Bulletin of the American Physical Society
51st Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 65, Number 4
Monday–Friday, June 1–5, 2020; Portland, Oregon
Session K01: Poster Session IIOn Demand

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Room: Exhibit Hall E 

K01.00001: Relativistic Effects on Subshell Energies for Superheavy Elements Ahmad K. Razavi, Rezvan K. Hosseini, David A. Keating, Steven T. Manson, Jobin Jose, Pranawa C. Deshmukh A study of the subshell energies of the superheavy elements Z$=$102, 112 and 118 has been performed at the DiracFock (DF) level and compared with nonrelativistic results to assess the qualitative and quantitative effects of relativistic interactions on the energies of the various subshells. The strength of these relativistic effects is of order Z$\alpha $, which is not small compared to unity for these elements, especially for inner shells. As a result, the energies of the inner shells are altered substantially by relativity, by as much as about 50 keV for 1s of Z$=$118, as compared to nonrelativistic energies. In addition, the wave functions of the inner shells are contracted by relativity, and these contracted wave functions screen the nucleus more effectively so that the outer shells experience a smaller effective nuclear charge, which tends to expand them. Thus, the relativistic contraction of the outer shell wave functions are counterbalanced by this expansion, leading to interesting phenomenology for outershell energies; this has been studied earlier at much lower Z [1,2]. [1] J.P. Desclaux and Y. K. Kim, J. Phys. B \textbf{6}, 1177 (1975); [2] B. R. Tambe and S. T. Manson, Phys. Rev. A \textbf{30}, 256 (1984). [Preview Abstract] 

K01.00002: Studies of high$n$, n$^{\mathrm{1}}$G$_{\mathrm{4}}$ and n$^{\mathrm{1}}$H$_{\mathrm{5}}$ strontium Rydberg states using microwaveoptical multiphoton excitation R. Brienza, G. Fields, F.B. Dunning, S. Yoshida, J. Burgdörfer We demonstrate that combined microwave/optical four and fivephoton excitation can be used to generate sizable numbers of high$n$, 120$\le n\le $160, strontium n$^{\mathrm{1}}$G$_{\mathrm{4}}$ and n$^{\mathrm{1}}$H$_{\mathrm{5}}$ Rydberg states, respectively, for use in studies of novel ultralongrange Rydberg molecules, of autoionization, and of planetary atoms. The quantum defects for both these states (and the n$^{\mathrm{1}}$I$_{\mathrm{6}})_{\mathrm{\thinspace }}$were measured using microwave spectroscopy and are in good agreement with theoretical predictions based on a twoactiveelectron model. [Preview Abstract] 

K01.00003: Generating up to 10$^{17}$ photons per second with energies reaching 400MeV Szymon Pustelny The Gamma Factory (GF) is a proposal aiming at generation of up to 10$^{17}$~photons/s of the energies reaching 400~MeV. This exceeds the available $\gamma$sources by several orders of magnitude. The idea is based on resonant scattering of “light” on ultrarelativistic (the Lorentz factor $\gamma_L$ between 10 and 2900) highlystripped (very few electrons) ions. Due to the relativistic Doppler effect, the energy of the incident photons is boosted in the ion frame 2$\gamma_L$ times. Since the energy can be tuned by changing $\gamma_L$, this enables conventionally unavailable spectroscopy of various physical systems. Due to the ultrarelativistic motion of the ions, in the lab frame, spontaneously emitted photons are directed along the ionpropagation direction, boosting the energy of the photons by another factor of 2$\gamma_L$. In turn, the energy of the photons is increased 4$\gamma_L^2$ (e.g., conversion of 100nm ``light'' into 10$^{15}$~m radiation). Intensity of the radiation is very high as the conversion is resonant. During the presentation, the principles of the GF will be discussed and challenges of optical pumping of such ultrarelativistic highly charged ions will be be discussed. Potential applications of the GF for ``exotic’’ atomic physics will be also presented. [Preview Abstract] 

K01.00004: A velocity characterized atomic hydrogen beam Samuel Cooper, Adam Brandt, Cory Rasor, Zakary Burkley, Dylan Yost We present a cryogenic and velocitycharacterized ground state (1S) and metastable (2S) atomic hydrogen source. We also present possibilities to manipulate the atomic trajectories through the 1S2S twophoton transition. For example, the twophoton transition can be used for laser cooling, or the trajectories of metastable 2S atoms can be affected with nearresonant visible wavelength lasers. [Preview Abstract] 

K01.00005: Sr+ isotope shift measurement Xiaoyang Shi, Michael Straus, Xinghua Li, Sean Buechele, Mingyu Fan, Craig Holliman, Andrew Jayich Precision isotope shift spectroscopy can improve our knowledge of atomic and nuclear structure. Combined with a King plot analysis, such measurements could also constrain sources of new physics beyond the standard model of particle physics. We present preliminary isotope shift measurements of the $5s\ ^2S_{1/2} \rightarrow 5p\ ^2P_{1/2}$ electric dipole transition with a precision at the 100 kHz level. With $^{88}$Sr$^+$, $^{86}$Sr$^+$ and $^{84}$Sr$^+$, we will measure the isotope shifts of the dipoleallowed $4d\ ^2D_{5/2} \rightarrow 5p\ ^2P_{3/2}$ transition, and the narrow $5s\ ^2S_{1/2} \rightarrow 4d\ ^2D_{5/2}$ electric quadrupole transition. We plan to work with the radioisotope $^{90}$Sr$^{+}$ to test for King plot nonlinearities. [Preview Abstract] 

K01.00006: Multiphoton processes in a waveguideconfined ensemble of lasercooled atoms Paul Anderson, Taehyun Yoon, Brian Duong, Michal Bajcsy We report the results and analysis of spectroscopy measurements of a ladderscheme implemented using lasercooled atomic cesium confined to a hollowcore photonicbandgap fiber with mode diameter of the guided light \textasciitilde 7um. This fiber allows us to both confine a large number of atoms (\textasciitilde 10,000) into a quasi1D geometry and guide light along the atom confining region. The setup grants us access to an atomic system with a large optical depth in excess of 100, as well as to high intensities of light at low power levels. Our goal is to demonstrate optical nonlinearities, such as wavelength conversion of single photons through fourwave mixing. As a precursor, we studied twophoton absorption of a weak probe in the presence of a strong pump coupling the excited states, expecting to see a single transparency window. Instead, we observed two and eventually three transparency windows for certain combinations of experimental parameters. We successfully modelled these phenomena by using additional atomic levels that the pump couples into as its power increases, resulting in multiphoton absorption. [Preview Abstract] 

K01.00007: Core polarizability of rubidium using Rydberg spectroscopy seth berl, Jirakan Nunkaew, Charles Sackett, Thomas Gallagher The electric polarizability of heavy alkali atoms includes a small but significant contribution from the ionic core. This contribution is important for precision applications such as blackbody radiation shifts in atomic clocks and interpreting parity violation measurements. The polarizability of the core can be determined through spectroscopy of high angular momentum Rydberg states. We present the results of a highprecision measurements of the intervals between the $\ell =$ 4 to 6 levels of rubidium Rydberg states of n$=$17 to 19. The measuurements have been done using radio frequency and microwave spectroscopy of atoms in a thermal beam. The measurement results are precise enough that it is necessary to consider nonadiabatic corrections to the core polarization. We find a dipole polarizability $\alpha_{\mathrm{d}} \quad =$ 9.127(7) a$_{\mathrm{0}}^{\mathrm{3}}$, about three times more precise than previous results and in good agreement with theoretical expectations. . [Preview Abstract] 

K01.00008: Experimental Study of the 4$^{\mathrm{3}}\Sigma _{\mathrm{g}}^{\mathrm{+}}$ and 3$^{\mathrm{3}}\Pi_{\mathrm{g}}$ States of Rubidium Dimer Phillip Arndt, Vladimir Sovkov, Rebecca Livingston, Brendan Rowe, Marjatta Lyyra, Ergin Ahmed We reports a highresolution experimental study and a numerical analysis of the 4$^{\mathrm{3}}\Sigma_{\mathrm{g}}^{\mathrm{+}}$ and 3$^{\mathrm{3}}\Pi_{\mathrm{g}}$ electronic states of rubidium dimer. In the experiment the Rb$_{\mathrm{2}}$ molecules were initially excited from the ground X$^{\mathrm{1}}\Sigma_{\mathrm{g}}^{\mathrm{+}}$ state to an intermediate level of the mixed A$^{\mathrm{1}}\Sigma _{\mathrm{u}}^{\mathrm{+}}$\textasciitilde b$^{\mathrm{3}}\Pi _{\mathrm{u}}$ manifold using a narrow band tunable TiSa laser. In the next step the probe laser, a narrow band dye laser tunable in the 1300014000cm$^{\mathrm{1\thinspace }}$range, excited the molecules further to the target states. The resonances of the probe laser were observed by detecting the total fluorescence from the excited states to the a$^{\mathrm{3}}\Sigma_{\mathrm{u}}^{\mathrm{+}}$ state in the 500nm range. Large number of rovibrational term values spanning a wide range of the rotational and vibrational quantum numbers were measured using the opticaloptical double resonance technique. Besides the term values, we observed the resolved fluorescence intensities with Condon structures from many of the levels. The RydbergKleinRees (RKR) potential energy curves were constructed and optimized to reproduce the experimental data reliably. [Preview Abstract] 

K01.00009: Xray spectroscopy of highly charged Fe plasma with the transitionedgesensorbased microcalorimeter at the NIST EBIT Yang Yang, Endre Takacs, Dipti FNU, Ralchenko Yuri, Galen O'Neil, Paul Szypryt, Joseph N. Tan, Aung S. Naing, Amy Gall, Nancy Brickhouse, Randall Smith, Adam Foster The electron beam ion trap (EBIT) facility at the National Institute of Standards and Technology (NIST) was used to produce xray spectra from highly charged ions of Fe with the beam energy varying between 6.6 keV and 18 keV. The spectra were recorded with an array of 192 transitionedge sensor (TES) based xray microcalorimeters [1] which covered the broadband energy range roughly from 500 eV to 10000 eV with an energy resolution of about 5 eV over this range. Calibration was performed using Kalpha emission lines from metallic Mg (1.25 keV), Al, Fe, Co and Ni (7.48 keV) produced by an external calibration source. The measured spectra clearly revealed the features due to the stabilizing radiative decays of high n autoionizing states as well as direct excitation lines. The analysis of the measured spectra was performed through the detailed collisionalradiative modeling of the nonMaxwellian plasma using the NOMAD code [2] which reproduced the resonance and excitation features. The interpretation of measurements as well as the details of theoretical simulations will be presented. [1] P. Szypryt et al., Rev. Sci. Instrum. 90, 123107 (2019). [2] Yu. Ralchenko and Y. Maron, J. Quant. Spectr. Rad. Transf. 71, 609 (2001). [Preview Abstract] 

K01.00010: Measurement of the lifetimes of the $7p \: ^2P_{3/2}$ and $7p \: ^2P_{1/2}$ states of atomic cesium Amy Damitz, George Toh, Nathan Chalus, Andrew Burgess, Poolad Imany, Daniel E. Leaird, Andrew M. Weiner, Carol E. Tanner, D. S. Elliott We report measurements of the lifetimes of the $7p \: ^2P_{3/2}$ and $7p \: ^2P_{1/2}$ states of cesium, $^{133}$Cs. We collect the fluorescence from the spontaneous decay of atoms in the excited $7p \: ^2P_{3/2}$ and $7p \: ^2P_{1/2}$ states and employ a timecorrelated singlephoton counting technique to obtain the lifetimes of these states. We use these measurements with previous determinations of other electric dipole matrix elements of cesium to determine the $\langle 5d\,^2D_{5/2}r 7p\,^2P_{3/2} \rangle$, $\langle 5d\,^2D_{3/2}r 7p\,^2P_{3/2} \rangle$, and $\langle 5d\,^2D_{3/2}r 7p\,^2P_{1/2} \rangle$ electric dipole matrix elements for cesium. The lifetimes and determined matrix elements provide a test of theoretical methods for calculating precise models of the electronic structure of cesium. [Preview Abstract] 

K01.00011: An Electron Microscope for Viewing a Deformed Nucleus Thomas Dellaert, Patrick McMillin, Anthony Ransford, Conrad Roman, Wesley Campbell The metastable $^2F_{7/2}$ state is predicted to be sensitive to the structure of the deformed ytterbium173 nucleus in two ways. First, the high multiplicity of the electronic state ($J=7/2$) allows the high spin ($I=5/2$) nucleus to leave fingerprints of its multipole moments on the hyperfine structure, up to and including (at least in principle) the nuclear magnetic 32pole moment. Using the fact that the F state is both longlived and easily read out using techniques developed for quantum information processing, we are performing the first spectroscopy of this hyperfine structure. Second, the electric quadrupole hyperfine interaction in $^{173}Yb^+$ has been predicted to quench 4 of the 6 hyperfine levels of the $^2F_{7/2}$ state from the 5year lifetime of the other isotopes to the clockfriendly timescale of about 1 day. We will present prospects for achieving subHz accuracy of the hyperfine splittings and lifetime measurements of the quenched hyperfine levels of $^{173}Yb^+$ and their implications for clockwork and electron microscopy of the shape of a nucleus. [Preview Abstract] 

K01.00012: Spectroscopy of one photon 5s  6s electric field induced magnetic dipole transition in Rb Mark Lindsay, Carson McLaughlin, Seth Orson, Randy Knize We are conducting a measurement of the electric field induced M1 magnetic dipole one photon 5s  6s transition in Rb in a cell at about 7 mTorr, using a 0.5 W cw single frequency doubled diode laser at 497 nm. We detect cascade fluorescence from the decay of the 6s state at 1367 and 780 nm, and measure the ratios of the strengths of the four hyperfine components. From this, we can obtain the ratio M$_{\mathrm{hf}}$/M of the M1 transition strength, as well as the ratio M/$\beta $ and \textbar $\alpha $/$\beta $\textbar of the scalar and tensor components of the Stark transition polarizabilities. [Preview Abstract] 

K01.00013: Precision spectroscopy in neutral beryllium9 Eryn Cook, Molly Herzog, Esther Kerns, Chelsea Perez, William Williams Fourelectron systems are the current testing ground for many advanced theoretical models and also tests of quantum electrodynamics. We present our current progress on updated experimental measurements for a variety of energy levels in neutral beryllium9, compare them to current theoretical predictions, and motivate future theoretical calculations to compare to these experimental results. [Preview Abstract] 

K01.00014: Xray spectroscopy of highly ionized atoms using Transition Edge Sensor (TES) microcalorimeters at the NIST EBIT Joseph Tan, P. Szypryt, G.C. O'Neil, E. Takacs, S.W. Buechele, A.S. Naing, D. A. Bennet, W.B. Doriese, M. Durkin, J.W. Fowler, J.D. Gard, G.C. Hilton, K.M. Morgan, C.D. Reintsema, D.R. Schmidt, D.S. Swetz, J.N. Ullom, Yu. Ralchenko NIST has built a new broadband Xray spectrometer from an array of 192 individual TES (Transition Edge Sensor) microcalorimeters, designed specifically for high resolution spectroscopy of Xray transitions in highly ionized atoms, spanning a spectral range from a few hundred eV to 20 keV. Commissioned recently at the NIST EBIT (electron beam ion trap) facility, this timeresolved, photoncounting TES Spectrometer is dubbed the acronym ``NETS''. We present the earliest NETS observations of Xray emissions from various ion species created in the NIST EBIT [1], which serve to illustrate its capabilities. Ongoing studies enabled by NETS, including tests of atomic theory and other potential applications, are also presented at this conference.~ [1] P. Szypryt, \textit{et al}., Rev. Sci. Instrum. \textbf{90}, 123107 (2019) [Preview Abstract] 

K01.00015: Analysis of Spectral Lines of Ni I and Ni II in the Ultraviolet and Visible Region Brynna Neff, Steve Bromley, Joan Marler A better understanding of the atomic properties of Ni could contribute to our understanding of astrophysical observations especially in the context of solar physics. Laboratory measurements can provide information important for interpreting these spectra and benchmarking theoretical calculations. There is still more work to be done in understanding the electronic structure for low charge states of Nickel. To this end, we perform analysis of UV/VIS spectroscopic data obtained from the Compact Toroidal Hybrid plasma experiment at Auburn University. We also look at relative line intensities by comparing intensities of multiple lines from the same upper energy state. We present spectral lines observed in this experiment for Ni I and Ni II. [Preview Abstract] 

K01.00016: Measuring the isotope shift with noisy lasers in pastic 3dprinted mounts Michael Crescimanno, Theodore Bucci, Jonathan Feigert, Brandon Chamberlain, Alex Giovannone We demonstrate the design, implementation and utility of a plastic (PLA) 3dprinted diode mount and associated simplified digital control system for free running laser diodes our students use to perform saturated absorption spectroscopy in Rubidium vapor for the determination of the isotope shift. We show this inexpensive, simpler approach to vapor cell nonlinear optics yields measurements which are statistically identical to those using commercial ECLDs and we compare the resulting isotope shift measurements to the accepted value found in high precision experiments. [Preview Abstract] 

K01.00017: Measurements of f, g, and hstate quantum defects in Rydberg states of potassium Charles Conover, Abe Hill, Huan Quang Bui We report measurements of the quantum defects for the f, g, and h Rydberg states in potassium for principal quantum numbers $n = 26  29$. We made millimeterwave measurements of the transition frequencies between $nd_j$ and the $n\ell$ states. Using the previously measured dstate quantum defects we can readily determine the $n\ell$ state quantum defects. We also report ionic dipole and quadrupole polarizabilities based on our measurements. The experiments were done in a magnetooptical trap. 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. Stray electric fields are nulled to less than 25 mV/cm in three dimensions using potentials applied to a set of mutually perpendicular rods surrounding the MOT cloud. Limits to the resolution of the measurements are due to the inhomogeneity of the stray fields. Our measurements of the fstate quantum defects are 5\% smaller than prior measurements and are, to the best of our knowledge, the first measurements of the g and hstate quantum defects. [Preview Abstract] 

K01.00018: Computing ionization rates from periodic orbits in chaotic Rydberg atoms Ethan Custodio, Kevin Mitchell When placed in a magnetic field, the electron trajectories of a classical hydrogenic atom are chaotic. The classical ionization rate of such a system can be computed with brute force Monte Carlo techniques, but these computations require enormous numbers of trajectories, provide little understanding of the dynamical mechanisms involved, and must be completely rerun for any change of system parameter, no matter how small. We demonstrate an alternative technique to classical trajectory Monte Carlo computations, based on classical periodic orbit theory. In this technique, ionization rates are computed from a relatively modest number, perhaps a few thousand, of periodic orbits of the system. One only needs the orbits' periods and stability eigenvalues. A major advantage is that as system parameters are varied, one does not need to repeat the entire analysis from scratch; one can numerically continue the periodic orbits as the parameters are varied. We demonstrate the periodic orbit technique for the ionization of a hydrogen Rydberg atom in applied parallel electric and magnetic fields. [Preview Abstract] 

K01.00019: Laser spectroscopy of metastable palladium at 340 and 363 nm Ibrahim Sulai, Peter Mueller Palladium has 6 stable isotopes. (A = 102, 104,105,106,108, and 110). We performed isotope shift measurements of the $4d^9 5s \, ^3D_3 \to 4d^9 5p \, ^3F_4 $ transition at 340 nm, and the $4d^9 5s \, ^3D_3 \to 4d^9 5p \, ^3P_4 $ transition at 363 nm. The measurements were performed using saturation absorption spectroscopy at the $\sim 1$ MHz level. In addition we also determined the hyperfine structure constants of Palladium105 (I=5/2), the only isotope with nonzero spin, for the states involved in the two transitions. These measurements will serve as a benchmark for upcoming laser spectroscopic investigations of neutron rich palladium isotopes as a probe of their nuclear structure. [Preview Abstract] 

K01.00020: A calibration method based on atomic spin selfsustaining vector magnetometer Qin Zhao, Boling Fan, Shiguang Wang, Lijun Wang The selfsustaining atomic magnetometer has the advantage of high sensitivity and long spin coherence lifetime, based on which we demonstrate a novel method to calibrate the magnetic coil constants precisely. Via nondestructive phase measurement and coherent optical pumping, the spin polarization of rubidium atoms is regenerated coherently and the Larmor precession signal is oscillating continuously. In this stable state, the calibrating capability is achieved by applying current to coils and scan the magnetic components along x and ydirection. The magnetic field magnitude is obtained from precession frequency and the coil constants can be derived from the fitting equation directly. The constants of coils in the experiment are 246.010±0.034 nT/mA and 197.452 ± 0.025 nT/mA in the x and ydirections, respectively [Preview Abstract] 

K01.00021: RMatrix Calculations of Plasma Opacities Anil Pradhan, Sultana Nahar, Lianshui Zhao, Werner Eissner, Regner Trampedach, Claudio Mendoza A renewed effort is in progress to implement the RMatrix (RM) methodology developed for the Opacity Project to compute astrophysical opacities. The coupled channel (CC) calculations should be of higher accuracy than the distorted wave (DW) approximation heretofore employed for opacities calculations, and would precisely incorporate autoionization and coupling effects. The resulting energy distribution of the RM opacity spectrum at solar interior conditions is found to be significantly different than the DW, and mean opacities are higher than other opacity models [1]. Results are compared with available experimental data as well as other theoretical models. A new treatment of plasma broadening of autoionizing resonances is described, as well as an improved EquationofState. Specific features of boundfree photoionization cross sections relevant to plasma opacity are illustrated. Convergence of CC wavefunction expansion with respect to the large number of target ion levels included in the calculations, and completeness using "topup" DW atomic data, is discussed. Future plans include extensive opacity calculations for iron and oxygen that are generally of higher abundance in stellar interiors than other metals. [1]. A.K. Pradhan and S.N. Nahar, PASP Conf. Ser., 515, 79, 2018. [Preview Abstract] 

K01.00022: Heperturbed H$_{2}$ spectra: unprecedented agreement between ab initio theory and experimental data Hubert Jozwiak, Michal Slowinski, Franck Thibault, Yan Tan, Jin Wang, AnWen Liu, ShuiMing Hu, Samir Kassi, Alain Campargue, Magdalena Konefal, Konrad Patkowski, Piotr Zuchowski, Roman Ciurylo, Daniel Lisak, Piotr Wcislo Hydrogen molecule perturbed by the helium atom constitutes the simplest benchmark system for performing the tests of the ab initio quantum scattering theory on the ultraaccurate experimental spectra. Here, we report a full description of the collisionperturbed shapes of rovibrational lines for this particular system. We demonstrate, for the first time, agreement between measured and ab initio computed collisionperturbed shapes of molecular lines at the subpercent level: the rootmeansquare difference between experimental and theoretical profiles is smaller than onehundredth of the profile amplitude. In the analysis described here, we employed the stateoftheart statistical model of the collisionperturbed shape of molecular lines, we obtained all the parameters of this model from quantum scattering calculations, and the dynamical calculations were performed on the most accurate potential energy surface to date. [Preview Abstract] 

