Charles Doret, Felix Knollman We report progress towards a precise measurement of the isotope shifts in the $4^2S_{1/2} \rightarrow 3^2D_{5/2}$ 729 nm electric quadrupole transition in Ca$^+$. We cotrap two isotopes and simultaneously excite both ions using frequency sidebands on a single laser, dramatically reducing systematic uncertainties from many sources such as laser frequency drift or magnetic field instabilities. Such measurements hold the potential to reach subHz precision, offering a path towards probing New Physics at long and intermediate length scales while also providing benchmarks for everimproving atomic and nuclear theory. [Preview Abstract] 

L01.00034: Optically detected transient nutation relaxation spectroscopy of electron spins in nanodiamonds JunHuo Hsieh, HsuanKai Huang, Jeson Chen, HsaoChih Huang, Oliver Y. Chen, HuanCheng Chang, MingShien Chang Nanoscale magnetic sensing has found important applications from material studies to life science, and a nitrogen vacancy center (NVC) in diamond$^{\mathrm{\thinspace }}$has been demonstrated as a superb magnetic nanoprobe, given the stability of the diamond material and high sensitivity of electron spin resonance (ESR). Conventional magnetic sensing with NVC is achieved via optically detected magnetic resonance (ODMR), in which ESR is detected optically. However, the requirement of relatively high microwave power and low ESR constract limits its sensitivity. Here, we demonstrate a new method to measure ESR using optically detected transientnutation relaxation of ESR. Compared to the ODMR with a typical contrast of 10{\%} in nanodiamonds, the signal spectrum, which is the transient nutation decay time constant under same microwave power, has a contrast of up to 93{\%}. The method gives 100 times sensitivity on the microwave power and potentially provides a new way for AC magnetic sensing in the nanometer scale. [Preview Abstract] 

L01.00035: Searching for the first excited nuclear state of $^{\mathrm{229}}$Th Xia Hua, Lin Li, ZhengTian Lu, Xin Tong The first excitation energy of $^{\mathrm{229}}$Th (Thorium) is only 7.8±0.5 eV and can be excited directly using lasers. Which makes the design of a nuclear clock based on the first excited nuclear state of $^{\mathrm{229}}$Th becomes possible. We are proposed to measure the energy of this first excited nuclear state of $^{\mathrm{229}}$Th based on $^{\mathrm{229}}$Th$^{\mathrm{3+}}$ coulomb crystals in vacuum chamber. The procedure includes 1) Preparation of $^{\mathrm{229}}$Th$^{\mathrm{3+}}$; 2) Confinement of $^{\mathrm{229}}$Th$^{\mathrm{3+}}$ using radio frequency quadrupole ion trap, together with Doppler laser cooling and high vacuum technology. Obtaining long lifetime and stabilized confined $^{\mathrm{229}}$Th$^{\mathrm{3+}}$ coulomb crystals; 3) Illuminating the $^{\mathrm{229}}$Th$^{\mathrm{3+}}$ Coulomb crystal with tunable lasers. Determine the energy range and lifetime of the first excited nuclear state of $^{\mathrm{229}}$Th. The probability of first excited nuclear state of $^{\mathrm{229}}$Th is small, makes it difficult to observe and measure directly. Alternate method is to measure the electron bridge to obtain information of the first excited nuclear state of $^{\mathrm{229}}$Th indirectly. [Preview Abstract] 

L01.00036: Efforts to Improve Precision Laser Spectroscopy of Helium Fine Structure Cory Nook, Garnet Cameron, David Shiner Precision spectroscopy of the 2$^{\mathrm{3}}$S to 2$^{\mathrm{3}}$P transitions in helium and their isotope shifts allows for one of the most sensitive tests of the electronelectron interaction in atomic physics as well as for a test of few body nuclear theory. Improving on our previous results requires better statistical precision and further studies of systematic uncertainties. Software and hardware improvements allow for time spent per data point to be reduced from 1s to 100 ms, which improves the averaging over residual system drifts and maintains SQRT(N) precision with increased signal strength. Signal strength improvements using a newly built custom fiber laser allows population transfer of $^{\mathrm{4}}$He/$^{\mathrm{3}}$He into the $+$ or  1 triplet state and increases signal by a factor of 2. A redesign of the apparatus to shorten the length and increase flexibility is underway and will allow for an increase in signal by a factor of 4. Efforts to improve long term data collection and reliability will be described and the current status of the measurements will be discussed. [Preview Abstract] 

L01.00037: ABSTRACT WITHDRAWN 

L01.00038: JILA's search for the electron electric dipole moment: an order of magnitude improvement in sensitivity Tanya Roussy, William B. Cairncross, Kia Boon Ng, Tanner Grogan, Yan Zhou, Yuval Shagam, Kevin Boyce, Antonio Vigil, Madeline Pettine, Jun Ye, Eric A. Cornell We have recently overhauled our experimental apparatus with an eye towards enhancing our sensitivity to the electron's electric dipole moment. We have developed techniques for lowdecoherence confinement, internal state cooling, multiresonance spectroscopy, quantumstate specific imaging, and differential readout achieving the quantum projection noise limit; all at the relatively high internal temperature of 10 K and all in a system which is being directly probed for beyondstandardmodel physics. Taken together, our advances will generate an order of magnitude improvement in sensitivity. Beyond these improvements, we are developing the next generation apparatus which will allow for a 100fold increase in count rates while still enjoying the distinct advantages of a trappedion system. [Preview Abstract] 

L01.00039: $^{87}$Sr 1D Optical Lattice Clock With a 124 K Silicon Cavity: Full Systematic Evaluation and Record Precision Tobias Bothwell, Dhruv Kedar, Eric Oelker, Colin Kennedy, John Robinson, Sarah Bromley, Ross Hutson, Lindsay Sonderhouse, Akihisa Goban, William Milner, Christian Sanner, Jun Ye We report on the full systematic evaluation of the JILA Sr1 optical lattice clock using a laser stabilized to a 124 K silicon cavity. This evaluation resulted in a factor of 10 improvement over our previous evaluation of JILA Sr1 for the systematic uncertainty [1]. After the systematic evaluation of the JILA Sr2 clock at 2.1$\times 10^{18}$ [2], it is now operating in a 3D lattice configuration. We perform an extensive comparison between JILA Sr1 and Sr2 clocks and determine independent clock stability of 4.8$\times 10^{17}$ at 1 s. With synchronous clock operation we achieve stability of 3.5$\times 10^{17}$ at 1 s and a precision of 6$\times 10^{19}$ in 1 hour of measurement. The stateoftheart precision and accuracy of this clock enables measurements for wideranging applications, from searches for dark matter to relativistic geodesy. \newline \noindent [1] Bloom, B. J., et al. "An optical lattice clock with accuracy and stability at the 10$^{18}$ level." Nature 506.7486 (2014): 71. \noindent [2] Nicholson, T. L., et al. "Systematic evaluation of an atomic clock at 2$\times 10 ^{18}$ total uncertainty." Nature communications 6 (2015): 6896. [Preview Abstract] 

L01.00040: SpinExchange Relaxation Free Magnetometer using Hybrid Pumping for the Global Network of Optical Magnetometers for Exotic Physics (GNOME) Perrin Segura, Sunyool Park, Eleda Fernald, Dhruv Tandon, Jason Stalnaker A network of optical magnetometers has the potential to detect proposed ‘pseudo magnetic’ effects from exoticspin couplings as the Earth passes through a topological defect in a coherent field of ultralight axionlike particles (a proposed candidate for dark matter). The Global Network of Optical Magnetometers to search for Exotic Physics (GNOME) is searching for such a transient signal, using contributions from multiple magnetometer stations to eliminate false positives. We provide an update on the construction of the Oberlin magnetometer: a RbK$^3$He spinexchange relaxation free (SERF) magnetometer, which has recently been upgraded to include hybrid pumping, where a pump laser polarizes Rb atoms in a vapor cell, which in turn polarizes K atoms through spin exchange collisions. The transmission of a probe laser resonant with the K $D_1$ transition through the cell is then monitored as an indicator of magnetic field strength. This process decreases the amount of scattered light from the K atoms, which can be reabsorbed by the surrounding K atoms and cause loss of polarization, and is thus expected to improve the sensitivity of the magnetometer. [Preview Abstract] 

L01.00041: Sensitivity improvement of nuclear magnetic resonance gyroscope with natural abundance of Xe gas Ye Jin Yu, Han seb Moon We investigated on the operation of Nuclear Magnetic Resonance gyroscope(NMRG) using two different isotopes of natural abundance of Xe gas, $^{\mathrm{129}}$Xe and $^{\mathrm{131}}$Xe independently and simultaneously. Rb atoms are used to make Xe hyperpolarized via spinexchange interactions which is highly affected by the optical pumping rate of Rb and the spin exchange rate between the two atoms. In this work, we present a sensitivity measurement results of NMRG using natural abundance Xe depending on the spin polarization degree of Xe adjusted by optical pump power and vapor cell temperature changes. [Preview Abstract] 

L01.00042: ABSTRACT WITHDRAWN 

L01.00043: Highflux atomic sources for Very Long Baseline Atom Interferometry D. Tell, H. Albers, E. Wodey, C. Meiners, R.J. Rengelink, C. Schubert, D. Schlippert, W. Ertmer, E.M. Rasel In atom interferometry, the interaction of light and matter enables a high degree of control over atomic ensembles, allowing them to be used as ultrasensitive probes in precision measurements. Instruments based on this technique have for instance been successfully used to sense accelerations and test fundamental theories.\\ The 10 m Hannover Very Long Baseline Atom Interferometry facility (VLBAI) exploits the linear scaling of acceleration sensitivity with the free fall distance. In order to reach its full potential, error sources need to be tackled on a level beyond stateoftheart experiments. Free fall times on the order of seconds necessitate very low spatial expansion, while for low shot noise and interleaved measurement scenarios, a high flux source of BoseEinstein condensates is indispensable.\\ We present two atomic sources for rubidium and ytterbium which will be implemented for drop and launch operation in the VLBAI facility. Starting with a high atomic flux, our scheme comprises the use of increased cooling laser power, dynamically shaped optical trapping potentials and deltakick collimation for a reduced expansion rate of the dilute atomic ensemble, showing promising perspectives for future interferometry operation. [Preview Abstract] 

L01.00044: Measuring cold atomic momentum distributions with matterwave interferometry Max Carey, Jack Saywell, David Elcock, Mohammad Belal, Tim Freegarde We describe the 1D measurement of the momentum distribution of cold atoms by matterwave interferometery. After introducing the concept with a 2pulse Ramsey sequence [1], we show an elegant practical application that employs a 3pulse MachZehnder interferometer [2] whereby, by varying the temporal asymmetry between the two free evolution periods, the momentum distribution is manifest in the frequency domain of the interferometer output. The technique, which is analogous to Fourier transform spectroscopy [3], is particularly suited to ultracold samples. We present specific results using a Raman pulse interferometer to measure the velocity distributions of freelyexpanding clouds of $^{85}$Rb atoms with temperatures of $33~\mu$K and $17~\mu$K. Quadrature measurement yields these distributions with excellent fidelity, comparing favourably with conventional Doppler and timeofflight techniques and revealing artefacts in standard Raman Doppler methods that we attribute to offresonant excitation [4]. [1] M. Carey et al., J. Mod. Opt. \textbf{65}, 657 (2018). [2] M. Carey et al., arXiv:1802.02190, submitted (2018). [3] A. A. Michelson, Lond. Edinb. Dubl. Phil. Mag. \textbf{31}, 338 (1891). [4] I. G. Hughes, J. Mod. Opt. \textbf{65}, 640 (2018). [Preview Abstract] 

L01.00045: Towards LaserCooled Polyatomic Molecules for Electron EDM Measurements Benjamin Augenbraun, Zack Lasner, Alexander Frenett, Hiromitsu Sawaoka, Calder Miller, Phelan Yu, Timothy Steimle, John Doyle Trapped ultracold molecules are a potentially powerful platform for probing timereversalsymmetry violating effects beyond the Standard Model, such as the electron electric dipole moment. However, lasercoolable diatomic molecules lack the parity doublet structure useful for suppressing key systematic errors. Certain polyatomic molecules simultaneously possess the desired parity doublet \emph{and} an electronic structure that allows for laser cooling. Thus a large, generic class of such species combines internal comagnetometers, the ability to trap large numbers for long times, and large effective electric fields that enhance the signature of timereversalviolating effects. We present progress toward laser cooling and trapping of Ybcontaining polyatomic molecules. A slow cryogenic buffergas beam of YbOH is characterized and work toward photon cycling in YbOH is presented. We also describe a novel magnetic decelerator for slowing molecular beams to near the capture velocity of 3D magnetooptical traps without scattering photons. In addition, we present observations of the EDMsensitive symmetric top molecule YbOCH$_3$. The measured FranckCondon factors indicate that YbOCH$_3$ is also amenable to laser cooling, as expected from theory, and a laser cooling scheme is presented. [Preview Abstract] 

L01.00046: The HUNTER Sterile Neutrino Search Experiment: 131Cs MagnetoOptical Trap Development Eddie Chang, Francesco Granato, Paul Hamilton, Eric Hudson, Basu Lamichhane, Frank Malatino, Charles Martoff, Peter Meyers, Andrew Renshaw, Christian Schneider, Peter Smith, Xunzhen Yu The HUNTER experiment (Heavy Unseen Neutrinos from Total EnergyMomentum Reconstruction) is a search for sterile neutrinos with masses in the keV range. The neutrino missing mass will be reconstructed from 131Cs electron capture decays occurring in a magnetooptically trapped (MOT) sample. Reactionmicroscope spectrometers will detect all charged decay products with high solid angle efficiency and LYSO scintillators read out by silicon photomultiplier arrays will detect xrays, each with sufficient resolution to reconstruct the neutrino missing mass. The short halflife of about 9.5 d of 131Cs paired with the requirement to run the experiment over timescales of order one year to obtain the target sensitivity present special challenges for the MOT. We will present progress on the 131Cs MOT development and implementation at UCLA. [Preview Abstract] 

L01.00047: ULTRAFAST AND STRONG FIELD PHYSICS' 

L01.00048: Resonant finalstate effects in timeresolved photoemission spectra from Ni(111) surfaces. Marcelo Ambrosio, Uwe Thumm Measured timeresolved interferometric (RABBITT) photoelectron spectra from Ni(111) surfaces recently indicated a finalstateinduced increase in the photoemission time delays at distinct photoelectron kinetic energies [1]. Motivated to examine and understand these finalstate shape resonances, we calculated timeresolved spectra and relative RABBITT phases from the $\Lambda $3$\beta $ and $\Lambda $3$\alpha $ bands of Ni(111) for the XUVpulsetrain and IRpulse parameters of Ref. [1]. Modeling the photoelectron finalstate wavefunction subject to an oscillatory model potential [2] and the IR laser field, we trace the resonantly increased photoemission time delay to an electronprobabilitydensity accumulation inside the substrate which occurs when the local electronic de Broglie wavelength matches the substrate lattice spacing [3]. [1] Tao et al., Science 353, 62 (2016). [2] Chulkov et al., Surf. Sci. 437, 330 (1999). [3] Ambrosio and Thumm, submitted for publication. [Preview Abstract] 

L01.00049: A Jones Calculus Approach to HighOrder Harmonic Generation in Bulk Crystals Erin Crites, Shima GholamMirzaei, Zain Khan, John E. Beetar, Mamta Singh, Michael Chini Highorder harmonic generation was first observed in bulk ZnO crystals in 2011. In transmission geometry, emitted harmonics are susceptible to changes in the driving laser polarization as it propagates through the bulk crystal. To avoid this, highorder harmonics from thin films or in a reflection geometry have been proposed. However, the reflection geometry introduces uncertainty in the measurements due to nonlinear reflection coefficients, and thin films are not available for all materials. Here, we present a new method for analyzing highorder harmonics generated in bulk crystals based on the Jones calculus approach to polarization. We show that nonlinear optical effects for midIR pulses in ZnO crystals do not significantly affect the polarization of the midIR at the crystal exit plane. Instead, the polarization of the midIR is mainly governed by the birefringence of the crystal, allowing us to predict the input polarization required to achieve a desired polarization state at the crystal exit for any orientation of the crystal's optic axis with respect to the driving laser polarization. We apply our analysis technique to highorder harmonics generated from ZnO and BaTiO3 bulk crystals to obtain orientation and ellipticitydependent harmonic spectra. [Preview Abstract] 

L01.00050: Strongfield ionization of oneelectron relativistic diatomic quasimolecules Dmitry A. Telnov, Dmitry A. Krapivin, John Heslar, ShihI Chu We perform a theoretical and computational study of relativistic oneelectron homonuclear diatomic quasimolecules subject to strong electromagnetic fields linearly polarized along the molecular axis. The timedependent Dirac equation is solved with the help of the generalized pseudospectral method in prolate spheroidal coordinates. We have found that the corresponding eigenvalue problem, solved with this method and numerical parameters used in our calculations, does not generate spurious states, at least among lowlying bound states. Relativistic and nondipole effects in ionization probabilities are analyzed for a set of quasimolecules with the nuclear charges 1 to 92 and appropriately scaled internuclear distances and field parameters (with such a scaling, nonrelativistic treatment returns identical results for all the quasimolecules in the set). Because of the relativistic transformation of the electronic structure, resonantly enhanced multiphoton ionization of different quasimolecules is actually observed at different scaled internuclear distances. Nondipole corrections to the ionization probability grow with increasing nuclear charge in the set of scaled quasimolecules. [Preview Abstract] 

