Bulletin of the American Physical Society
52nd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 66, Number 6
Monday–Friday, May 31–June 4 2021; Virtual; Time Zone: Central Daylight Time, USA
Session H10: Out-of-Equilibrium Quantum DynamicsLive
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Chair: Chen-Lung Hung, Purdue University |
Wednesday, June 2, 2021 8:00AM - 8:12AM Live |
H10.00001: Disorder in order: localization in a randomless cold atom system Félix Rose, Richard Schmidt We present a mapping between the Edwards model of disorder, describing a single particle subjected to the potential of randomly-positioned scatterers, and the Bose polaron problem of a light impurity interacting with a Bose-Einstein condensate (BEC) of heavy atoms. The time evolution of the impurity emulates the disorder-averaged dynamics of the Edwards model. The mapping offers a new experimental setup to investigate the physics of Anderson localization. It is valid in any space dimensions and can be extended to include interactions between bosons, several particles, and arbitrary scattering and confining potentials. We focus on the case of an impurity interacting with a one-dimensional BEC through a repulsive contact interaction. The polaron model is studied by means of a variational approach, which can be benchmarked against the corresponding, exactly-solvable disorder model. While the simple Chevy Ansatz misses the localization physics entirely, a more involved coherent state Ansatz combined with the Lee-Low-Pines transform captures the qualitative physics of disorder. |
Wednesday, June 2, 2021 8:12AM - 8:24AM Live |
H10.00002: Observation of an analogue to the Cosmic Hubble Friction in a Bose Einstein Condensate Swarnav Banik, Monica Galan, Hector Martinez, Madison J Anderson, Stephen Eckel, Ian Spielman, Gretchen K Campbell We have simulated the cosmological Hubble friction using a toroidal Bose-Einstein condensate (BEC) of 23Na atoms. Where scalar fields in a BEC (such as phonons) have behavior analogous to cosmological scalar fields. We have observed both damping and growth of the phonon field when the toroidal BEC is expanded or contracted respectively. This is analogous to the damping or enhancement of cosmological fields due to Hubble friction. Furthermore, the measured strength of the Hubble friction is in agreement with recently published theory. In addition, we have also performed a systematic study of the Doppler shifts due to the phonon dynamics. |
Wednesday, June 2, 2021 8:24AM - 8:36AM Live |
H10.00003: Does a disordered isolated Heisenberg spin system thermalize? Titus Franz, Adrien Signoles, Renato Ferracini Alves, Clement Hainaut, Nithiwadee Thaicharoen, Sebastian Geier, Andre Salzinger, Annika Tebben, Shannon Whitlock, Gerhard Zürn, Matthias Weidemüller The far-from-equilibrium dynamics of generic disordered systems is expected to show thermalization, but this process is yet not well understood and shows a rich phenomenology ranging from anomalously slow relaxation to the breakdown of thermalization. While this problem is notoriously difficult to study numerically, we can experimentally probe the relaxation dynamics in an isolated spin system realized by a frozen gas of Rydberg atoms. By breaking the symmetry of the Hamiltonian with an external field, we can identify characteristics of the steady-state magnetization, including a non-analytic behavior at zero external fields. These can be understood from mean-field, perturbative, and spectral arguments. The emergence of these distinctive features allows falsifying whether the experiment satisfies Eigenstate Thermalization Hypothesis (ETH). |
Wednesday, June 2, 2021 8:36AM - 8:48AM Live |
H10.00004: Nonlinear interferometry beyond classical limit facilitated by cyclic dynamics Qi Liu, Ling Na Wu, Jia Hao Cao, Tian Wei Mao, Xin Wei Li, Shuai Feng Guo, Meng Khoon Tey, Li You Quantum metrology employs entanglement to improve measurement signal-to-noise ratio. The conventional approach based on reducing quantum noise with entangled states always demands low-noise detection. An alternative route magnifies signal instead by using nonlinear interferometry with nonlinear ‘path’ splitter and recombiner, typically with the latter being the time reversal of the former to facilitate efficient detection. However, it is difficult to implement time-reversed nonlinear dynamics in a general many-body system. Here, we present an idea to implement nonlinear interferometry without invoking time reversal. Instead of time-reversed evolution, we time the system’s return to the immediate vicinity of initial state based on cyclic quantum dynamics. Utilizing the quasi-periodic spin mixing dynamics in a three-mode 87Rb atom spinor condensate, we implement such a `closed-loop' nonlinear interferometer and achieve a metrological gain of $3.87_{-0.95}^{+0.91}$ decibels over the classical limit for a total of 26500 atoms. The demonstration we present unlocks the high potential of nonlinear interferometry by allowing the dynamics to penetrate into deep nonlinear regime, which gives rise to highly entangled non-Gaussian state. Our approach for bypassing time reversal may open up new opportunities in the experimental investigation of researches that are typically studied by using time reversal protocols. |