K01.00023: Influence of reagent rotation on exchange reaction rates in the $\mathrm{Li} + \mathrm{Li_2^*(A^1\Sigma_u^+)}$ system Jacob Fanthorpe, Ramesh Marhatta, Mark Rosenberry, Paul Oxley, Brian Stewart We have measured collisioninduced leveltolevel inelastic and reactive rate constants for the system \begin{equation} \ ^7\mathrm{Li}_2^*(\mathrm{A}^1\mathrm{\Sigma}_u^+)(v_i,j_i)+\ ^7\mathrm{Li} \rightarrow \ ^7\mathrm{Li}+\ ^7\mathrm{Li}_2^*(\mathrm{A}^1\mathrm{\Sigma}_u^+)(v_f,j_f) \end{equation} under singlecollision conditions at a temperature of 933K. The experiment was conducted for $j_i = $ 3  64 and $v_i =$ 2  5. We report over 1400 leveltolevel inelastic and reactive rate constants with $5\le \Delta v \le 2$ and $40\le \Delta j \le 50$ . By varying initial rotational energy by more than two orders of magnitude, we are able to report the effect of initial molecular rotation on reactive energy transfer in $\mathrm{Li}_2\mathrm{Li}$ collisions for the first time and compare the results with theory. Reactive $j_f$distributions are well modeled by a modified statistical theory. We employ quasiclassical trajectory simulations in conjunction with Reverse Monte Carlo methods to fit a modified LEPS potential surface to our experimental data. Simulations using this fitted potential surface allow us to compare the $j_i$ dependence of total reactive cross sections with theory. [Preview Abstract] 

K01.00024: Observation of Universal Efimov's Ratios across an IntermediateStrength Feshbach Resonance in $^{39}\mathrm{K}$ Michael Van de Graaff, Xin Xie, Roman Chapurin, Matthew Frye, Jeremy Hutson, Jose D'Incao, Paul Julienne, Jun Ye, Eric Cornell Efimov's original scenario is featured by an infinite number of threebody bound states (trimers) accumulating at unitarity where $E=1/a=0$. The binding energies of these trimers have a selfsimilar structure with a fixed scaling factor between adjacent branches. This scheme is valid in the zerorange limit and in real systems only applies to highlyexcited trimers with finiterange interactions. In this work, we unambiguously measured the benchmarks associated with the Efimov spectrum in $^{39}\mathrm{K}$, denoted as $a_{}^{(n=0)}$, $a_{*}^{(n=1)}$ and $a_{+}^{(n=0)}$, with $n$ indexing the parentage of trimer. $a_{}^{(n)}$ are triatomic resonances at $a<0$, $a_{*}^{(n)}$ are scattering resonances between atoms and Feshbach molecules at $a>0$, $a_{+}^{(n)}$ are interference minima in threeatom recombination at $a>0$. We report a universal ratio $a_{*}^{(1)}/a_{}^{(0)}$ on the two lowestlying trimers. The withintenpercent consistency between this ratio and zerorange result implies that finite range perturbations are suppressed as expected for Feshbach resonances with intermediate strength. We introduce multichannel van der Waals threebody model that can reproduce all three benchmarks. [Preview Abstract] 

K01.00025: Building a Quantum Defect Theory model for Ultracold collisions of Lithium atoms. Alyson Laskowski, Nirav Mehta For small separation distances, the atomatom interaction is characterized by a deep potential well on the order of a few thousand Kelvin, while at larger separations distances, the interaction is modeled by a shallow attractive tail with energies on the order of $\mu K$ or $m K$. We are building a QDT model to describe the collisions of ultracold lithium atoms. We use the Morse/longrange potential model of Le Roy [J.Chem.Phys. 131,204309 (2009)], which accurately represents the shortrange, deep potential well, and reduces to the Van der Waals $C_6/r^6$ (with higher order corrections) at long range. For these calculations, we have used a numerical variant of QDT based on Milne phase amplitude method that is capable of treating higher partial waves[PRA 87,032706 (2013)], which we have tested previously using square wells at short range against exact numerical solutions. We are now extending calculations of bound state energies, phase shifts and cross sections to incorporate multichannel effects within the lowest manifold of $X^1\Sigma^{+}_{g}$ potentials. [Preview Abstract] 

K01.00026: ElectronImpact Ionization of He $1s 2s$ $^3S$ M. S. Pindzola, J. P. Colgan Electronimpact ionization cross sections are calculated for the $1s 2s$ $^3S$ excited state of the He atom. A timedependent closecoupling method is used to calculate both single and double ionization cross sections. Theoretical double ionization cross sections are compared with crossedbeams experimental measurements at LouvainlaNeuve, Belgium. [Preview Abstract] 

K01.00027: Dielectronic Recombination in O$^{4+}$ Above and Below the Ionization Threshold S. D. Loch, M. S. Pindzola Relativistic perturbation theory calculations are carried out for O$^{4+}$ $1s^2 2s^2$ + e > O$^{3+}$ $1s^2 2p^2 3l (l=0,1,2)$ dielectronic recombination. We find that 37 of the 57 levels in the $1s^2 2p^2 3l$ configurations lie above the O$^{4+}$ ionization limit. The largest cross sections are found at 1.7 eV for the $1s^2 2p^3 3d$ configuration. [Preview Abstract] 

K01.00028: Partial time delays in elastic electron scattering by rectangular potential well with arising discrete levels. Miron Amusia, Arkadiy Baltenkov, Igor Woiciechowski We have investigated the partial EisenbudWignerSmith time delays for slow electrons scattered by rectangular attractive potentials as functions of the potential parameters, such as the potential well depth and the potential radius. We have focused our consideration on the vicinities of the parameters of the potential that are close to their critical values. The critical values are those, at which the bound states with zero binding energy appear in the potential well. The evaluations are performed mainly analytically. Specifically, we have considered potential depths U and potential radii R, in which the potential supports several discrete s, p and dlevels. Despite the potential simplicity, the presented analysis makes it possible to observe some specific features in the time delay behavior that have general character. It should be emphasized that although the investigated features of the consideredtime delays were obtained for the simple rectangular potential well, it is not difficult to generalize the consideration for any shortrange potential, obtaining qualitatively the same results. [Preview Abstract] 

K01.00029: \textbf{Collisions of electrons with Fe atoms at E}$=$\textbf{ 1eV  1 MeV:} \textbf{A Relativistic investigation} Bidhan C. Saha, Arun K. Basak, M. Alfaz Uddin, A. K. Fazlul Haque, M. A. R. Patoary, M. M. Haque, M. Shorifuddoza, M. H. Khandker, R. Hassan A complex optical potential embodying the static, exchange, polarization and absorption effects is developed to solve Dirac relativistic equation in partial waves [1,2] for calculating elastic and inelastic cross sections due to $e^{}  $Fe scattering at E $=$ 1 eV 1 MeV. We present here the differential, integral, momentum transfer and viscosity cross sections along with their spin polarization. We also report the details of the critical minima in the elastic differential cross sections, the absorption, and total cross sections. For the critical minima due to electron impact there are neither any experimental nor any theoretical study presently available. Our predicted cross sections agree nicely with experimental and other theoretical findings. Details will be presented at the conference. [1] A. K. F. Haque, M. A. Uddin, D. H. Jakubassa  Amundsen, and Bidhan. C. Saha, J. Phys. B \textbf{ 51}, 175202 (2018). [2] Haque \textit{et al}. Elastic scattering of e$^{\mathrm{\pm }}$ by Cd, Hg and Pb atoms at 1eV $\le $E $\le $1 GeV. AQC 83 [\textit{in press}], 2020. [Preview Abstract] 

K01.00030: Impementation of a multipass laser system on a freefree apparatus B.N. Kim, C.M. Weaver, N.L.S. Martin, B.A. deHarak A freefree experiment investigates the emission or absorption of photons when an electron scatters from an atom in a laser field. For pulsed lasers of repetition rates of tens of hertz, and pulse durations of tens of nanoseconds, the experimental livetime is a few microseconds per year; typical experiments can take well over a week of continuous data taking. We have therefore developed and installed a multipass laser system on our freefree apparatus. The principal of the system is to use a Pockels cell to rotate the laser polarization $90^\circ$ as the beam enters a circuit which passes through the electronscattering interaction region and then returns to a polarizing beamsplitter cube (PBS) placed just before the (now deactivated) Pockels cell. The orientation of the PBS is such that the beam is reflected through $90^\circ$ and therefore trapped in the circuit of path length 20~ns. Preliminary results are encouraging: the multipass system results in an increase of the freefree signal by a factor of 6.5, with a corresponding improvement in statistics from 3.6$\sigma$ to 8.1$\sigma$, over a single pass system. We will present a progress report on this system and plans to install a similar one on a second freefree apparatus. [Preview Abstract] 

K01.00031: Lowenergy electron elastic collisions with Th, Pu, Am, No and Lr actinide atoms Zineb Felfli, Kelvin Suggs, Alfred Z Msezane Recently, the experiment [1] measured the electron affinity (EA) of Th for the first time to be 0.608 eV. Following [2] we have used our robust Reggepole methodology to probe negativeion formation in the atoms Th, Pu, Am, No and Lr through the electron elastic total cross sections (TCSs) calculations. The TCSs are found to be characterized by ground, metastable and excited anionic formation, requiring careful identification. New manifestations in the TCSs for the Pu, Am, No and Lr atoms have been discovered; namely, atomic and fullerene molecular behavior near threshold [3]. Also, a polarizationinduced metastable cross section with a deep RamsauerTownsend (RT) minimum near threshold has been identified in the Am TCSs, which flips over to a shape resonance appearing very close to threshold in the TCSs for No. We have attributed these peculiar tunable behaviors in the TCSs to size effects impacting significantly the polarization interaction. This provides a novel mechanism of tuning a shape resonance and RT minimum through the polarization interaction via the size effect. Our extracted anionic binding energies from the TCSs are compared with available EAs. 1. R. Tang \textit{et al}, Phys. Rev. Lett. \textbf{123}, 203002 (2019) 2. Z. Felfli and A.Z. Msezane, Appl. Phys. Research \textbf{11}, 52 (2019) 3. A.Z. Msezane and Z. Felfli, Chem. Phys. \textbf{503}, 50 (2018) . [Preview Abstract] 

K01.00032: Time delay of slow electrons by a diatomic molecule described by nonoverlapping atomic potentials model. Miron Amusia, Arkadiy Baltenkov We study the elastic scattering of slow electrons by twoatomic molecule in the frame of nonoverlapping atomic potentials model. The molecular continuum wave function is represented as a combination of a plane wave and two spherical $s$waves, generated by the centers of atomic spheres. The asymptotic of this function determines in closed form the amplitude of elastic electron scattering. We show that this amplitude cannot be represented as a series of spherical functions. Therefore, it is impossible to use straightly the usual Smatrix methods to determine the scattering phases for nonspherical targets. We show that far from molecule the continuum wave function can be presented as an expansion in other than spherical orthonormal functions. The coefficients of this expansion determine the molecular scattering phases for nonspherical molecular systems. We calculated the scattering phases in the framework of an analytically solvable model and demonstrated the internal fundamental shortcoming of existing approaches. In the frame of the suggested approach, we calculate the Wigner times delay for slow electron scattered by twoatomic target. In principle, our approach can be easily generalized, thus permitting consideration of a multiatomic molecule as a scattering target. . [Preview Abstract] 

K01.00033: Theoretical Studies of Dissociative Recombination of Electrons with SH$^+$ Ions D.~O. Kashinski, A.~P. Hickman, J.~Zs. Mezei, I.~F. Schneider, D. Talbi We are investigating the dissociative recombination (DR) of electrons with the molecular ion SH$^+$, i.e. $e^ + \mathrm{SH}^+ \rightarrow \mathrm{S + H}$. SH$^+$ is found in the interstellar medium, and understanding its loss through DR will lead to more accurate astrophysical models. Recently we addressed the $^2\Pi$ potential energy curves (PECs) of SH as a DR pathway\footnote{Kashinski \emph{et al.}, J.\,Chem.\,Phys. \textbf{146}, 204109\,(2017)}. We have extended this work to investigate alternate DR pathways. Early results suggest that directmechanism DR through a $^4\Pi$ pathway may resolve the lowenergy ($< 10\,\mathrm{meV}$) discrepancy between experimentally determined rate coefficients and those determined through the indirect mechanism DR $^2\Pi$ pathway. PECs are obtained by performing large active space multireference configuration interaction (MRCI) electronic structure calculations for several values of SH separation. Rydbergvalence coupling has proven to be important. The block diagonalization method is used to disentangle interacting states forming a diabatic representation of the PECs. The status of this ongoing work will be presented at the conference. [Preview Abstract] 

K01.00034: Negative ion formation in lowenergy electronfullerene collisions: Fullerene anionic catalysis Zineb Felfli, Kelvin Suggs, Nantambu Nicholas, Alfred Z Msezane Negativeion formation in the fullerene molecules C$_{\mathrm{44}}$, C$_{\mathrm{60}}$, C$_{\mathrm{100}}$, C$_{\mathrm{124}}$, C$_{\mathrm{128}}$ and C$_{\mathrm{136}}$ is explored through lowenergy electron elastic scattering total cross sections (TCSs) calculations using our robust Reggepole methodology. We find that the TCSs are characterized generally by ground, metastable and excited negative ion formation during the collisions, RamsauerTownsend minima and shape resonances. The novelty and generality of the Reggepole approach is in the extraction of the negative ion binding energies (BEs) of complex heavy systems from the calculated TCSs. For ground states collisions these BEs correspond to the electron affinities (EAs), yielding excellent agreement with measured EAs for C$_{\mathrm{20}}$ through C$_{\mathrm{92}}$ [1, 2]. Utility of the formed fullerene negative ions is demonstrated in the catalysis of water oxidation to peroxide and water synthesis from H$_{\mathrm{2}}$ and O$_{\mathrm{2}}$ using the anionic fullerene catalysts C$_{\mathrm{20}}$\textbf{\textasciimacron }  C$_{\mathrm{136}}$\textbf{\textasciimacron }$_{\mathrm{.}}$ DFT transition state calculations found C$_{\mathrm{52}}$\textbf{\textasciimacron }and C$_{\mathrm{60}}$\textbf{\textasciimacron } numerically stable for both water and peroxide synthesis, C$_{\mathrm{100}}$\textbf{\textasciimacron } increases the energy barrier the most and C$_{\mathrm{136}}$\textbf{\textasciimacron } the most effective catalyst in both water synthesis and oxidation to H$_{\mathrm{2}}$O$_{\mathrm{2}}$. \begin{enumerate} \item A. Z. Msezane and Z. Felfli, Chem. Phys. \textbf{503}, 50 (2018) \item Z. Felfli and A.Z. Msezane, Euro. Phys. J. D \textbf{72}, 78 (2018) \end{enumerate} [Preview Abstract] 

K01.00035: Pulse duration dependence of strongfieldinduced fragmentation of ethylene and acetylene molecules Yubaraj Malakar, Farzaneh Ziaee, Surjendu Bhattacharyya, Keyu Chen, Kurtis Borne, Wright Lee Pearson, Daniel Rolles, Artem Rudenko Understanding the fragmentation of small polyatomic molecules induced by a strong laser field is one of the key steps towards lasercontrolled chemistry. For hydrocarbons, such fragmentation dynamics often involve hydrogen migration in different stages of the breakup process. Here we show how the breakup patterns of ethylene and acetylene molecules exposed to intense 800 nm laser fields change as a function of a laser pulse duration. Performing coincident momentum imaging of ionic fragments resulting from two and threebody breakup of doubly and triply ionized molecules, we trace the signatures of hydrogen migration, analyze the role of different intermediate states, and discuss possible contributions of ``concerted'' and ``sequential'' fragmentation pathways. [Preview Abstract] 

K01.00036: A classical model of channelclosing effects on strongfield ionization B.A. deHarak, V.C. ViteriPflucker, B. Koirala, Y.A. Elmadny, D. Chetty, R.D. Glover, I.V. Litvinyuk, R.T. Sang Atoms in strong laser fields can ionize by absorbing energy from multiple photons so that an electron has sufficient energy to escape (multiphoton ionization), or by having the depth of its potential well lowered enough that an electron has a significant chance of tunneling out through the barrier (tunnel ionization). One might expect that as the intensity of the laser field increases, the probability that the atom will ionize increases until an intensity is reached that guarantees ionization. However, as the intensity increases the ground state of the atom is stark shifted so that a greater amount of energy is required for ionization to occur. In the multiphoton ionization model this shifting of the ground state energy results in a point being reached where the minimum number $n$ of photons that must be absorbed has increased to $n + 1$ (the ionization channel that corresponds to $n$ photon absorption has closed). The probability of absorbing $n + 1$ photons is much lower than for absorbing $n$ photons, so the probability of ionization decreases as the intensity increases past this point. Here we present a classical model of the effects of channel closing on ionization probabilities, and apply it to simulate strongfield experiments on argon. [Preview Abstract] 

K01.00037: High Harmonic Generation (HHG) from ZnO crystals by twocolor pulses Francisco Navarrete, Uwe Thumm While HHG from gaseous atoms is relatively well understood, HHG in solids is still debated and has been scrutinized experimentally only recently [1,2]. Even though the typical setup for HHG uses singlecolor intense midIR laser pulses, there has been interest in analyzing the effects of coherently adding a second or higher harmonic pulse, to characterize the frequency response of the sample and obtain more efficient HH conversion [3,4] . We investigated intra and interband contributions to HHG in ZnO model semiconductors driven by 1600 nm pump and 800 nm probe laser pulses with variable relative delay (pulse shape). We numerically calculated HH spectra by solving the timedependent Schr\”odinger equation in singleactiveelectron approximation within an adiabatic basisset expansion, including the entire first Brillouin Zone, and analyze HH yields and cutoff frequencies as a functions of the pulse shape and intensities. [1] F. Navarrete, et al., Phys. Rev. A 100, 033405 (2019). [2] S. Ghimire, et al., Nat. Phys, 7, 138 (2011). [3] Z. Wang, et al., Nat. Comm. 8, 1686 (2017). [4] T. T. Luu and H. J. W\"orner Phys. Rev. A 98, 041802(R) (2018). [Preview Abstract] 

K01.00038: Lightfield driven electron dynamics in graphene Christian Heide, Tobias Boolakee, Heiko B. Weber, Peter Hommelhoff Graphene is a unique material for lightfieldcontrolled electron dynamics inside of a (semi) metal. Its Dirac cone dispersion relation represents a twolevel system to study intricately coupled intraband motion and interband (LandauZener) transitions driven by the optical field of phasecontrolled fewcycle laser pulses [1, 2, 3, 4]. Based on the coupled nature of the intraband and interband processes, we observe repeated coherent LandauZener transitions between valence and conduction band separated by around half an optical period of $\sim$1.3 fs, fully supported by numerical simulations. Because of the extremely fast dynamics, fully coherent LandauZenerStückelberg (LZS) interferometry manifests itself in ultrafast current injection, with a recordfast turnon timescale of 1 fs for a current in a metal. Moreover, we could show complex electron trajectory control by tailoring the polarization state of the driving laser pulses. This way, we can manipulate LZS interference [3].\\ $[1]$ T. Higuchi, C. Heide et al., Nature 550, 224–228 (2017)\\ $[2]$ C. Heide, T. Boolakee et al., NJP 21, 045003 (2019)\\ $[3]$ C. Heide, T. Higuchi et al., PRL 121, 207401 (2018)\\ $[4]$ C. Heide, M. Hauck et al., Nat. Photonics (2020) https://doi.org/10.1038 /s4156601905806 [Preview Abstract] 

K01.00039: Highharmonic generation (HHG) enhancement from Crdoped MgO V. Nefedova, F. Navarrete, S. Froehlich, N. TancogneDejean, W. Boutu, M. F. Ciappina, D. Gauthier, A. Hamdou, S. Kaassamani, A. Rubio, U. Thumm, H. Merdji HHG from crystals is a source of coherent extreme ultraviolet (XUV) attosecond radiation [1] and reveals bandstructure information of the sample [2]. Increasing the HHG yield and HH cutoff frequency are fundamental goals in the development of efficient XUV sources, which we aim for by investigating the effects of doping on HHG spectra. The presence of dopants results in new electronic states in the band gap, as well as lattice defects, which modify the minimum band gap. Because the interband HHG yield depends exponentially on the minimum bandgap energy of the solid [3], we expect a substantial change of the HHG yield by doping [4]. We measured impurityenhanced HHG yields [5] and analyze our experimental spectra in comparison with numerical solutions of the Semiconductor Bloch Equations. [1] G. Vampa, et al., IEEE J. Sel. Top. Quantum Electron. 21, 8700110 (2015). [2] N. TancogneDejean, et al., Phys. Rev. Lett. 118, 087403 (2017). [3] F. Navarrete, et al., Phys. Rev. A 100, 033405 (2019). [4] T. Huang, et al., Phys.Rev. A 96, 043425 (2017). [5] V. Nefedova, et al., arXiv:2001.00839 (2020). [Preview Abstract] 

K01.00040: Ultrafast laserassisted photoprotection mechanism in the adenine cation Vincent Wanie, Erik Maansson, Simone Latini, Fabio Covito, Mara Galli, Enrico Perfetto, Gianluca Stefanucci, Hannes Hubener, Umberto De Giovannini, Mattea Castrovilli, Andrea Trabattoni, Fabio Frassetto, Luca Poletto, Jason Greenwood, Francois Legare, Mauro Nisoli, Angel Rubio, Francesca Calegari Attosecond pulses have become a mature tool for tracking in real time nuclear and electronic dynamics in systems with increasing complexity. Our particular interest is the ultrafast response of DNA building blocks upon irradiation, from which photostability and bond breaking emerge. Through timeresolved photofragmentation measurements, we demonstrate a laserassisted photoprotection scheme in the adenine nucleobase. Surprisingly, a path to retain the molecule structurally intact arises when a near infrared (NIR) pulse is sent precisely 2.3 fs after ionization by an isolated attosecond XUV pulse. Without the properly timed NIR, the singly or doubly photoionized adenine dissociates, as confirmed by TDDFT simulations. Rate equations and abinitio manybody timedependent calculations based on Green's function associate this characteristic 2.3 fs delay to the population of a specific shakeup state after XUV ionization, driving the electronic density away from the molecular plane. Depletion of this shakeup state by the NIR pulse accounts for internal energy removal from the molecule and leads to a stable dication. [Preview Abstract] 