L01.00051: Comparison of numerical methods for High Harmonic Generation (HHG) in 1D solids. Marcelo, J. Ambrosio, Francisco Navarrete, Uwe Thumm The recent renewed interest in HHG from solid targets started with the experiment by Ghimire et al. [1]. Based on numerical models for HHG by electronic currents that are induced by a driving laser pulse in the substrate, interband and intraband transitions are currently being discussed for solid HHG [2,3]. As the characterization of HHG spectra in numerical studies requires the repeated solution of the TDSE in a large space of driverpulse, substrate, and model parameters, it is desirable to identify fast and accurate numerical methods. We benchmarked five numerical schemes: second order Magnus expansion (ME), CrankNicolson (CN), RungeKutta of orders 2(3) and 4(5), and Leapfrog and compared their performance with regard to CPUtime and accuracy (wavefunctionnorm preservation and signal/noise level of the calculated HHG spectra). We find that the ME and CN methods produced very similar HHG spectra and the best norm preservation, with the ME approach being the faster of the two. [1] Ghimire et al., Nat. Phys. 7, 138141 (2011); Nat. Phys. 437, 330 (2019). [2] Wu et al., Phys. Rev. A 91, 043839 (2015). Vampa et al., Phys. Rev. B 91, 064302 (2015). TancogneDejean et al., Phys. Rev. Lett. 118, 087403 (2017). Hawkins et al., Phys. Rev. A 91, 013405 (2015). [3] Navarrete et al., in preparation. [Preview Abstract] 

L01.00052: A simple model to describe C$_{\mathrm{60}}$~photoemission measurements by the inclusion of atomic carbon emissions. Maia Magrakvelidze, Himadri Chakraborty We previously used KohnSham timedependent local density approximation (TDLDA) [1] with Leeuwen and Baerends exchangecorrelation functional [2] to calculate the total photoionization cross section of C$_{\mathrm{60}}$ where the core of sixty C$^{\mathrm{4+}}$ ions is smeared in a spherical jellium shell. This implied 240 valence electrons to be entirely delocalized by being oblivious to Coulomb potentials of C atoms. While the result qualitatively showed two plasmon resonances, as observed in experiments [3,4], the absolute value of the cross sections veered far from the measurements. This must be due to the effect of emissions from sixty C centers omitted in the jellium theory. To test, we calculate the photo cross section of a C atom in TDLDA and admix this result, times sixty, with the C$_{\mathrm{60}}$ jellium result by ensuring that the total oscillator strength stays conserved in order to retain participations of the same 240 electrons. Even though the scheme misses the interference between C$_{\mathrm{60}}$ and C emissions, the fit has produced a far improved quantitative agreement with experiments above 15 eV photon energy. [1] Choi et al, PRA 95, 023404 (2017) [2] van Leeuwen et al, PRA 49, 2421 (1994) [3] Hertel et al, PRL 68 784 (1992) [4] Reinkoster et al, JPB 37 2135 (2004) [Preview Abstract] 

L01.00053: Direct Signatures of LightInduced Conical Intersections on the Field Dressed Spectrum of Na$_{\mathrm{2}}$. Gábor József Halász, Tamás Szidarovszky, Attila G. Császár, Lorenz S. Cederbaum, Ágnes Vibók Rovibronic spectra of the fielddressed homonuclear diatomic Na$_{\mathrm{2}}$ molecule are investigated to identify direct signatures of the lightinduced conical intersection (LICI) on the spectrum. The theoretical framework formulated allows the computation of the (1) fielddressed rovibronic states induced by a mediumintensity continuouswave laser light and the (2) transition amplitudes between these fielddressed states with respect to an additional weak probe pulse. The fielddressed spectrum features absorption peaks resembling the fieldfree spectrum as well as stimulated emission peaks corresponding to transitions not visible in the fieldfree case. By investigating the dependence of the field dressed spectra on the dressingfield wavelength, in both full and reduceddimensional simulations, direct signatures of the LICI can be identified. These signatures include (1) the appearance of new peaks and the splitting of peaks for both absorption and stimulated emission and (2) the manifestation of an intensityborrowing effect in the fielddressed spectrum. [Preview Abstract] 

L01.00054: Mapping Electric Fields in Space and Time with SolidState High Harmonic Generation M. Taucer, G. Vampa, T. J. Hammond, X. Ding, X. Ropagnol, T. Ozaki, S. Delprat, M. Chaker, N. Thire, B. Schmidt, F. Legare, D. Klug, A. Naumov, D. Villeneuve, A. Staudte, P. Corkum Evenorder harmonics, which are normally forbidden in centrosymmetric media, can be produced in the presence of a symmetrybreaking electric field. This principle has long been known in the perturbative regime, where electric fields can enable second harmonic generation.We demonstrate the extension of this technique to the nonperturbative regime, showing that highorder harmonics allow us to measure electric fields in solid matter. We illuminate Si and ZnO samples with ultrafast midinfrared pulses, with intensity on the order of $1~\rm{TW}/\rm{cm}^2$. Symmetrybreaking fields are provided by voltage pulses applied to electrodes at the semiconductor surfaces, or, in a second experiment, by a THz transient. The even harmonic emission measures the electric field in time, with subpicosecond temporal resolution. In addition, we can image even harmonics to reveal the spatial distribution of fields. The technique is a flexible alloptical probe of fields, which can combine high spatial and temporal resolution. [Preview Abstract] 

L01.00055: BesselBessel laser bullets: momentum and energy considerations Yousef Salamin Bessel beams carry orbital angular momentum (OAM). Opening up the Hilbert space of OAM to information coding makes Bessel beams potential candidates for utility in data transfer and optical communications. The ultrashort and tightlyfocused analog of a nondiffracting and nondispersing laser Bessel beam is often referred to as a laser bullet. Analytic expressions for the timeaverage densities of energy, linear momentum, energy flux, and angular momentum, associated with the fields of a laser {\it BeseelBessel bullet} in an underdense plasma, are presented here. [Preview Abstract] 

L01.00056: The role of intermediate resonances in population of Rydberg states excited by a strong laser pulse Joel Venzke, Yonas Gebre, Zetong Xue, Agnieszka JaronBecker, Andreas Becker We have studied structures of Rydberg state populations for hydrogen and helium atoms via multiphoton transitions induced by intense laser pulse using numerical solutions of the timedependent Schr\"odinger equation. In the results will consider the dependence on wavelengths from ultraviolet to infrared, which allow us to analyze the role of intermediate states shifted in and out of multiphoton resonances. The impact of the lowlying excited states on the angular momentum distributions in Rydberg states will be discussed. [Preview Abstract] 

L01.00057: Crystal Symmetry and Polarization of Highorder Harmonics in ZnO C. D. Lin, Shicheng Jiang, Shima GholamMirzaei, E. Crites, J. Beetar, T. Lu, M. Chini We carried out a joint theoretical and experimental study on the orientation dependent parallel and perpendicular HHG from the acut of ZnO. It was found that the dependence of parallel and perpendicular polarizations on the crystal orientation for all odd harmonics are nearly identical, but they are quite different from even harmonics which also show little order dependence. Two general features are: 1)parallel even harmonics and perpendicular odd harmonics vanish when the laser polarization is perpendicular to the mirror plane; 2) perpendicular even and odd harmonics vanish when the laser polarization is parallel to the mirror plane. These general behaviors have also observed in other prior experiments. Our theoretical model shows that a 1D twoband model is adequate for describing harmonics from ZnO if the phase of the transition dipole is correctly treated. We conclude that polarization properties of HHG from solids are mostly governed by symmetry properties of the target and not dependent on the excitation mechanisms such as Berry curvature, band curvature or interband excitation. [Preview Abstract] 

L01.00058: Dominance of correlation and relativistic effects on photodetachment time delay well above threshold. Soumyajit Saha, Pranawa Deshmukh, Anatoli Kheifets, Steven Manson Wigner time delay [1] in photodetachment from the 3$p_{\mathrm{3/2}}$ and 3$p_{\mathrm{1/2}}$ subshells of Cl have been studied in the vicinity of the 2$p_{\mathrm{3/2}}$ and 2$p_{\mathrm{1/2}}$ thresholds, using the relativisticrandom phase approximation (RRPA). The results show time delay spectra dominated by manybody correlations along with very complicated dependence on the energy over a broad energy range. In addition, the time delay spectra of the two spinorbit split 3$p $subshells differ significantly from one another, thereby revealing the importance of relativistic effects even in the case of a lowZ system. Work partially supported by SERB (India) and the US DOE. [1] E. P. Wigner, Phys. Rev. \textbf{98}, 145 (1955). [Preview Abstract] 

L01.00059: Recovery Time of Matter Airy Beams Glenn Dusing, Torrey Saxton, Zachary Temple, Allison Harris Airy beams have been studied in an optical context since their discovery in the late 1970s and have found numerous applications in technologies such as microscopy and optical trapping. Many of these applications are based on the wave packets' unique features such as zero or minimal diffraction, selfacceleration, and selfhealing. Recently Airy beams have been produced using electrons and these matter waves exhibit many of the same unique characteristics of their optical counterparts. We use our Path Integral Quantum Trajectory (PIQTr) model to present a study of the recovery time of damaged matter Airy wave packets in free space and a nonlinear Kerrtype medium. We show that in free space the recovery time increases approximately linearly with mass and is independent of other kinematical parameters such as momentum, velocity, and spatial width. In the Kerrtype medium, recovery time is decreased compared to free space and does not scale linearly with mass. [Preview Abstract] 

L01.00060: Angular interferences of sequentially ionized doublecontinuum wave packets Xiao Wang, Francis Robicheaux When two electrons are sequentially ionized from an atom, if the second electron is much faster than the first electron, postcollision interaction (PCI) appears and plays an important role. In this presentation, two specific scenarios are discussed: a belowthreshold photoexcitation followed by an Auger decay, and sequential ionizations of double wave packets. After the postcollision interactions between the two electron, the correlated distributions of final energy and relative angle between the two electrons are studied. Interference patterns are found with respect to the relative angle between the two ionized electrons. Fully quantum calculations based on timedependent Schr\"odinger equations and classical trajectory Monte Carlo methods were used to study properties of these interference patterns. Furthermore, we also studied effects from the laser pulses that used to ionize or excite the electrons, including frequency, frequency chirping, and time width. The discoveries on the interference patterns in twoelectron atoms can be generalized to other systems containing sequentially ionized electrons with different energies. [Preview Abstract] 

L01.00061: Topological effects in highharmonic spectra of graphene Christoph Juerss, Helena Drueeke, Dieter Bauer Among the many interesting properties of graphene are its topological edge states. We investigate differences in the high harmonic spectra due to the influence of these edge states for finite graphene systems coupled to an electric field by using time dependent density functional theory (TDDFT) as well as a tightbinding approach. The influence of the polarization of the field on the spectra is presented as well. Ribbonlike systems are of particular interest, because their gapped bandstructures cause a suppressed harmonic yield for energies below the band gap compared to a plateau at higher energies. A similar feature has recently been observed in spectra of certain topological states of onedimensional chains [1, 2, 3]. [1] Dieter Bauer and Kenneth K. Hansen, \emph{Highharmonic generation in solids with and without topological edge states}, Phys. Rev. Lett. 120, 177401 (2018) [2] Helena Dr{\"u}eke and Dieter Bauer, \emph{Robustness of topologically sensitive harmonic generation in laserdriven linear chains}, arXiv:1901.01437 [3] Christoph J{\"u}r{\ss} and Dieter Bauer, \emph{manuscript in preparation} [Preview Abstract] 

L01.00062: Monitoring photoinduced charge carrier dynamics in Au nanoparticlesensitized TiO2 with timeresolved Xray photoelectron spectroscopy. Mario Borgwardt, Johannes Mahl, Friedrich Roth, Wolfgang Eberhardt, Oliver Gessner The combination of plasmonic metal nanoparticles (NPs) and photocatalytically active semiconductor (SC) materials provides a promising route toward improved solar energy conversion schemes. The currently accepted model for plasmoninduced chargeseparation processes is based on ultrafast surface plasmon damping and dephasing, resulting in the population of hot electrons that are able to undergo transfer to the semiconductor. A considerable number of timeresolved studies in the visible and IR regime have been reported, which are mainly sensitive to the free electron charge densities in the SC acceptor. Very little information, however, is available about timedependent charge and energydistributions from the viewpoint of the plasmonic NPs and about the transient interfacial band structure. Here, we study a model system consisting of a nanoporous TiO2 layer sensitized with gold nanoparticles (Au NPs) using picosecond laser pump  Xray probe photoelectron spectroscopy (trXPS). The elementspecificity of trXPS allows to simultaneously monitor both local charge distributions as well as local band structure dynamics from the individual perspectives of the electron donor (Au NPs) and the electron acceptor (TiO2). [Preview Abstract] 

L01.00063: Characterizing strongfieldinduced molecular dynamics employing timeenergyfrequency analysis of vibrational wave packet motion Yubaraj Malakar, Wright Lee Pearson, Balram Kaderiya, Mohammad Zohrabi, Kanaka Raju Pandiri, Farzaneh Ziaee, Itzik BenItzhak, Daniel Rolles, Artem Rudenko, Shan Xue, AnhThu Le We employ timeresolved 3D momentum imaging combined with channel and energyresolved Fourier spectroscopy to study pathways of strongfield ionization and fragmentation of CH$_{\mathrm{3}}$I, and to map vibrational wave packet dynamics in the intermediate neutral and cationic states. Analyzing the delaydependent signals of bound parent ions as well as CH$_{\mathrm{3}}^{\mathrm{+}}$ and I$^{\mathrm{+n}}$ ($n=$1,2,3) ionic fragments recorded in a pumpprobe measurement with two 25 fs, 780 nm laser pulses, we disentangle different reaction channels based on the measured charge states, kinetic energies and angular distributions. Energyresolved Fourier spectra and the absolute phases of vibrational wave packets extracted from these delaydependent measurements provide specific information about the intermediate states contributing to particular reaction pathways. [Preview Abstract] 

L01.00064: Control of multiphoton transitions without pulse shaping Andras Csehi We propose a scheme to induce total population inversion between two indirectly coupled states of an atom. In contrast to wellknown pulse shaping techniques, where the temporal intensity or phase of the laser field is modulated to maximize the population transfer, here we use a single unshaped Gaussian laser pulse of constant frequency to completely invert the population between the ground state and an excited state of the system, for which a direct transition is forbidden. In our numerical study, multiphoton transitions of atomic sodium are considered in the presence of dynamic Starkshifts (DSS) and a detailed analysis is given about the pulse duration and detuning dependence of the efficient population inversion between the 3s and 4s states. [Preview Abstract] 

L01.00065: Femtosecond snapshots of nano crystalline response to XFEL pulse trains Yoshiaki Kumagai, Gilles Doumy, Anthony DiChiara, Tijana Rajh, Elena Shevchenko, Haidan Wen, Linda Young, Andre Al Haddad, Christoph Bostedt, Andreas Galler, Jan Offermann The European XFEL enables sequential singleshot diffraction snapshots at megahertz repetition rates. These rapidfire pulses have been successfully applied for serial femtosecond crystallography [1,2] where a fast flowing target delivers a new sample between shots. However, the use of highrepetitionrate pulses for an individual fixedinplace target depends critically on understanding the response of the target damage to which limits the usable fluence per image. We have investigated the response of a CdSe nanocrystalline target using a novel pulseondemand method where sequential singleshot diffraction images were acquired for a variable number of xray pulses over a wide range of fluence. Unusual features appear in the diffraction pattern and morphology that can be used to model the target response. [1] M. L. GrŸnbein\textit{ et al}., Nat. Commun.\textbf{ 9}, 3487 (2018 [2] M. O. Wiedhorn\textit{ et al}., Nat. Commun. 9, 4025 (2018) [Preview Abstract] 

L01.00066: Measuring subfemtosecond xray pulses with angular streaking Siqi Li, P. Bucksbaum, E. Champenois, J. Cryan, T. Driver, J. Duris, R. Coffee, A. Gatton, Z. Huang, J. Knurr, M.F. Lin, J. MacArthur, T. Maxwell, M. Nantel, A. Natan, J. O'Neal, N. Shivaram, P. Walter, T. Wolf, A. Marinelli, M. Kling, P. Rosenberger, G. Hartmann, W. Helml The recent development of subfemtosecond xray pulses from freeelectron lasers has called for a high resolution measurement scheme to characterize such short pulses and the electronic dynamics they induce. The angular streaking technique exploits the phasedependent momentum shift experienced by the photoelectrons ionized by xray pulses in the presence of a circularly polarized streaking laser field. We present a method to extract the temporal and spectral profiles of an electronic wavepacket produced by xray ionization from the photoelectron momentum distribution. We use this method to demonstrate the attosecond operation of a soft xray FEL, and study attosecond electron dynamics in xray photoionization. [Preview Abstract] 

