Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session Q34: Precision Many Body PhysicsFocus Recordings Available
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Sponsoring Units: DCOMP DAMOP DCMP Chair: Nicholas Pike, UES, Inc Room: McCormick Place W-193A |
Wednesday, March 16, 2022 3:00PM - 3:36PM |
Q34.00001: Transition from an Atomic to a Molecular Bose–Einstein condensate Invited Speaker: Cheng Chin Molecular quantum gases (that is, ultracold and dense molecular gases) have many potential applications, including quantum control of chemical reactions, precision measurements, quantum simulation and quantum information processing. For molecules, to reach the quantum regime usually requires efficient cooling at high densities, which is frequently hindered by fast inelastic collisions that heat and deplete the population of molecules. Here we report the preparation of two-dimensional Bose–Einstein condensates (BECs) of spinning molecules by inducing pairing interactions in an atomic condensate near a g-wave Feshbach resonance. The trap geometry and the low temperature of the molecules help to reduce inelastic loss, ensuring thermal equilibrium. From the equation-of-state measurement, we determine the molecular scattering length to be + 220(±30) Bohr radii (95% confidence interval). We also investigate the unpairing dynamics in the strong coupling regime and find that near the Feshbach resonance the dynamical timescale is consistent with the unitarity limit. Our work demonstrates the long-sought transition between atomic and molecular condensates, the bosonic analogue of the crossover from a BEC to a Bardeen−Cooper−Schrieffer (BCS) superfluid in a Fermi gas. In addition, our experiment may shed light on condensed pairs with orbital angular momentum, where a novel anisotropic superfluid with non-zero surface current is predicted, such as the A phase of 3He. |
Wednesday, March 16, 2022 3:36PM - 3:48PM |
Q34.00002: Vector Magnetometry with Microwave-Assisted Optical Pumping in Warm Rubidium Vapor Ying-Ying Lu Vector magnetometers are used in areas such as spacecraft navigation and bio-magnetism. The precision and calibration of many vector magnetometers depend on external field sources and additional instrumentation, whose stability may drift. I describe a vector magnetometry method using microwave-assisted optical pumping, in which a microwave field resonant to the ground state hyperfine splitting of 87Rb pumps an ensemble of warm rubidium vapor, in addition to a strong optical pump beam, and a weaker optical probe beam. The proposed method allows us to detect fields in the in the tens of mT regime and more importantly, the direction of the DC magnetic field relative to the microwave field. I present theoretical details as well as preliminary data demonstrating measurements of a DC magnetic field. These measurements were taken when the DC field was aligned at various angles relative to the microwave magnetic field alignment. I compare theoretical and experimental differences in the measurements. |
Wednesday, March 16, 2022 3:48PM - 4:00PM |
Q34.00003: Precision Measurements with Optically-levitating Nanospheres Nia Burrell Measuring short-range forces such as deviations to Newtonian gravity or Casimir forces requires precision sensitivity. Optically-levitating nanospheres in vacuum have experimentally been shown to present excellent sensitivity at the zeptonewton scale. Our experiment makes use of an optically levitating 300 nm silica sphere in vacuum. We plan to use this system to search for a Yukawa-type correction to Newtonian gravity. Furthermore, successful execution of our experiment can allow us to investigate other short-range surface-force phenomena as well. |
Wednesday, March 16, 2022 4:00PM - 4:12PM |
Q34.00004: A super-radiant interferometer of spin-1 atoms with Heisenberg scaling in sensitivity Pratik Adhikary, Arnab Sarkar, Shubham Jaiswal, Arif W Laskar, Diptarka Das, Saikat Ghosh Precision measurement in metrology has gained enormous attention in the last decade, both in optomechanics and atomic systems, where improvement in measurement sensitivity has acquired a pivotal role in research. Here we report that by storing an optical field in a laser-cooled 87Rb atomic cloud prepared in a spin-1 manifold, one can achieve a massive gain in retrieve signal by increasing coupling field strength due to collective spin excitation. This observation leads to a novel super-radiant interferometer where optical field first store in an atomic medium as dark state polaritons, evolve for a finite storage time, acquire an atomic phase difference, and finally interfere and convert back into optical signal. As a result, both the atomic and optical phases can be measured with high precision. The collective enhancement of sensitivity increases nonlinearly with number of atoms beyond the standard quantum limit. Moreover, one can further increase sensitivity by increasing the storage time, and the simplicity of the experimental setup can lead to a compact device that can be used as high precision magnetic field sensors with non-classical scaling in sensitivity. |