K01.00041: Correlation effects on plasmonic photoelectrons in C\textunderscore 60 and C\textunderscore 240. Maia Magrakvelidze, Himadri Chakraborty We investigate the effect of electron correlations in the C60 and C240 molecules stimulated by light. The KohnSham equations of the valence electron clouds of the molecules are solved to obtain the ground state structures in the density functional theory [1]. Considering the dipole response of the systems to the incoming photon, the energy dependent induced electrondensities are then computed from the many body susceptibility in a linear response frame. This yielded the complex radial induced potentials which, at plasmon energies, probed the collective response of the molecules. This response suppresses the photon's dipole field, while inducing a strong attractive force, over the giant resonance region [2]. The effect of this force is revealed in the bindingwell shapes of the imaginary parts of the induced potentials. Because of this transient attraction, the temporal delay of the photoelectron emission can be observably affected [3]. [1] J. Choi et al ., Phys. Rev. A, 95, 023404 (2017) [2] I. V. Hertel et al., Phys. Rev. Lett, 68, 784 (1992) [3] T. J. Barillot et al., Phys Rev. A, 91, 033413 (2015). [Preview Abstract] 

K01.00042: Investigation of coupled nuclear and electronic motion in H2 photoionization Anna Wang, Andrei Kamalov, Philip Bucksbaum, James Cryan, Vladislav Serov, Alexander Bray, Anatoli Kheifets We investigate coupled nuclear and electronic dynamics in the photoionization time delays of H$_2$. We use a RABBITT technique to measure the photoionization time delays for several vibrational states of H$_2^+$ across a wide range of photoelectron kinetic energies. We observe discrepancies between our measured photoionization delays and a theoretical model which incorporates the vibrational state dependent ionization potential, but neglects motion of the nuclei. This difference between measurement and theory might indicate time variation of the scattering potential caused by nuclear dynamics. We explore the relative importance of these dynamics near the ionization threshold. [Preview Abstract] 

K01.00043: Dichroism in ionization of oriented Li(2p) atoms by circularly polarized laser radiation. David Atri Schuller, Klaus Bartschat, Nicolas Douguet, Nish de Silva, Santwana Dubey, Daniel Fischer In this joint theoretical and experimental project, we investigate the response of laserexcited Li atoms prepared in the (2p,$m\!=\!+1$) state to circularly polarized infrared (IR) radiation with the same or opposite helicity of the initial state. Our calculations are based on the singleactive electron (SAE) approximation, in which the valence electron is moving in the field of the Helike Li$^+$($\rm 1s^2$) core and subjected to fewcycle intense laser pulses. The peak intensity, pulse length, and wavelength of the probe laser are varied to simulate the experimental conditions. We study the dichroism $D = (S_{\rm co}  S_{\rm counter})/(S_{\rm co} + S_{\rm counter})$, where $S_{\rm co}$ and $S_{\rm counter}$ are the signals obtained for corotating and counterrotating pump and probe laser fields, respectively. Results will be presented for both the energy spectrum and the momentum distribution of the ejected electrons. Good agreement between theory and experiment is obtained, thereby allowing us to study detailed effects such as resonant excitation via Rydberg states and the helicitydependent appearance of the AutlerTownes effect. [Preview Abstract] 

K01.00044: Noncollinear XUVIR fourwavemixing to study the dynamics of dark states. Sergio YanezPagans, Nathan Harkema, Islam Shalaby, Arvinder Sandhu Ultrafast electron dynamics associated with dark states, i.e., excited states that are not accessible through singlephoton transitions, cannot be probed using traditional photoabsorption techniques. Characterization of the dynamical evolution of these states is possible through the use twophoton excitations; however, greater insights can be gained through noncollinear fourwave mixing (NFWM). By using tunable nearinfrared (NIR) femtosecond pulses and extreme ultraviolet (XUV) attosecond pulse trains we invoke nonlinear parametric processes for investigations of dark state dynamics. The noncollinear configuration for wavemixing provides versatility and has the advantage of yielding backgroundfree signals. We use these studies investigate the lifetimes of autoionizing states in argon and oxygen. [Preview Abstract] 

K01.00045: A combined Bspline Rmatrix approach for the study of timedependent multielectron dynamics in complex atoms. Kathryn Hamilton, Oleg Zatsarinny, Klaus Bartschat Experiments with ultrafast lasers are becoming increasingly focused on the role of multi\electron effects~[1] and the capabilities of midIR lasers~[2], both of which present considerable challenges to current computational methods. A successful timedependent multi\electron approach, therefore, requires two things: a compact, accurate atomicstructure description, and an efficient timepropagation scheme. Given their individual desirable characteristics and common $B$spline basis, the timeindependent $B$spline atomic \hbox{$R$matrix} code (BSR)~[3] and the $R$matrix with timedependence method (RMT)~[4] are natural choices to provide, respectively, the atomicstructure description and propagation scheme for probing timedependent behaviors in general atomic systems. We present our efforts in combining the two approaches, which we hope will enable the investigation of phenomena such as autoionization and spinorbit dynamics~[5] in multi\electron systems. [1] T.~Mazza et al., Nat.\ Commun.~{\bf 6} (2015) 6799. [2] T.~Gaumnitz et al., Opt.\ Express~{\bf 25} (2017) 27506. [3] O.~Zatsarinny, Comput.\ Phys.\ Comm.~{\bf 174} (2006) 143. [4] A.~C. Brown et al., Comput.\ Phys.\ Comm.~(2019) 107062. [5] J.~Wragg et al., Phys.\ Rev.\ Lett.~{\bf 123} (2019) 163001. [Preview Abstract] 

K01.00046: Exchange effects on timeresolved photoemission Zain Khan, Luca Argenti The $1s2s$ singlet and triplet metastable states of the helium atom, which have remarkably long lifetimes, can be conveniently generated in a helium gas sample by discharge currents. In this work, we study theoretically the effect of exchange parity on the timeresolved photoionization of the atom from these two metastable states. In particular, we compare the nonresonant photoemission delays to the $1s\varepsilon_\ell$ and $2\ell\varepsilon_{\ell'}$ channels, as well as the resonant pumpprobe ionization to the $2\ell\varepsilon_{\ell'}$ channels, mediated by the autoionizing doublyexcited states that converge to the $2s/2p$ He$^+$ threshold. [Preview Abstract] 

K01.00047: Propensity rules and interference effects in laserassisted photoionization of noble gases and closedshell negative ions Jan Marcus Dahlström, Mattias Bertolino, David Busto, Felipe Zapata We investigate the angleresolved photoelectron spectra from laserassisted photoionization, where an atom is photoionized by a field in the XUV range with an additional laser field in the IR range which \textit{dresses} the atom, $ A + \gamma_{\mathrm{XUV}} \pm q \gamma_{\mathrm{IR}} \to A^+ + e^, $ for helium and neon atoms using an \textit{ab initio} method based on timedependent surface flux and configuration interaction singles. We have found an interplay between a radial propensity rule and an angular interference effect to interpret the angular probability distribution (PAD) of the photoelectron, in which we find a different number of minima comparing absorption and emission processes with the magnetic quantum number resolved. In the lowenergy limit the propensity rule explains why there is a difference between the PADs for absorption and emission processes in the continuum. In the highenergy limit, however, the PAD is mostly explained by the interference effects of partial waves, as expected from the softphoton approximation. We further compare the results obtained in atoms to those in closedshell negative fluorine ion where the remaining neutralized target exerts only a shortrange potential, as opposed to the longrange Coulomb potential from ionized atoms. [Preview Abstract] 

K01.00048: A multicolor interferometric method for extracting phase information on continuumcontinuum couplings. Kathryn Hamilton, Thomas Pauly, Klaus Bartschat, Nicolas Douguet, Divya Bharti, Anne Harth The reconstruction of attosecond beating by interference of twophoton transitions (RABBITT) [1] method is a widely employed technique to measure attosecond time delays of photoionization processes. One consequence of this technique is the introduction of an additional component to the time delay, the continuumcontinuum (CC) time delay~[2], caused by the interaction of the probe field with the photo\electron. While well studied theoretically, this CC time delay is difficult to observe experimentally~[3]. Following up on the method outlined in~[4] for atomic hydrogen, we describe an approach capable of isolating this CC delay for Ar, which is experimentally easier to access. We show theoretical predictions obtained by the multi\electron $R$matrix with time dependence method (RMT)~[5] for two RABBITT measurements of the $3p$ photoionization delay in argon with different orders of CC transitions. The results will be compared with data from experiments currently in progress. [1] P.~Paul et al., Science {\bf 292} (2001) 1689. [2] J.~Dahlstr{\"o}m et al., Chem. Phys. {\bf 414} (2013) 53. [3] J. Fuchs et al., Optica {\bf 7} (2020) 154161. [4] A.~Harth et al., Phys.\ Rev.\ A~{\bf 99} (2019) 023410. [5] A.~C. Brown et al., Comput.\ Phys.\ Comm.~(2019) 107062. [Preview Abstract] 

K01.00049: Sideband oscillations in fourphoton RABBIFT scans. David Atri Schuller, Kathryn Hamilton, Klaus Bartschat, Nicolas Douguet, Divya Bharti, Anne Harth Extracting sideband phase information from standard \hbox{RABBITT} (reconstruction of attosecond beating by interference of {\bf two}photon transitions) scans is a common technique to measure atto\second time delays in photoionization [1]. Here we further investigate the {\bf four}photon setup (RABBIFT), suggested in~[2], where the intensity of the sidebands generated by a probe frequency $\omega_p$ oscillates according to $I(\tau) \propto$ cos$(4\,\omega_p\tau+\Delta \phi_{\epsilon})$, where $\tau$ is the delay between the XUV and IR pulses and $\Delta \phi_{\epsilon}$ is an energydependent phase. Here we examine the intensity and pulselength dependence of $\Delta\phi_{\epsilon}$ for realistic experimental setups ($I_{\rm XUV} = 10^9\,$W/cm$^2$, $I_{\rm IR} = 10^{11}10^{12}$\,W/cm$^2$, pulse lengths $20100\,$fs) by comparing RABBIFT scans from {\it ab initio} TDSE calculations~[3] for atomic hydrogen produced by different probe pulse durations and intensities. Preliminary results suggest a nonnegligible dependence of $\Delta\phi_{\epsilon}$ on the latter parameters. [1]~P.~Paul et al., Science {\bf 292} (2001) 1689. [2]~A.~Harth et al., Phys. Rev. A~{\bf 99} (2019) 023410. [3]~N.~Douguet et al., Phys. Rev. A~{\bf 93} (2016) 033402. [Preview Abstract] 

K01.00050: Shakeup photoemission delay in Neon Saad Mehmood, Didarul Alam, Nicolas Douguet, Stefan Donsa, Luca Argenti In the ionization of an atom, electrons emerge from different shells with different delays. A longstanding controversy surrounding the measured ($21\pm5$~as at 105~eV) and computed ($\leq 10$~as) time delay difference between the $2s$ and $2p$shell photoemission from neon [1] has been explained in a recent experimental work [2]. Shakeup channels, which were not resolved in [1], were responsible for the discrepancy between theoretical calculations and the experimental data. This new finding, however, still awaits quantitative theoretical confirmation. In particular, it is still to be determined whether other channels beyond the one identified as being responsible for the measurement bias, might also contribute. In this work, we report advances of a theoretical study conducted with the \footnotesize\textsc{NEWSTOCK} {\it ab initio} method to analyze and quantify the effect of shakeup channels above 70~eV photon energy in neon. [1] M. Sch\"{u}ltze {\it et al.} Science {\bf 328} 1658 (2010), [2] M. Isinger {\it et al.} Science {\bf 358} 893 (2017). [Preview Abstract] 

K01.00051: Argon dark autoionizing states decay probed with fourwave mixing Coleman Cariker, Luca Argenti Ultrafast pumpprobe spectroscopies employing trains of attosecond pulses have emerged as a useful tool for studying electron dynamics in atoms and molecules. In the first implementations of these schemes, pump and probe pulses are collinear and have commensurable frequencies. As a consequence, multiple distinct processes give rise to overlapping signals that are difficult to disentangle. Recent experimental advances have led to the extension of the original schemes to more general noncollinear fourwave mixing spectroscopies with independently tunable probe pulses. These spectroscopies spatially separate signals arising from different excitation pathways. Here, we present an \emph{ab initio} calculation of the fourwavemixing signal from the argon atom, excited to the $3s^{1}n\ell$ autoionizing states by an extreme ultraviolet attosecond pulse train, and probed by two independent angled IR pulses. The calculation accounts for the collective emission from the interaction region and are in good agreement with measurements from the group of Arvinder Sandhu. Furthermore, using an essentialstates model, we investigate how the resonant fourwave mixing signal depends on the lifetimes of the bright and dark autoionizing states, whose radiative coupling dominate the spectrum. [Preview Abstract] 

K01.00052: Vibrational coherence induced by intramolecular photoelectron scattering Bejan Ghomashi$^{2,4}$, Nicolas Douguet$^{3}$, Luca Argenti$^{4,5}$ We study theoretically in real time, with the help of a 1D model, the photoionization of a neutral heteronuclear diatomic molecule from a localized core orbital. The nuclear motion is modeled with a simple harmonic oscillator, with identical parameters in both the neutral and ionized state of the molecule, within the BornOppenheimer approximation. Even within this elementary framework, the system exhibits strong deviations from the Frank Condon approximation, due to the recoil associated to the photoelectron emission, and to the intramolecular scattering of the photoelectron. As a consequence, the ionization of the molecule leaves behind a vibrationally excited ion. The vibrationally resolved signals in the photoelectron spectrum map holographically the intramolecular photoelectron scattering dynamics as well as the coherence of the vibrational state of the residual ion. We compute the timedependent density matrix and Wigner distribution of the parention, and show that the ion residual coherence manifests itself in an effective delay in the periodic oscillation of the excited vibrational wave packet created by the ionization event. [Preview Abstract] 

K01.00053: Towards Observing Site Selective Chemistry in Real Time Gilles Doumy, Dimitrios Koulentianos, Stephen Southworth, Linda Young, Xuechen Zheng, Junzi Liu, Lan Cheng The possibility of siteselective photochemistry, where element and site selective excitation or ionization using xray photons guides the outcome of the dissociation has been an intriguing problem since the advent of high average flux sources at synchrotrons. So far, only limited selectivity has been observed, hinting at efficient charge redistribution before decay processes happen. The ability to probe this process as it happens is now becoming a reality at xray free electron lasers, with the ability to produce two pulses commensurate with the corehole lifetimes, with very different photon energies, and soon high repetition rates. By initiating an inner shell process at one molecular site and probing at another place in the molecule, one will be able to observe the evolution of the electronic properties, starting from the ionization energies of the core excited states. Making sense of the data will require comparison with high accuracy computational predictions, such as using our newly developed scalarrelativistic deltacoupledcluster method. We will present calculations for a class of fluoroalkane molecules that will be the focus of a demonstration experiment at LCLS this year. [Preview Abstract] 

K01.00054: Femtosecondresolved multiphoton ionization of C60 using Xray pump Xray probe with the LCLS FEL Nora Berrah We studied the timeresolved ionization of C$_{\mathrm{60}}$ using Xray pump Xray probe with 640 eV photons to examine the role of chemical effects, such as chemical bonds and charge transfer, on the fragmentation following multiple ionization of the molecule. The advanced simulations revealed that despite substantial ionization induced by the ultrashort (20 fs) Xray pump pulse, the fragmentation of C$_{\mathrm{60}}$ is considerably delayed. This work uncovered the persistence of the molecular structure of C$_{\mathrm{60}}$, which hinders fragmentation over a timescale of hundreds of femtoseconds. Furthermore, we demonstrate that a substantial fraction of the ejected fragments are neutral carbon atoms. [Preview Abstract] 

K01.00055: Stateselective Pumpprobe Studies on CO$_{\mathrm{2}}$ with Extreme Ultraviolet (XUV) and Nearinfrared (NIR) Pulses Anbu Venkatachalam, Kanaka Raju Pandiri, Jan Troß, Yubaraj Malakar, Seyyed Javad Robatajazi, Shashank Pathak, Itzik BenItzhak, Artem Rudenko, Daniel Rolles Stateselective excitation to a single (or a small subset of) excited neutral or ionic state(s), versus excitation to many possible states, with a broadband pulse is a powerful tool for the study and control of ultrafast molecular dynamics. We use a singleharmonic extreme ultraviolet (XUV) pulse, produced as the 11$^{\mathrm{th}}$ harmonic of an 800nm nearinfrared (NIR) laser, to ionize carbon dioxide (CO$_{\mathrm{2}})$ to the vibrationally excited ground (X $^{\mathrm{2}}\prod_{\mathrm{g}})$ state or to the first excited (A $^{\mathrm{2}}\prod_{\mathrm{u}})$ state of the monocation (CO$_{\mathrm{2}}^{\mathrm{+}})$. Using a delaycontrolled NIR probe pulse, the monocation is fragmented via different pathways to yield CO$^{\mathrm{+}}$ or O$^{\mathrm{+}}$ fragments. By comparing the results to a second measurement performed with the 13$^{\mathrm{th}}$ harmonic and to a similar pumpprobe experiment with a comb of harmonics, where the excited ionic state is determined by photoelectron and photoion coincidence, we can clearly separate the role played by each ionic state and confirm the role of molecular rotation in the timedependent ion yields. [Preview Abstract] 

K01.00056: RIXS Reveals Hidden Electronic Transitions of the Aqueous OH Radical L Young, G Doumy, P Ho, AM March, SH Southworth, Y Kumagai, A Al Haddad, MF Tu, L Kjellson, JE Rubensson, ZH Loh, T Debnath, M Bin Mohd Yusof, C Arnold, R Santra, WF Schlotter, S Moeller, G Cosolovich, J Koralek, M Minitti, M Simon, ML Vidal, S Coriani, K Nanda, AI Krylov We present RIXS spectra of the shortlived hydroxyl radical formed via proton transfer after ionization of pure liquid water [1]. Photoexcitation at the OHresonance at 526 eV gives rise to an energy loss feature at 4 eV, corresponding to the localized A$\leftarrow$X transition of the OH$(aq)$ radical  which is hidden by charge transfer transitions in the direct UV absorption spectrum. Theoretical calculations predict relative intensities of localized and deloclized RIXS transitions for OH$(aq)$ and the OH$^(aq)$ anion. Timeresolved RIXS highlights the localized transitions in the transient OH$(aq)$ radical and may be used to track the electronic state evolution of this chemically aggressive species. [1] ZH Loh {\it et al.} Science {\bf367}, 179182 (2020) [Preview Abstract] 

K01.00057: Vibrational relaxation of photoexcited electrons in fullerenes Esam Ali, Mohamed Madjet, Himadri Chakraborty Electronphonon coupling in stimulated molecular systems underpins the mobility and collection of carriers in organic devices [1], finds applications in radiation damage or astrochemistry, besides fundamental interests [2]. We study the vibrational relaxation dynamics of photoexcited electrons to the fullerene bandedge driven by electronphonon coupling. Time dependent density functional approach in the frame of nonadiabatic molecular dynamics (MD) [3] is used for simulations. MD with fewest switches surface hopping technique versus solving Schrodinger equation will be compared. Transition dipole moments, nonadiabatic electronphonon couplings, and ultrafast timedependent population decays from initially populated excited states will be presented. The work may motivate and complement recent interests [2] in ultrafast relaxation measurements in molecules by attosecond XUV pulses. [1] A. V. Akimov and O.V Prezhdo, \textit{J. Chem. Theory Comput.} \textbf{9}, 11 (2013); [2] Marciniak \textit{et al., Nature Comm.} \textbf{10}, 337 (2019); [3] Madjet \textit{et al., Phys. Chem. Chem. Phys.} \textbf{18}, 5219 (2016). [Preview Abstract] 

K01.00058: Study of Optically Excited Nitrobenzene through Nonlinear Ultrafast Polarization Spectroscopy Richard Thurston, Matthew Brister, Liang Tan, Niranjan Shivaram, Daniel Slaughter A Kerr gating pulse induces a third order nonlinear polarization response in a media of interest. This response can then sampled by a probing pulse resulting in a change in polarization of the probe that can be measured using the technique of optical Kerr effect spectroscopy. Such techniques have been used in the past to study dynamics in solid, liquid and gas phase systems on picosecond and femtosecond time scales. With the addition of a third excitation pulse, the nonlinear response of the system due to the gating pulse is modified. Here, we present measurements and electronic structure calculations of optically excited liquid nitrobenzene and discuss potential origins of the ultrafast polarization response of the system. We then discuss the extension of this method to study ultrafast dynamics in polyatomic gas phase systems. [Preview Abstract] 

K01.00059: Neutral dissociation and strongfield ionization of iodinecontaining halomethanes studied by timeresolved coincident ion momentum imaging Farzaneh ziaee, K. Borne, Kanka Raju P., T. Severt, Y. Malakar, B. Kaderiya, I. BenItzhak, A. Rudenko, D. Rolles, R. Forbes We study the UVinduced dissociation and NIRstrongfield ionization of CH3I and iodinecontaining dihalomethanes using a timeresolved coincident ion momentum imaging technique. Upon absorption of a single 263 nm photon, the molecules dissociate primarily via CI bond cleavage, and the dissociating neutral molecule is then ionized after a variable time delay by an intense 23fs 790 nm pulse. We compare the observed delaydependent ion kinetic energy release to a numerical model that relates the experimental data to the shape of the dissociative neutral and di/tricationic potential energy curves. Our timeresolved coincidence data also allows identifying competing two and threephoton excitation channels in the pump step. [Preview Abstract] 

K01.00060: Quantum wavemechanics of the simple pendulum via nondiffracting pendulum optical beams Enrique Galvez, Jake Freedman, Joel Auccapuclla, Yingsi Qin, Kristina Wittler We simulate quantummechanical probabilities for the simple pendulum using nondiffracting optical beams bearing Mathieu spatial modes. These are solutions to the Helmholtz equation in elliptical coordinates, whose angular form is identical to the Schrodinger equation for the simple pendulum. As a consequence the intensity of the modes in the Fourier plane are a direct mapping of the quantum mechanical probability. We investigate stationary states and wavepackets dynamics of the pendulum via modal superpopositions. [Preview Abstract] 