L01.00067: Frequencyresolved~xray~scattering Noor AlSayyad, Matthew Ware, James Glownia, Jordan O'Neal, Philip Bucksbaum In a series of experiments at the LINAC Coherent Light Source (LCLS), the timeresolved xray scattering (TRXS) from molecular iodine was measured after excitation by an 800 nm, 520 nm, and a combination of 800 and 520 nm laser pulses. The measured TRXS is used to generate a frequency scattering spectrum by taking a temporal Fourier transform along the laserpumpxrayprobe delay axis. This is known as frequencyresolved xray scattering (FRXS). Using FRXS, vibrational and dissociative motion are separated in the spectrum allowing for the easy characterization of motion. An overview of FRXS measurements will be presented. For dissociations, velocities and initial positions are measured, and for vibrations, the equilibrium position, amplitude of motion, and beat frequency are measured. [Preview Abstract] 

L01.00068: Native frames: Separating sequential from concerted threebody fragmentation T. Severt, B. Jochim, P. Feizollah, Kanaka Raju P., J. Rajput, B. Berry, B. Kaderiya, F. Ziaee, D. Rolles, A. Rudenko, K. D. Carnes, B. D. Esry, I. BenItzhak, R. Strom, A. L. Landers, D. Reedy, B. Griffin, D. Call, J. B. Williams, W. Iskander, K. A. Larsen, A. Gatton, E. G. Champenois, M. M. Brister, D. S. Slaughter, T. Weber During the fragmentation of polyatomic molecules, two or more bonds may break in a sequential manner. To interpret the multibody breakup, it is beneficial to separate the concerted from the sequential fragmentation contributions. Recently, we proposed the native frames method to accomplish this goal, using the strongfield threebody fragmentation of OCS as an example [PRL \textbf{120}, 103001 (2018)]. This method allows us to separate the contributions of sequential breakup in any observable derived from the measured threedimensional momentum distributions by exploiting the rotation of the intermediate moiety. In this poster, we will highlight results from a few polyatomic molecules using strongfield ionization as well as singlephoton double ionization. [Preview Abstract] 

L01.00069: QUANTUM INFORMATION AND QUANTUM OPTICS 

L01.00070: UltraHigh Fidelity Operation of the $^{133}$Ba$^+$ qubit Justin Christensen, David Hucul, Eric R. Hudson, Wesley Campbell Trapped ions are attractive qubit hosts due to their long coherence times and straightforward manipulation via electromagnetic fields. Future faulttolerant quantum computers will not only require ultrahigh fidelity gate operations, which has been the focus of recent efforts, but also ultrahigh fidelity state preparation and measurement (SPAM), which is currently orders of magnitude lower. We present recent work with the synthetic trappedion qubit $^{133}$Ba$^+$, a radioactive isotope of barium with a 10.5yr halflife. The spin1/2 nucleus, visible wavelength electronic transitions, and longlived $^2$D$_{5/2}$ state make this trappedion qubit ideal for ultrahigh fidelity work. We demonstrate fast, ultrahigh fidelity operation of $^{133}$Ba$^+$ resulting in an average SPAM fidelity of 0.9997, the highest reported of any qubit of any architecture. Future directions as well as straightforward ways to increase this SPAM fidelity beyond fault tolerance thresholds will also be discussed. [Preview Abstract] 

L01.00071: Multimode Quantum Nonlinear Optics in Rydberg Atomic Ensembles Fan Yang, YongChun Liu, Li You Optical nonlinearity at the singlephoton level can facilitate photonic quantum information processing. Recent studies in Rydberg atomic ensembles indicate that strong and longrange photonic interactions can be created by mapping photons to Rydberg polaritons. This work develops a framework for interacting photonic polaritons in the multimode regime. The presence of nonlocal photonphoton interactions is found to destroy the energy or momentum matching conditions between distinct propagating polaritons, and consequently gives rise to blockaded coupling between them. Such a blockade mechanism protects the system from interactioninduced dissipation and enables highly tunable fewphoton nonlinearities, which consequently facilitates the construction of singlephoton quantum switch, deterministic generation of entangled photon pairs, as well as spinexchange collisions between singlephotons. [Preview Abstract] 

L01.00072: Natural Limits on Refractive Index in MultiLevel Systems Robert McCutcheon, Susanne Yelin We consider the refractive indices and electric susceptibilities of two, three, and fourlevel systems. There has been growing interest in finding materials with a high index of refraction, but there are natural limitations on the index that can be attained by controlling basic multilevel systems with external fields. We explain how the ensemble density in a medium is an important practical limitation and use this to calculate a baseline value for the refractive index of a twolevel system. We show how the additional transitions and fields in three and fourlevel systems give greater control over the refractive index and consider other properties that can, in principle, affect it in linear regimes. An example calculation for a fourlevel system shows how the frequency of one external field can affect the refractive index experienced by a probe field, and the limits of this method are discussed. These considerations could be useful in proposals for achieving an enhanced refractive index using multilevel systems. [Preview Abstract] 

L01.00073: Robust information storage in warm alkali vapor using slow twisted light: an experiment for the advanced undergraduate laboratory Kefeng Jiang, Ken DeRose, Linzhao Zhuo, Jet Sethi, Thomas Li, Samir Bali We endeavor to create an undergraduatefriendly experimental demonstration of slowed and stored twisted light in warm alkali vapor. First, we create slow Gaussian pulses of light propagating at 350 m/s through warm Rubidium gas, and elucidate experimentally the role played by the narrow spectral window of a few kHz due to electromagnetically induced transparency (EIT). The importance of pump intensity optimization is emphasized. Further, by measuring the EIT linewidth as a function of relative pumpprobe angle we obtain direct experimental proof of Dickenarrowing in warm alkali vapor. An application of slow light to the field of quantum information is that now the experimenter supposedly has more time to encode/decode information. However, this also means the stored information has more time available to dissipate away. We describe our experimental progress toward propagating a slow twisted light pulse through warm Rb vapor, showing that the topological stability of the pulse allows for robust storage of information. [Preview Abstract] 

L01.00074: Universal Photonic Quantum Interface for a Quantum Network Jian Wang, YuHao Pan, BiHeng Liu, YunFeng Huang, ChuanFeng Li, GuangCan Guo Active research on mesoscopic quantum systems has increased our understanding of and ability to control quantum objects, allowing the construction of a universal form for quantum networks that consist of more than one physical system. This kind of quantum network is anticipated to enable the building of quantum infrastructure, such as longdistance quantum communication and distributed quantum computers, and motivates the establishment of photonic quantum interfaces that are compatible with physical systems. Here, a universal photonic quantum interface is experimentally developed with the benefit of a unique, specially designed entangled photon source. The detailed experimental results show that this configuration can satisfy all the urgent demands for a photonic quantum interface, including the accurate matching of the working wavelength and bandwidth and specifically, the entanglement ability (F$=$89.6{\%}~S$=$2.36±0.03). The realization of this universal photonic quantum interface is expected to expedite the construction of much more complex quantum networks and to be a major step in the area of optical engineering and control [Preview Abstract] 

L01.00075: Dispersion Enhanced Laser Frequency Sensitivity and Stability via Fourwave Mixing Savannah Cuozzo, Eugeniy Mikhailov We report on tuning the response of the laser wavelength via assistance of the intracavity highly dispersive medium in the fourwave mixing regime in Rb. By varying experimental parameters such as pump laser frequency, atomic density, and pump power, we can either increase the sensitivity of the lasing frequency to the cavity length change by at least a factor of $10^8$, compared to traditional lasers, or completely suppress such sensitivity. The former regime is useful for sensitive displacement tracking, temperature sensing and optical gyroscopes. The latter regime is useful for precision metrology where high stability frequency references are required. [Preview Abstract] 

L01.00076: Optically pumped Rb atoms in warm cell for photon frequency conversion Micha{\l} J. Piotrowicz, John F. Reintjes, Adam T. Black, Alex Kuzmich, Mark Bashkansky We have investigated optical pumping of Rb87 atoms to $F = 2$, $m_F = 2$ state in warm vapor cell. We present the influence of buffer gas and temperature of the cell on the pumping efficiency and preservation of the state. The optically pumped atoms are used to convert 795 nm photons to telecom wavelength in a four wave mixing process. Population transfer of atoms to one $m_F$ state increases the optical depth of the sample for conversion process as well as reduces the noise photons. [Preview Abstract] 

L01.00077: A high power solidstate laser system for lithium atom experiments Francisco Fonta, Andrew Marcum, Arif Mawardi Ismail, Kenneth O'Hara Frequency doubled 1342 nm solidstate ring lasers are a promising alternative to external cavity diode lasers and tapered amplifiers for producing light around the lithium D line resonances. They are capable of achieving the significantly higher power necessary for many cuttingedge experiments. To this end we present an 888 nm pumped Nd:GdVO4 ring laser with a 1.8 nm tuning range centered around 1341.2 nm. We then frequency double this laser to achieve high power light near 671 nm. Furthermore, we provide a high resolution measurement of the gain spectrum of Nd:GdVO4 around 1342 nm and characterize the thermal lensing due to the highpower pump laser in our system. [Preview Abstract] 

L01.00078: A shared ion trap quantum computer for the general research community Richard Rademacher, Matthew Day, Noah Greenberg, Rajibul Islam, Crystal Senko Some major barriers in the use of ion traps for quantum computation and simulation are the expense of the apparatus, and the technical knowledge necessary to convert circuitlevel descriptions of quantum algorithms into the laser timing pulses and associated controls. We present the design for a multiuser, 10qubit quantum computer that brings useability closer to the general research community. A new, custom control system provides users with remote control capability at various levels of abstraction: timing, gate, and circuit. Provisions for control of all hardware is provided along with builtin calibration, safety interlocks, advanced timing control and arbitrary pulse generation. A major innovation is a new individual laser addressing scheme for ion gates. This addressing scheme will use modular fibrecoupled components to split, modulate, and array the Raman addressing beams in order to reduce crosstalk between ion sites. The combination of multiuser control on a modern ion trap platform brings performance, and useability to both the experimentalist and theorist. [Preview Abstract] 

L01.00079: Rydbergdressed interactions for quantum metrology Victoria Borish, Ognjen Markovic, Jacob Hines, Monika SchleierSmith Rydberg dressing provides a versatile way to create strong coherent interactions between groundstate 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 optical lattice. We present progress in Rydberg dressing on the clock transition of cesium via singlephoton excitation to nP states. This will allow us to explore optimal routes to generating longrange entanglement with local interactions, including comparing quantumcritical vs. dynamical approaches. [Preview Abstract] 

L01.00080: NearUnitary Spin Squeezing in $^{171}$Yb in an optical cavity Edwin Eduardo Pedrozo Penafiel, Simone Colombo, Boris Braverman, Akio Kawasaki, Chi Shu, Zeyang Li, Enrique Mendez, Megan Yamoah, Leonardo Salvi, Daisuke Akamatsu, Yanhong Xiao, Vladan Vuletic In this work, we experimentally demonstrate the generation of a nearunitary SSS in an ensemble of $^{171}$Yb atoms created by a oneaxis twisting interaction using cavity feedback squeezing [1]. The nearunitary spin squeezing is engineered between the magnetic sublevels of the ground state of $^{171}$Yb using light detuned from the system's resonances [2]. The observed spin noise suppression and metrological gain are limited by the state readout to 9.4(4)~dB and 6.5(4)~dB, respectively, while the generated states offer a spin noise suppression of 15.9(6)~dB and a metrological gain of 12.9(6)~dB over the SQL. When limiting the squeezing to 30\% of unitarity, we demonstrate an interferometer that improves the averaging time over the SQL by a factor of 3.7(2). This squeezing can be mapped in the future onto an optical transition to improve the performance of an $^{171}$Yb stateoftheart clock. [1] M. H. SchleierSmith et al. Phys. Rev. A 81, 021804(R) (2010). [2] Y.L. Zhang et al. Phys. Rev. A 91, 033625 (2015). [Preview Abstract] 

L01.00081: Lambdatype electromagnetically Induced transparency of a thermal Rb85 vapor in a magnetic field Lu Ma, Georg Raithel We measure electromagnetically induced transparency (EIT) on ground hyperfine levels of thermal Rb85 atoms in a buffergasfree spectroscopy cell using two 780nm phaselocked pump and probe lasers. A small magnetic field is applied to split the magnetic sublevels of the ground and excited states. The EIT windows are formed due to coherent superpositions of Zeemanshifted groundstate hyperfine levels coupled to a common intermediate 5$P_{3/2}$ Zeeman level. The EIT signals are observed and mapped out against a background signal affected by opticalpumping for different magnetic field strengths. The linewidth dependence on the probe and pump laser powers is also studied. The density operator and the absorption of the sample are modeled with a MonteCarlo approach that includes all Zeeman sublevels and opticalpumping effects. The simulation results match the measured data very well. A brief description of the electronics and the optical setup are also included in the poster. [Preview Abstract] 

L01.00082: Matterwave soliton based rotation sensing Yogesh Patil, Hil Fung Harry Cheung, Sunil Bhave, Mukund Vengalattore Atom interferometers can in principle achieve rotation sensitivities much better than the best current optical gyroscopes. ~However, the practical realization of compact, trappedatom rotation sensors have been limited by significant technical and fundamental constraints. ~We propose and evaluate an integrated platform for Sagnac interferometry using matterwave solitons generated and confined in a quasi1dimensional evanescent wave optical dipole trap around a microtoroidal resonator. ~Numerical simulations based on the truncated Wigner approximation (TWA) show that the nondispersive nature of solitons allows us to substantially increase the effective area enclosed by the Sagnac interferometer arms  enabling a projected shotnoise limited phase sensitivity of 10 mrad/$\surd $Hz and a rotation sensitivity below 8 x 10$^{\mathrm{7}}$ rad/s/$\surd $Hz. We also discuss prospects of using the intrinsic interactions within the soliton as a means of obtaining spinsqueezing and enhanced interferometric contrast. [Preview Abstract] 

L01.00083: A Nanoscale Interface between Atoms and Photons Polnop Samutpraphoot, Tamara Dordevic, Paloma Ocola, Hannes Bernien, Alexander Zibrov, Vladan Vuletic, Mikhail Lukin The realization of strong atomphoton interactions is a central theme in quantum optics and an essential prerequisite for future quantum applications. We achieve such interactions using a hybrid system of neutral atoms and optical photons coupled via a nanoscale photonic crystal waveguide cavity. Here, we demonstrate strong coupling between the cavity and two individual atoms trapped in optical tweezers. Our experimental effort aims at creating entangled states between two atoms using interactions mediated by cavity photonsa cornerstone for building scalable quantum gates. [Preview Abstract] 

L01.00084: Progress towards quantum memory in telecommunication band Haoquan Fan, Donny R. Pearson, Elizabeth A. Goldschmidt The ondemand transfer of quantum states between photons and matter, i.e., quantum memory, is critical for future quantum communications. Quantum memory is a key element for quantum repeaters, which are required to transmit quantum information over long distances. Rareearth ions (REI) in crystals offer excellent properties for quantum memories, such as long coherence time, highdensity, and the potential for integration into photonic devices. Erbium (Er), in particular, allows quantum memory in the telecommunications band, providing a pathway toward practical realization of quantum repeaters suited for modern optical communication standards. In addition, Er has a near infrared transition that should allow quantum memory with built in frequency conversion from the near infrared to the telecommunications band. Such frequency conversion is useful for interfacing between different quantum systems. A major challenge in working with Er is the difficulty in optical pumping, although some progress has been made recently optically pumping on the telecommunications transition at low temperature and high magnetic field. We report progress investigating optical pumping on the near infrared transition in Er:YVO. [Preview Abstract] 

L01.00085: Entanglement swapping of polarization entangled photon pairs from Dopplerbroadened atomic ensemble. Jiho Park, Heonoh Kim, Han seb Moon We experimentally observed entanglement swapping of two independent polarization entangled photon pairs generated by spontaneous fourwave mixing(SFWM) in Dopplerbroadened $^{\mathrm{87}}$Rb atomic ensemble. Polarization entangled photon pairs are generated in sagnac interferometer configuration which enable us to produce four Bell states in stable condition and performed Bellstate analysis with a fidelity of 93{\%}. We also demonstrated entanglement swapping by utilizing the polarization entangle photon pairs with polarization projective measurement. The results shown here would be an important contribution to an atomphoton interface in the field of quantum optics. [Preview Abstract] 

L01.00086: Atomic quantum memory in two limits: the AutlerTownes splitting protocol vs. the electromagnetically induced transparency protocol Lindsay LeBlanc, Anindya Rastogi, Erhan Saglamyurek, Taras Hrushevskyi, Scott Hubele AutlerTownes splitting (ATS) and electromagnetically induced transparency (EIT) are related but distinct quantum optical phenomena: EIT is described by quantum interference between transition pathways, while ATS is a manifestation of the ac Stark shift. Likewise, the mechanisms underlying lightstorage techniques based on EIT and ATS manifest opposite limits of the lightmatter interaction due to their inherent adiabatic vs.\ nonadiabatic nature. Numerical simulations show that the EIT protocol, which relies on signal delay via slow light and must be optimized by shaping the control pulses, operates best in the adiabatic regime and is wellsuited to narrowband signal storage. In contrast, we show that the ATS memory, which relies on re\"emission for signal delay and can be optimized via pulsearea control, is efficient even in the nonadiabatic regime and is best suited for broadband signals. We determine optimal conditions for each protocol and analyze ambiguous regimes in the case of broadband storage, where nonoptimal memory implementations can possess characteristics of both EIT and ATS protocols. These fundamental differences are demonstrated in a proofofconcept rubidium coldatoms experiment. We also report on other recent experiments using ATS quantum memory. [Preview Abstract] 