Wednesday, March 16, 2022 4:12PM - 4:24PM |
Q34.00005: Neutrality of matter search with levitated microspheres Nadav Priel, Gautam Venugopalan It is commonly accepted that the charge of the electron is equal in magnitude to the charge of the proton. This observation has been tested with great precision over the last century and has supporting arguments from the theory side. However, the measurement of this equality is a sensitive tool to probe new physics as it is breaking down in a few suggested extensions of the standard model. We report on a neutrality of matter test conducted with optically levitated microspheres. In this test, the electrostatic response of a micron size sphere with an equal number of protons and electrons is measured with very high sensitivity. This technique is complementary to other methods used to test matter neutrality in the past. The current sensitivity is not due to fundamental physical limitations and ongoing improvements of the system targeting better background mitigation and modeling, together with improved force sensitivity, are expected to further extend the parameter space covered by the technique. |
Wednesday, March 16, 2022 4:24PM - 4:36PM |
Q34.00006: Target–BEC pairs atomtronic rotation sensor Mark A Edwards, Charles B Henry, Oluwatobi Adeniji We describe an idea for an atomtronic rotation sensor consisting of a rectangular array of pairs of target–Bose-Einstein condensates (BECs). A target BEC is a condensate confined in the "target” trap which is a 2D channel potential consisting of a central well surrounded by a ring–shaped channel. A condensate formed in such a potential will have a central disk condensate inside of a concentric ring–shaped condensate. We assume that the rest frame of the target–BEC–pair array is rotating at some speed, ΩR , with respect to a frame at rest with respect to the “fixed stars”. The purpose of the sensor described here is to measure ΩR . We show that a single target-pair BEC having circulation in one of the rings will undergo circulation transfer when a barrier potential is turned on where the rings overlap. If ΩR > Ωc , where Ωc is some rotating-frame speed threshold, and that no transfer occurs if ΩR < Ωc. It is also the case that Ωc depends on Ub,max , the maximum barrier strength. Thus an array of such target-pair BECs, where barriers of different maximum strengths are applied, can bound the value of ΩR . We have simulated such a system for different rotation speeds and locations of the array relative to the location of the rotation axis. We will discuss the potential perfomance of such systems and the possible ranges of ΩR that could be measured. |
Wednesday, March 16, 2022 4:36PM - 4:48PM |
Q34.00007: Modeling atom interferometry experiments with Bose-Einstein condensates in power–law potentials Mark A Edwards, Charles B Henry, Robert Sapp, Andrew Smith, Cass A Sackett, Charles W Clark, Stephen G Thomas Recent atom interferometry (AI) experiments involving Bose–Einstein condensates (BECs) have been conducted under extreme conditions of volume and interrogation time. Numerical solution of the standard mean–field theory applied to these experiments presents a nearly intractable challenge. We present an approximate variational model that provides rapid approximate solutions of the rotating–frame Gross–Pitaevskii equation for a power–law potential. This model is well–suited to the design and analysis of AI experiments involving BECs that are split and later recombined to form an interference pattern. We derive the equations of motion of the variational parameters for this model and illustrate how the model can be applied to the sequence of steps in a recent AI experiment where BECs were used to implement a dual–Sagnac atom interferometer rotation sensor. We use this model to investigate the impact of finite–size and interaction effects on the single Sagnac–interferometer phase shift. |
Wednesday, March 16, 2022 4:48PM - 5:00PM |