K01.00061: Interfacing single photons from a quantum dot with fiberconfined cold atomic ensemble Divya Bharadwaj, Paul Anderson, Jiawei Qiu, Yujia Yuan, Mohd Zeeshan, Rubayet Al Maruf, Philip Poole, Dan Dalacu, Michael Reimer, Michal Bajcsy We report our progress on development of a proofofprinciple hybrid quantum repeater. We generate entangled photon pairs from InAsP quantum dots (QD) embedded in semiconductor nanowire and store them in a quantum memory based on an ensemble of lasercooled caesium atoms confined inside a hollowcore optical fiber. We also investigate the wavelength conversion of single photons generated by the QD (894.6 nm) to telecom wavelength through fourwave mixing in the fiberconfined cloud. Our approach combines the advantages available from a deterministic and tunable solidstate source of bright entangled photon pairs with the potential for longlived quantum memory and highefficiency wavelength conversion that are achievable in laser cooled atomic cloud with large optical depths and tight confinement. [Preview Abstract] 

K01.00062: Towards Near IR and Telecom Photons Entangled With Ba+ James Siverns, John Hannegan, Jake Cassell, Qudsia Quraishi Towards Near IR and Telecom Photons Entangled With Ba$^{+}$ J. D. Siverns, J. Hannegan, J. Cassell, and Q. Quraishi Quantum memories with matterflying qubit entanglement may be used to establish a quantum network, however photons from trapped ions have limited range. We present our progress in generating matterentangled photons either at telecom wavelengths or at wavelengths compatible with neutral Rb[1,2]. This platform provides both long distance compatible, and userdefined, wavelengths for entanglementbased networking. A highNA lens is used to collect single 493nm photons, polarizationentangled with a single Ba$^+$ ion, and a nonlinear waveguide converts these photons to 780nm in a single stage or to telecom wavelengths using twostages. We discuss singlephoton production rates, conversion efficiencies, noise properties and factors affecting the entanglement fidelity. Finally, we examine potential rates and fidelities for homogenous Ba$^+$Ba$^+$ entanglement as well as for hybrid Ba$^+$Rb entanglement. [1] J. D. Siverns, J. Hannegan, Q. Quraishi, Sci. Adv. 5 (10), eaav4651 (2019) [2] A. N. Craddock, J. Hannegan, D. Ornelas, et al., PRL, 123, 213601 (2019) [Preview Abstract] 

K01.00063: Praseodymium ions for solid state quantum memory. Aditya Sharma, Robinjeet Singh, Martin Ritter, Eli Weissler, Kumel Kagalwala, Elizabeth Goldschmidt, Zachary Levine, Alan Migdall 

K01.00064: Abstract Withdrawn Macroscopic superpositions of coherent spin states (CSSs), or spin cat states (SCSs), are promising candidates for quantumenhanced measurement [1]. They are ideally generated from CSSs through oneaxis twisting dynamics [2]. This work reports our investigation for their generation via dipoledipole interaction (of strength g) between two spin systems whose collective spin operators are described by S and J, respectively. Starting from CSSs for both systems $S$ and $J$, the total system is found to evolve into a SCS at time $t=\pi /g$. The time evolution of the maximum increased variance $V_{+} =(\Delta S_{\psi } )_{\max }^{2} $, normal to the mean spin $\langle S\rangle $, is explicitly presented, whose peak can be regarded as an indicator of the generation of SCS. Our analytical result indicates that the halfwidth of the peak scales as $\propto 1/(N_{j}^{1/2} \sin \theta_{j} )$, where $\theta_{j} $ is the polar angle of the initial CSS for system $J$. This implies we can speed up the generation of SCS through proper tuning of the particle number $N_{j} $ and polar angle $\theta_{j} $. In addition, effects of decoherence will also be discussed. [1] L. Pezze et al., Rev. Mod. Phys. 90, 035005 (2018). [2] M. Kitagawa et al., Phys. Rev. A 47, 5138 (1993). 

K01.00065: Locally addressable cold atomic gas coupled to a high finesse optical cavity Emma Deist, Johannes Zeiher, Aron Lloyd, Alec Bohnett, Dan StamperKurn The study of manybody quantum systems via weak measurement and at the single atom level enables better understanding and control of such systems. Here we report on the first calibrations of an experimental apparatus 1) in which an atomic quantum gas is strongly coupled to an optical cavity and 2) with which we will locally address individual components of the gas for read out and control. The optical cavity is in a near concentric geometry with small radius of curvature mirrors to ensure high cooperativity while preserving transverse numerical aperture for local optical addressing. Optical addressing will be achieved by the trapping of atoms in individual far offresonant optical tweezers imaged onto the atoms through a high numerical aperture objective. We plan to destructively image the atomic cloud through the high resolution objective as well as to nondestructively monitoring the cloud dynamics though the dispersive interaction between the atoms and the cavity photonic mode by measuring the cavity output with a heterodyne detector. The combination of local addressability with nondestructive measurement presents the opportunity to use this apparatus to explore local Hamiltonian engineering, quantum measurement, open many body quantum dynamics, and quantum feedback. [Preview Abstract] 

K01.00066: Rydberg entanglement and clock operation in alkalineearth atom arrays~ Adam Shaw, Ivaylo Madjarov, Jacob Covey, Joonhee Choi, Anant Kale, Hannes Pichler, Alex Cooper, Vladimir Schkolnik, Jason Williams, Manuel Endres Alkalineearth atoms individually trapped in optical tweezers have gained prominence in recent years for their potential to combine quantum metrology, simulation, and computation in a single platform. Here we present our recent results in these directions with a dynamically reconfigurable 1D array of strontium atoms, showing both highfidelity entanglement and detection of Rydberg states, and separate development of an atomicarray optical clock. Both results exploit the clock state, which we use as a metastable groundstate~to achieve singlephoton Rydberg excitation and commensurately high Rabi frequencies. We observe both nonblockaded and blockaded Rabi oscillations with highfidelity (\textgreater 0.99) and detect the Rydberg state with similarly high fidelity through autoionization of the Rydberg electron. These results set the stage for current investigations into manybody physics and the development of quantum gates. [Preview Abstract] 

K01.00067: Realtime tracking and stabilization of cavitycoupled atomic gases Julian Wolf, Johannes Zeiher, Josh Isaacs, Jonathan Kohler, Dalila Robledo, Dan StamperKurn Ultracold atoms dispersively coupled to optical cavities are an ideal testbed for studying quantum measurement and control. Through sensitivity to the atomic state, an optical field in cavity can apply coherent backaction, modifying the dynamics of an atomic ensemble. In addition, photons leaving the cavity carry information about the realtime dynamics of the atomic ensemble. Here, we show how tracking of the dispersive cavity shift enables the noninvasive study of the time evolution of the atom number. We track the realtime evolution of the atom number during evaporative cooling in a cloud of lasercooled atoms. The minimallyinvasive measurement allows for extracting twotime atom number correlation functions, which provide further insight into the evaporation dynamics. Using feedback, we demonstrate the preparation of atomic ensembles with subPoissonian shottoshot atom number fluctuations. In a different set of experiments, we investigate dynamics of the collective spin of an atomic ensemble. Tracking the realtime energy exchange between light and spin reveals autonomous stabilization of the spin to the cavity drive. Our results illustrate the interplay of measurement and feedback in optical cavities and pave the way for future studies of feedbackstabilized atomic systems. [Preview Abstract] 

K01.00068: Experimental study of Spontaneous Emission in the Quantum Walk Jerry Clark, Gil Summy, Yingmei Liu, Sandro Wimberger We have recently realized a quantum walk of a BoseEinstein Condensate (BEC) of Rubidium 87 atoms by applying a periodic kicking potential to change the momentum state of the atoms and using microwave pulses to control the internal state. This periodic potential was generated by two counterpropagating, offresonant frequency stabilized laser beams. This setup is stable to generate a quantum walk for tens of steps, however, it is affected by spontaneous emission induced by the same laser beams used to generate the kicking potential. We have investigated this spontaneous emission by varying a few parameters including the power of the kicking laser beams. The results of this study allow us to determine the robustness of the quantum walk during the experiment. These findings can also be used in other related experiments involving the use of BECs as a basis. [Preview Abstract] 

K01.00069: Steadystate phase diagram of a weakly driven chiralcoupled atomic chain HsiangHua Jen A chiralcoupled atomic chain of twolevel quantum emitters allows strong resonant dipoledipole interactions, which enables significant collective couplings between every other emitters. This chiralcoupled system can be made of an atomnanofiber or atomwaveguide interface, where nonreciprocal decay channels emerge. We theoretically study distinct interactiondriven quantum phases of matter with chiral couplings and infiniterange dipoledipole interactions mediated by onedimensional nanophotonics systems. The steadystate phase diagram in the low saturation limit involves states with extended distributions, crystalline orders, biedge/hole excitations, and a region of chiralflow dichotomy. We distinguish these phases and regions by participation ratios and structure factors, and find two critical points which relate to decoherencefree subradiant sectors of the system. We further investigate the transport of excitations and emergence of crystalline orders under spatiallyvarying excitation detunings, and present nonergodic butterflylike system dynamics in the phase of extended hole excitations with a signature of persistent subharmonic oscillations. Our results pave the way toward simulations of manybody states in nonreciprocal quantum optical systems. [Preview Abstract] 

K01.00070: Strong coupling of two individually controlled atoms via a nanophotonic cavity Polnop Samutpraphoot, Tamara Dordevic, Paloma Ocola, Brandon Grinkemeyer, Hannes Bernien, Crystal Senko, Vladan Vuletic, Mikhail Lukin We demonstrate photonmediated interactions between two individually trapped atoms coupled to a nanophotonic cavity. Specifically, we observe collective enhancement when the atoms are resonant with the cavity, and level repulsion when the cavity is coupled to the atoms in the dispersive regime. Our approach makes use of individual control over the internal states of the atoms, their position with respect to the cavity mode, as well as the light shifts to tune atomic transitions individually, allowing us to directly observe the anticrossing of the bright and dark twoatom states. These observations open the door for realizing quantum networks and studying quantum manybody physics based onatom arrays coupled to nanophotonic devices. [Preview Abstract] 

K01.00071: LightAtom Interfaces from $10^9$ to $10^14$ Hz David Meyer, Zachary Castillo, Kevin Cox, Paul Kunz The character of specific lightatom interactions is a critical aspect to nearly all quantum technologies, from sensors to simulators to memories and repeaters. We consider the design of this interface for two ongoing experiments in our lab: a Rydberg electric field sensor and a multiplexed quantum memory. Rydberg electric field sensors suffer in sensitivity from the limited coupling strength to freespace modes as compared to antennabased sensors. We will present our progress at increasing this coupling by orders of magnitude, opening the door to truly quantumoptical regimes. Our coldatom quantum memory experiment takes advantage of a unique ringcavity design to achieve strong coupling. Furthermore, our system is able to write, store, and readout hundreds of holograms in our atoms. This unique combination of large multiplexing capacity with efficient strong coupling to a single optical mode enables a path to a functional quantum repeater. [Preview Abstract] 

K01.00072: Mechanical modes of an `Alligator' photonic crystal waveguide. Zhongzhong Qin, JeanBaptiste Beguin, Alexander Burgers, Xingsheng Luan, SuPeng Yu, H Jeff Kimble We present our experimental observations on optomechanical coupling for guided optical light fields of an `Alligator' photonic crystal waveguide (APCW). Quasiodd harmonics of the fundamental mechanical mode are observed for optical light frequency in the waveguide regime, while both quasiodd and quasieven harmonics are observed for optical light frequency near the bandedge of the APCW. A novel theoretical model of transduction mechanisms is developed to explain the experimental observations. [Preview Abstract] 

K01.00073: Engineering AtomPhoton and AtomAtom Interactions with Silicon NanoPhotonics Artur Skljarow, Wolfram Pernice, Harald Kuebler, Robert Loew, Tilman Pfau, Hadiseh Alaeian Interfacing thermal atomic vapors with Nanophotonics on a chip provides a unique testbed for manipulating the interaction of atoms with photons and other atoms on a miniaturized scale. We studied an integrated silicon photonic chip, composed of several subwavelength ridge and slot waveguides, immersed in a microcell with rubidium vapor. Employing twophoton excitation, including a telecom wavelength, we observed that the guided mode transmission spectrum gets modified when the photonic mode is coupled to rubidium atoms through its evanescent tail. The tight confinement of the field around the waveguide leads to a large optical nonlinearity at the telecom wavelength within the FemtoWatt power range. To benefit further from the small mode volume below the difraction achievable in Nanodevices, we investigated the coupling of atomic vapor to slot waveguides. The slot mode constrains the probed atomic density to an effective onedimension hence leading to geometry dependent atomlight and atomatom interactions. The results of this study help to understand the capabilities and limits of hybrid systems of thermal atoms and Nanophotonics and pave the way towards onchip, integrated and atombased quantum technologies. [Preview Abstract] 

K01.00074: Microring Resonators on a Suspended Membrane Circuit for Atom–Light Interactions TzuHan Chang, Brian Fields, May Kim, Xinchao Zhou, ChenLung Hung Atoms that are trapped and interfaced with light in nanophotonic circuits form an exciting new platform for applications and fundamental research in quantum optics and manybody physics. The ability to induce tunable longrange atomatom interactions with photons, and the formation of an organized atom–nanophotonic hybrid lattice presents a novel opportunity to explore collective quantum optics and manybody physics. Our system is based on high quality silicon nitride microring resonators fabricated on a transparent membrane substrate. This platform is compatible with laser cooling and trapping with cold atoms and with potentially high cooperativity parameters C $\approx$ 500, thus holding great promises as an onchip atom cavity QED platform. We present our ongoing experiment effort for coupling atoms to a microring and further fabrication improvements for quality factor for creating strong atomphoton coupling. [Preview Abstract] 

K01.00075: Reduced volume and reflection for optical tweezers with radial LaguerreGauss beams JeanBaptiste S. B\'eguin, Zhongzhong Qin, Julien Laurat, Xingsheng Luan, Alexander P. Burgers, H. Jeff Kimble Our progress to develop advanced capabilities for the integration of cold atoms and nanophotonics is documented at https://doi.org/10.1364/OPTICA.384408. At DAMOP we will describe a critical new component of this effort related to coherent superpositions of radial LaguerreGauss beams that lead to tightly focused optical tweezers with reduced volume and increased particle trapping frequency. Beyond freespace, such superpositions can enable the efficient transport of atoms via optical tweezers directly to trap sites near the surfaces of nanoscopic optical devices. More generally, the rapid variation of the Gouy phase for wavelengthscale focal regions could enable phasecontrast microscopy within heterogeneous sample volumes. [Preview Abstract] 

K01.00076: Topological Quantum Matter Made of Light Lukas Palm, Claire Baum, Matt Jaffe, Logan Clark, Nathan Schine, Ningyuan Jia, Jonathan Simon Topological states of matter can be realized using cavity Rydberg polaritons, quasiparticles composed partly of cavity photons and partly of atomic Rydberg excitations. These polaritons interact strongly thanks to the Rydberg excitations and have individual particle behaviors determined by their photonic degree of freedom and shaped through a twisted optical cavity. We recently demonstrated that this hybrid system is a fruitful platform for building strongly correlated quantum states in an artificial gauge field by preparing a synthetic twoparticle Laughlin state of photons for the first time. Building on this pioneering work, we describe our recent efforts to enable larger systems by designing a highly degenerate cavity in combination with improved state readout through Rydberg enhanced imaging. [Preview Abstract] 

K01.00077: Doing more with FabryPerot resonators: lowloss intracavity optics and realtime dynamics Lavanya Taneja, Mark Stone, Aziza Suleymanzade, Jonathan Simon Recent developments have shown that FabryPerot resonators are a powerful tool for manipulating and characterizing light, and present unique opportunities to tailor the dispersion of strongly interacting photons when combined with Rydberg EIT. To extend these exciting possibilities, we are exploring the limits of optical resonators, demonstrating that intracavity lenses and electrooptic crystals can be incorporated without significantly impacting the resonator finesse (${>10}^{3})$. Introduction of lenses opens avenues for aberrationcompensation and stronger lightmatter coupling, while electrooptics present possibilities to explore Floquet physics with optical photons. We also employ the intracavity electrooptic modulator to achieve MHzbandwidth resonator locking. Finally, we demonstrate spacetimeresolved measurement of the transverse motional dynamics of intracavity photons, paving the way for exploring curved space dynamics of photons on multiply connected surfaces. [Preview Abstract] 

K01.00078: 3D Printing an External Cavity Diode Laser Housing Erik Brekke, Tyler Bennett, Eric Hazlett The ability to control the frequency of an external cavity diode laser is an essential component for undergraduate laboratories through atomic research. Typically the housing for the diffraction grating and piezo is either commercially purchased or milled from metal. Here we present an alternative to these more expensive options using 3D printing, a commonly available tool in many physics departments. We have examined the laser performance using atomic spectroscopy and selfheterodyne interferometry. The performance and affordability of these designs make them an appealing option for future use. [Preview Abstract] 

K01.00079: Dualwavelength laser frequency stabilization on a single ULE cavity for strontium Rydberg experiments Yi Lu, Joseph Whalen, Soumya Kanungo, F. Barry Dunning, Thomas Killian A narrowlinewidth stable laser is crucial for both laser cooling and Rydbergatom creation in cold atomic gases. Here we present a dualwavelength laser frequency stabilization system based on a single ultra low expansion (ULE) reference cavity that is suitable for laser cooling on the strontium $^1S_0$$^3P_1$ intercombination line and exciting atoms to the triplet Rydberg series. The standard PoundDreverHall (PDH) technique is used to lock a 689nm diode laser and a 640nm optical parametric oscillator seeded by a 1064nm fiber laser. The 689nm laser is used for laser cooling on the $^1S_0$$^3P_1$ line and also provides the first photon in the twophoton Rydberg excitation. The 640nm light is frequency doubled to excite the $^3P_1$ state to a Rydberg level. The frequencies of both lasers are tunable while locked by adjusting the offset frequencies (provided by electrooptic modulators) between the lasers and the cavity modes. A servo bandwidth of 1.2MHz is achieved for the 689nm system while the 640nm laser has a target lock bandwidth of 30kHz due to the slower response of the fiber master. Longterm drift of the ULE cavity is measured to be $\sim$25kHz/day and is compensated by continual offsetfrequency adjustment. [Preview Abstract] 

K01.00080: An OpticallyLocked Interferometer for Attosecond Pump Probe Setups John Vaughan, Joseph Bahder, Brady Unzicker, Davis Arthur, Morgan Tatum, Trevor Hart, Geoffrey Harrison, Spenser Burrows, Patrick Stringer, Guillaume Laurent Ultrafast pumpprobe measurements at the attosecond time scale are generally achieved by exposing the target to both an attosecond pump pulse and a phaselocked IR probe field, with a variable time delay between the two. To fully exploit the temporal resolution of attosecond pulses for timeresolved studies, the time delay between the pump and probe pulses must be controlled with attosecond resolution as well. This requires the ability to linearly vary the delay with time steps of the order of the pulse duration (or less), and maintain it to any desired value over extended periods of time. We present the design and performance of an active stabilization system for attosecond pumpprobe setups based on a Mach Zehnder interferometer configuration. The system employs a CW laser propagating coaxially with the pump and probe beams in the interferometer. The stabilization is achieved with a standalone feedback controller that adjusts the length of one of its arms to maintain a constant relative phase between the CW beams. With this system, the time delay between the pump and probe beams is stabilized within 10 as rms over several hours. [Preview Abstract] 

K01.00081: Cavityenhanced detection of transient absorption signals Fernanda C. RodriguesMachado, Pauline Pestre, Liam Scanlon, Shirin A. Enger, Lilian I. Childress, Jack C. Sankey We present a simple, highdutycycle, cavityenhanced optical absorption measurement technique based on a delaylimited PoundDreverHall sideband locking technique. The chosen circuit naturally provides realtime readout of the amplitude quadrature, which can be mapped onto the cavity's internal loss rate. Our proofofconcept device comprises a 5cmlong FabryPerot cavity with a 400 kHz bandwidth (finesse 7000, 400 ns power ringdown), and a feedback bandwidth of several MHz, limited primarily by the group delay of our electronics. This technique could readily be applied to other optical resonators such as fiber cavities, with potential applications in radiation dosimetry. [Preview Abstract] 

K01.00082: A robust, fielddeployable, lowcost modelocked laser oscillator for deployed optical atomic clocks. Henry Timmers, Dylan Tooley, Bennett Sodergren, Ryan Robinson, Kurt Vogel, Kevin Knabe Frequency combs have been investigated in the laboratory over the course of the last 25 years in a wide range of implementations and applications including but not limited to optical atomic clocks, precision metrology, precision spectroscopy, LIDAR, and lowphasenoise RF generation. While the Nobel prize winning technology of frequency combs have shown their usefulness in a variety of applications, there have been few demonstrations of this technology in realworld applications. Here we present a modelocked oscillator that has been designed to be environmentally robust and low cost, while maintaining suitability for use in frequency comb applications. Vescent Photonics has designed environmentally robust oscillators and frequency combs for government programs including satellites and terrestrial moving platforms. These designs allow for repetition rate matching at the time of manufacture, which is an important consideration for integration of this technology into several key applications. Vescent Photonics will report on the performance, environmental robustness, and cost of these fiber laser systems. [Preview Abstract] 

K01.00083: Generating HighPower Bragg Pulses for Atom Interferometry Andrew Neely, Zack Pagel, Weicheng Zhong, Holger Müller Achieving lower systematic errors in atom interferometry calls for greater optical power. To this end, we are building a highpower quasi CW laser system, generating 150$\mu$s pulses with a 100Hz repetition rate of light near the 852 nm D2 line of Cesium by amplifying a 500mW Nd:YAG CW seed to produce up to 10 kW peak power at 1064 nm in 1 J pulses. This is converted to several kW of peak power at 532 nm using second harmonic generation in LBO. We will use this to pump optical parametric amplification in periodically poled SLT, seeded by spectroscopically stabilized 852 nm light. This system is designed to deliver more than 1 kW peak power and should allow us to realize higherorder Bragg diffraction in our atomic fountain, a major step towards a higher precision measurement of the fine structure constant. [Preview Abstract] 