L01.00087: Locally addressable atomic manybody quantum system coupled to a high finesse optical resonator Justin Gerber, Emma Dowd, Johannes Zeiher, Dan StamperKurn The study of manybody quantum systems via weak measurement and at the single atom level will provide a deeper understanding of these systems and provide a basis for novel control techniques. Here we report on the construction of an experimental apparatus in which an atomic manybody system will be strongly coupled to an optical cavity and with which we will be able to locally address the individual components of the manybody system for read out and control. The interaction of atoms with the photonic modes of a high finesse optical cavity allows for the ability to engineer interactions between the atoms as well as the ability to sensitively measure their quantum state. Local addressability will be facilitated by optical potentials imaged onto the atoms through a highresolution objective transverse to the cavity axis. This apparatus will provide the capability to locally engineer manybody Hamiltonians for quantum simulation, to introduce tunable dissipation into the quantum system and to strongly and weakly measure manybody correlation functions. Weak continuous measurement combined with local dynamical control of the Hamiltonian opens the door to manybody quantum feedback and novel control schemes. [Preview Abstract] 

L01.00088: Numerical Simulations of the Fast Adiabatic Transport of an Ultracold Quantum System Junjiang Li, E. Carlo Samson We study numerically the spatial transport of the ultracold atoms at very short time intervals without loss of fidelity. In many quantum technologies, one often needs to transport a quantum system through space rapidly while preserving fidelity. Among the many protocols designed to address this, shortcuts to adiabaticity (STA) is of special interest as it is incredibly robust against different kinds of quantum systems. However, its implementation requires an auxiliary potential be provided over a large region of space, which can be difficult to satisfy experimentally. One of the specific goals is to determine the relationship between the minimum transfer time and the minimum range of the auxiliary potential. To that end, we studied the behavior of BoseEinstein condensates being transported by the STA protocol by numerically solving the GrossPitaevskii equation. Specifically, we are investigating the correlation between transport times and the necessary spatial extent of the auxiliary potential for a coherent transport. Preliminary results show an inverse correlation, which implies a limit on how fast a system can be transported when this protocol is implemented in experiments. We evaluate the performance of this fast transport protocol using experimentally feasible parameters. [Preview Abstract] 

L01.00089: Symmetry and bandwidth constrained deep reinforcement machine learning for quantum control of atomic and superconducting systems Philip Johnson, Anthony Santana, Dennis Lucarelli Machine learning techniques are becoming an important tool in quantum information science, particularly for quantum control and quantum state and process tomography. There is a tension, however, between taking advantage of the highly optimized performance offered by the use of machine learning techniques, and the desire to gain insights into basic physical principles useful for guiding future experimental and theoretical investigations. We will describe our recent work applying deep reinforcement learning techniques, including modified versions of Qlearning, to the optimal quantum control of ultracold atomic and superconducting systems in the presence of leakage dynamics. We use a basis of bandlimited functions to constrain the learning to physically realistic control fields, and investigate the impact of exploiting additional dynamical symmetries to reduce simulation size and complexity, with the goal of trading away a modest degree of optimization for more efficient algorithm performance and greater insight into system dynamics. [Preview Abstract] 

L01.00090: Scattering from the dark and adversarial modes: new selforganisation phases Davide Dreon, Andrea Morales, Philip Zupancic, Xiangliang Li, Alexander Baumgärtner, Tilman Esslinger, Tobias Donner A BoseEinstein Condensate (BEC) inside an optical resonator can undergo a phase transition to a selforganised state when illuminated with a reddetuned pump beam. In our recent experiment, we study the interaction of the BEC with two nondegenerate polarisation modes of a cavity. I will show how the couplings to the two modes, which are independently tuned via the scalar and the vectorial part of the atomic polarisability, give rise to competing selforganisation phases In a second experiment, we explore the blue side of the atomic resonance. We observe that selforganisation is still possible despite the atoms being expelled from the light fields, suppressing photon scattering. Moreover, the repulsive lattices induce nontrivial modifications of the band structure and the dispersive shift triggers dynamics of the order parameter, both effects leading to richer phase diagrams. [Preview Abstract] 

L01.00091: Strong atomlight interaction with trapped atoms on a microring resonator TzuHan Chang, Brian Fields, May Kim, ChengAn Chen, ChenLung Hung We describe the design and fabrication of an efficient, scalable atomlight photonic interface based on silicon nitride microring resonator on a transparent silicon oxidenitride multilayer membrane. This novel photonic platform is fully compatible with freespace cold atom laser cooling and stable trapping at around 100 nm from the microring surface using optical tweezers or a twocolor evanescent wave optical trap running at magic wavelengths. We demonstrate small radius (R $ \sim 15 \mu$m) microrings with high quality factor Q $=$ 338,000, projecting a single atom cooperativity parameter of C $>$ 25 and a vacuum Rabi frequency of $g/2\pi$ = 174 MHz. We demonstrate that single atoms can be directly loaded near the surface of a microring structure using optical tweezers and can be fluorescence imaged with high fidelity. We discuss our ongoing experiment effort for coupling single atoms to a microring and further fabrication improvements for quality factor Q $>$ 1 million for creating strong atomphoton coupling. [Preview Abstract] 

L01.00092: Laser frequency noise spectrum and linewidth using a fiber interferometer James D White, Lincoln D Turner, Andrew J McCulloch, Robert E Scholten Laser frequency noise is converted to an electrical noise spectrum using an unbalanced MachZehnder fiber interferometer with short pathlength imbalance and an audio spectrum analyzer. Linewidths are calculated from integration of the frequency noise spectra are consistent with threecornerhat heterodyne beatnote measurements. The method provides frequency noise measurements like those obtained with a highfinesse cavity but using common lab components, with the additional benefits of requiring neither multiple lasers nor many kilometers of singlemode optical fiber. [Preview Abstract] 

L01.00093: A highpower, narrow, blue continuouswave laser by intracavity frequency doubling of a tapered amplifier laser Lin Su, Mark Stone, Aziza Suleymanzade, David Schuster, Jonathan Simon Highpower, narrow lasers at visible and UV wavelengths are essential for manipulating highlyexcited atoms. We present progress toward a homebuilt laser at 481nm to drive the transition between the first excited state and Rydberg states of rubidium atoms. A selfseeded tapered amplifier laser first generates more than 2 Watts of light at 962 nm. Optical feedback is provided by a reflective volume Bragg grating with a narrow 23 GHz bandwidth, suppressing mode hopping. Then, a resonant buildup cavity housing a nonlinear MgOdoped PPSLT crystal is expected to frequency double with a design based on Koustubh Danekar, Ali Khademian, and David Shiner, "Blue laser via IR resonant doubling with 71{\%} fiber to fiber efficiency," Opt. Lett. 36, 29402942 (2011). We hope to achieve blue power of nearly 2 Watts with a linewidth down to 10 kHz. All our techniques are highlytransferable to making lowcost lasers at other visible and UV frequencies. [Preview Abstract] 

L01.00094: Spectral shaping of the biphoton state from multiplexed thermal atomic ensembles T. H. Chang, G. D. Lin, H. H. Jen We theoretically investigate the spectral property of a biphoton state from multiplexed thermal atomic ensembles. This biphoton state originates from the cascade emissions, which are generated by two weak pump fields under the fourwave mixing condition. The cascade configuration composes of lower and upper transitions, where for rubidium atoms they can be $\ket{5S_\frac{1}{2}}$, $\ket{5S_\frac{3}{2}}$, and $\ket{6S_\frac{1}{2}}$, respectively. We obtain the spectral property under different superradiant decay rates of the lower transition ($\ket{5S_\frac{1}{2}}$ to $\ket{5S_\frac{3}{2}}$), excitation pulse durations, and temperature of the medium. By multiplexing multiple thermal atomic ensembles with frequencyshifted cascade emissions, we are able to shape the spectral function of the biphoton state. The entropy of entanglement, which can be quantified by Schmidt decomposition, increases with more multiplexed ensembles involved. We also investigate the lowest entropy of entanglement allowed in the multiplexing scheme, which is preferential for generating a pure single photon source. The multimode structures created by multiplexing atomic ensembles are useful in longdistance quantum communication and multimode quantum information processing. [Preview Abstract] 

L01.00095: Experimentally Robust Selftesting for Bipartite and Tripartite Entangled States WenHao Zhang, Geng Chen, ChuanFeng Li, GuangCan Guo Selftesting is a method with which a classical user can certify the state and measurements of quantum systems in a deviceindependent way. In particular, selftesting of entangled states is of great importance in quantum information processing. An understandable example is that the maximal violation of the ClauserHorneShimonyHolt inequality necessarily implies that the bipartite system shares a singlet. One essential question in selftesting is that, when one observes a nonmaximum violation, how far is the tested state from the target state (which maximally violates a certain Bell inequality)? The answer to this question describes the robustness of the used selftesting criterion, which is highly important in a practical sense. Recently, J. Kaniewski derived two analytic selftesting bounds for bipartite and tripartite systems. In this Letter, we experimentally investigate these two bounds with highquality twoqubit and threequbit entanglement sources. The results show that these bounds are valid for various entangled states that we prepared. Thereby, a proofofconcept demonstration of robust selftesting is achieved, which improves on the previous results significantly. [Preview Abstract] 

L01.00096: Observing outofequilibrium quantum dynamics with a dipolar interacting spin ensemble in diamond Chong Zu, Francisco Machado, Bryce Kobrin, Thomas Mittiga, Satcher Hsieh, Prabudhya Bhattacharyya, Tim Hoehn, Soonwon Choi, Norman Yao We introduce a novel platform, based upon P1 centers (substitutional nitrogen defects) in diamond, to simulate nonequilibrium quantum spin dynamics. In particular, we show the ability to directly control the disorder strength, the interaction Hamiltonian and the effective P1 density using a combination of static and driven fields. By preparing a low entropy initial state, we probe the nanoscale spin diffusion of P1 centers, ultimately observing the emergence of hydrodynamics. Finally, by implementing dynamical decoupling sequences in a diamond nanopillar, we demonstrate the modification of interactions between P1 centers, providing evidence for the coherent nature of the spin dynamics. [Preview Abstract] 

L01.00097: SSource Construction of Manybody States Christopher Olund, Maxwell Block, Snir Gazit, John McGreevy, Norman Yao Ssource is a method to construct a thermodynamic manybody wave function by iteratively building the ground state of a size 2L system from the ground state of the same system at size L. This is achieved by repeatedly optimizing a local unitary quantum circuit. We consider perturbative expansions of manybody wave functions with large gaps and derive the scaling of the error in the optimal ssource construction of the state. By doing this, we demonstrate that one can in principle parametrically reduce the errors by allowing our circuit to contain unitaries acting at longer distances, in agreement with the prediction that states can be perfectly constructed using quasilocal unitaries. We also present some further numerical benchmarking of the algorithm, and consider whether we can improve errors by rescaling the Hamiltonian parameters as a function of system size, following the intuition from renormalization group flow. [Preview Abstract] 

L01.00098: Single photon Chern insulator in superconducting microwave lattices Clai Owens, Brendan Saxberg, Ruichao Ma, David Schuster, Jonathan Simon We present our latest progress towards developing a new architecture for quantum simulation of 2D materials with Hamiltonians that include both magnetic fields and particle interactions. We construct lattices for microwave photons from tunnel coupled microwave cavities that are both low loss and compatible with Josephson junction mediated particle interactions. We introduce a synthetic gauge field for the photons by coupling the cavities to tuned ferrite spheres made of yttrium iron garnet (YIG). We employ seamless 3D microwave cavities all machined from a single block of niobium so our metamaterial is scalable and directly compatible with the cQED toolbox. After observing topologically protected chiral edge states with microsecond lifetimes circling the superconducting lattice, we now push to couple qubits to lattice sites in order to both add onsite interactions and single photon sources. [Preview Abstract] 

L01.00099: Programmable nonlocal interactions in an ensemble of spin1 atoms Avikar Periwal, Emily Davis, Gregory Bentsen, Eric Cooper, Monika SchleierSmith Cavity QED experiments provide an ideal framework for understanding quantum systems with longrange interactions. We report on experiments featuring longrange spinspin interactions between atoms in an optical cavity, driven by a control field that provides flexibility for tuning the strength, sign (ferromagnetic or antiferromagnetic), and spatial structure of interactions., Our experimental setup, which combines nonlocal interactions with local imaging and addressing, was recently used to image nonlocal spin exchange in a system with alltoall interactions [PRL 122, 010405 (2019)]. Extensions of our scheme allow for realizing XXZ models of tunable anisotropy (including isotropic Heisenberg or Ising interactions), and for pruning the interaction graph to form more exotic models. Studying the time evolution of these models experimentally promises insight on quantum dynamics that cannot be easily analytically or numerically obtained. [Preview Abstract] 

L01.00100: Fair sampling of weighted ground state configurations in quantum annealing Bhuvanesh Sundar, David Damanik, Leonardo DuenasOsorio, Kaden Hazzard Several problems in science and engineering, such as finding ground states of frustrated spin systems or an engineering network’s reliability, require finding all the solutions of an optimization problem. Recently, quantum annealing, which solves the optimization problem by finding the ground states of a classical Hamiltonian, has become a popular tool. However, the commonly used form of quantum annealing often exponentially (in the number of bits) or completely suppresses some ground states, thereby rendering it an unreliable method to find all the desired solutions. We propose a driver Hamiltonian for quantum annealing that results in a final wavefunction which is an equal superposition of all the ground states of the final Hamiltonian, with these ground states encoding the solutions of the optimization problem. We extend our proposal even to cases where the ground states need to be weighted unequally, a requirement in several engineering problems. We show that implementing a single annealing experiment with our driver Hamiltonian is only polynomial slower than implementing common driver Hamiltonians. Finally, we construct quantum circuits to implement the annealing on a quantum computer. [Preview Abstract] 

L01.00101: Singleelectron qubits in a planar Penning trap Sam Fayer, Melissa Wessels, Gerald Gabrielse Planar Penning traps could provide a scalable architecture for one electron qubits. A prototype trap was designed with the optimal geometry, fabricated with minimal imperfections, and tested to characterize its properties. A number of narrow axial resonances from loaded electrons have been measured, showing this planar trap to be sufficiently harmonic to detect electron clouds of small sizes, down to those consistent with a single electron. These would offer the possibility of building an array of coupled singleelectron qubits for quantum information studies. [Preview Abstract] 

L01.00102: Adiabaticity in state preparation for spin squeezing of $10^{11}$ Atoms Shenchao Jin, Han Bao, Junlei Duan, Xingda Lu, Heng Shen, Yanhong Xiao Spin squeezed state (SSS) is a manybody entangled state of great interest to precision measurements and quantum information science. Here we report the realization of quantumnondemolitionmeasurement based spin squeezing of $10^{11}$ atoms in a $^{87}Rb$ vapor cell in free space. The greatest challenge to obtain quantum squeezing in our experiment is to overcome classical noises whose power can dominate over atom projection noise power by a factor equal to the number of atoms. In order to solve this problem, we have developed the technique of adiabatic pulse control to prepare a coherent spin state that is strictly along the magnetic field and orthogonal to the probe field’s wave vector. This has removed the adverse effects of unwanted classical spin component in the quantum noise detection, and thus forms a key element in the success of squeezing an ensemble with both large particle number and large volume. We present experiment results and a theoretical model to demonstrate the efficacy of the adiabatic pulse control. [Preview Abstract] 

L01.00103: Characterizing Errors in EntangledAtom Interferometry Brandon Ruzic, Constantin Brif, Grant Biedermann Recent progress in generating entanglement between neutral atoms provides opportunities to advance quantum sensing technology. In particular, entanglement can enhance the performance of accelerometers and gravimeters based on lightpulse atom interferometry. We study the effects of error sources that may limit the sensitivity of such devices, including errors in the preparation of the initial entangled state, spread of the initial atomic wave packet, and imperfections in the laser pulses. Based on the performed analysis, entanglementenhanced atom interferometry appears to be feasible with existing experimental capabilities. This work is supported by the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology {\&} Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DENA0003525. [Preview Abstract] 

L01.00104: Phase Sensitive Optomechanical Amplifier for Quantum Noise Evasion in Interferometric Sensors Aaron Markowitz, Gautam Venugopalan, Kevin Kuns, Yuntao Bai, Chris Wipf, Yanbei Chen, Rana Adhikari When making quantumlimited optomechanical measurements, one can improve sensitivity beyond the standard quantum limit by taking advantage of correlations in the observables of the ‘squeezed’ sensing light field. However, optical losses mix unsqueezed vacuum field into the squeezed sensing field, thus increasing quantum noise in the observable containing the signal. We present a phasesensitive ponderomotive preamplifier consisting of a pumped traveling wave cavity, balanced in a MachZehnder interferometer to reduce sources of technical noise. Squeezed, signaldominated input fields are amplified far above the vacuum level, so downstream losses do not significantly degrade the measurement signaltonoise. We analyze the utility of this amplifier for a LIGOtype interferometer, and this class of device is applicable to many interferometric sensors. [Preview Abstract] 

L01.00105: Multiphoton Floquet exceptional points Hossein Jooya, Adi Pick, Nimrod Moiseyev, Hossein R. Sadeghpour Exceptional points (EPs) are special modal degeneracies in nonHermitian systems, which have recently drawn a lot of interest due to their counterintuitive optical properties. In this work, we explore the effects of EPs on multiphoton absorption in microwavedriven superconducting transmon qubits. Multiphoton transitions are modeled using a nonperturbative FluoquetLiouville supermatrix approach, which takes into account radiative damping via the density matrix formulation. EPs are found by controlling the power and frequency of the driving microwave field, and their effect on multiphotoninduced resonance fluorescence is demonstrated numerically. [Preview Abstract] 