Q34.00008: Atomtronic Datta-Das transistor using ultracold Strontium atoms Chetan Sriram Madasu, Mehedi Hasan, ketan rathod, Chang Chi Kwong, david wilkowski We report experimental demonstration of atomtronic Datta-Das transistor in free space with ultracold strontium atoms as the (spin) carriers. Datta-Das transistor is a device in which the spin current from source to drain is controlled by the gate voltage similar to a conventional FET where electric charge current from source to drain is controlled by the gate voltage. In the experiment, we simulate a beam of spin-polarized atoms passing through a gate region made of three gaussian beams coupled to a tripod-like energy level scheme and control their final spin orientation. We use the ratio of Rabi frequencies of the tripod lasers as the gate parameter, the analogue of the gate voltage, to characterize the atomtronic Datta-Das transistor. We show that the spin rotation can be well controlled and it is robust to a wide range of velocities of the atoms. We also discuss about the sensitivity of the spin rotation with the gate parameter to the geometry of the laser beams. |
Wednesday, March 16, 2022 5:00PM - 5:12PM |
Q34.00009: Improving the sensitivity of cold-atom inertial sensors using robust control Russell Anderson, Viktor Perunicic, Stuart Szigeti, Matt Goh, Jack Saywell, Philip Light, Nathanial Wilson, Alistair Milne, Michael Biercuk Cold-atom sensors have demonstrated state-of-the-art inertial measurements in laboratory environments. Future generations of atomic inertial sensors aim to achieve this performance in compact and rugged form factors, enabling new capabilities in navigation, hydrology, and space-based gravimetry. However, there are significant challenges to achieving laboratory performance in real-world environments. In particular, deploying a cold-atom sensor onboard a moving platform (e.g. a ship or plane) degrades measurement sensitivity by many orders of magnitude, or even prevents sensor operation altogether. Here we show that error-robust quantum control can suppress dominant noise sources due to platform motion, reducing the performance gap between laboratory operation and real-world field deployment. We use a custom-built flexible optimization package, which exploits automated analytic differentiation and stochastic optimization, to efficiently create broadband robust beamsplitter and mirror pulses. Through simulated operation under realistic vehicle motion, we verify that these robust control solutions suppress the effect of transverse accelerations by considerably in a single-axis sensor. |
Wednesday, March 16, 2022 5:12PM - 5:24PM |
Q34.00010: Towards levitated, macroscopic-scale atom interferometry with strontium for precision gravity gradiometry Natasha Sachdeva, Kenneth DeRose, Tejas Deshpande, Jonah Glick, Yiping Wang, Tim Kovachy Light-pulse atom interferometry is a versatile and powerful tool for conducting precise measurements of fundamental constants, testing general relativity, searching for signatures of new physics, and investigating quantum mechanics on a macroscopic scale. For atom interferometry, pulses of light are used to create the atom optics equivalents of beam-splitters and mirrors. Recent advances in atomic clocks have illustrated the advantages of using strontium, an alkali-earth atom, over the typically used alkali atoms due to its decreased sensitivity to backgrounds such as magnetic fields. We present progress toward the realization of a two-meter atomic fountain at Northwestern University that will be used to develop atom interferometry with large spacetime areas and long interrogation times by levitating the atoms using optical lattices. Initial interferometry will be performed using sequential Bragg transitions for the atom optics pulses. Large spatial separations are enabled in part by spectral engineering of the atom optics beams to compensate for intensity-dependent phase shifts. The two-meter fountain will be used for precision gravitational measurements such as a measurement of the gravitational constant G and for a precise test of the inverse-square law for gravity. |
Wednesday, March 16, 2022 5:24PM - 5:36PM |
Q34.00011: Detecting modified Vacuum Fluctuations using geometric phase acquired by an accelerated atom Navdeep Arya, Vikash Mittal, Kinjalk Lochan, Sandeep K Goyal Quantum field fluctuations can get modified due to the observer’s motion or a change in the boundary conditions on the field. Such modifications of quantum field fluctuations may result in effects like the Unruh effect and the Hawking Radiation. Experimental verification of these predictions requires extreme acceleration (or gravity). Here, we study the modified vacuum fluctuations perceived by an accelerated atom inside an electromagnetic cavity. The boundary effects due to the cavity walls can be separated from the inertial contribution and the non-inertial contribution arising from the atomic acceleration. |
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