K01.00084: Generating GreenbergerHorneZeilinger States in Remote Trapped Ions Harris RutbeckGoldman, Paige Haas, David Hucul, Zachary Smith, Michael Macalik, Justin Phillips, James Williams, Carson Woodford, Boyan Tabakov, KathyAnne BrickmanSoderberg Quantum networks promise ultrasecure lines of communications that are both tamper proof and tamper evident. Remote entanglement, the required firststep towards a quantum network, has been demonstrated in a number of systems. Here we describe a protocol to extend twoqubit remote entanglement to generate a GreenbergerHorneZeilinger (GHZ) state comprising three remote trappedion qubits. Twoparticle remote entanglement combined with local operations and communication of classical bits can generate largescale, networksized, multiparticle entanglement for distributing quantum information. Quantum communication channels are desirable as they may enable secure links that could reveal the presence of eavesdroppers and protect critical information. [Preview Abstract] 

K01.00085: Measurement of Dickenarrowed optical transitions in warm alkali vapor for different buffer gas pressures Kefeng Jiang, Jianqiao Li, Ken DeRose, Linzhao Zhuo, Samir Bali We demonstrate the quadratic dependence on the relative pumpprobe beam angle of the electromagnetically induced transparency narrowed transition linewidth  a defining signature of Dicke narrowing of the optical transition linewidth. We vary the buffer gas pressure thus varying the atomic spatial localization and hence the size of the “quantization box” causing the Dicke narrowing. By carefully defining the zerovalue for the relative angle where the linewidth is measured to be a minimum, we find that our data agrees with the theory better than ever before, with no fitparameters. A Ramseylike measurement of ground state decay rates between hyperfine and Zeeman sublevels is performed to investigate the lower limit on the EIT linewidth for case where the pump and probe are perfectly collinear. [Preview Abstract] 

K01.00086: Yb Rydberg Atom Arrays Sam Saskin, Jack Wilson, Yijian Meng, Shuo Ma, Rohit Dilip, Alex Burgers, Jeff Thompson Arrays of lasercooled neutral atoms in optical tweezers are a promising platform for quantum science, because of their flexibility and the potential for strong interactions via Rydberg states. Recent experiments with alkalineearth atoms have demonstrated significant advantages in terms of coherence and control. We will present recent results with Yb Rydberg atoms in optical tweezer arrays, including novel spectroscopy of Yb Rydberg states, trapping Yb Rydberg atoms in tweezers using the polarizability of the Yb+ ion core, and progress towards qubit operations using the $^{171}$Yb nuclear spin levels. [Preview Abstract] 

K01.00087: Dynamics of entanglement entropy and particle number distribution in disordered, free fermionic systems Razmik Unanyan, Maximilian KieferEmmanouilidis, Jesko Sirker, Michael Fleischhauer The information contained in a quantum state $\rho$ is quantified by the entanglement entropy $S=\textrm{tr}(\rho \ln \rho)$, which is difficult to measure. For systems with particle number conservation, $S$ is the sum of the number entropy, $S_N$, and the configuration entropy, $S_{conf}$, which have been measured recently in a coldgas experiment [1]. We here show that for systems of noninteracting fermions, including the case of disorder, the time evolution of the second Renyi entropy $S^{(2)}=\ln\textrm{tr}(\rho^2)$ is determined by the exponent of corresponding number entropies. As a consequence in free fermionic systems a dynamical growth of entanglement is always related to a slower growth of the number entropy. We numerically illustrate this for different tightbinding fermionic models including the case of offdiagonal disorder for which the entanglement entropy shows an ultra slow, double logarithmic growth in time and give an outlook to interacting systems showing manybody localization.\\ [1] A. Lukin, \textit{et al.} \textit{Probing entanglement in a manybody localized system}, Science \textbf{364}, 256 (2019). [Preview Abstract] 

K01.00088: MeasurementInduced Phase Transitions in Longrange Quantum Circuits Maxwell Block, Yimu Bao, Soonwon Choi, Ehud Altman, Norman Yao Recent theoretical work has demonstrated a phase transition in the dynamics of quantum entanglement, originating from competition between scrambling unitary evolution and unwanted coupling to a classical bath, represented by measurements. In realistic systems, the presence of longrange interactions often allows for parametrically faster scrambling dynamics, which may qualitatively modify the transition. In this poster, we show this is indeed the case: longrange interactions change the universality of the transition. More specifically, we study 1D longrange quantum circuits, interspersed with projective measurements, where each unitary is a random twoqubit Clifford gate with range sampled from a $1/r^\alpha$ power law distribution. We find that the parameter 𝛼 of the interaction has a dramatic effect: for $\alpha>3$, the critical exponents agree with studies of nearestneighbor hybrid circuits, while for $\alpha<3$ the critical exponents change continuously with $\alpha$. Moreover, for $\alpha<2$ the arealaw scaling crosses over to a subvolume law scaling in which entanglement entropy grows with system size, even under high measurement rates. We conclude with a resource analysis of realizing the transition in several AMO quantum simulators. [Preview Abstract] 

K01.00089: Observation of nanoscale hydrodynamics in a strongly interacting dipolar spin ensemble in diamond Francisco Machado, Chong Zu, Bingtian Ye, Bryce H Kobrin, Thomas Mittiga, Satcher Hsieh, Prabudhya Bhattacharyya, Tim O Hoehn, Soonwon Choi, Christopher Laumann, Dmitry Budker, Norman Y Yao Bridging the gap between the microscopic description of quantum manybody dynamics and its macroscopic emergent phenomena remains an important open problem. We experimentally tackle this challenge by probing the nanoscale diffusion in strongly interacting solidstate spin ensembles in diamond. More specifically, we harness nitrogenvacancy (NV) centers as effective nanoscale quantum probes to initialize and detect the local spin polarization in a highdensity ensemble of substitutional nitrogen defects (P1 centers). After preparing an outofequilibrium initial state of the P1 ensemble, we monitor its quantum quench dynamics and observe that the late time behavior can be described by emergent hydrodynamics, from which we extract the diffusion coefficients. To establish a quantitative connection between the observed hydrodynamics and the underlying microscopic Hamiltonian, we develop an effective semiclassical description for the spin dynamics. Crucially, this description allows us to understand how the interplay between disorder and longrange interactions leads to diffusiveyet nongaussiandynamics in the experimental observations. [Preview Abstract] 

K01.00090: Nonequilibrium dynamics of a superfluid Fermi gas with timeperiodic modulation: Higgs mode and higherorder harmonic excitation KuiTian Xi, Qijin Chen, Gentaro Watanabe Motivated by the recent experiment on observation of the Higgs mode in a strongly interacting superfluid Fermi gas [A. Behrle \textit{et al}., Nat. Phys. \textbf{14}, 781 (2018)], we study the nonequilibrium dynamics of a superfluid Fermi gas with a timeperiodic modulation in the BCSBEC crossover by solving the timedependent Bogoliubovde Gennes (BdG) equations. By tuning the modulation amplitude and frequency of the coupling constant, we have demonstrated that the Higgs mode can be excited with the timeperiodic modulation. For a small modulation amplitude, the longlived Higgs mode comparing to the current experimental result exists when the modulation frequency is slightly reddetuned. When the modulation frequency is bluedetuned, the singleparticle excitation appears along with the Higgs mode. For a large modulation amplitude, the higherorder harmonic excitation is generated due to the nonlinearity. The exploration of other optimal ways of exciting the Higgs mode in a superfluid Fermi gas is also discussed. [Preview Abstract] 

K01.00091: Towards quantum gas microscopy of fermions in pbands Jin Yang, Liyu Liu, Jirayu Mongkolkiattichai, Jae Woo Kim, Davis Garwood, Grace Minesinger, Peter Schauss Quantum gas microscopy is a novel technique which can realize singlesite and singleatom resolved detection of strongly correlated quantum gas in optical lattices. We report our recent progress on constructing a quantum gas microscope enabling the imaging of Lithium 6 in pbands. In addition to the ground band, higher bands are an essential ingredient in Hubbard models for real materials leading to important new effects like orbital ordering which are not well studied up to now. Exotic quantum phases arise by competition between orbital ordering and spinordering. Here, we present our latest progress towards the preparation of a twodimensional Fermi gas and discuss our approach to implementing a twodimensional optical lattice and loading the atoms into this lattice. [Preview Abstract] 

K01.00092: Search for the FFLO Phase in the 1D3D Crossover of a SpinImbalanced Fermi Gas Jacob A. Fry, Bhagwan D. Singh, Randall G. Hulet 

K01.00093: Abstract Withdrawn Characterizing the dynamics of vortices in a strongly interacting Fermi gas is critical in understanding the quantum turbulence of a manybody system. Of particular interest is the annihilation dynamics of vortices with opposing signs. A clearer picture of the nonequilibrium dynamics, such as the KibbleZurek(KZ) mechanism, can be obtained once we clarify the annihilation dynamics of vortices. One of the key issues for investigating the annihilation dynamics of vortices is the small size of the vortex core and the limited imaging resolution. Conventionally, this problem has been circumvented by applying a timeofflight(TOF) before imaging. Here, we intend to resolve this limit by employing a noncycling transition for \textit{in situ} optical imaging in a strongly interacting Fermi gas of $^{\mathrm{6}}$Li. Moreover, we plan to investigate the nature of the vortex dynamics and its core structure across the BCSBEC crossover, where the microscopic physics of superfluidity evolves from a BardeenCooperSchrieffer(BCS) superfluid of longrange Cooper pairs to a BoseEinstein condensate of tightly bound diatomic molecules. 

K01.00094: Measurement of spin susceptibility in ultracold lithium6 gases by a radiofrequency method Feng Xiong, Yun Long, Colin Parker Cold atoms have been widely applied in simulating material systems, and in particular ``pseudogap'' effects in the BECBCS crossover model make for interesting comparisons to the highTc cuprates. We present a radiofrequency (RF) method to create imbalances between equilibrium RFdressed states and measure the equilibrium spin susceptibility of lithium6 atoms in a trap with a magnetic gradient. We will present a conceptual overview of this method, which relies on the small but nonzero difference in the magnetic moment between hyperfine states. For this purpose, the second lowest two hyperfine states of lithium6 are chosen so that we can take advantage of their large magnetic differential moment. Here we emphasize the experimental setup, including the imaging system, and show benchmarking measurements for the spin susceptibility of weakly interacting gases, the dressedspin relaxation time, and discuss possible parasitic effects. [Preview Abstract] 

K01.00095: Controlling spin and thermoelectric transport in an atomic transport experiment Philipp Fabritius, Samuel Hausler, Martin Lebrat, Jeffrey Mohan, Mohsen Talebi, Laura Corman, Tilman Esslinger We report on the control of the thermoelectric transport properties of a strongly interacting Fermi gas flowing through a quasitwodimensional contact and second on the control of spin inside a quantum point contact (QPC) and the effects of dissipation on a superfluid. The versatility of coldatom techniques allows us to precisely define a QPC using light potentials, to directly measure particle, heat and spin currents and to tune interatomic interactions. In a first experiment, we probe the thermoelectric effects induced by a temperature difference across a twodimensional channel. We use an attractive gate beam as well as an repulsive wall beam to change the relative strength of channel and reservoir contributions to the thermoelectric transport. This allows us to tune the particle transport going from hot to cold to going from cold to hot. In a second experiment, we locally lift the spin degeneracy of atoms inside the QPC usingan optical tweezer tuned very close to atomic resonance. Tuning the laser further away from the atomic resonance we also look at how a superfluid is reacting to dissipation and how its transport properties are effected. These results open the way to the quantum simulation of the coupling between spin, heat and particle currents with cold atoms. [Preview Abstract] 

K01.00096: Observation of Phase Coherence and Superfluidity in a Strongly Interacting Twodimensional Fermi Gas Thomas Lompe, Niclas Luick, Lennart Sobirey, Markus Bohlen, Hauke Biss, Henning Moritz We present our studies of phase coherence and superfluidity in strongly interacting twodimensional Fermi gases. We observe phase coherence by creating a tunnel junction in a homogeneous 2D Fermi gas and measuring the frequency of Josephson oscillations as a function of the phase difference across the junction. We find excellent agreement with the sinusoidal current phase relation of an ideal Josephson junction. We probe superfluidity by dragging a periodic potential through a homogeneous 2D gas and observing the characteristic onset of dissipation above a critical velocity $v_c$. We measure the excitation spectrum of a lowtemperature system as a function of interaction strength and find that for a gas of tightly bound molecules there is a welldefined phononic excitation at the speed of sound, as expected from the Landau criterion. This phononic excitation persists into the crossover regime until pair breaking becomes the primary mechanism of dissipation on the BCS side of the resonance. We also present our progress towards studying the temperature dependence of the excitation spectrum to determine the critical temperature for superfluidity of a 2D Fermi gas as a function of interaction strength. [Preview Abstract] 

K01.00097: Transport dynamics of fermions in an optical lattice Rhys Anderson, Darby Bates, Frank Corapi, Cora J. Fujiwara, Vijin Venu, Fudong Wang, Peihang Xu, Frederic Chevy, Joseph H. Thywissen We measure the conductivity spectrum of ultracold fermionic atoms in an optical lattice through highresolution imaging in a quantum gas microscope. By applying a timevarying force to atoms confined to the lattice, we sample their current response at multiple frequencies. We observe that the current response scales linearly with the forcing, providing an experimental demonstration of Ohm's Law for neutral atoms. Broadening of the conductivity spectrum under varying external parameters elucidates how the dissipation of current is affected by fermionfermion collisions. Furthermore, the spectral weight of the response satisfies a sum rule in the limit of small lattice depth, but diminishes as the depth or temperature increase, reflecting an increase in the bandaveraged effective mass. This spectral weight characterizes the strength of the current response to an impulse, and therefore underpins the resistivity. As our measurements approach a hightemperature regime, its inverse is shown to approach Tlinear behaviour. The recent implementation of a DMD in the system allows for further flexibility in studying and probing the dynamics. This tool enables the creation of customizable local potentials for both initiating and modifying current response. [Preview Abstract] 

K01.00098: SU(N) enhanced interactions and reduced number fluctuations in a quantum degenerate Fermi gas Thomas Bilitewski, Lindsay Sonderhouse, Christian Sanner, Ross B. Hutson, Akihisa Goban, Lingfeng Yan, William R. Milner, Ana Maria Rey, Jun Ye We study theoretically and experimentally an interacting $SU(N)$ Fermi gas of $\,{}^{87}$Sr, where N can be as large as 10, in the quantum degenerate regime. The presence of $N$ distinct spin species results in an enhanced interaction due to the larger number of available scattering partners, thus, leading to significant interaction effects even for a nominally weakly interacting gas. Using all 10 spin states during evaporation allows to have efficient sample preparation while reaching deep degeneracy, with $T/T_F = 0.07$ in under 3 s. We employ a kinetic approach and scaling ansatz to obtain the equilibrium and out of equilibrium phase space distribution of the interacting harmonically trapped gas, which allow us to extract the insitu and timeofflight density profiles as well as the isothermal compressibility. While generically the effects of lower temperature or interactions are difficult to disentangle, we demonstrate the interacting nature of the system via the timeofflight density anisotropy. The experimentally measured density profiles and number fluctuations are in good agreement with the theoretical predictions, and enable a precise thermometry and characterisation of the interacting quantum gas. [Preview Abstract] 

K01.00099: Highpower optical transport of ultracold fermions using focustunable lens Jere Mäkinen, Gabriel Assumpcao, Yunpeng Ji, Grant Schumacher, Franklin Vivanco, Nir Navon We present an alloptical setup designed to transport a trapped cold cloud of $^6$Li over a macroscopic distance of 30 cm, based on a focustunable lens. We transport the atoms from the initial preparation chamber to a dedicated glass cell with increased optical access by displacing the focus of the focustunable lens. We estimate the transport efficiency by measuring the atom number and temperature both before and after the transfer. We further characterize the loading and posttransport focus stability. We show that the atom number and focus fluctuation amplitudes can be greatly reduced by an stabilization of lens temperature and the focustunable lens control current. We demonstrate the robustness of the optical transport by preparing a molecular BEC after transporting the atoms to the glass cell. [Preview Abstract] 

K01.00100: Quantum Turbulence: Generation and Evolution in Bosonic and Fermionic Superfluids Khalid Hossain, Michael Forbes, Konrad Kobuszewski, Piotr Magierski, Gabriel Wlazlowski Interactions between quantized vortices govern the generation and decay of quantum turbulence. Accurate simulation of the vortex dynamics employing models like timedependent Superfluid Local Density Approximation (TDSLDA) can be computationally quite expensive for a macroscopically large Fermionic sample. To understand these interactions and the instabilities inherent to the turbulent regimes, we propose using Extended Thomas Fermi (ETF) model, similar to the GrossPitaevskii (GPE) with a finite temperature extension. In this work, we investigate the role of temperature in the evolution of turbulence in the Unitary Fermi Gas (UFG) and validate against TDSLDA. [Preview Abstract] 

K01.00101: Homogeneous Fermi Gases in the BECBCS Crossover Yunpeng Ji, Gabriel Assumpcao, Jere Makinen, Grant Schumacher, Philip Tuckman, Franklin Vivanco, Nir Navon 

K01.00102: Abstract Withdrawn The advantage of deep reinforcement learning (DRL) [1] over traditional control theory has been demonstrated for broad topics including adiabatic quantum computation, quantum control, and quantum state preparation. In this work, proximal policy optimization algorithm [2] is adapted to update neural network during training due to its sophisticated control of both discrete and continuous parameters. We will first illustrate enhanced spin squeezing based on oneaxis twisting interaction aided by discrete operations as a benchmark to test our DRL frame [3]. A simple control protocol is successfully uncovered that provides enhanced squeezing to near the Heisenberg limit. We then employ the DRL agent to study quantum state preparation in a spin1 atomic BoseEinstein condensate (BEC) with consecutive controlled parameters, for both ideal (no decoherence) and realistic (loss included) models. Based on the protocols from DRL, we observe fast and effective controlled generations of both TwinFock state and Dicke state in our rubidium87 BEC system. [1] M. Bukov et al, Phys. Rev. X 8, 031086 (2018), [2] J. Schulman et al, arXiv:1707.06347 (2017). [3] F. Chen et al, Phys. Rev. A 100, 041801(R) (2019). 

K01.00103: Spinoscillation dynamics beyond the singlemode approximation for a harmonically trapped spin1 BoseEinstein condensate Jianwen Jie, Qingze Guan, Shan Zhong, Arne Schwettmann, Doerte Blume Compared to singlecomponent BoseEinstein condensates, spinor BoseEinstein condensates display much richer dynamics. In addition to density oscillations, spinor BoseEinstein condensates exhibit intriguing spin dynamics that is associated with population transfer between different hyperfine components. This work analyzes the validity of the widely employed singlemode approximation when describing the spin dynamics in response to a quench of the system Hamiltonian. The singlemode approximation assumes that the different hyperfine states all share the same timeindependent spatial mode, i.e., the field operator for each of the hyperfine states is expanded in terms of one and the same spatial basis state. This implies that the resulting spin Hamiltonian only depends on the spin interaction strength and not on the density interaction strength. Taking the spinor sodium BoseEinstein condensate in the $f=1$ hyperfine manifold as an example, it is found that the singlemode approximation misses, in some parameter regimes, intricate details of the spin and spatial dynamics. Our results have implications for a variety of published and planned experimental studies. [Preview Abstract] 
On Demand 
K01.00104: Optimizing the Efficiency of Spin Singlet Production in LatticeConfined Spinor Condensates Jared Austin, Zihe Chen, Zachary Shaw, Lichao Zhao, Yingmei Liu Manybody spin singlet states have been widely suggested as ideal candidates in investigating quantum metrology and quantum memory. In this poster, several experimental sequences for producing spin singlets in an antiferromagnetic spinor condensate confined by a cubic optical lattice are presented. We demonstrate how to optimize spin singlet production efficiency by properly varying the initial atom number distributions, which are precisely measured from nonequilibrium spin dynamics. Two experimental methods for detecting spin singlet states are also discussed. [Preview Abstract] 

K01.00105: Microwave Control of Spin Dynamics in F=1 Sodium Spinor BoseEinstein Condensates Qimin Zhang, Shan Zhong, Jianwen Jie, Qingze Guan, Isaiah Morgenstern, Hio Giap Ooi, Anita Bhagat, Delaram Nematollahi, Hyoyeon Lee, D. Blume, Arne Schwettmann We present our latest experimental data on controlling spin dynamics in F=1 sodium spinor BoseEinstein condensates via microwave dressing. By applying quenches and timedependent microwave pulse sequences, we implement nonlinear atom interferometry in spinspace in the long evolution time regime, $t \gg h/c$, where $c$ is the spindependent interaction energy. We also investigate the breakdown of commonly made approximations such as the singlemode approximation and the undepleted pump approximation for certain parameters. [Preview Abstract] 

K01.00106: Creation of a Skyrmion in a BiaxialNematic Magnetic Phase Alina Blinova, Tuomas Ollikainen, Yixin Xiao, Mikko M{\"o}tt{\"o}nen, David Hall Spin2 BoseEinstein condensates exhibit several magnetic phases with symmetries different from those of the spin1 case, extending the variety of possible topological excitations. For example, threedimensional skyrmions in the spin2 biaxial nematic (BN) phase involve a topologically nontrivial winding in the order parameter, where the space is described at each point by the orientation of a square . We present evidence for the creation of a threedimensional BN halfskyrmion using magnetic imprinting techniques, as well as progress towards the experimental realization of a full BN skyrmion [Preview Abstract] 

K01.00107: Bulk Viscosity and the Virial Expansion for a ThreeComponent Fermi Gas in One Dimension Jeff Maki, Carlos Ordonez We explore the transport properties of threecomponent Fermi gases confined to one spatial dimension, interacting via a threebody interaction, in the high temperature limit. At the classical level, the threebody interaction is scale invariant in one dimension. However, upon quantization, an anomaly appears which breaks the scale invariance, similar to twobody interactions in two dimensions. The anomaly will naturally lead to a finite viscosity, as scale invariance is broken. We calculate the bulk viscosity in the hightemperature limit and compare the result to the twobody anomalous interaction in two dimensions. We show there is an exact mapping between these two anomalous systems in the high temperature limit. [Preview Abstract] 

K01.00108: Methods for Loading Heavy Metals into the Clemson EBIT Richard Mattish, Timothy Burke, Steven Bromley, Joan Marler The Clemson University EBIT (CUEBIT) facility allows for the creation and study of highly charged ions (HCIs). Up until now, only elements existing as gases at room temperature have been loaded and studied in the CUEBIT (e.g. Ar, O, C from CO2). However, for studying metal HCIs of interest to astronomers (e.g. Fe, Ag, Au), it is necessary to find a method to load these solids into the CUEBIT. We investigated two methods, laser ablation and thermal evaporation, which allow for the loading of neutral metals into the CUEBIT. A timeofflight mass spectrometer and a quartz crystal microbalance were used to evaluate the particle yield of each of these methods. [Preview Abstract] 