L01.00106: Strongly Interacting mmWave and Optical Photons with Rydberg Atoms Mark Stone, Aziza Suleymanzade, Lin Su, David Schuster, Jonathan Simon We outline progress towards a hybrid experimental system for engineering strong interactions between single optical and mmwave photons using Rydberg atoms as an interface. Entanglement between photons with gigahertz and optical frequencies creates a new platform to access exotic photonic quantum states as well as powerful new techniques in quantum computing and simulation. We will present recent experimental developments including highQ tunable cavities at 100 GHz, optical cavities which are robust to vibrations inside a pulse tube cryostat, and trapping and cooling atoms in a cryogenic MOT. [Preview Abstract] 

L01.00107: Sensitivity comparisons of Rydberg sensors and classical antenna at radio frequencies Zachary Castillo, David Meyer, Fredrik Fatemi, Kevin Cox, Paul Kunz We compare a Rydbergatom electric field sensor to classical antennas with particular focus on sensitivity. The two systems’ sensitivities differ over practical frequency ranges from 10 kHz to 100 GHz due to basic physics considerations. Additionally, we show results from our second generation experiment, aimed at recordlevel electric field sensitivity and extreme wideband operation. [Preview Abstract] 

L01.00108: DEGENERATE GASES AND MANYBODY PHYSICS 

L01.00109: Measurement of the spindensity wave propagation speed in a spinor BoseEinstein condensate Deokhwa Hong, Joon Hyun Kim, Yongil Shin We experimentally measure the propagation speed of spindensity waves in a spin1 antiferromagnetic spinor BoseEinstein condensate of $^{23}$Na atoms. Spindensity waves are generated by perturbing the condensate with a focused laser beam, whose frequency is tuned between the $D_1$ and $D_2$ transitions of the Na atom to generate a spindependent potential, which is attractive for the $m=1$ spin component and repulsive for the $m=1$ spin component. By abruptly turning off the laser beam placed at the center of the condensate, we create a magnetization pulse wave that is a composite of a density dip of the $m=1$ component and a density bump of $m=1$, and we measure its propagation speed in the condensate. The measured propagation speed is compared with that of massdensity wave which is excited in a similar manner with a spinindependent 532 nm laser beam. We find that the propagation speed of spindensity wave is about 20% of that of massdensity wave, showing that the spindependent interaction coefficient for the Na atom in the $F=1$ state is twice larger than the conventional value from [PRL 99, 070403 (2007)]. [Preview Abstract] 

L01.00110: Spinsqueezed atomic crystal Emilia Witkowska, Dariusz Kajtoch, Alice Sinatra We propose a method to obtain a regular arrangement of twolevel atoms in a threedimensional optical lattice with unit filling, where all the atoms share internal state coherenceand metrologically useful quantum correlations. Such a spinsqueezed atomic crystal is obtained by adiabatically raising an optical lattice in an interacting twocomponent BoseEinstein condensate. The scheme could be directly implemented on a microwave transition with stateofthe arttechniques and used in opticallattice atomic clocks with bosonic atoms to strongly suppress thecollisional shift and benefit from the spins quantum correlations at the same time. [Preview Abstract] 

L01.00111: FermionMediated Interactions Between Bosons in a Quantum Degenerate $^{133}$Cs$^6$Li BoseFermi Mixture Geyue Cai, Krutik Patel, Brian DeSalvo, Cheng Chin We observe fermionmediated interactions between bosonic atoms of $^{133}$Cs embedded in a degenerate Fermi gas (DFG) of $^6$Li atoms. The mediated interaction is the spinless analog of the RKKY (RudermanKittelKasuyaYosida) mechanism. Deep in quantum degeneracy, the strong mass imbalance and the different quantum statistics between two species lead to the BoseEinstein Condensate (BEC) that is fully immersed in the DFG. From in situ imaging of the mixture, we observe an effective attraction between bosons and the formation of BoseFermi solitions, in full consistency with the predictions. In addition, we perform a measurement of the BEC's dipole oscillation near an interspecies Feshbach resonance. The interspecies interactions modify trapping frequency and damping rate of the BEC in the presence of the DFG. [Preview Abstract] 

L01.00112: Tan Contact Matrix and Universal Relations for 1D Spinor Quantum Gases Shah Saad Alam, Han Pu The Tan contact and associated universal relations have been previously studied for a few kinds of spinor quantum gases, such as spinzero/half fermions, bosons, SU(N) symmetric or multicomponent gases. Based on our previous work on interacting spinor quantum gases with arbitrary spins, we present results on the Tan contact matrix and its connection to the large momentum tail for arbitrary spin gases with spindependent interactions at arbitrary strengths. We further discuss the connection between the Tan contact matrix and two body density matrices, energetics and other universal relations. [Preview Abstract] 

L01.00113: Quantum Optics with Matter Waves Michael Stewart, Ludwig Krinner, Joonhyuk Kwon, Arturo Pazmino, Alfonso Lanuza, Xiaoyu Yang, Dominik Schneble Ultracold atoms in optical lattices realize a tunable open quantum system in the context of matterwave emission into vacuum. We have recently realized such a quantum optical system and demonstrated [1] that it can be used to study emission phenomena in a wide range of parameter regimes, including those which are difficult to access in analogous optical cases, e.g. photonic band gap materials. We describe our experiments and theoretical modeling in detail and present further progress with our novel platform. \newline \newline [1] L. Krinner, M. Stewart, A. Pazmiño, J. Kwon, D. Schneble, Nature \textbf{559}, 589 (2018) [Preview Abstract] 

L01.00114: ABSTRACT WITHDRAWN 

L01.00115: Quantum droplet in a mixture of Rb and Na BoseEinstein condensates Zhichao GUO, Fan Jia, Lintao Li, Dajun Wang According to the meanfield theory, an atomic BoseEinstein condensate (BEC) will collapse when the interaction between atoms is attractive. However, the mixture of two BECs with attractive interspecies interaction can be stabilized by the beyond meanfield LeeHuangYang correction in the format of selfbound quantum droplets [1, 2, 3]. In this poster, I will present our progress in studying the heteronuclear quantum droplet with the double BEC of Rb and Na atoms. With the help of an interspecies Feshbach resonance, we have created double BECs with nearly arbitrary interaction strengths and signs. When setting the interspecies scattering length to larger enough negative values, we observe the selfbound behavior as the signature of the NaRb droplet during the time of flight expansion upon releasing the mixture from the optical trap. Future plan for studying the phase diagram and formation dynamics will also be discussed. [Preview Abstract] 

L01.00116: Alloptical production of lithium6 molecular BoseEinstein condensates in excited hyperfine levels Feng Xiong, Yun Long, Vinod Gaire, Cameron Caligan, Colin Parker We demonstrate the achievement of molecular BECs of lithium6 in its lowest and second lowest hyperfine state pairs at 0.05 microkelvin by an alloptical method. At such temperature, the mixture of the lowest two states has a condensate fraction of 36{\%} with 9E$+$4 atoms while mixture of the second lowest two states has a condensate fraction of 28{\%} with 3.2E$+$4 atoms. Our method, although being mostly standard, introduces several unique features. For example, we add a few refinements to the Bittertype magnetic bias coils. Utilizing a highvacuum chamber, our design preserves a lot of optical access for future experiments and minimizes the use of active elements. By using a single tapered amplifier, we realize slowing and Dopplercooling. We also implement a phase contrast imaging system to investigate the imbalances between hyperfine states in lithium. [Preview Abstract] 

L01.00117: Molecular production in a quenched unitary Bose gas Victor Colussi, Silvia Musolino, Servaas Kokkelmans As the quenched unitary Bose gas evolves, the buildup of correlations leads to the formation of extended pairs bound purely by manybody effects, analogous to the phenomenon of Cooper pairing in the BCS regime of the Fermi gas\footnote{V. E. Colussi, S. Musolino, S. J. J. M. F. Kokkelmans, PRA 98, 051601(R) (2018)}. We study how correlation growth, bound pairs, and threebody losses emerge in the fraction of unbound atoms remaining post sweep, finding quantitative agreement with experiment\footnote{C. Eigen, J. A.P. Glidden, R. Lopes, N. Navon, Z. Hadzibabic, and R. P. Smith, PRL 119, 250404 (2017)} and speculate on discrepancies. We also highlight more recent efforts to study effects of higherorder correlations in the manybody dynamics, including the Efimov effect. [Preview Abstract] 

L01.00118: Digital holographic microscopy for ultracold atoms Francisco SalcesCarcoba, Christopher Billington, Emine Altuntas, Yuchen Yue, Ian Spielman We review two technical applications of digital holographic microscopy for imaging $^{87}$Rb BoseEinstein condensates (BECs). First, by recording an offaxis hologram, we refocus the reconstructed object field and study the possibility of recovering nearly diffractionlimited images without modifying the physical setup. Finally, we show that this technique allows direct observation of both the real and imaginary parts of the atomic susceptibility, effectively allowing for continuous tuning between fardetuned imaging methods (e.g. phase contrast) and resonant imaging (e.g, absorption) with no alterations to the system’s hardware. [Preview Abstract] 

L01.00119: Probing the roton excitation spectrum of a stable dipolar Bose gas Gabriele Natale, Daniel Petter, Rick van Bijnen, Alexander Patscheider, Manfred J. Mark, Lauriane Chomaz, Francesca Ferlaino To understand the fundamental thermodynamical properties of superfluid 4He, the concept of roton, a particular elementary excitation, has been important. Such elementary excitation, which gives rise to an energy minimum at finite momentum in the dispersion relation, results from the strong interactions occurring in this dense quantum liquid. A similar phenomenon has been predicted in dipolar quantum gases[1] despite their weakly interacting character. Such an interesting finding roots in the longrange (momentumdependent) and anisotropic nature of the dipoledipole interaction. We here report the measurement of the excitation spectrum of a stable dipolar BEC[2], in a cigar shape trap, over a wide range of momenta which include the roton momentum. We also find that for a narrow range of interaction strengths, when the roton gap vanishes, it is possible to drive our system in a metastable supersolid state. Remarkably, this state possesses both densitymodulation and phasecoherence whose lifetime is limited by 3 body losses. [1] L Santos, et. al., PRL 90, 250403, 2003 [2] D. Petter, et. al., arXiv:1811.12115 (2018) [Preview Abstract] 

L01.00120: Universal dynamical scaling of twodimensional vortices in a strongly interacting fermionic superfluid XiangPei Liu, XingCan Yao, Youjin Deng, XiaoQiong Wang, YuXuan Wang, ChunJiong Huang, Xiaopeng Li, YuAo Chen, JianWei Pan Dynamical formation and annihilation of vortices and antivortices play a key role in the celebrated BerezinskiiKosterlitzThouless (BKT) theory, a universal topological mechanism describing exotic states of matter in low dimensions. Here we study the annihilation dynamics of a large number of vortices and antivortices generated by thermally quenching a fermionic superfluid of Li6 atoms in an oblate optical geometry. Universal algebraic scaling laws in both time and space are experimentally revealed over a wide interaction range, from the attractive to the repulsive side across the Feshbach resonance, and further found to agree with a Glauber dynamics in Monte Carlo simulation of the classical XY model and with fieldtheoretical calculations. Our work provides a direct demonstration of the universal vortex dynamics underlying the BKT theory. [Preview Abstract] 

L01.00121: Fingering instabilities and pattern formation in a twocomponent dipolar BoseEinstein condensate KuiTian Xi, Tim Byrnes, Hiroki Saito We study fingering instabilities and pattern formation at the interface of an oppositely polarized twocomponent BoseEinstein condensate (BEC) with strong dipoledipole interactions (DDIs) in three dimensions. It is shown that the rotational symmetry is spontaneously broken by fingering instabilities when the DDIs are strengthened. Frogshaped and mushroomshaped patterns have been shown with different strengths of the DDIs. A Bogoliubov analysis gives a qualitative understanding of the interfacial instabilities of the two dipolar BECs, and a dispersion relation similar to that in classical fluids is obtained. Spontaneous density modulation and dipolar domain growth in the dynamics have also been demonstrated, in which we have analyzed the characteristic sizes of the dipolar domains corresponding to different patterns at the initial and later times in the evolution. We have also investigated the parameter dependence of the ground states, and found that the droplet patterns are formed due to the population imbalance in the two components. Labyrinthine patterns grow as the trap ratio increases, and a striped phase appears as the angle of tilted polarization increases. Our findings may establish further connections between superfluids and classical fluids. [Preview Abstract] 

L01.00122: Repulsive Fermi Polarons and Their Induced Interactions in Binary Mixtures of Ultracold Atoms Georgios Koutentakis, Simeon Mistakidis, Garyfalia Katsimiga, Peter Schmelcher We explore repulsive Fermi polarons in onedimensional harmonically trapped fewbody mixtures of ultracold atoms using as a case example a ${}^6$Li${}^{40}$K mixture. A characterization of these quasiparticlelike states, whose appearance is signalled in the impurity's radiofrequency spectrum, is achieved by extracting their lifetime and residua. Increasing the number of ${}^{40}$K impurities leads to the occurrence of both single and multiple polarons that are entangled with their environment. An interactiondependent broadening of the spectral lines is observed suggesting the presence of induced interactions. We propose the relative distance between the impurities as an adequate measure to detect induced interactions independently of the specifics of the atomic mixture, a result that we showcase by considering also a ${}^{6}$Li${}^{173}$Yb system. This distance is further shown to probe the generation of entanglement independently of the size of the bath (${}^{6}$Li) and the atomic species. The generation of entanglement and the importance of induced interactions are revealed with an emphasis on the regime of intermediate interaction strengths. [Preview Abstract] 

L01.00123: Ytterbium Fermi gases for impurity physics Oscar Bettermann, Nelson Darkwah Oppong, Giulio Pasqualetti, Luis Riegger, Immanuel Bloch, Simon Foelling As an alkalineearthlike atom, Ytterbium features two longlived states without angular momentum, the ground state and a metastable "clock" state, allowing for the realization of Fermionic gases with an additional orbital degree of freedom. This orbital degree can be used to implement different types of impurity systems. In Ytterbium173, an interorbital Feshbach resonance between the ground state and the clock state enables the study of strongly interacting twoorbital manybody systems. Using a onedimensional optical lattice, we study the resulting Fermi polarons in two dimensions. We find clearly defined polarons both on the repulsive and the attractive side of the resonance, with a long lifetime of the repulsive 2D polaron. The metastable state also enables statedependent potentials, which was proposed for studying Kondotype impurity physics, or the Kondo lattice model. For this, the existence of a spinexchange interaction is crucial. We investigate the interaction properties of Ytterbium171, and find an antiferromagnetic interorbital spin exchange, in contrast to the known ferromagnetic coupling in Ytterbium173. This should enable future orbital physics implementations to access both the ferro and the antiferromagnetic regime. [Preview Abstract] 

L01.00124: Stable longitudinal spin domains in a nondegenerate gas S. D. Graham, D. Niroomand, R. J. Ragan, J. M. McGuirk We demonstrate that linear effective magnetic fields can stabilize longitudinal spin domains in a weaklyinteracting gas of $^{87}$Rb atoms above quantum degeneracy. Coherent spinrotating interactions are modified by applying a small linear effective magnetic field that varies the local Larmor precession. Adding small effective magnetic fields with gradients that oppose the initial spin gradient in the domain wall stabilizes the spin domains. Experimental results over a range of cloud temperatures, densities, and linear effective magnetic fields are compared to solutions of a quantum Boltzmann equation in the hydrodynamic and collisionless regimes. In the hydrodynamic regime, the measured stabilizing gradients agree well with the quantum Boltzmann theory. However, the stabilizing gradients in the collisionless regime deviate from the quantum Boltzmann theory as the mean free path becomes comparable to the domainwall width. To better study both regimes, finer control over the initial domainwall width is attained using a digital micromirror device. [Preview Abstract] 

L01.00125: $p$wave Feshbach resonances and threebody losses in quasi1D spinpolarized $^6$Li gases Ruwan Senaratne, YaTing Chang, Danyel CavazosCavazos, Randall Hulet $p$wave Feshbach resonances in ultracold Fermi gases present an opportunity to observe $p$wave pairing and nontrivial topological states, such as Majorana edge modes. However, the enhanced losses near such resonances have prevented such investigation. A reduction in the threebody losses in a spinpolarized gas of $^6$Li atoms in the lowestenergy spin state near the $p$wave Feshbach resonance at approximately 159 G is expected when confined to quasi1D. We present measurements of these threebody losses in quasi1D tubes as functions of confinement, temperature and magnetic detuning from this resonance, as well as the results of coupledchannel calculations of the pwave scattering amplitude under these conditions. We also report on the prospect of observing $p$wave pairing in this system, and present an experimental setup using a digital micromirror device (DMD) and bluedetuned light to produce the hard boundaries necessary to simulate the Kitaev chain hamiltonian and observe Majorana edge modes. [Preview Abstract] 

L01.00126: Measurement of the Dynamical Structure Factor of a Strongly Interacting 1D 6Li Fermi Gas Danyel CavazosCavazos, YaTing Chang, Ruwan Senaratne, TsungLin Yang, Pjotrs Grišins, Zhenghao Zhao, ChungYou Shih, Thierry Giamarchi, Randall G. Hulet Interacting Fermi gases confined to 1D can only support collective excitations, and thus are governed by the TomonagaLuttinger liquid (TLL) theory, in which collective excitations decouple into charge and spin modes. Lowenergy excitations for these systems are characterized by a soundlike spectrum, and the corresponding spin and chargewaves differ in their propagation speed. We present measurements of the dynamical structure factor $S(q,\omega)$ using the two lowest hyperfine levels of $^6$Li as a pseudospin$1/2$ system. 1D confinement is realized via a 2D optical lattice. Bragg spectroscopy is used to measure the density (“charge”) mode excitation spectrum of the gas. We set $q$ by fixing the angle between the two Bragg beams, and $\omega$ is the frequency difference between them. We vary the interaction strength using a Feshbach resonance. $S(q,\omega)$ agrees well with the TLL theory. To measure the spin mode, we propose using bluedetuned light that is patterned with a digital micromirror device (DMD) and superimposed into our lattice potential to reduce the inhomegenous broadening in the excitation spectrum, as well as using the $2S$$3P$ transition in the UV rather than the $2S$$2P$ transition. [Preview Abstract] 

L01.00127: Thermoelectric transport through an atomic quantum point contact Laura Corman, Dominik Husmann, Martin Lebrat, Samuel H\"{a}usler, Philipp Fabritius, JeanPhilippe Brantut, Tilman Esslinger Thermoelectricity describes the phenomenon by which a temperature gradient drives transport of energy and particles and vice versa. It is of great technological importance for cooling materials or power generation, but it is also a fundamental probe of the physics of the medium in which the energy and particle currents are created. Experimentally, thermoelectric effects have already been studied with two reservoirs of weakly interacting ultracold fermionic lithium atoms connected by a twodimensional constriction. \newline Here, we control these effects in our ultracold atom transport setup by modifying the properties of both the constriction and the reservoirs to explore new conduction regimes, reducing the dimension of the constriction to that of an atomic quantum point contact and setting the interactions in the reservoirs to the unitary regime. The evolution of particle and energy currents to a temperature gradient are strongly modified compared to the weakly interacting case, where a transient particle imbalance builds up before relaxing. In the strongly interacting regime, this imbalance persists for accessible experiment times, realizing an equivalent of the fountain effect for fermions [1]. \newline [1] D. Husmann et al., PNAS 115, 8563 (2018) [Preview Abstract] 

L01.00128: ABSTRACT WITHDRAWN 

L01.00129: Microscopic studies of doped coldatom FermiHubbard antiferromagnets Geoffrey Ji, Christie Chiu, Annabelle Bohrdt, Muqing Xu, Justus Brüggenjürgen, Michael Knap, Eugene Demler, Fabian Grusdt, Daniel Greif, Markus Greiner Ultracold fermions in optical lattices offers new perspectives for studying the physics of strongly correlated materials. We use this experimental platform to implement the FermiHubbard model, a paradigmatic model thought to capture the physics of hightemperature superconductivity, the pseudogap, and other phenomena containing longstanding open questions. The additional tool of quantum gas microscopy enables siteresolved readout and access to projections of the manybody wavefunction in the Fock basis. We report on our most recent studies of doped antiferromagnets in 2D, where there is no universally agreedupon mechanism describing the interplay between hole motion and antiferromagnetic order. [Preview Abstract] 

L01.00130: SelfConsistent Spin Texture in a Quantum Gas through OptoMagnetic Effects Katrin Kroeger, Nishant Dogra, Manuele Landini, Lorenz Hruby, Francesco Ferri, Rodrigo RosaMedina, Tobias Donner, Tilman Esslinger Placing a multilevel atomic BoseEinsteinCondensate inside a high finesse optical cavity allows to explore various scenarios of lightmatter interaction. In this work, we investigate the influence of optomagnetic effects on the selforganization phase transition [M. Landini et al., PRL 120, 223602 (2018)]. Controlling the polarization of an offresonant transverse pump laser field allows to identify the roles of the scalar and the vectorial components of the atomic polarizability tensor. For a multicomponent condensate, we observe a competition between selforganization patterns modulating either density or magnetization. Beyond a critical ratio of vectorial over scalar coupling, a spin texture is created. We develop an extension of the Dicke model and find excellent agreement with the experimental data. Our findings demonstrate a direct competition between selforganization patterns in a single mode optical cavity, paving the way to the exploitation of optomagnetic effects for quantum simulation. [Preview Abstract] 

L01.00131: Spin Phases of Strongly Interacting TwoComponent BoseHubbard Model Sagarika Basak, Han Pu We study onedimensional strongly interacting twocomponent bosons in an optical lattice with intercomponent conversion using SchriefferWolff transformation and spinwave expansion towards obtaining spin phases in the deep Mott regime. Such a system can be experimentally realized by considering the two component bosons to be the two internal states of an atom. Previous work studying twocomponent BoseHubbard model in deep Mott region with interparticle interaction (Phys.~Rev.~A \textbf{92}, 041602(R), 2015) shows Mott, xy ferromagnetic, and disordered spin phases. The present consideration of intercomponent conversion in the deep Mott regime shows the presence of such spin phases with additional parameters and the possibility of new spin phases. Restriction to only onsite conversion and constraining the two bosons (same internal state) to be converted simultaneously, we obtain antiferromagnetic symmetry in contrast to xy ferromagnetic symmetry. The intercomponent conversion also lowers the variational energy and shows different phases in the mean field. This provides an additional and an easier tool to tweak this system to obtain different spin phases. [Preview Abstract] 

L01.00132: Exploring 3D topological matter with spinorbitcoupled fermions in optical lattices Chengdong HE, Bo Song, Sen Niu, Long Zhang, Zejian Ren, Entong Zhao, XiongJun Liu, GyuBoong Jo Ultracold atoms offer a promising testbed for the experimental study of topological matter. Various topological models have been recently realized in 1D and 2D atomic systems. While 3D topological matter with rich physics remains unexplored due to experimental complexity. Here we report, for the first time, the realization of a 3D nodal line semimetal in optical lattices with SO coupled ultracold fermions. The 3D topological band structure is achieved by stacking 2D Dirac semimetal in the $x$$y$ plane along $z$ direction in Ramandressed optical lattices. $k_z$ resolved spin texture measurement technique based on emergent magnetic group symmetry has been developed to detect 3D topological state. Spin texture in a specific $k_z$ plane can be directly imaged with different Zeeman splitting. 3D nodal lines can be reconstructed with this pseudotomography method. Band inversion lines, the bulk counterparts of Fermi arc states, can be extracted from quench dynamics, which reconfirmed the realization of topological phase. Our detection technique can be broadly applied to characterizing 3D topological states with similar symmetries, which provides a new possibility to study exotic quantum physics in higher dimensions. [Preview Abstract] 

L01.00133: Transport and Dynamics of a BoseEinstein Condensate (BEC) on a Synthetic Hall Cylinder ChuanHsun Li, Yangqian Yan, Sayan Choudhury, David B. Blasing, Qi Zhou, Yong P. Chen Interplay between matter and fields in physical spaces with nontrivial geometries can give rise to many unexpected phenomena. However, their realizations are often impeded by experimental constraints. Highly controllable atomic systems hold promises to create synthetic quantum matters inaccessible in other systems. We have realized a BEC on a synthetic cylindrical surface, composed of a real spatial dimension and a curved synthetic dimension formed by cyclicallycoupled atomic spin states, subject to a net radial synthetic magnetic flux. The BEC on such a Hall cylinder has properties unattainable by its counterpart in a 2D plane. We observe Bloch oscillations of the BEC with doubled periodicity of the band structure, analogous to traveling on a M\"{o}bius strip in momentum space, reflecting band crossings protected by a nonsymmorphic symmetry that underlines the emergent crystalline order in the BEC wavefunction. We further demonstrate such topological operations as gapping the band crossings and unzipping the cylinder, and study other dynamics and transport phenomena such as charge pumping. Our work opens the door to engineering synthetic gauge fields in synthetic curved spaces with nontrivial geometries and/or topologies and observing intriguing phenomena inherent to such spaces. [Preview Abstract] 

L01.00134: COLD ATOMS, IONS, MOLECULES, AND PLASMAS 

L01.00135: CARBON NANOTUBES AS ELECTRON EMITTERS TO GENERATE PLASMA IN AIR AND AIR/GAS MIXTURES Nazieh Masoud, Kevin Martus, Daniel Murnick A plasma source using a 10kV electron beam generated from a carbon Nanotube (CNT) was developed to produce plasmas in air or in air/gas mixtures. The CNT is located in a small lowpressure (106 mbar) cell with a 300 nm thick SiNx window to transmit the electrons to the high pressure plasma region. The source was operated with ambient air or with Argon (Ar) or Helium (He) gas flow across the SiNx window forming an air/gas mixture. Emission spectroscopy revealed a variation of species that was dependent on the electron beam energy and the gas flow conditions (type of gas, flow rate, and location of gas source relative to the SiNx window). OH line at 310 nm was found only with an Ar gas flow, whereas, the He flow yielded an N2+ emission at 391 nm. Spatial distribution studies indicated that the thickness of the generated plasma plume reached about 4 mm (2 mm) when He (Ar) gas is flowed on the SiNx window, and 3 mm with air alone. Plasma reactive species were found in the region outside of visible plasma plume (afterglow). When the gas flowed from a source 2.0 cm in front of the SiNx window, the volume of plasma extended from the surface of SiNx window to the gas source. Species throughout the plasma length change between the surface of the SiNx window to the source of the gas. [Preview Abstract] 

L01.00136: Optical Dipole Trapping of Holmium Christopher Yip, Donald Booth, Huaxia Zhou, Jeffrey Collett, Mark Saffman Neutral Holmium$'$s 128 ground hyperfine states, the most of any nonradioactive element, is a testbed for quantum control of a very high dimensional Hilbert space, and offers a promising platform for quantum computing. Its high magnetic moment also makes magnetic trapping a potentially viable alternative to optical trapping. Previously we have cooled Holmium atoms in a MOT on a 410.5 nm transition, characterized its Rydberg spectra, and made measurements of the dynamic scalar and tensor polarizabilities. We report here on progress towards narrow line cooling and magnetic trapping of single atoms. [Preview Abstract] 

L01.00137: A Study of the Velocity Dependence of the ARP Force Yifan Fang, Brian Arnold, Harold Metcalf The huge optical force enabled by multiple adiabatic rapid passage (ARP) sequences results from coherent exchange of momentum between atoms and light at a high repetition rate.\footnote{H.Metcalf, Rev.Mod.Phys. \textbf{89} 041001 (2017).} We have been studying its dependence on atomic velocity F$_{ARP}$($\upsilon$). We use counterpropagating beams from phaselocked lasers, perpendicular to an atomic beam, and measure the deflection of atoms out of the beam. We simulate the Doppler shifts of a transverse atomic velocity by oppositely detuning the frequency of the two light beams. The overall features of F$_{ARP}$($\upsilon$) in our experiments match well with our simulations over a wide range of atomic velocities. However, some detailed structures of F$_{ARP}$($\upsilon$) remain to be explained. In order to gain more insight into these structures, we have measured F$_{ARP}$($\upsilon$) over a range of interaction times and are also working on varying the repetition rate of momentum exchange to ameliorate the effects of sweep imperfections. [Preview Abstract] 

L01.00138: Antistokes luminescence of the NVcenter in diamond from a 785 nm pump beam Stephen Potashnik, John Barkyoumb, Ross Fontenot, Danielle Braje, Linh Pham In this work, we report the Stokes and antiStokes luminescence from nitrogenvacancy (NV) diamond samples. Several previous studies have predicted lasercooling through antiStokes emission of the NV center in diamond [1]. For any possibility of laser cooling, the NV center must be pumped with laser light of longer wavelength than the peak of the phononsideband luminescence from the 637 nm zerophonon line of the main 3E $\to $3A2 emission. In this work we observe and report the spectrum of antiStokes emission from a CVDgrown diamond excited with a 785 nm diode laser. The existence of the antiStokes emission is necessary but not sufficient to predict laser cooling. We also report on the application to this system of a method developed previously to determine cooling from change (increase) of Stokes luminescence intensity in CdSe/ZnS QDs [2]. This method involves the observation of the conventional luminescence in a thermally isolated sample excited by a 520 nm green diode laser. The 520 nm measurement is alternated with excitation of any potential cooling from the 785 nm antiStokes excitation. *BAI, Inc. [1] M. Kern et al., Phys Rev B 95, 235306 (2017). [2] R. Fontenot et al., ECS Trans., 80, 1483 (2017). [Preview Abstract] 

L01.00139: Loading of lasercooled caesium atoms into a hollowcore fiber aided by an axicongenerated funnel beam Paul Anderson, ShengXiang Lin, Behrooz Semnani, Taehyun Yoon, Brian Duong, Michal Bajcsy Lasercooled atoms confined inside a hollowcore photoniccrystal fiber with a red detuned dipole trap guided by this optical waveguide offer an excellent platform for studies of lightmatter interactions. We recently demonstrated loading of $\sim$10$^4$ caesium atoms into a photonicbandgap fiber with a $\sim$7$\mu$m diameter hollowcore and their confinement inside the core with a magic wavelength ($\sim$935nm) dipole trap [1]. This experiment used the potential created by the trap beam exiting the fiber tip and expanding in free space to guide the atoms from a freefalling lasercooled cloud into the fiber core. However, the loading efficiency in this approach is relatively low and highly sensitive to the alignment of the falling atom cloud with the fiber. Here, we present the results of an enhanced loading procedure using a bluedetuned hollowbeam formed with a pair of axions to create a funnelshaped potential, which robustly guides the falling atoms towards the fiber tip. This guiding further improves the loading efficiency by allowing us more freedom to optimize our initial cooling procedure. [1] T. Yoon and M. Bajcsy, arXiv:1812.02887 (2018) [Preview Abstract] 

L01.00140: Engineering Subwavelength Optical Landscapes using Stroboscopic Techniques TszChun Tsui, Sarthak Subhankar, Yang Wang, Steve Rolston, James Porto In coldatom experiments, the wavelength of the laser field involved usually sets a limit on the size of structures that can be resolved. To beat the diffraction limit, we exploit the nonlinear optical response of a threelevel system coupled to two light fields to create ultranarrow barriers with widths less than $\frac{\lambda}{50}$. These deltalike barriers allow us to create lattices with a lattice spacing of $\frac{\lambda}{2N}$ stroboscopically, where N are integers. We also demonstrate a new imaging technique for probing the wavefunction of atoms trapped in optical lattices with a spatial resolution of $\frac{\lambda}{50}$ and a submicrosecond temporal resolution, thereby introducing superresolution microscopy to the field of coldatom systems. With this technique, we study the static and dynamic properties of wavefunctions of atoms in different potential landscapes. [Preview Abstract] 

L01.00141: Interplay between anisotropy and dimensionality in fewbody bound states of quantum magnets Jugal Talukdar, D. Blume Spin systems have been studied extensively for many decades and ultracold atoms provide a new pathway for realizing and probing spin systems. The Heisenberg Hamiltonian, e.g., has been realized experimentally using cold atoms loaded into optical lattices and twomagnon bound states have been probed. We include an anisotropy in the Heisenberg Hamiltonian and analyze the resulting eigen spectrum and eigen states. Specifically, we report our theoretical progress on understanding the criteria for the existence of two and threebody bound states in different dimensions. [Preview Abstract] 

L01.00142: Brillouin resonances and Brownian ratchets in dissipative optical lattices Alexander Staron, Ajithamithra Dharmasiri, Anthony Rapp, Samir Bali A Brownian ratchet is a device that operates away from thermal equilibrium and is used to produce directed motion without a net force. Dissipative optical lattices allow us to precisely tune the noisecoupling between the system and the environment, enabling a search for stochastic resonances. In order to characterize our optical lattice, we measure vibrational and propagation modes in the transmission spectrum of a weak resonant light beam. We find that the weak probe introduces a propagating modulation that ``ripples'' through the lattice and ``drags'' along some cold atoms. We propose to elucidate the interplay between the vibrational frequency, the modulation frequency, and the photon scattering rate by performing detailed pumpprobe spectroscopy measurements using different probe polarizations and angles. We will compare our pumpprobe data with timeofflight fluorescent imaging of the atoms diffusing through the optical lattice using a homebuilt, submillisecond, lowjitter imaging system. We propose to explore parameter space for the optimal settings to achieve maximum ratchet efficiencies. Our goal is to understand how to create artificial Brownian nanoratchets with efficiencies that can come close to rivaling natural biomolecular motors. [Preview Abstract] 

L01.00143: Intraband conductivity of fermions in an optical lattice Peihang Xu, Rhys Anderson, Fudong Wang, Vijin Venu, Stefan Trotzky, Frederic Chevy, Joseph Thywissen We discuss how to measure the conductivity spectrum in low frequency regime of neutral fermionic $^{40}$K in a cubic optical lattice. A periodic force is applied to the atoms by sinusoidally displacing the trapping potential. The centre of mass response of the atoms, which can be treated as the mass current, is captured insitu by a highresolution fluorescence imaging system. In the linear response regime, the ratio between current and force gives the conductivity, through Ohm's law. With the ability to detect both onaxis and offaxis conductivity, the full conductivity tensor is obtained. Joule heating is also observed through measurements of the energy absorption rate, and compared to the real conductivity. For various lattice depths, temperatures, interaction strengths, and fillings, we measure both real and imaginary conductivity, up to a frequency sufficient to capture transport dynamics within the lowest band. The spectral width of the real conductivity reveals the current dissipation rate, and the integrated spectral weight is related to thermodynamic properties of the system through a sum rule. We observe that a finite lattice depth causes relaxation of current due to the breaking of Galilean invariance, which enables damping through collisions between fermions. [Preview Abstract] 