K01.00109: Towards QuditBased Quantum Computing Pei Jiang Low, Brendan White, Matthew Day, Usman Khan, Mia Shi, Colin Parkyn, Crystal Senko We present recent progresses in realizing quditbased quantum computing with barium ions. Quantum state manipulations and measurements are paramount to quantum computation. In our proposed qudit measurement scheme, high fidelity is achieved by shelving computational qudit states in the 6S$_{\mathrm{1/2}}$ level to the metastable 5D$_{\mathrm{5/2}}$ level, which has transition wavelength of approximately 1762 nm. Therefore, spectroscopy of 6S$_{\mathrm{1/2}}$ to 5D$_{\mathrm{5/2}}$ states is a crucial preparatory data for our quditbased computing scheme, and we report on our recent progress on this experiment. From our prior theoretical investigation, qudit manipulation can be done practically with either direct transitions with microwave or Raman transition. As a preliminary experiment, we have chosen microwavedriven control. To have sufficient control on qudit manipulation, phase, frequency and amplitude control of microwave radiation are required. We report on the architecture of this infrastructure and our progress on this experiment. [Preview Abstract] 

K01.00110: BackgroundFree State Detection of $^{88}$Sr$^{+}$ Optical Qubits Colin Bruzewicz, Jules Stuart, David Reens, Robert Niffenegger, Robert McConnell, John Chiaverini, Jeremy Sage Statedependent fluorescence detection schemes that rely on optical excitation and detection at the same wavelength are subject to undesirable background counts due to, for example, excitation light scattered by nearby optics. Here, we eliminate scattered light background counts for an optical $^{88}$Sr$^{+}$ qubit by implementing a twostep excitation protocol and detecting light at a wavelength separated by hundreds of nanometers from that of the excitation lasers. This technique uses the $4D_{3/2}$ and $5P_{1/2}$ levels to detect the $5S_{1/2}$ qubit state without populating the $4D_{5/2}$ qubit state. With increased laser intensity to quickly drive the dipoleforbidden $S_{1/2}\to D_{3/2}$ transition and two laser frequencies to address both ground state Zeeman sublevels, we achieve photon count rates that permit highfidelity state detection and also demonstrate motional state cooling using this pathway. Additionally, this twostep readout scheme may find use in applications, such as in integrated photonic devices, where visible and NIR excitation light is preferred to the blue and UV light used in singlewavelength state detection. [Preview Abstract] 

K01.00111: An Experimental Apparatus for Generation and Isolation of Highly Charged Ions with Low Ionization Thresholds Aung Naing, David La Mantia, Joseph Tan Access to highly charged ions (HCIs) for various applications has been somewhat limited by the need to use expensive, dedicated facilities such as electron beam ion traps (EBITs). The use of highfield permanent magnets has made it possible to construct smaller EBITs and other ion traps. Such lowmaintenance systems will be useful in applications such as the development of xray transitionedgesensors [1]. Other potential uses include creating certain HCIs, such as Pr$^{\mathrm{9+}}$ and Nd$^{\mathrm{10+}}$, proposed for the development of nextgeneration atomic clocks, or the search for variation in the finestructure constant [2]. At NIST, a miniaturized EBIT using NdFeB magnets has been built as a source of ions with relatively low ionization thresholds (\textless 1000 eV). To isolate ions of interest, we are building a permanent magnet Penning trap with a trap center magnetic field of $\approx $ 0.75 T. Preliminary ion extraction results with noble gas HCIs are presented. Measurements of the lifetimes in metastable states of Snlike Pr$^{\mathrm{9+}}$ are planned after the laserablationbased metal loading system becomes operational. The mobility of the apparatus would facilitate its use in various experiments. [1] P. Szypryt, et al., Rev. Sci. In. 90, 123107 (2019), [2] M. Safronova, et al., PRL 113, 030801 (2014) [Preview Abstract] 

K01.00112: Metastable qubits in trapped Calcium43 ions Isam Moore, Jeremy Metzner, Alexander Quinn, David Wineland, David Allcock While all of the basic primitives required for universal \newline quantum computing (QC) have been demonstrated in trappedion qubits with high fidelity, it is currently not possible to simultaneously realize the highest achieved fidelities in a single ion species. This can be a serious impediment to the development of practical quantum computers. However, there are possibilities for achieving highfidelity and full functionality in a single species with the use of multiple internal levels: augmenting existing species with new functionality. Specifically, essential dualspecies capabilities can be developed in the Calcium43$+$ ion through novel encoding schemes in metastable states, allowing userselectable, ionspecific activation of the necessary functions on demand (e.g. storage, coupling to motion, cooling, and state preparation and measurement). I will present simulation results and progress towards experimental implementation of highfidelity preparation and readout procedures in metastable states of Calcium43$+$. [Preview Abstract] 

K01.00113: Iontrapping lab setup for quantum information experiments Alexander Quinn, Jeremy Metzner, Daniel Moore, Vikram Sandhu, Dave Wineland, David Allcock The Allcock group at the University of Oregon is in the process of setting up a new ion trap lab. The broad purpose of our setup is to trap $+$Ca43 ions and use them for quantum information experiments. We are currently building and integrating: a macroscopic, linear Paul trap that will operate at room temperature; an ultrahigh vacuum system; and a compact, rackmounted laser system for ion cooling, state preparation, state readout, and logic gates. The apparatus includes an imaging system for collecting light from trapped ions for either counting photons or imaging individual ions, and a control system, based on ARTIQ hardware, gateware, and software, for managing and analyzing experiments. [Preview Abstract] 

K01.00114: On direct geneation of ionphoton entanglement at telecom wavelengths in 171Yb+ Wance Wang, Connor Goham, Andrew Laugharn, Joseph W Britton Entanglement between smallscale quantum processors and flying qubits is the building block of quantum networking. Leading ionphoton entanglement demonstrations at telecom wavelengths achieve highfidelity over distances up to 50 km [0,1]. These demonstrations used quantum frequency conversion and 40Ca+ ions. Here, we explore entanglement between 171Yb+ ions and photon polarization states at 1350 nm (P3/2D3/2) and 1650 nm (P3/2D5/2). A cavitymediated Raman interaction increases IR photon generation and collection efficiency. Driving the SD quadrupole transition can map Dstate coherences to the longlived HF qubit. We also consider photon frequency qubits as an approach that decreases sensitivity to birefringence. Relative to twospecies proposals, our approach avoids QFC, secondary ion species and swap gates [2]. [0] M. Bock, et al, Nature Communications (2018)9:1998 [1] V. Krutyanskiy, et al, NPJ Quantum Information (2019)5:72 [2] C. Crocker, et al, Optics Express(2019)27:20:28143 [Preview Abstract] 

K01.00115: Towards Building an Openaccess Trapped Ion Quantum Information Processor for the Research Community Nikolay Videnov, Noah Greenberg, Richard Rademacher, Matthew Day, Crystal Senko, Rajibul Islam Trapped ions are a leading platform for quantum information processing with pristine qubits, fully connected interaction graphs, and long coherence times. Trapped ion NISQ processors have enabled an immense variety of research in academic and private sector groups, and are highly oversubscribed. A shared openaccess processor would facilitate many research programs, particularly those requiring fine control over lowlevel hardware. In this poster, we present the progress towards developing QuantumIon  an openaccess trappedion quantum information processor at University of Waterloo. We present innovative approaches to the optical, mechanical, and control challenges. A guidedlight platform which combines stateoftheart glass micromachining technologies will provide fully controllable individual addressing for up to 16 Ba+ ions. The control system will use a distributed configuration of fast commercial FPGAs capable of providing real time branching decision logic. Using established networking protocols pulled from a variety of industries this control system straightforwardly scales to increasing numbers of qubits and even increasing numbers of networked traps. [Preview Abstract] 

K01.00116: Towards a large scale fullyprogrammable trappedion quantum spin simulator Sainath Motlakunta, Chungyou Shih, Nikhil Kotibhaskar, Manas Sajjan, YiHong Teoh, Zewen Sun, Roland Hablutzel, Fereshteh Rajabi, Rajibul Islam A trappedion quantum simulator can simulate models of quantum manyparticle systems that may be otherwise intractable, such as frustrated spin systems and fundamental forces in high energy physics. Our trapping architecture is based on a multisegmented `blade electrode' Paul trap, capable of producing anharmonic confining potentials to trap and control a long chain ($>$50) of Ytterbium ions with nearuniform spacing. A holographic optical addressing system is integrated for aberrationcorrected optical engineering, providing the capability to exert programmable and dynamic control over nontrivial manybody Hamiltonians at the level of individual ionspins and interactions between them. Leveraging powerful modern machinelearning tools [1], the quantum simulator can in principle be programmed to realize an arbitrarily connected spin network, allowing the simulation of dynamical spin systems on arbitrary lattice geometries in higher dimensions. \\ \text{[1]} Yi Hong Teoh , Marina Drygala, Roger G. Melko, and Rajibul Islam, \textit{Quantum Science and Technology} \textbf{5}, 024001 (2020) [Preview Abstract] 

K01.00117: Ultralongrange molecules and ultracold heavy Rydberg systems Frederic Hummel, Peter Schmelcher, Herwig Ott, Hossein Sadeghpour Ultralongrange Rydberg molecules (ULRMs) are bound states between a Rydberg atom and one or more groundstate atoms with bond lengths on the order of thousands of Bohr radii. The binding originates from electronatom scattering and leads to exotic oscillatory potential energy surfaces that reflect the probability density of the Rydberg electron. Heavy Rydberg systems (HRS) are highly excited, binary atomic systems, which consist of a positive and a negative ion. The large reduced mass leads to high principal quantum numbers up to several thousand, which can be achieved in ultracold samples. We here propose an experimentally feasible and efficient protocol to create HRS via photoassociation to an intermediate ULRM. The Rabi coupling is typically in the MHz range and the permanent electric dipole moments of the HRS can be as large as one kiloDebye. We identify specific transitions which place the creation of the heavy Rydberg system within immediate reach of experimental realization. [Preview Abstract] 

K01.00118: Nonadiabatic Quantum Interference Effects and Chaoticity in the Ultracold Li + LiNa $\to$ Li$_2$ + Na Reaction Brian Kendrick, James Croft, Naduvalath Balakrishnan, Ming Li, Hui Li, Svetlana Kotochigova Quantum reactive scattering calculations for the ultracold Li + LiNa $\to$ Li$_2$ + Na reaction are presented which include both the ground and first excited doublet electronic states. In the interaction region the excited electronic state exhibits a conical intersection with the ground electronic state. This intersection is energetically accessible even in the ultracold regime for Li + LiNa collisions with ground state reactants. A numerically exact fulldimensional timeindependent scattering method based on hyperspherical coordinates is used to compute the total, vibrationally, and rotationally resolved nonthermal rate coefficients for collision energies between $1\,{\rm nK}$ and $0.3\,{\rm K}$. A significant enhancement or suppression of up to two orders of magnitude is observed in many of the rotationally resolved rate coefficients. These effects are due to constructive or destructive quantum interference between the two scattering amplitudes which encircle the conical intersection. A statistical analysis of the rotational distributions shows a Poisson behavior which is indicative of the underlying classically chaotic dynamics. [Preview Abstract] 

K01.00119: A few interacting fermions near the unitarity limit Michael D Higgins, Chris H Greene Interacting fewfermion systems have been extensively studied in atomic physics, and their behavior at very large scattering lengths continues to pose stringent theoretical challenges. One naturally occurring class of systems that are close to unitarity arises in the nuclear fewbody problem: key examples are the fewneutron systems that interact through the strong force. The $n$$n$ two body $s$wave scattering length is large ($\simeq$ $18.9$ fm) compared to the range of the interaction ($\simeq$ 12 fm), which provides good criteria for studying nearunitarity physics. Lowenergy scattering of the three neutron (3$n$) and four neutron (4$n$) systems are studied in the framework of the adiabatic hyperspherical method using an ExplicitlyCorrelated Gaussian basis. The 4$n$ problem is treated in the symmetry $J^{\pi}=0^{+}$ and $J^{\pi}=\frac{3}{2}^$ for the 3$n$ system. These symmetries lead to the strongest attraction between the neutrons due to the large, negative twobody singlet $s$wave scattering length. The nuclear interaction considered is a version of the Argonne nuclear potentials, the AV$8'$ potential, fitted to gaussians. The lowest few potentials are obtained and the energydepenent phaseshift and time delay are computed for the lowest potential in each case. [Preview Abstract] 

K01.00120: Using a MagnetoOptical Trap (MOT) to teach Experimental and Computational Methods in Undergraduate Physics. D.~O. Kashinski, L.~E. Harrell, K. Ingold, C.~S. Gerving We are using coldatom physics to motivate our culminating undergraduate seniorlevel ``Experimental Methods in Physics'' course. Students continue to develop upon and refine previouslyintroduced computational methods by numerically solving a host of nonanalytical problems, including a semiclassical simulation of atomic motion in a MOT. After an extensive literature review and basic laboratory instruction the studentteams endeavor to create a MOT. Previous experimental and theoretical coursework is reinforced through the handson setup of the cooling and repump laser systems and use of saturated absorption spectroscopy to observe the hyperfine structure of Rb. Finally, to form the MOT of $^{87}$Rb, students combine the light into a standalone vacuum cell that includes a Rb source and coils to establish an appropriate magnetic field gradient (manufactured by ColdQuanta). Time permitting, students then characterize the MOT by comparing their results to simulations. Updates and results from the second iteration of this new course will be presented at the meeting. [Preview Abstract] 

K01.00121: Rovibrational optical cooling of $Rb_{2}$ in a supersonic beam Manuel Alejandro Lefran Torres, Henry Fernandes Passagem, Cristian MojicaCasique, Eduardo da Costa Paul, Marcos Roberto Cardoso, Luis Marcassa In this work, we propose to optically cool the rotation and the vibration of $Rb_{2}$ molecules in a supersonic beam by applying a broadband light source. Such source consists of a tapered amplifier laser with frequencyshifted feedback, around 682 nm, which can drive transitions from $\nu_{x}, J_{x}$ $X^{1}\Sigma_{g}^{+}$ ground state to the $b^{1}\Pi_{u}$ excited potential. The spectrum of our source is such that the $\nu_{x}, J_{x} = 0$ $X^{1}\Sigma_{g}^{+}$ ground state will be a dark state. The molecules will be observed by photoionization technique, through transitions from the $\nu_{x}, J_{x}$ to $\nu, J_{x}$ of the $b^{1}\Pi_{u}$ potential using a CW diode laser, and then photoionized by a 532 nm pulsed laser. Such technique will allow us to resolve the rotational distribution of the $\nu_{x}=0$. Theoretical simulations indicate that we should be able to perform the rovibrational cooling in less than 300 $\mu$s. [Preview Abstract] 
On Demand 
K01.00122: A Buffer Gas Beam Source for Barium Monofluoride and Progress Towards Laser Cooling of the Molecular Beam Ralf Albrecht, Marian Rockenhaeuser, Tim Langen Cold molecular gases are the starting point for a large number of novel and interdisciplinary applications ranging from few and manybody physics to cold chemistry and precision measurements. Especially heavy polar molecules, such as barium monofluoride, are perfect candidates for tests of fundamental symmetries and studies of complex quantum systems with strong, longrange interactions. However, in comparison to atoms, the preparation of molecular gases in the subKelvin regime is complicated by their complex vibrational and rotational level structure and the lack of closed transitions for optical cycling. Nevertheless, thanks to favorable FranckCondon factors and selection rules, quasicycling transitions can be identified for many molecular species, including barium monofluoride. In this contribution, we will report on our buffer gas beam source for slow and internally cold barium monofluoride molecules. Moreover, we will present our progress towards onedimensional Doppler cooling of the molecular beam. [Preview Abstract] 

K01.00123: $^{\mathrm{23}}$Na$^{\mathrm{87}}$Rb polar molecules in 3D optical lattice Junyu He, Junyu Lin, Dajun Wang In recent years, ultracold polar molecules have attracted more and more attentions due to their many potential applications. However, several recent experiments have observed strong inelastic losses even for ultracold molecules in their absolute ground states. While it is generally agreed that this unexpected loss is due to the formation of twomolecule complexes, no clear remedy to this issue is known other than isolating these molecules from each other. Here we report our progress on creating a sample of groundstate $^{\mathrm{23}}$Na$^{\mathrm{87}}$Rb molecules in 3D optical lattices. With a strong enough lattice potential, longlived samples with lifetime of more than 10 seconds are observed. We will also discuss the investigation on the coherence between nuclear hyperfine levels and dipolar effects between adjacent lattice sites. [Preview Abstract] 

K01.00124: Threebody collisions of ultracold dipolar molecules Lucas Lassabli{\`e}re, Goulven Qu{\'e}m{\'e}ner A lot of effort is devoted nowadays to produce ground state ultracold molecules in high densities. Twobody collisions as well as threebody collisions can occur in those gases. In this poster, we present the hyperspherical formalism used to describe threebody collisions. We adapated the formalism of Kendrick et al. [1] to three identical particles such as dipolar molecules and including an electric field. To avoid numerical limits, we found a model to treat the dipolar molecules without their internal rotational structure. With this formalism, we can compute the adiabatic energies and rate coefficients for the threebody collisions. [1] B. K. Kendrick et al., J. Chem. Phys 110, 6673 (1999). [Preview Abstract] 

K01.00125: Exotic dipole traps for $^{23}$Na$^{40}$K molecules Andreas Schindewolf, Roman Bause, Ming Li, XingYan Chen, Marcel Duda, Svetlana Kotochigova, Immanuel Bloch, XinYu Luo Mixing rotational states of dipolar molecules is essential to utilize their dipolar interaction and to simulate spin systems. We use a rotationalstatesensitive electronic transition to create a highlytunable optical dipole trap for NaK molecules. By tuning the trapping light over a range of 10 GHz we can switch between a 'magic' and two 'tuneout' conditions for the states $v=0, J=0\rangle$ and $v=0, J=1\rangle$, while maintaining molecule lifetimes of about $1$ s or longer [1]. Here, $v$ is the vibrational and $J$ the rotational quantum number of the electronic ground state. The transition can be used to achieve long coherence times in superpositions of rotational states and to realize novel cooling schemes in optical lattices. [1] R. Bause et al., arXiv:1912.10452. [Preview Abstract] 

K01.00126: Optical cycling, radiative deflection, and laser cooling of metal monohydride molecules Rees McNally, Qi Sun, Ivan Kozyryev, Sebastian VazquezCarson, Konrad Wenz, Tianli Wang, Tanya Zelevinsky The past decade has seen major advances in direct laser cooling of diatomic and even polyatomic molecules, including trapping of ultracold samples for several species. A critical requirement for direct laser cooling is the demonstration of sustained optical cycling without loss to dark states, and control over the molecules spatial degrees of freedom using laser light. Here we present the first demonstration of optical cycling, radiative deflection, and Sisyphus cooling for barium monohydride molecules (BaH). This adds a new class of diatomic molecules, the alkaline earth monohydrides, to the rapidly expanding set of laser cooled molecules. Optical cycling rates are measured via depletion of the ground vibrational state and deflection of the molecular beam. Our results are consistent with the maximum scattering rate obtainable, based on a simulation of the Lindblad master equation for the complete system. Sisyphus cooling was carried out along one transverse dimension of a cryogenic buffer gas beam. Prospects for confinement in a magnetooptical trap will be discussed. We will also present preliminary results on optical cycling and manipulation of CaH, a lighter alternative to BaH. [Preview Abstract] 

K01.00127: Toward nondestructive, dispersive imaging of ultracold molecules Michael Highman, Qingze Guan, Garrett Williams, Eric Meier, Ming Li, Svetlana Kotochigova, Vito Scarola, Brian DeMarco, Bryce Gadway There is currently a lack of highfidelity and nondestructive imaging strategies for generic diatomic molecules, in particular for the commonly used bialkalis. Here, we propose and describe a technique to address this shortcoming using naturally occurring optical birefringence of excited rotational states. We will also discuss current experimental progress toward the creation of groundstate sodiumrubidium molecules and the demonstration of this proposed imaging scheme. [Preview Abstract] 

K01.00128: Novel LaserCoolable Molecular Species Nathaniel Vilas, Benjamin Augenbraun, Zack Lasner, Alex Frenett, Hiromitsu Sawaoka, Calder Miller, Zhijing Niu, Daniel Abdulah, Louis Baum, Debayan Mitra, Christian Hallas, Shivam Raval, Andrew Winnicki, Timothy Steimle, John Doyle Laser cooling techniques have recently been extended to diatomic and polyatomic molecules. The molecules that have so far been laser cooled are highly symmetric, linear molecules. Previous cooling schemes have relied crucially on these high symmetry states. Here, we identify several new classes of lasercoolable molecules with complex molecular and electronic structure. Among these are nonlinear symmetric top molecules like CaOCH$_3$ [1], asymmetric rotors including CaSH and CaNH$_2$ [2], and exotic molecules with multiple optical cycling centers, such as CaCCSr [3]. We discuss ongoing experimental and theoretical work, including dispersed fluorescence spectroscopy, demonstrations of optical photon cycling, and structural calculations. The addition of such species to the lasercooled molecular toolbox will lend itself to diverse applications ranging from quantum computing and simulation to quantum chemistry to precision measurements and fundamental physics. [1] Yu et. al., New J. Phys. 21, 093049 (2019). [2] Augenbraun et. al., arXiv:2001.11020 (2020). [3] Ivanov et. al., J. Phys. Chem. Lett. (2020). [Preview Abstract] 

K01.00129: Magnetooptical forces applied to polyatomic molecules Louis Baum, Nathanial Vilas, Christian Hallas, Shivam Raval, Benjamin Augenbraun, Debayan Mitra, John Doyle In recent years, laser cooling has been successfully applied to diatomic molecular systems, resulting in robust magneto optical traps (MOTs) and grey molasses cooling to the $\mu$Kelvin temperature regime. Polyatomic molecules have additional (controllable) degrees of freedom, compared to their diatomic counterparts, that provide further advantages for a myriad of applications in quantum science [13]. Here we present the onedimensional magnetooptical cooling and compression (1D MOT) of a cryogenic buffergas beam [4] of calcium monohydroxide (CaOH) molecules [5]. We establish a quasiclosed cycling transition and scatter 10$^3$ photons per molecule, with this number limited predominantly by interaction time. The resulting cooling and compression lead to an increase in onaxis molecular beam brightness and a reduction of temperature from 8.4 mK to 1.4 mK. This demonstration realizes a significant milestone on the route towards a 3D MOT of CaOH and the laser cooling of polyatomic molecules into the $\mu$Kelvin regime . [1] Kozyryev and Hutzler, PRL 119, 133002 (2017). [2] Yu et. al., New J. Phys. 21 093049 (2019) [3] Wall et. al., New J. Phys. 17, 025001 (2015). [4] Hutzler et. al., Chem. Rev. 112, 9 4803 (2012) [5] Baum et. al., arXiv 2001.10525 [Preview Abstract] 

K01.00130: Microwave control of ultracold molecular collisions Tijs Karman Microwaves can be used to engineer longrange interactions between ultracold polar molecules. Resonant dipoledipole interactions induce strong interactions and high scattering rates in molecules collisions. Repulsive longrange interactions can be used to shield molecules from shortrange loss. [Preview Abstract] 

K01.00131: Observation of Magnetic Feshbach Resonances in LiYb Mixtures Jun Hui See Toh, Alaina Green, Xinxin Tang, Katie McCormick, Hui Li, Ming Li, Eite Tiesinga, Svetlana Kotochigova, Subhadeep Gupta We observe multiple interspecies magnetic Feshbach resonances between the openshell Li and the closedshell Yb ground state atom [1]. We resolve closelylocated resonances that arise from a weak separationdependent hyperfine coupling between the nuclear spin of ${}^{173}$Yb and the electronic spin of ${}^6$Li, and confirm their magnetic field spacing by ab initio electronicstructure calculations. Resonances are identified via traploss spectroscopy with the mixtures in a crossed optical dipole trap and varying magnetic field. The asymmetric loss profiles of the resonances show that threebody recombination in fermionic mixtures has a pwave Wigner threshold. We plan to apply these resonances towards magnetoassociation of ultracold YbLi molecules in the electronic ground state. The ${}^2 \Sigma$ YbLi molecule possesses both electric and magnetic dipole moments that can be utilized towards ultracold chemistry, quantum manybody physics, and quantum information. [1] A. Green et al. arXiv: 1912.04874 (2019) [Preview Abstract] 

K01.00132: Controlled Interactions of Polar Molecules in Two Dimensions William Tobias, Kyle Matsuda, Luigi De Marco, Giacomo Valtolina, JunRu Li, Jun Ye Degenerate polar molecules, which interact via longrange, anisotropic potentials, allow access to rich manybody physics. One challenge for realizing manybody interacting systems is the short molecular lifetime relative to the interaction energy, which is limited by chemical reactions and photoinduced loss of collision complexes. By confining potassiumrubidium molecules to two dimensions and applying an electric field to polarize the dipoles perpendicular to the plane of motion, we demonstrate strong suppression of inelastic loss and a corresponding enhancement of elastic collisions. We present preliminary results of direct evaporation of molecules, as well as progress towards singlesite microwave addressing of molecules in an optical lattice and measurement of the dipolar interaction shift. [Preview Abstract] 

K01.00133: Towards Scalable Generation and Control of Ultracold SinglyTrapped NaK Molecules Xiu Quan Quek, Krishna Chaitanya Yellapragada, Mohammad Mujaheed Aliyu, Wei Hong Yeo, Huanqian Loh Ultracold polar molecules have been shown to possess longlived coherent states and longrange electric dipole interactions, making them ideal candidates for applications in largescale quantum information processing and quantum memory. The generation of these molecules involves starting from arrays of two atomic species cooled to the ground motional state of tightly focused optical dipole traps, before merging the atoms using Feshbach interactions and performing stimulated Raman adiabatic transfer into the molecular ground state. When combined with reconfigurable dipole trap arrays, a high degree of control over system Hamiltonians can be achieved, which is ideal for quantum simulation. We present the experimental progress made towards achieving this goal, primarily the efforts in cooling and trapping of single Na and K atoms for eventual generation of NaK molecules. [Preview Abstract] 

K01.00134: Singlet Pathway to the Ground State of Ultracold Polar Molecules Sofia Botsi, Anbang Yang, Sunil Kumar, Sambit B. Pal, Mark M. Lam, Ieva Cepaite, Andrew Laugharn, Kai Dieckmann We demonstrate a twophoton pathway to the ground state of $^{\mathrm{6}}$Li$^{\mathrm{40}}$K molecules that involves only singlettosinglet optical transitions. We start from a molecular state which contains a significant admixture from the singlet ground state potential by selecting the Feshbach resonance for molecule association. With the only contributing singlet state to the molecular state being fully stretched and with control over the lasers polarization we address a sole hyperfine component of the excited A$^{\mathrm{1}}\Sigma^{\mathrm{+}}$ potential without resolving its hyperfine structure. This scheme ensures access to only one ground state hyperfine component with sufficient FranckCondon factors and moderate laser powers for both coupling transitions. Its implementation results in large and balanced Rabi frequencies, a favorable condition for the coherent transfer to the ground state. We perform dark resonance spectroscopy to precisely determine the transition frequencies of the states involved. The strong dipolar nature of $^{\mathrm{6}}$Li$^{\mathrm{40}}$K is revealed by Stark spectroscopy, as it is necessary for the study of dipolar interactions in an optical lattice. [Preview Abstract] 

K01.00135: The diatomic molecular spectroscopic database Xiangyue Liu, Stefan Truppe, Gerard Meijer, Jesus PerezRios The spectroscopic constants of molecules contain crucial information regarding the electronic structure and properties of molecules and hence are of great interest in the atomic, molecular, and optical physics community. In this work, we develop a userfriendly and interactive website in which the user can get access to the spectroscopic constants and FranckCondon factors of polar diatomic molecules. The spectroscopic constants are retrieved directly from the website or through our application programming interface. The registered users can also upload data to the database after authorization. This datadriven website may help to target the possible candidates for a range of applications, such as molecular laser cooling. [Preview Abstract] 

K01.00136: Towards strongly correlated 2D gases of ultracold dipolar NaCs molecules Claire Warner, Niccolo` Bigagli, Aden Lam, Ian Stevenson, Sebastian Will Ultracold dipolar ground state molecules open up new avenues to study manybody quantum systems with longrange dipoledipole interactions and promise to become a novel platform for quantum simulation. In this project, we aim to use ultracold molecules of sodiumcesium (NaCs) to study strongly correlated quantum phases. Sodiumcesium molecules feature chemical stability in the ground state and an electric dipole moment of 4.6 Debye. We plan to create these molecules from ultracold mixtures of sodium and cesium and will report on progress towards simultaneous cooling of the two atomic species to quantum degeneracy, as well as preliminary studies of interactions in this new atomic mixture. We will trap the mixture in two dimensions using an accordion lattice potential, explore intra and interspecies Feshbach resonances, study the impact of reduced dimensionality on molecule formation, and identify a pathway towards the molecular ground state of NaCs. [Preview Abstract] 

K01.00137: Toward Microscopy of a Degenerate Bose Gas of Polar Molecules Jason Rosenberg, Lysander Christakis, Geoffrey Zheng, 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 toward a new apparatus to perform siteresolved microscopy of a degenerate Bose gas of polar $^{\mathrm{23}}$Na$^{\mathrm{87}}$Rb molecules confined within a 2D optical lattice. We have constructed a rubidium quantum gas microscope, and we are currently working toward the production of groundstate NaRb molecules. We plan to overlap dual 2D Mott insulators of sodium and rubidium atoms before adiabatically sweeping across the Feshbach resonance to form weaklybound molecules. Following STIRAP to the molecular ground state, evaporation can then proceed using invacuum electrodes to generate a strong electric field orthogonal to the lattice plane, suppressing inelastic collisions. These electrodes also allow us to tune the interactions between the molecules. We will perform quantum gas microscopy by dissociating the molecules and performing siteresolved fluorescence imaging of the constituent atoms. [Preview Abstract] 

K01.00138: Towards a Quantum Gas Microscope for LaserCooled Molecules Yukai Lu, Connor Holland, Lawrence Cheuk Ultracold molecules, with their rich internal structure and longrange dipolar interactions, could be a powerful platform for applications ranging from quantum simulation and information processing to ultracold chemistry. Here we report on progress towards a new apparatus for lasercooled CaF molecules. Our apparatus is designed to produce large samples of trapped molecules while allowing detection and control at the single molecule level. These capabilities could be important for future explorations in quantum science, such as simulating spin models and building molecular qubits. [Preview Abstract] 

K01.00139: Coherent spinrotation state transfer in TlF Olivier Grasdijk, Mick Aitken, David DeMille, Jakob Kastelic, David Kawall, Steve Lamoreaux, Oskari Timgren, Konrad Wenz, Tristan Winick, Trevor Wright, Tanya Zelevinsky The aim of CeNTREX (Cold molecule Nuclear TimeReversal Experiment) is to search for the proton’s electric dipole moment by exploiting the Schiff moment of $^{205}$TlF in the polar molecule thallium fluoride (TlF). To maximize the molecular flux, an electrostatic quadrupole lens is employed to collimate a TlF beam. After rotational cooling, the first few rotational ground states of a cold TlF beam have been emptied into a single J=0 hyperfine level in the $^1\Sigma^+$ electronic ground state. In order to populate a weakfield seeking state that the lens can optimally affect, microwaves are required to transfer TlF from J=0 to J=2. Transitioning from this state preparation region into the electrostatic quadrupole field of the lens will induce nonadiabatic transitions to unwanted states due to rapidly changing fields. This poster describes the recent progress in efficient, coherent spinrotation state transfer in TlF. [Preview Abstract] 

K01.00140: Development of the Axion Resonant InterAction DetectioN Experiment (ARIADNE) Chloe Lohmeyer, Nancy Aggarwal, Zhiyuan Wang, Wenxin Xie, Nicole Wolff, Andrew Geraci The Axion Resonant Interaction Detection Experiment (ARIADNE) will look for monopoledipole interactions mediated by the QCD axion field in the mass range of 1$\mu $eV to 6meV. Modulating an unpolarized Tungsten mass in close proximity to polarized helium3 gas creates an effective transverse magnetic field as seen by the He3 spins, which drives a nuclear magnetic resonance transition. The experimental principles, the expected challenges of the experiment, as well as the latest updates will be discussed. [Preview Abstract] 
On Demand 
K01.00141: Progress of CeNTREX: Cold Molecule Nuclear Time Reversal Experiment Michael Aitken, Olivier Grasdijk, Jakob Kastelic, Oskari Timgren, Konrad Wenz, Tristan Winick, Trevor Wright, David DeMille, David Kawall, Steve Lamoreaux, Tanya Zelevinsky The baryon asymmetry of the universe—the presence of matter in far greater abundance than antimatter—is an ongoing scientific mystery. Since the Big Bang is expected to have produced matter and antimatter in equal amounts, physicists have developed theories to account for the processes that have led to this asymmetry. Many of these theories predict a violation of the T (time reversal) symmetry at levels that exceed the Standard Model predictions. The existence of a nuclear Schiff moment is an example of such a T violating phenomenon. Our experiment, the Cold Molecule Time Reversal Experiment, or CeNTREX, is designed to measure the Schiff moment of the thallium nucleus. I present progress towards this measurement, including a cryogenic buffer gas beam of thallium fluoride (TlF) molecules and spectroscopic characterization of TlF with an ultraviolet laser system. Additionally, I report on future steps and the experimental layout for measuring the Schiff moment of thallium using TlF. [Preview Abstract] 

K01.00142: Upgrading the ACME electron EDM search with a molecular lens Xing Wu, Daniel G. Ang, James Chow, David DeMille, John M. Doyle, Gerald Gabrielse, Zhen Han, Bingjie Hao, Peiran Hu, Nicholas Hutzler, Daniel Lascar, Siyuan Liu, Cole Meisenhelder, Takahiko Masuda, Cristian D. Panda, Noboru Sasao, Satoshi Uetake, Koji Yoshimura Measurements~of the electron~electric dipole moment (EDM) using cold molecules~set very powerful constraints on Tviolating new physics beyond the Standard Model. The best upper limit on the electron EDM was recently set by the ACME collaboration: \textbar de\textbar \textless 1.1E29 e\textbullet cm [Nature~562,~355 (2018)], using thorium~monoxide (ThO). A major upgrade in statistics for next generation of ACME is now underway, using a molecular lens to focus molecule flux into the EDM measurement region. Here, we report the first measurements [arXiv:1911.03015] of relevant properties of the Q state, which appears ideal for molecular lensing. Also, we demonstrate a doubleSTIRAP procedure that transfers population into and out of the Q state with 90{\%} efficiency. These combined with trajectory simulations on an electrostatic hexapole allow us to project a signal rate improvement by over an order of magnitude relative to an unfocused molecular beam. [Preview Abstract] 

K01.00143: Progress towards improved precision of the electron and positron magnetic moment measurement Samuel Fayer, Xing Fan, Thomas Myers, Benedict Sukra, Gerald Gabrielse The measurement of the electron magnetic moment, measured to a precision of 0.28 ppt [1], gives one of the most stringent tests of the standard model, with an intriguing discrepancy of 2.4 standard deviations between the measurement and the prediction [2,3]. An apparatus has been developed~which reduces the effects from external magnetic and vibration noise, thought to have caused the largest systematic uncertainty in the previous measurement. These advances and new techniques are aimed at~obtaining a measurement an order of magnitude more precise [4]. Positrons from a student safe source will be used to measure the positron magnetic moment two orders of magnitude more precisely and give the most precise lepton test of CPT invariance.~ 1. D. Hanneke, S. Fogwell, and G. Gabrielse,~Physical Review Letters~100~(2008) 120801 2. T. Aoyama, T. Kinoshita, M. Nio, Atoms 7 (2019) 28. 3. R. H. Parker,~C. Yu,~W. Zhong, B. Estey, and H. M\"{u}ller,~Science~360~(2018) 191 4. G. Gabrielse, S. E. Fayer, T.G. Myers, X. Fan, Atoms 7 (2019) 45.~~ [Preview Abstract] 

K01.00144: Search for Axion topological defects using the Global Network of Optical Magnetometers for Exotic physics (GNOME) Hector Masia Roig, Joseph A. Smiga The Global Network of Optical Magnetometers for Exotic physics (GNOME) is a network of geographically separated, timesynchronized atomic magnetometers and comagnetometers in magnetically shielded environments. This configuration allows monitoring the energy splitting of Zeemann sublevels in an atomic ensemble continuously and simultaneously at different places all over the Earth. Axionlike particles could form topological defects that couple to atomic spins. Such an interaction would alter the Zeeman sublevel energy splitting producing a transient signal in the magnetometer network. The Earth’s movement is used to probe different regions of the galaxy for such defects. Possible candidates for the topological defects are domain walls which would be observed as an event plane crossing the earth following a predictable signal pattern. A timedomain analysis method was developed to look for correlations between the different magnetometers compatible with an axion domainwall$^2$ . These methods are applied to the data gathered by GNOME in order to identify possible axion domainwall events. $^2$ H.MasiaRoig, J. A. Smiga et al., arXiv:1912.0872 [Preview Abstract] 

K01.00145: SpinExchange Relaxation Free Magnetometer for the Global Network of Optical Magnetometers for Exotic Physics (GNOME) Dhruv Tandon, Eleda Fernald, Jay McClendon, Perrin Segura, Heather Pearson, Sun Yool Park, Jason Stalnaker Ultralight axionlike particles are a possible candidate for dark matter. These particles could result in cosmic topological defects such as domain walls or axion stars. The Global Network of Optical Magnetometers to search for Exotic Physics (GNOME) is looking for a transient signal caused by exoticspin couplings as the Earth passes through such topological defects. We describe the Oberlin magnetometer station and present its performance during the latest GNOME science run. The magnetometer consists of a singlebeam, spinexchange relaxationfree (SERF) magnetometer that uses a vapor cell of potassium atoms with helium as a buffer gas. The cell is housed inside a fourlayer magnetic shield. We use circularly polarized light resonant with $D_1$ transition to optical pump the atoms into a magnetically sensitive dark state. The transmission through the vapor cell is monitored and fed back to magnetic field coils to maintain zero field inside the cell. We also discuss the implementation of a comagnetometer configuration that has the potential to improve the sensitivity of the detector. [Preview Abstract] 

K01.00146: Local dark matter density estimation using Doppler spectroscopy of stars and pulsar timing David Phillips, Aakash Ravi, Nicholas Langellier, Malte Buschmann, Benjamin Safdi, Ronald Walsworth Doppler spectroscopy of stars has been extremely successful in the detection of exoplanets. We show that this technique can also be used to directly measure the gravitational potential of the Milky Way galaxy, and thereby determine the local dark matter density without any assumptions of dynamic equilibrium. In our work, we present a realistic strategy to observe the differential accelerations of stars in our Galactic neighborhood with nextgeneration telescopes, and provide numerical simulations of the expected sensitivity of such a program. We also present preliminary results of similar acceleration measurements derived from pulsar timing data, with an analysis of systematic errors. [Preview Abstract] 

K01.00147: Update on the search for dark matter transient signatures using the GPS atomic clocks Tyler Daykin, Colin Bradley, Guglielmo Panelli, Trevor Maddox, Ben Roberts, Geoffrey Blewitt, Andrei Derevianko A network of quantum sensors, such as the network of 32 Rb and Cs atomic clocks suited aboard the Global Positioning System (GPS), have shown to be a capable aperture for searching for exotic physics, such as clumpy dark matter. Topological Defect dark matter (DM) is an example of clumpy dark matter, which may take the form of a 0D monopoles or Qballs, 1D strings, or 2D domain walls. For a 2D domain wall, the expected DM signal in the atomic clock data is a sweeping chirp in the clock data as the DM wall propagates the GPS constellation. A Bayesian statistical method is employed to search the 20 years of archival GPS data for transient dark matter signatures from 2D thin domain walls. For each potential dark matter candidate event, we carry out parameter estimation for the velocity, and geometry of the DM encounter. If no dark matter events are observed then powerful constraints may be placed on these models by computing the posterior distribution for the coupling strength. [Preview Abstract] 

K01.00148: Searching for a relaxion halo with the Global Network of Optical Magnetometers for Exotic physics (GNOME) Tatum Wilson, Rayshaun Preston, Christopher Palm, Christopher Verga, Szymon Pustelny, Derek Jackson Kimball The relaxion is a hypothetical ultralight boson proposed to solve the hierarchy problem [Graham, Kaplan, and Rajendran, Phys. Rev. Lett. {\textbf{115}}, 221801 (2015)]. Relaxions are also a dark matter candidate. The relaxion field couples to atomic spins and would lead to an oscillating signal detectable with atomic magnetometers. It is possible that relaxions collect in a halo in the gravitational potential of the Earth or Sun. In this scenario, the relaxion density is much greater than the average dark matter density in the Milky Way, resulting in enhanced signals [Banerjee et al., Communications Phys. {\textbf{3}}, 1 (2020)]. The Global Network of Optical Magnetometers for Exotic physics (GNOME) is an array of geographically separated, timesynchronized, atomic magnetometers whose purpose is to search for correlated signals heralding exotic physics [Afach et al., Physics of the Dark Universe {\textbf{22}}, 162 (2018)]. We discuss a search algorithm for GNOME data based on crosscorrelation analysis that targets signals produced by a relaxion halo. [Preview Abstract] 

K01.00149: Search for Axion Stars Using the Global Network of Optical Magnetometers for Exotic Physics (GNOME) Perrin Segura, Tatum Wilson, Heather Pearson, Madeline Monroy, Ibrahim Sulai, Derek Jackson Kimball, Jason Stalnaker The Global Network of Optical Magnetometers for Exotic physics (GNOME) searches for evidence of exotic spin coupling between elementary particle spins and topological defects in a field of ultralight axionlike particles (a possible candidate for dark matter). One of the network's search targets is a proposed dark matter structure known as an axion star or Qball. We present an analysis method designed to search for evidence of such structures. The analysis includes an initial stage based on the excess power technique that identifies transient oscillatory signals coincident across multiple detectors. This is followed by a consistency check in which the relative signal amplitudes in each station and the sensitive axis of each detector are used to establish the most likely magnitude and direction of the event. [Preview Abstract] 

K01.00150: Noise characterization of atomic magnetometers on the GNOME network Ibrahim Sulai, Sebastian Ascoli The GNOME (Global network of atomic magnetometers for exotic physics) experiment comprises a network of shielded atomic magnetometers designed to search for spin interactions with fields that have been proposed in various extensions of the standard model such as axions. The experiment relies on the stable operation of the sensors over long ($\sim$ months) intervals. Our goal is to develop a noise model for each sensor on the network which can be used in subsequent analyses. We report on (1.) a characterization of the noise nonGaussianity during a dedicated observational run, and (2.) an excess power analysis of the data in search of signals coincident with known astrophysical events. [Preview Abstract] 

K01.00151: Search for Exotic Field Emission from the GW170817 Binary Neutron Star Merger Using GPS Atomic Clocks Colin Bradley, Dailey Conner, Arko Pratim Sen, Paul A. Ries, Blewitt Geoffrey, Derevianko Andrei Bosonic fields beyond the standard model of particles are proposed as constituents of dark matter and dark energy, and they appear as potential solutions to the strongCP and hierarchy problems. These fields interact feebly with the standard model particles and fields; therefore, precision quantum sensors are an ideal candidate for detection. We focus on fields generated from highly energetic astrophysical events such as binary neutron star and binary black hole mergers and look for their signatures in GPS atomic clock data. For these signatures to be correlated with LIGO triggers, the fields must be ultrarelativistic and ultralight. We implement the excess power statistic method and search for exotic field signatures in GPS clock data near the binary neutron star merger measured by LIGO in August of 2017 (GW170817). [Preview Abstract] 

K01.00152: A Multiplexed Strontium Optical Lattice Clock for Tests of Fundamental Physics Xin Zheng, Brett Merriman, Haoran Li, Shimon Kolkowitz 

K01.00153: Abstract Withdrawn In a $^{\mathrm{129}}$Xe$^{\mathrm{131}}$XeRb system, polarized Rb atoms both hyperpolarize the Xe isotopes and work as a sensor of the Xe nuclear spins. The system has two important systematic effects. One is due to the quadrupole splitting of the $^{\mathrm{131}}$Xe (I $=$ 3/2) precession spectrum. We use elongated cells to resolve the splitting and suppress this effect. The other systematic effect comes from the polarized Rb atoms. Due to the Fermi contact interactions, the effective magnetic field of the polarized Rb atoms experienced by the Xe nuclear spins is amplified by a factor $\kappa $. There is a difference between the two $\kappa $ factors of the two Xe isotopes. We measure the small difference under various experiment conditions, and use a polarization modulation scheme to suppress the Rb atom polarization during signal detection. We will present the investigation results and latest performance of this comagnetometer. This system could be applied in many precision measurements such as the search for monopoledipole interactions. 