L01.00144: Spin Transport in a Mott Insulator of Ultracold Fermions Matthew A. Nichols, Lawrence W. Cheuk, Melih Okan, Thomas R. Hartke, Enrique Mendez, T. Senthil, Ehsan Khatami, Hao Zhang, Ningyuan Jia, Martin W. Zwierlein Transport measurements provide a fundamental characterization of the dynamic response of a quantum system that is perturbed from equilibrium. In this poster, using a quantum gas microscope, we study spin transport in the 2D FermiHubbard model, a model that is believed to capture essential features of hightemperature superconductivity. To realize the FermiHubbard model, we confine ultracold 40K atoms in two hyperfine states with differing magnetic moments in a homogeneous square optical lattice. We then apply a magnetic field gradient and examine how the two spin distributions evolve in linear response in real time. For a halffilled system in the strongly correlated regime, we observe spin dynamics which are diffusive in nature and we extract both the spin conductivity and the diffusion coefficient. We compare these findings with novel numerical linkedcluster expansion (NLCE) calculations. [Preview Abstract] 

L01.00145: Phase space methods for studying the disordered Hubbard model Sean R. Muleady, Itamar Kimchi, Rahul Nandkishore, Ana Maria Rey Ultracold atoms in optical lattices provide a platform for studying localization and relaxation dynamics in isolated quantum systems, offering insight into the interplay between disorder and interactions. However, very little is known about the nonequilibrium behavior of such systems, especially in higher dimensions where the physics is often beyond the reach of numerical and analytical tools. Here, we theoretically study doublon decay in the stronglyrepulsive, disordered Hubbard model, characterizing the dynamics in different regimes in terms of experimentally accessible quantities. We develop and apply extensive numerical simulations based on the discrete truncated Wigner approximation (dTWA) which allows us to access excitedstate dynamics and longtime relaxations for large systems in higher dimensions. This work is relevant for current optical lattice experiments in disordered, interacting systems. [Preview Abstract] 

L01.00146: he 2F7/2 state of Yb+ as a resource for achieving ultrahigh SPAM fidelity Anthony Ransford, Conrad Roman, Wesley Campbell The unique, lowlying f state in yb$+$ is currently employed in quantum information science almost exclusively for making clocks and opticalfrequency qubits. We describe how this resource can be used with the ground state manifold to aid in the scaling of trapped Ion quantum information science. Narrowband optical pumping into the F7/2 from one of the conventional S1/2 qubit states is projected to achieve a higher state preparation and measurement (spam) fidelity than any other demonstrated technique. As it is based on frequencyselective optical pumping, this scheme is straightforward, does not require extreme polarization purity or intensity control, and can be implemented by any groups already using YB$+$ with very few changes to their apparatus. [Preview Abstract] 

L01.00147: Towards Experimental Determination of Ionization Rates and Ion Velocity Distributions in $^{9}$Be H. M. Knaack, J. Keller, S. C. Burd, J. P. Penttinen, E. Kantola, M. Guina, D. Leibfried, D. H. Slichter, A. C. Wilson Surfaceelectrode ion traps are a promising technology for scaling up quantum information processing experiments, but their relatively shallow trap depths can make ion loading less efficient. To counteract this loss in efficiency, it is advantageous to understand the process more quantitatively. To this end we have built a dedicated test chamber with a channel electron multiplier to measure the quantity and velocity distribution of beryllium ions produced in vacuum via different schemes. One such scheme uses a novel source of laser light at 235 nm for photoionization of neutral beryllium atoms. This light is produced by frequencyquadrupling an infrared VECSEL to produce more than 50 mW of light at 235 nm. [Preview Abstract] 

L01.00148: Quantum simulations and force sensing experiments with 2D arrays of hundreds of trapped ions M. Affolter, K.A. Gilmore, J.E. Jordan, J.J. Bollinger, A. Shankar, A. SafaviNaini, R.J. LewisSwan, A.M. Rey, M. Holland We summarize recent experimental work with 2D arrays of hundreds of trapped $^{9}$Be$^{+}$ ions stored in a Penning trap. The goal of this work is quantum simulations and sensing with large trapped ion crystals. For improved sensing and simulation fidelity, electromagnetically induced transparency (EIT) cooling has recently been implemented\footnote{J.E. Jordan et al., https://arxiv.org/abs/1809.06346.}, with near ground state cooling observed for all the drumhead modes. Future experiments will investigate extending EIT cooling to 3D crystal arrays. We will also discuss recent improvements in the phase stability of the spin dependent, opticaldipole force, which enables new phasecoherent force sensing protocols, and the reduction of spontaneous emission in quantum simulation through parametric amplification. Preliminary force sensing experiments carried out with an rf tickle far from the axial centerofmass (COM) mode show a single measurement enhancement of 2 over previous work\footnote{K.A. Gilmore et al., Phy. Rev. Lett. \textbf{161}, 263602 (2017)}. On resonance with the COM mode, the projected electric field sensitivity is $<0.5$~(nV/m)/$\sqrt{\textrm{Hz}}$, providing opportunities to search for dark matter such as axions and hidden photons. [Preview Abstract] 

L01.00149: Towards optically trapped 2d ion crystals for quantum simulation Matt Grau, Christoph Fischer, Oliver Wipfli, Jonathan P. Home Quantum simulation using atomic systems has the potential to overcome the limitations of classical computers when calculating manybody spin Hamiltonians. Arrays of trapped ions are attractive platform for quantum simulation due to the high level of single particle control combined with the intrinsic long range Coulomb interaction that can be used to engineer tunable spinspin couplings. However, varying lattice geometry is challenging with current trapping techniques. We are developing a new apparatus to trap arrays of ions in optical lattices, which combine the flexible geometry found in neutral atom experiments with the high degree of control and large interaction strengths found in ion experiments. Arrays of around 40 ions could be trapped with interion distances of under 10 microns, and also with low residual heating rates due to offresonant scattering and laser fluctuations. This will be made possible by using a deep lattice potential formed by the large optical intensity in a high finesse optical cavity. Operating the optical lattice at a wavelength that traps both neutral atom and ions will allow us to deterministically load neutral atoms in a designed geometry before photoionizing insitu. Experimental progress towards these goals will be described. [Preview Abstract] 

L01.00150: Modeling nonadiabatic transport of a trapped ion through a single mode optical cavity Wance Wang, Andrew Laugharn, Joseph W. Britton The cavity QED strong coupling limit has long been accessible to neutral atoms, solid state qubits and trapped ion ensembles but was only recently accessed using a single trapped ion [1]. A leading challenge for ions is perturbation of the trap potential due to stray charges attached to the dielectric cavity mirrors, a problem exacerbated by the drive to small mode volume cavities. This poster explores an alternate approach. We model the nonadiabatic transport of lasercooled ions ejected from an ion trap and guided through the waist of an optical cavity. Shielding excludes RF potentials and stray laser light from the cavity. An uncertainty analysis identifies design constraints compatible with interactions in Lamb Dicke limit. We also consider ion beam interactions with the nearfield of highQ photonic structures and prospects for deceleration, sympathetic cooling and recapture of ions in a secondary ion trap. This approach is informed by recent demonstrations of transport gates [2,3] and focusing of lasercooled ion beams [4]. \\[4pt] [1] H. Takahashi, et al, arXiv 180804031 (2018), [2] L.E. de Cerc, et al, PRL 116 (2016), [3] D. Leibfried, et al, PRA 76, 032324 (2007), [4] G. Jacob, et al, PRL 117, 043001 (2016) [Preview Abstract] 

L01.00151: Multiscale quantum defect theory Bo Gao We present a quantum defect theory of twobody interaction for a reference potential consisting of multiple terms of the form of $C_m/r^m$ with $m>2$, each with its distinctive length scale $\beta_m = (2\mu C_m/\hbar^2)^{1/(m2)}$. We discuss the motivations and applications of the theory, and show how it can be formulated as an extension and a generalization of the singlescale theory of Gao [Physical Review A \textbf{78}, 012702 (2008)]. The atomatom longrange interaction of the form $C_6/r^6C_8/r^8C_{10}/r^{10}$ is used as an example in the context of the general formulation. [Preview Abstract] 

L01.00152: Magnetic Feshbach Resonances in Ultracold Yb+Li Alaina Green, Jun Hui See Toh, Xinxin Tang, Subhadeep Gupta We have observed interspecies magnetic Feshbach resonances between the openshell Li and the closedshell Yb ground state atom. Resonances are detected via atom loss spectroscopy across different magnetic field ranges on an atomic mixture of $^{6}$Li and $^{173}$Yb in a crossed optical dipole trap. Our observations are in good agreement with theoretical predictions (performed by the group of S. Kotochigova, Temple University) of resonance locations based on twophoton photoassociation (PA) spectroscopy performed in our group. Our PA work also provides an updated value of the swave scattering length for YbLi. In addition to our spectroscopic observations, we will also report on the associated coupling mechanisms responsible for the Feshbach resonances in this nonbialkali system. These interspecies magnetic Feshbach resonances may be used to associate free atom pairs of ultracold atoms into ground state YbLi molecules. Unlike dipolar bialkali molecules, the YbLi molecule possesses both electric and magnetic dipole moments, making it a candidate system for a rich variety of quantum simulations. [Preview Abstract] 

L01.00153: Universal ThreeBody Parameter of HeavyHeavyLight systems with negative intraspecies scattering length Huili Han, Caiyun zhao, tingyun Shi we investigate the dependence of Threebody Parameter on the intraspecies interaction in heteronuclear atomic systems. Through calculating the $a^{\scriptscriptstyle(1)}_{}$ for ten mass imbalanced systems, we predict the universal dependence of $a^{\scriptscriptstyle(1)}_{}$ on the background scattering length $a_{\scriptscriptstyle HH}$. We find that the $a_^{\scriptscriptstyle(1)}$ have a dramatically strong dependence on the background scattering length $a_{\scriptscriptstyle HH}$ for the mass lessimbalanced systems, and for the strong mass imbalanced systems, the interspecies interaction plays less important role in determining the value of $a_^{\scriptscriptstyle(1)}$. Specially, when the homonuclear atoms are in resonance, the $a^{\scriptscriptstyle (1)}_{}$ is nearly a constant expressed in terms of the van der Waals length $r_{\scriptscriptstyle vdW,HL}$: $a^{\scriptscriptstyle (1)}_{} = (6.3 \pm 15\%) r_{\scriptscriptstyle vdW,HL}$. [Preview Abstract] 

L01.00154: Controlling the Stereodynamics of Cold Molecular Collisions N. Balakrishnan, J. F. E. Croft, Meng Huang, Hua Guo We report numericallyexact quantum scattering calculations for lowenergy collisions of quantumstate prepared HD with H$_2$. Excellent agreement is obtained with recent measurements of Perreault et al. for the angular distribution of scattered HD at a collision energy of $\sim$ 1 K. By statepreparation of the HD molecules, control of the angular distribution of scattered HD was demonstrated. The stereodynamic control is achieved by the ability to choose a single or a coherent superposition of quantum states. We present a firstprinciples simulation of the experiment which enables us to attribute the main features of the observed angular distribution to a single $L=2$ partialwave shape resonance. [Preview Abstract] 

L01.00155: Observation of resonant dipole collisions in ultracold $^{\mathrm{23}}$Na$^{\mathrm{87}}$Rb rotational mixtures Junyu He, Xin Ye, Junyu Lin, Dajun Wang We report the investigation on resonant dipole collisions between different rotational states of ultracold bosonic $^{\mathrm{23}}$Na$^{\mathrm{87}}$Rb molecules. In a mixture of two rotational states with opposite parities, such interaction naturally arises without the need for external electric fields. The strength of this resonant dipole interaction can be tuned by preparing molecules in different rotational Zeeman states with microwave spectroscopy. In our experiment, the effect of the resonant dipole interaction and its state dependence are revealed by measuring the loss rate constants of different mixtures. [Preview Abstract] 

L01.00156: Towards a Molecular Quantum Gas Microscope Lysander Christakis, Jason Rosenberg, Elmer GuardadoSanchez, Waseem Bakr Recent years have seen rapid progress in creating and studying ultracold gases of polar molecules. These molecules are attractive candidates for quantum simulation of manybody systems, such as the XXZ model of quantum magnetism, due to their longrange anisotropic interactions and rich internal structure. Here we present our progress towards the construction of a new apparatus to perform siteresolved quantum gas microscopy on stronglyinteracting dipolar $^{\mathrm{23}}$Na$^{\mathrm{87}}$Rb molecules confined within a 2D optical lattice. We will form the molecules by coherently assembling cold sodium and rubidium atoms from atomic Bose condensates. Our experiment features invacuum electrodes to tune the interactions between the molecules as well as a highresolution objective for imaging. We plan to perform quantum gas microscopy by dissociating the molecules in a way sensitive to their rotational state, laser cooling the constituent atomic species, and detecting the scattered photons. [Preview Abstract] 

L01.00157: Deflection of a CaF Molecular Beam Using the Bichromatic Force Scott Galica, Leland Aldridge, Daniel McCarron, Edward Eyler, Phillip Gould We demonstrate that a bichromatic standingwave laser field can exert a significantly larger force on a molecule than ordinary radiation pressure. Our experiment\footnote{S.E. Galica, L. Aldridge, D.J. McCarron, E.E. Eyler, and P.L. Gould, Phys. Rev. A \textbf{98}, 023408 (2018).} measures the deflection of a pulsed supersonic beam of CaF molecules by a twofrequency 531 nm laser field near resonance with the very nearly closed X(v = 0)  B(v’ = 0) transition. A skewed magnetic field prevents population from accumulating in dark magnetic sublevels. The transverse momentum transfer is measured with a scanning slit. The molecules are excited immediately upstream of the slit, using the X(v = 0)  A(v’ = 1) transition at 583 nm, and the fluorescence which passes through the slit is monitored. The inferred force as a function of relative phase of the two frequencies is in reasonable agreement with numerical simulations\footnote{L. Aldridge, S.E. Galica, and E.E. Eyler, Phys. Rev. A \textbf{93}, 013419 (2016).} of the bichromatic force in this multilevel system. The large magnitude of the force, coupled with the reduced rate of spontaneous emission, indicates its potential utility in the slowing and manipulation of molecular beams. This work was supported by NSF and BSF. [Preview Abstract] 

L01.00158: Cold molecule assembly and nondestructive detection near a photonic nanostructure Ming Zhu, May Kim, Jesús PérezRíos, ChenLung Hung Photoassociation (PA) is among the most powerful techniques to assemble molecules directly from cold and ultracold atoms into their deeply bound molecular states. However, PAsynthesized molecules can populate a sea of final (meta) stable rovibronic levels following radiative decay from the initial excited molecular state. To detect the final state population, conventional detection techniques such as resonance enhanced multiphoton ionization method have been widely adopted, which inevitably destroys PAassembled molecules. In our experiment, we perform PA of cold atoms in the nearfield of a nanophotonic resonator. We aim at inducing strong coupling of the excited state molecule to the resonator mode to selectively enhance the radiative decay probability into the molecular rovibronic ground state. Meanwhile, the nanophotonic resonator also serves as an efficient moleculephoton interface, guiding the emitted photon for nondestructive molecular state detection following PAsynthesis. Here, we discuss our apparatus for cold molecule assembly on a nanophotonic resonator, and present our progress towards nondestructive detection of PAsynthesized molecules and enhancement of ground state molecule assembly. [Preview Abstract] 

L01.00159: Progress towards lasercooled CH molecules Lucas Railing, Jamie Shaw, Daniel McCarron We present an experimental effort to extend newly developed molecular laser cooling and trapping techniques to produce ultracold samples of CH radicals. Our approach uses two complementary techniques to apply significant optical forces to slow, cool and trap a beam of CH molecules from a cryogenic buffer gas beam source. The first uses intense bichromatic laser light on the X$^{\mathrm{2}}\Pi $A$^{\mathrm{2}}\Delta $ transition to apply coherent stimulated forces to initially deflect and then slow the molecular beam. The second uses the radiative force from optical cycling on the X$^{\mathrm{2}}\Pi $B$^{\mathrm{2}}\Sigma^{\mathrm{}}$ electronic transition for laser cooling and trapping. We project that the bichromatic force will be up to 50 times larger than the maximum radiative force while also reducing the spontaneous emission rate by a factor of two. The proposed optical cycling schemes for CH rely on established techniques previously demonstrated using other molecular species. CH molecules offer favorable properties for laser cooling and will ultimately provide access to tests of ultracold organic chemistry using a simple molecular species. This simplicity will enable future comparisons to calculations by quantum chemists. [Preview Abstract] 