K01.00154: MEMS uniform nonmagnetic heating device for miniaturized atomic magnetometer Zhi Liu, Kaifeng Yin, Bangcheng Han, Heng Yuan, Binquan Zhou, Xiangyang Zhou, Xiaolin Ning, Jingyi He, Yang Yang Miniaturized atomic magnetometer can be used for magnetoencephalogram source localization. The key technology of atomic magnetometer, vapor cell contained alkali metal atoms, requires a uniform temperature field to achieve superior sensitivity. In this study, ITO (Indium Tin Oxide) which is transparent and conductive is proposed as heating resistance wires to fabricate the heating films. A 300nm thick ITO film can transmit 95{\%} of light without affecting the polarization state of the light. Consequently, the vapor cell can be heated in five surfaces to achieve the uniform temperature field without considering the impact to the optical path. According to the experimental results, the proposed heating films can achieve 200 degrees Celsius, which can support alkali metal atoms such as potassium and rubidium sufficiently. Furthermore, two ITO layers with the same shaped island by insulation layer that configures the current to double back on itself to reduce the magnetic field caused by heating current. In addition, in the condition of the input bias of 50kHz AC, lowfrequency magnetic field noise can be reduced. The proposed MEMS uniform nonmagnetic heating device can be used in atomic devices such as chip scale atomic magnetometer and gyroscope. [Preview Abstract] 

K01.00155: An Atomic Gradiometer with Two Parallel Elliptically Polarized Laserpumped Used for Magnetocardiography Kaifeng Yin, Zhi Liu, Jing Wang, Yan Yin, Qaunpu Liu, Fengwen Zhao, Binquan Zhou A new type of compact atomic gradiometer was designed and integrated. The gradiometer utilizes two parallel elliptically polarized light beams to optically pump atoms. To achieve higher sensitivity, the gradiometer works in the SERF regime. The circularly polarized components of both elliptical laser beams are used to polarize atoms, while the linearly polarized components are used to detect the atoms' spin polarization state. These two parallel beams of the gradiometer do not interfere with each other and can work independently in the magnetometer mode or constitute a gradiometer. The sensitivity of the magnetometer is near 22 fT/$\sqrt{\mathrm{Hz}} $, and the corresponding gradient sensitivity can reach 14 fT/cm/$ \sqrt{\mathrm{Hz}} $ on a 1 cm baseline. Using this gradiometer, magnetocardiography measurement was successfully performed. The experimental results show that in a poor magnetic shielding environment, the magnetometer cannot clearly measure the magnetocardiography signals due to the fluctuations of the environmental magnetic field, while the gradiometer can successfully extract clear magnetocardiography signals. The commonmode rejection ratio, bandwidth and working range of the magnetic gradiometer were also measured and explained. [Preview Abstract] 

K01.00156: MEMS nonmagnetic electric heating chip for integrated atomic sensors Xiaoyang Liang, Yuchen Jia, Binquan Zhou The alkali metal vapor cell of most atomic devices requires high temperature and nonmagnetic environment, while the heating current will introduce additional magnetic field and unexpected magnetic flux density gradient. It is necessary to develop a nonmagnetic heater for atomic devices. In this paper, a new design for nonmagnetic heating chip, fabricated by the MEMS technique, is proposed for the integrated atomic sensors. Platinum (Pt) is chosen as the material of resistance. The chip is composed of two layers of the same serpentineshaped resistors to cancel the magnetic flux density. There are two sets of wires in each layer used as a thermometer resistor and a heating resistor forming a feedback loop of temperature control. The integration of heating and temperature measurement is beneficial for the miniaturization of physics package. The simulation results show that magnetic effect between layers can be reduced by 4 orders than in one layer. The experiment results show that the temperature coefficient of resistance (TCR) is approximately 0.224{\%}/K. The consistency of the resistance is better than 97.7{\%}. The fluctuation of temperature at 383.15 K is under 10 mK. The magnetic flux density introduced by the current in the Z direction is 0.22146 nT/mA. [Preview Abstract] 

K01.00157: A method to measure the residual magnetic field in the magnetic shields of a compact nuclear spin comagnetometer Yuchen Jia, Xiaoyang Liang, Wenfeng Wu, Binquan Zhou The compact comagnetometers are widely used because of its advantage to suppress the error induced by magnetic field fluctuation. The measurement of the residual magnetic field is valuable in the development of comagnetometers. However, it is difficult to put external sensors into the small magnetic shields, and the direct insitu measurement is affected by light shifts and nuclear polarization. In this paper, we put forward a method to eliminate these effects and obtain the real magnetic field in the magnetic shields. Firstly, the measured residual magnetic field orthogonal to the pump beam has linear relationship to the probe intensity, and the real residual field is the intercept on y axis. Then this field can be compensated to zero, and finally we get the residual magnetic field parallel to the pump beam by measuring the resonance frequency shift when the main magnetic field and pumping light are flipped simultaneously. The experiment is implemented on a set of compact cylinder magnetic shields, and the results show that the axial and radial residual magnetic field is 58 nT and 8.5 nT, respectively. This method can obtain the real residual magnetic field in the compact magnetic shields, which is useful for the research of magnetic shields design and demagnetization. [Preview Abstract] 

K01.00158: The KRb3He comagnetometer for the GNOME Mikhail Padniuk, Szymon Pustelny Atomic magnetometers are used to search for exotic physics. Yet, to limit the role of the magnetic field, such devices are typically operated as comagnetometers. A specific example of the comagnetomer is the system based on the mixture of a noble gas and alkalimetal vapor occupying the same glass cell. Coupled evolution of these spin samples at a specific magnetic field (socalled selfcompensation mode) enables suppression of magnetic noise leaving nonmagneticcoupling sensitivity unaffected. We describe the progress in construction of a KRb3He magnetometer at the Jagiellonian University in Kraków. Due to operation in the spinexchange relaxation free regime at the selfcompensating mode, the comagnetometer is characterized with high sensitivity to nonmagnetic coupling. Careful investigation of the role of various experimental parameters will be presented. Future application of the comagnetometer in the Global Network of Optical Magnetometers for Exotic physics searches, searching for topological dark matter, will be also discussed. In the future, the comagnetometer will be used to search for domain walls of axionlike fields and axion planets or stars, which, within various models, are viable darkmatter candidates. [Preview Abstract] 
Not Participating 
K01.00159: Velocity Map Imaging of Trapped Cold Molecular Ions Elizabeth West, Eric Hudson Velocity map imaging (VMI) is a standard technique of gasphase chemistry enabling the detailed investigation of molecular structure and reaction dynamics with an energy resolution that can exceed $h \times 1\;\mathrm{GHz}$. In typical VMI, the species of interest are initially neutral. We describe progress towards realizing a new type of VMI technology in which the species of interest are trapped, cold atomic and molecular cations. This extension of the VMI technique could be used to explore new realms of ion and plasma chemistry and bring to bear the many established advantages of ion traps, including long interaction times, singleparticle addressability, and the ability to prepare purestate ultracold reactants. We present preliminary data on VMI of photodissociated cold BaCl${}^+$ from a linear quadrupole ion trap. [Preview Abstract] 
Not Participating 
K01.00160: Lowcost handheld filter spectrometer for water quality measurements Theodore A. Corcovilos, Erin Bair, Thomas R. Aumer, Spencer Graves, Michael J. Van Stipdonk Many common chemical sensors for environmental contaminants are based on a change in optical absorbance. The gold standard for measuring optical absorbance is UV/VIS spectrometry, but this typically requires an expensive benchtop instrument. Here we present a handheld low resolution filterbased spectrometer that measures optical absorbance in six wavelength bands of the visible spectrum, built for less than \$100. This is sufficient to quantify the absorbance of several common colorbased chemical sensors used for the detection of contaminants in water. We demonstrate our device by measuring fluoride concentrations in drinking water samples using an EPAapproved protocol (EPANERL 340.1) and show that our 6channel device outperforms singlewavelength photometric measurements taken with an industrystandard commercial photometer in both detection threshold and sensitivity. [Preview Abstract] 
Not Participating 
K01.00161: Towards a selfconsistent approach to model cool hydrogen plasma emission Mark Zammit, James Colgan, Dmitry Fursa, Igor Bray, Christopher Fontes, David Kilcrease, Peter Hakel, Jeffery Leiding, Eddy Timmermans Cool (molecular) plasmas are ubiquitous throughout the Universe. Practically all opacity and emissivity studies of molecular plasmas are conducted utilizing data or codes taken from several different sources. To this end, we are developing a fully generalizable selfconsistent approach to model cool hydrogen (H$_2$ and H$_2^+$) plasmas opacity and emissivity. Here we present results of cool hydrogen plasmas emission, and investigate the importance of electronic excited states. [Preview Abstract] 
Not Participating 
K01.00162: Phase sensitivity and noise reduction in a twopump fourwave mixing process Erin Knutson We show a new multipump fourwave mixing configuration, with a potentially useful phasedependence. We find that, for certain phase values of the input probes, the intensity noise of any output mode can be lower than that of its phaseinsensitive counterpart. This lowernoise amplification has been demonstrated previously in atomic four wave mixing, but only with the use of significantly more complex experimental configurations, e.g. dual homodyne detection or cascaded vapor cells. Additionally, our method naturally results in four beams that can be squeezed or quantum correlated with one another. This result has obvious applications in the simplification of quantum optical experiments that involve the generation or amplification of more than two correlated modes. We describe how our findings may further be employed in a ``touchless'' or interactionfree SU(1,1) interferometry scheme, wherein a phase measurement may be made remotely on a pair of modes without introducing loss or destroying any squeezing between them. [Preview Abstract] 
Not Participating 
K01.00163: Evidence for Bosonization in a threedimensional gas of SU($N$) fermions Entong Zhao, Song Bo, Chengdong He, Elnur Hajiyev, Zejian Ren, Jeongwon Lee, GyuBoong Jo A multicomponent Fermi gas with SU($N$) symmetry is expected to behave like spinless bosons when the number of internal states $N$ becomes large weakening constraints from the Pauli exclusion principle. In this poster, we report direct evidence for bosonization by the measurement of contacts in a threedimensional (3D) SU($N$) fermionic gas of $^{173}$Yb with tunable $N$. Imaging the column integrated momentum distribution with a high signaltonoise ratio, we find that the contact per spin approaches a constant with a $1/N$ scaling in the low fugacity regime. This scaling reveals the vanishing role of the fermionic statistics in thermodynamics, and unfolds the intriguing nature of bosonization in 3D SU($N$) fermions. In addition, we will discuss complementary characterization of SU($N$) fermions including the collective modes and the machine learning aided study of a threedimensional gas of SU($N$), which could be alternative route to reveal bosonization. [Preview Abstract] 
Not Participating 
K01.00164: Interacting fermions in driven optical lattices: gauge fields and coherent control AnneSophie Walter, Kilian Sandholzer, Joaquin Minguzzi, Konrad Viebahn, Frederik Goerg, Tilman Esslinger Driving quantum systems out of equilibrium can generate exotic and novel phases of matter. Floquet engineering focuses on the realization of effective, static Hamiltonians by driving systems periodically in time. In the pursuit of simulating lattice gauge theories in the laboratory, we present the successful implementation of a twofrequency driving scheme in a Hubbard dimer, which explicitly breaks timereversal symmetry and allows to engineer densitydependent Peierls phases. We demonstrate the winding structure of this phase around a Dirac point in the driving parameter space. In Floquet schemes, in general, the choice of driving frequencies for the implementation of effective Hamiltonians is limited by resonances to energetically higherlying modes, e.g. transitions to higher Bloch bands of an optical lattice. We implement a coherent control scheme by which we overcome this frequency constraint. By adding a second drive at twice the frequency and tuning the relative phase between the two drives we achieve destructive interference of the two paths. This extends the lifetime of the spin correlations in our manybody system by more than two orders of magnitude compared to the singlydriven system. [Preview Abstract] 
Not Participating 
K01.00165: Ferromagnetism and PhaseSeparation in Confined Fermionic 1D Systems Georgios Koutentakis, Simeon Mistakidis, Peter Schmelcher Lieb and Mattis have shown that ferromagnetism is impossible to achieve in the ground state of fermionic systems, our work focusses on identifying stable ferromagnetic correlations emanating in the excited states of 1D ultracold systems of few fermions. The stability of such correlations can be attributed to the Hund exchange interaction inherent in those setups. However, these ferromagnetic correlations are connected to neither the stability of the magnetization nor the phase separation of the spincomponents, contrary to the well enstablished framework of the Stoner instability. [Preview Abstract] 
Not Participating 
K01.00166: New Control and Measurement Techniques for Spin1 Ensembles Lin Xin, Matthew Boguslawski, Maryrose Barrios, Sami Hakani, Julia Cohen, Michael Chapman The more complicated quantum phase space of spin1 atoms compared to the spin1/2 case offers unique capabilities, but also provides unique challenges for quantum control and measurement. Our work with ultracold, spin1, rubidium 87 atoms in an alloptical trap has given us insight into how holonomictype schemes could be realized in an atomic system. We demonstrate the creation and readout of a nonAbelian geometric phase in a spin1 quantum system. Furthermore, by implementing microwave techniques to selectively isolate hyperfine states, we are able to construct multilevel transitions with an accuracy of 99.5{\%}. We will discuss how these techniques can be applied to quantum metrology, quantum gates, and quantum tomography with spin1 systems. [Preview Abstract] 
Not Participating 
K01.00167: Recent Progress with Cryogenic 2D Ion Trap Arrays J.F. Niedermeyer, J. Keller, K.C. McCormick, S.L. Todaro, F.W. Knollmann, D.J. Wineland, D.H. Slichter, A.C. Wilson, D. Leibfried Twodimensional arrays of ions in individual microtraps are a promising technology for quantum computation and simulation. In collaboration with Sandia National Laboratories, we have developed microfabricated surface electrode traps that confine three ions on the vertices of equilateral triangles, with each ion confined in a separate potential well. This feature, and the small interion distance (30 $\mu$m), allows for selective coupling between ions that can be dynamically changed during single experiments. In principle, this approach enables simulation of arbitrary, tunable spinlattice Hamiltonians. Quantum simulations of bosons in synthetic magnetic fields can also be performed using motional excitation of the ions (phonons), and not internal ion states, as the controllable quantum system of interest. In an effort to reduce motional decoherence of the ions, as desired for these simulations, the traps are operated at cryogenic temperatures ($\sim$4 K). We report progress on trapping and manipulating ions in these 2Darray traps. [Preview Abstract] 
Not Participating 
K01.00168: Progress towards dipolephonon quantum logic with trapped ions Lu Qi, Evan Reed, Will Staples, Ziyi Wang, Jyothi Saraladevi, Eric Pretzsch, Kenneth Brown, Welsey C. Campbell, Eric R. Hudson, Michael C. Heaven Molecular ions are proposed to be promising candidates for high precision measurements of fundamental constants, cold chemistry dynamics control, and quantum information processing. Particularly with regards to quantum computer engineering, the rich internal structures and long range dipoledipole interactions between molecular ions offer a means of potentially overcoming some of the current problems of atomic ion platforms. \footnote{E. Hudson and W. Campbell, 10.1103/PhysRevA.98.040302.}\footnote{ W. Campbell and E. Hudson, arXiv:1909.02668.}. Here, we report our progress towards dipolephonon interaction with molecular and atomic ions. A Calcium ion is cooled near its motional ground state and is used to excite a dipole transition of a cotrapped molecular ion by delicately controlling the phonons. Progress towards dipolephonon logic gate is also presented. [Preview Abstract] 
Not Participating 
K01.00169: Multichannel quantumdefect theory for anisotropic interactions Ningyi Du, Bo Gao We present a general formulation of multichannel quantumdefect theory (MQDT) for anisotropic longrange potentials. The theory greatly expands the types of interactions, including complex interactions involving molecules, that can be treated and understood systematically. It promotes MQDT into a general theory of interactions and establishes a foundation for new classes of quantum theories for chemical reactions, fewbody systems, and manybody systems. [Preview Abstract] 
Not Participating 
K01.00170: Concept of arrangement in an $N$body quantum system Bo Gao We discuss the concept of ``arrangement'', traditionally found in the context of fewbody rearrangement collisions, in a more general context of an $N$body quantum system. We show that for an $N$body quantum system with attractive interactions that can bind the constituent particles, the concept of arrangement provides both a necessary and an important basis for understanding its complexity and the general structure of its Hilbert space. The concept is a necessary part of a foundation for a more complete understanding of $N$body quantum systems, especially those made of atoms and molecules. [Preview Abstract] 
Not Participating 
K01.00171: Towards a quantum gas microscope for molecules Sarah Bromley, Andrew Innes, Jonas Matthies, Lewis McArd, Jonathan Mortlock, Apichayaporn Ratkata, Simon Cornish We report progress towards the building of a quantum gas microscope for molecules that has the flexibility to produce RbCs or KCs diatomic molecules. A quantum gas microscope for molecules combines the stateoftheart imaging and addressing techniques currently employed in atomic quantum gas microscopes and applies them to molecule experiments. The longrange dipoledipole interactions between heteronuclear polar molecules will allow for studies, all with single latticesite resolution, of extended Hubbard models, which are expected to exhibit much richer manybody physics, including novel checkerboard, star, and stripe phases. [Preview Abstract] 
Not Participating 
K01.00172: Ultracold chemistry and dynamics of Li+CaF collisions Masato Morita, Qian Yao, Changjian Xie, Hua Guo, Brian K. Kendrick, N. Balakrishnan Ultracold polar molecules are actively being explored as potential candidates for quantum simulation, quantum information processing, and precision testing of fundamental physics. Polar molecules involving alkaline earth atoms such as CaF have attracted considerable attention and direct laser cooling and trapping of CaF have recently been reported. A secondstage cooling may involve sympathetic collisions with ultracold alkali metal atoms such as Li but its applicability may be limited by exothermic reactive scattering. Here we explore elastic and inelastic (reactive) collisions of Li with CaF molecules in the cold and ultracold regime. In particular, we report the characteristics of highly anisotropic potential energy surface of Li+CaF and LiF+Ca obtained from extensive ab initio calculations and quantum scattering calculations of the ultracold Li+CaF$\to$ LiF+Ca chemical reaction using hyperspherical coordinates. [Preview Abstract] 
Not Participating 
K01.00173: Optimisation of a cryogenic buffergas cell for maximum molecule flux Manuel Koller, Florian Jung, Jindaratsamee Phrompao, Thomas Gantner, Isabel M. Rabey, Martin Zeppenfeld, Gerhard Rempe Cold polyatomic molecules provide fascinating research possibilities in physics and chemistry. The workhorse for producing cold molecules is buffergas cooling. Here, we present a comprehensive theoretical and experimental study of molecule flux from a buffergas cell, operating in the effusive regime. Technical details of improvements to the cell design and temperature are shown. In addition, an investigation into both moleculemolecule boosting and helium boosting effects is also presented. By decreasing the cell length [1], reducing boosting into the cell and improving the temperature of our system, we have increased our signal by more than a factor two. In combination with our centrifuge decelerator, these molecule fluxes are now sufficient to study cold collisions between trapped polyatomic molecules. [1] Gantner et al., arXiv:2001.07759 [Preview Abstract] 
Not Participating 
K01.00174: Crystal Damage Mapping with NV Centers in Diamond for Directional Dark Matter Detection David Phillips, Mason Marshall, Raisa Trubko, Pauli Kehayias, Matthew Turner, Mark Ku, Alex Sushkov, Ronald Walsworth A proposed diamondbased detector for weakly interacting massive particle (WIMP) dark matter would combine the advantages of solidstate semiconductor detectors with directional detection capability, allowing WIMP searches below the neutrino floor. This crucially relies on the ability to detect and map damage to the diamond crystal lattice at the nanoscale, to determine the direction of incoming WIMP candidates. Nitrogen vacancy (NV) centers are a prime candidate to enable this because of their strain sensitivity and wellcharacterized quantum properties. We present recent progress on techniques using NV centers to locate and map nuclearrecoilinduced damage, including crystal lattice strain and induced lattice vacancies. [Preview Abstract] 

K01.00175: A MultiIon Photonic Integrated Optical Clock David Reens, Jules Stuart, Robert Niffenegger, Colin Bruzewicz, Cheryl SoraceAgaskar, Dave Kharas, Jeremy Sage, John Chiaverini, Robert McConnell Optical atomic clocks based on single trapped ions boast impressive stability and accuracy, but extension to multiple cotrapped ions is hindered by their strong Coulomb repulsion and associated quadrupole shifts. An alternative path is to multiplex the entire trapping apparatus, a feat made accessible by chip scale traps with photonic integration. This multiplicity brings new opportunities for improved shortterm stability, Dicknoise suppression, and simultaneous Zeeman sublevel interrogation. While chip traps bring challenges for clock operation, particularly with regard to motional excitation, they also offer greater control over blackbody radiation and a clearer path towards portability. We explore these new opportunities with multiple $^{88}$Sr$^+$ ions loaded in separate zones of a fully photonic integrated chip trap and clocked on the $^5S_{1/2}$ to $^4D_{5/2}$ forbidden optical transition. [Preview Abstract] 
Not Participating 
K01.00176: A femtotesla pulsed gradiometer using multipass cells at finite fields Wonjae Lee, Mark Limes, Elizabeth Foley, Thomas Kornack, Michael Romalis We describe a $^{\mathrm{\thinspace 87}}$Rb scalar gradiometer using two multipass cells which increase the path length of the probe beam by one order of magnitude. This gives a much higher optical depth on resonance, which is crucial for quantumnondemolition (QND) measurements. As a result, we can directly record a large optical rotation. When the optical rotation exceeds $\pi $/4 radians, the optical rotation signal wraps around, showing multiple zerocrossings in a single Larmor period. This exotic signal gains a higher signal intensity, which indicates that a single photon can interact with higher number of alkali atoms. The magnetic field sensitivity then can reach beyond the naive CramerRao lower bound, the minimum bound for the estimated frequency variance of a sine wave in the presence of photon shot noise. The lower probe power consumption is also critical for development of a miniaturized magnetometer. We have implemented a novel method of zerocrossing detection of the wrapped signals. We report a magnetic sensitivity of 7 fT/$\surd $Hz in the geomagnetic field range, which agrees well with the quantum spin noise limit. [Preview Abstract] 
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