L01.00160: Dipolar quantum droplets Fabian Boettcher, JanNiklas Schmidt, Matthias Wenzel, Mingyang Guo, Tim Langen, Tilman Pfau The interplay of the shortrange and isotropic contact interaction and the longrange and anisotropic dipolar interaction, allows for many interesting phenomena. In the case of competing interactions the meanfield contribution can get very small so that beyond meanfield effects start to play an important role and can actually stabilize an otherwise collapsing system. In our experiment with dysprosium atoms we observed a phasetransition between a gas and a liquid, characterized by the formation of selfbound droplets. These droplets show a saturation of the peak density with higher number of atoms like other liquids, even though they are 100 million times less dense than liquid helium droplets. With our experiment we can study a single selfbound droplet and measure the critical atom number for the phase transition between liquid droplet and expanding gas, extending for more than an order of magnitude in the atom number. Furthermore we show that the tendency of the system to form selforganized structures allows us to dynamically create states with transient supersolid properties close to the actual ground state. [Preview Abstract] 

L01.00161: Exploring a dipolar Luttinger liquid from the Tonks to the superTonks regimes KuanYu Li, Wil Kao, KuanYu Lin, Benjamin Lev A wide range of exotic quantum manybody phases and nonequilibrium dynamics may arise from the unusual properties of highly magnetic dysprosium confined to one dimension. We have previously explored the controlled breakdown of integrability in a dipolar quantum Newton's cradle created using the controllability of the dipolar interaction in 1Dconfined dysprosium. Here, we report new work on exotic equilibrium properties of 1D dysprosium gases. We observe a dipolar confinement induced resonance and use it to create a dipolar Luttinger liquid in both the Tonks and superTonks regimes. We present results characterizing this resonance as well as collective oscillation measurements that reveal these regimes. [Preview Abstract] 

L01.00162: Experimental setup of ultracold Rydberg atoms Chuyang Shen, Cheng Chen, Xiaoling Wu, Yue Cui, Shen Dong, Meng Khoon Tey, Li You Strong interaction between Rydberg atoms makes them ideal systems for quantum information processing and quantum simulation. In this poster, we will report our recent progress on constructing a machine for trapping ultracold rubidium atoms in their Rydberg states. For good optical, our system has two main science chambers: a MOT chamber and a Rydberg chamber. We use a moving optical tweezer to move atoms from the MOT chamber to the Rydberg chamber over 22 cm, achieving a transfer efficiency of 70{\%}. A twocolor laser system used for exciting the atoms to the Rydberg states would be discussed. A microscope setup featuring an aspheric lens placed in the Rydberg chamber for siteresolved detection would also be shown. [Preview Abstract] 

L01.00163: Experimental study of photoionization of ultralongrange Rydberg molecules in 1064nm dipole trap Jin Yang, James Shaffer Rydberg molecules have been an active and attractive research area for over a decade. This is not only because Rydberg molecules have exaggerated properties, such as giant size \textasciitilde 100nm and permanent dipole moments \textasciitilde kdebye, but also because they are good candidates to explore manybody physics. Properties of Rydberg molecules have been obtained using spectroscopy in an ultracold environment. However, up to now there is little reported on the decay processes of Rydberg molecules. What we know is, when photoionized, both atomic ions and molecular ions can be generated. Here we report our recent experimental research on the photoionization process of Cs Rydberg molecules loaded in a crossed 1064nm dipole trap. We found the dominant product of photoionization of Cs Rydberg molecules is Cs$_{\mathrm{2}}^{\mathrm{+}}$ molecular ions but they can be photodissociated into Cs$^{\mathrm{+}}$ atomic ions by the trapping laser. The rates of photoionization provide insight into the molecular decay mechanisms. [Preview Abstract] 

L01.00164: Expansion of an Ultracold Plasma with an Exponential Density Profile MacKenzie Warrens, Grant Gorman, Thomas Killian Ultracold neutral plasmas (UNPs) provide a powerful platform for studying a wide range of fundamental plasma processes, including the expansion of a plasma into surrounding vacuum. Most previous experiments with UNPs have been performed with plasmas possessing a Gaussian density profile, for which the expansion is well characterized and provides a useful diagnostic of initial electron temperature and threebody recombination in the plasma. A defining characteristic of a Gaussian plasma is selfsimilar expansion, which gives important time scales and length scales. While Gaussian plasmas are well understood, other interesting initial profiles have not been explored. This poster describes the expansion dynamics observed for UNPs formed by photoionizing a cold atomic gas from a quadrupole magnetic trap, which creates a plasma with an initial exponential, or ``cuspy,'' density distribution. We find that while the cuspy plasma does not selfsimilarly expand and other expansion details are different, important expansion time scales and length scales can be identified that are similar to the situation for a Gaussian plasma. [Preview Abstract] 

L01.00165: Electric Field Response of Highly Magnetized Ultracold Plasma Electrons John Guthrie, Puchang Jiang, Jacob Roberts Through their cold temperatures, ultracold plasma electrons can be highly magnetized with laboratoryscale magnetic fields. We have created ultracold plasmas in such a highly magnetized regime where the Larmor radius of the electron motion is the shortest relevant plasma length scale for the electrons. Short electric field pulses can be used to excite electron oscillations and drive electron escape from these ultracold plasmas. This oscillation motion can be used to determine the electronion collision rate in this highly magnetized regime. There are experimental complications in analyzing the electron response to such short pulses in magnetized ultracold plasmas, however. We describe these limitations and their resolution as well as presenting the measurement techniques used for determining the electronion collision rate. [Preview Abstract] 

L01.00166: Spectroscopy, buffer gas cooling and radiation pressure slowing of AlF molecules Stefan Truppe, Silvio Marx, Sebastian Kray, Maximilian Doppelbauer, Simon Hofsaess, H. Christian Schewe, Boris Sartakov, Gerard Meijer The aluminum monofluoride molecule (AlF) is an excellent candidate for laser cooling and magnetooptical trapping with high density. We present spectroscopic results necessary for laser cooling and trapping experiments and show first results on buffer gas cooling and radiation pressure slowing of AlF. We determine the energy levels in the X$^1\Sigma^+,v=0$ state and within each $\Omega$manifold in the a$^3\Pi,v=0$ state with a relative accuracy of a few kHz and the hyperfine splitting in the A$^1\Pi, v=0$ state with a few MHz. We also record laser excitation spectra in electric fields up to 150 kV/cm to determine the electric dipole moments in all three states with high accuracy. To determine the number of photons the AlF molecules scatter from a single laser we measure the transition strength of the A$^1\Pi, v'=0 \leftarrow$ a$^3\Pi,v''=0$ and A$^1\Pi,v'=0 \leftarrow$ X$^1\Sigma^+,v''=1$ band relative to the A$^1\Pi,v'=0 \leftarrow$ X$^1\Sigma^+,v''=0$ band. We also characterize a cryogenic buffer gas beam of AlF and present first results on radiation pressure slowing using a counterpropagating laser tuned to the Q(1) line of the A$^1\Pi, v'=0\leftarrow$ X$^1\Sigma^+,v''=0$ band near 227.5 nm. [Preview Abstract] 

L01.00167: State Dependent Collisions and Quantum Simulation with Tweezer Arrays of Ultracold Lasercooled Molecules Sean Burchesky, Loic Anderegg, Yicheng Bao, Lawrence Cheuk, John Doyle, KangKuen Ni, Wolfgang Ketterle Utilizing our recent optical array of single ultracold calcium monofluoride (CaF) molecules, we present ongoing work towards implementing internal state control of the molecules and tweezer merging to build a clean platform for collisional studies. We also present work towards dynamical tweezer rearrangement to deterministically create defect free arrays, which would be an ideal starting point for molecular qubits and quantum simulation of spin lattice Hamiltonians. [Preview Abstract] 

L01.00168: Tunable Three Body Loss in a Rydberg EIT medium Andrew Hachtel, Przemek Bienias, Alexander Craddock, Elizabeth Goldschmidt, Michael Gullans, Dalia Ornelas, Yidan Wang, Alexey Gorshkov, J.V. Porto, Steve Rolston The combination of atomic Rydberg interactions with electromagnetically induced transparency (EIT) is a promising candidate for a wide range of applications for quantum optics, quantum information protocols, and the study of manybody physics. These systems provide a novel platform to study fewbody physics where the dimensionality, mass, strength, and sign of the interactions are widely controllable and tunable, as has been demonstrated in recent experiments observing the formation of two and threephoton bound states. In this work, we present preliminary experimental results demonstrating threebody loss in the dispersive regime of RydbergEIT medium. Additionally, we show that the magnitude of this loss can be tuned with experimental parameters. [Preview Abstract] 

L01.00169: Measurements of pstate fine structure and quantum defects for Rydberg states of potassium Charles Conover, Huan Bui We determined the finestructure and quantumdefect expansion parameters for Rydberg pstates in potassium. We made measurements of the transition frequencies between $ns_{1/2}$ and $np_{1/2}$ and $np_{3/2}$ states in the hyperfine PaschenBack limit for n = 30 to 37. The data provide a direct measure of the pstate finestructure intervals and, using the previously measured sstate quantum defects, allow calculation of the pstate quantum defects. The experiments were done in a magnetooptical trap (MOT) where the cloud is centered at a location where the magnetic field could be adjusted by changing the relative intensities of the counterpropagating laser beams of the MOT. The cold atoms are excited to Rydberg states in steps from $4s$ to $5p$ and from $5p$ to $nd_j$ states using crossed, focussed (waist size 100 $\mu$m), lasers at 405 nm and 980 nm. Within the excitation volume, the MOT magnetic field has a variation of about 0.15 G, broadening the mmwave transitions by 100300 kHz. Stray electric fields are nulled in three dimensions using potentials applied to a set of mutually perpendicular rods surrounding the MOT cloud. Fine structure intervals are measured to an accuracy of $5 \times 10^{5}$ and the sp transitions are measured to an accuracy of $2 \times 10^{7}$. [Preview Abstract] 

L01.00170: An optogalvanic flux sensor for trace gases Patrick Kaspar, Johannes Schmidt, Fabian Munkes, Denis Djekic, Patrick Schalberger, Holger Baur, Robert Loew, Tilman Pfau, Jens Anders, Norbert Fruehauf, Edward Grant, Harald Kuebler We demonstrate the applicability of a new kind of gas sensor based on Rydberg excitations. From a gas mixture the molecule in question is excited to a Rydberg state, by succeeding collisions with all other gas components this molecule gets ionized and the emerging electron and ion can then be measured as a current, which is the clear signature of the presence of this particular molecule. As a first test we excite Alkali Rydberg atoms in an electrically contacted vapor cell \textbf{[1,2]} and demonstrate a detection limit of 100 ppb to a background of N$_{\mathrm{2}}$. For a real life application, we employ our gas sensing scheme to the detection of nitric oxide at thermal temperatures and atmospheric pressure \textbf{[3].} We are planning to reduce the detection limit to 1 ppb using state of the art cw lasers for the Rydberg excitation of NO. This is a competitive value for applications in breath analysis and environmental sensing. [1] D. Barredo, et al., \textit{Phys. Rev. Lett.} \textbf{110}, 123002 (2013) [2] J. Schmidt, et al., \textit{SPIE} \textbf{10674} (2018) [3] J. Schmidt, et al., \textit{Appl. Phys. Lett.} \textbf{113}, 011113 (2018) [Preview Abstract] 

L01.00171: Localization, scarring, and the effects of disorder on Rydberg atoms and other excited systems Matthew Eiles, Andrew Hunter, Alexander Eisfeld, JanMichael Rost We present an investigation of wave function localization in the excited states of separable Hamiltonia perturbed by small, shortrange impurities. In this context we explore possible connections between Andersontype localization, classical periodic orbits, quantum degeneracies, and disordered environments. As a prototype system we focus on a Rydberg atom immersed in a cloud of ground state atoms, e.g. an ultracold gas or an optical lattice. As a consequence of their high degeneracy, which reflects the underlying symmetry of the Hamiltonian, the perturbed Rydberg states can localize due to these perturbations. Similar behavior has also been witnessed in other model systems, for example the case of a twodimensional harmonic oscillator and other central power law potentials, and so we attempt to develop a theoretical framework to explain the common behavior found in these different systems. [Preview Abstract] 

L01.00172: A tunable ECDL at 480 nm for $^{\mathrm{87}}$Rb Rydberg physics Dario D'Amato, John Huckans We have designed and built a tunable nominal 50 mW external cavity diode laser at 480 nm to excite $^{\mathrm{87}}$Rb atoms to highlying Rydberg states via the twophoton 5S$_{\mathrm{1/2\thinspace }}\to $ 5P$_{\mathrm{3/2}} \quad \to $ nD$_{\mathrm{5/2\thinspace }}$pathway (in conjunction with a 780 nm laser). Our design is based on a lowcost nominal 488 nm single transverse mode laser diode, without any special coating or wavelength postselection requested of the manufacturer. Stable and modehop free tuning over a wide frequency range has been achieved through a careful analysis of the grating feedback geometry. We have also designed and started construction of an optical transfer cavity stabilization system to achieve a nominal 10 kHz laser linewidth. [Preview Abstract] 

L01.00173: Towards quantum simulation with $^{23}$Na$^{40}$K molecules in optical lattices Xinyu Luo, Frauke Seeßelberg, Roman Bause, Marcel Duda, Xingyan Chen, Ming Li, Svetlana Kotochigova, Immanuel Bloch, Christoph Gohle We review recent progresses towards simulating quantum manybody physics with polar $^{23}$Na$^{40}$K molecules in optical lattices. First, we extend the coherence time of rotational state by one order of magnitude to about 10 ms in a dilute gas using a spindecoupled magic trap. We observe densitydependent coherence times, which can be explained by dipolar interactions in the bulk gas. Second, we demonstrate a rotationdependent dipole trap by utilizing a rotational transition manifold $ X^1 \Sigma^+, v=0, J=0,1\rangle \to  b^3\Pi, v=0, J=0,1,2 \rangle$. The configuration of the trap can be tuned between magic, tuneout, and antimagic by changing the laser detuning in a few GHz. The photon scattering rate in the trap is negligible thanks to the narrow linewidth of the transition. Finally, we report the progress of preparing high filling $^{23}$Na$^{40}$K molecules in a 3D optical lattice. [Preview Abstract] 

L01.00174: Attosecond photoelectron holography in strong field tunneling ionization Yueming Zhou, Mingrui He, Jia Tan, Wei Cao, Min Li, Peixiang Lu Watching the valence electron move in molecules on its intrinsic timescale has been one of the central goals of attosecond science and it requires measurements with subatomic spatial and attosecond temporal resolutions. We propose photoelectron holography in strongfield tunneling ionization, which results from the interference of the tunneling and the rescattering electron wavepackets, to access this realm. We will first show with this method, the structure informationthe phase of the scattering amplitudecan be extracted. We will also show that the attosecond charge migration in molecules can be directly measured and the tunneling ionization time in strong laser field can be determined by this timeresolved photoelectron holography. [Preview Abstract] 

L01.00175: Swap cooling of trapped ions by resonant charge exchange with ultracold atoms Sourav Dutta, S. A. Rangwala We demonstrate, for the first time, a novel ion cooling method based on resonant charge exchange collisions between trapped ions and their parent neutral atoms [1]. The experiments are performed in a hybrid atomion trap consisting of a Paul trap for ions and a magnetooptical trap for atoms. Specifically, we observe that cooling of trapped $^{\mathrm{133}}$Cs$^{\mathrm{+}}$ ions by $^{\mathrm{133}}$Cs atoms is more efficient than cooling of $^{\mathrm{133}}$Cs$^{\mathrm{+}}$ ions by $^{\mathrm{85}}$Rb atoms. This observation cannot be explained by considering elastic collisions alone, signaling the presence of an additional mechanism in the parentdaughter CsCs$^{\mathrm{+}}$ case, which is cooling by resonant charge exchange (RCE). We additionally find that, on an average, cooling by RCE can be more efficient than elastic collisions despite that fact that the RCE cross section is much lower than the elastic collision cross section. This happens because a single RCE collision is two orders of magnitude more efficient at cooling than a single elastic collision, in our energy regime. The results have implications for future studies on charge transport by electron hopping in ultracold atomion system. [1] Phys. Rev. A 97, 041401(R) (2018) [Preview Abstract] 

L01.00176: Lightinduced Azimuthal Gauge Potentials and Spinorbitalangularmomentum coupling in BoseEinstein condensates YuJu Lin, PaoKang Chen, LiRen Liu, NengChun Chiu, HongRen Chen, KuanYu Lin, MengJu Tsai, Sungkit Yip, Yuki Kawaguchi, MingShien Chang We demonstrate coupling between the atomic spin and orbitalangularmomentum (OAM) of the atom's centerofmass motion in a BoseEinstein condensate (BEC), referred to as ``spinorbitalangularmomentum coupling''. This is achieved by using two copropagating Ramandressing beams to couple the atoms in the hyperfine spin F$=$1 manifold while transferring orbitalangularmomentum (OAM) to the atoms' centerofmass. One of the Raman beam is a LaguerreGaussian (LG) beam carrying OAM of light. In this system, we create synthetic azimuthal gauge potentials which act as effective rotations. We exploit the azimuthal gauge potential to demonstrate the HessFairbank effect, the analogue of Meissner effect in superconductors. Here, the BEC in the absolute ground state is a coreless vortex state and transits into a polarcore vortex when the synthetic magnetic flux is tuned to exceed a critical value. Our demonstration serves as a paradigm to create topological excitations by tailoring atomlight interactions. Further, the gauge field in the stationary Hamiltonian opens a path to investigating rotation properties of atomic superfluids under thermal equilibrium. [Preview Abstract] 
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