Wednesday, June 2, 2021 8:48AM - 9:00AM Live |
H10.00005: Using a mapping as a probe for heating suppression in periodically driven many-body quantum systems: a mean-field example with Bose gases Axel Pelster, Etienne Wamba By using our recent results on the exact mappings between time evolutions of different quantum many-body systems [Phys. Rev. A 94, 043628 (2016)], we construct a mean-field model of many-body systems with rapid periodic driving. The single-particle potential and the inter-particle interaction strength are both time-dependent at once, in related ways. We map the evolutions of the model system onto evolutions with slowly varying parameters. Such a mapping between a Floquet evolution and a static or slow process allows us to investigate non-equilibrium many-body dynamics and examine how rapidly driven systems may avoid heating up, at least when mean-field theory is still valid. From that special but interesting case, we learn that rapid periodic driving may not yield to heating because the time evolution of the system has a kind of hidden adiabaticity, inasmuch as it can be mapped exactly onto that of an almost static system. |
Wednesday, June 2, 2021 9:00AM - 9:12AM Live |
H10.00006: Probing Multi-Site Correlators in a Bose Hubbard lattice Brendan Saxberg, Gabrielle Roberts, Andrei Vrajitoarea, Margaret G Panetta, Ruichao Ma, David I Schuster, Jon Simon Microwave photons can be engineered to exhibit strong interactions and create highly correlated quantum states using superconducting quantum circuits and the circuit QED framework. Using qubits as interacting lattice sites and coupling these sites together, we build a 1D Bose-Hubbard lattice for strongly interacting photons. In previous work, we developed a method to dissipatively stabilize our lattice in an incompressible state, and applied it to our system to realize an n=1 Mott insulating phase of light. Recent improvements to our apparatus enable us to use our site- and time- resolved readout to probe multi-site correlations and thus characterize delocalized lattice states. We discuss experiments on our system such as melting our prepared Mott insulator into a superfluid by adiabatically tuning the volume of our chain and investigate correlations during both the cooling and the steady state. The local control over Hamiltonian parameters makes superconducting circuits a versatile platform for studying the relationship between highly correlated quantum matter and quantum thermodynamics. |
Wednesday, June 2, 2021 9:12AM - 9:24AM Live |
H10.00007: Probing many-body noise in a strongly interacting two-dimensional spin ensemble ---- Part I: Experiment Emily J Davis, Bingtian Ye, Francisco Machado, Simon Meynell, Thomas Mittiga, William K Schenken, Maxime Joos, Bryce H Kobrin, Yuanqi Lyu, Dolev Bluvstein, Soonwon Choi, Chong Zu, Ania C Jayich, Norman Y Yao Two-dimensional systems of strongly interacting, highly coherent, and optically addressable spins present opportunities in both quantum simulation and sensing. While obtaining such a system in a solid-state platform has traditionally proved challenging, recent progress in delta-doped diamond growth has enabled the fabrication of a novel sample containing a thin layer of nitrogen-vacancy (NV) and substitutional nitrogen (P1) defects in a diamond lattice. We expect that this hybrid NV-P1 spin system is two-dimensional, i.e., that the layer thickness is smaller than the average spin-spin spacing; however, measuring the dimensionality conclusively presents a new and separate challenge. In this talk, we establish the two-dimensional nature of our sample via a characterization technique based upon the system's intrinsic many-body dynamics. In particular, by studying the decoherence dynamics of the NV spins, we directly measure the dimensionality of the interacting P1 spin ensemble. This work opens the door to understanding both static and dynamical properties of many-body systems more broadly, by generalizing our method of mapping dimensionality onto the dynamics of an NV probe spin. |
Wednesday, June 2, 2021 9:24AM - 9:36AM Live |
H10.00008: Towards single ion addressing in a 2D crystal of 40Ca+ Brian J McMahon, Jonathan R Jeffrey, Brian Sawyer Two-dimensional (2D) Coulomb crystals of cold atomic ions are a proven resource for studies of quantum many-body physics and precision sensing. Single-site operations allow for fine control of many-body interactions in quantum simulation protocols such as quantum approximate optimization. We report progress towards individual ion addressing within a rotating 2D crystal of 40Ca+ confined in a compact Penning trap constructed with permanent magnets. We address a subset of co-trapped ions using a stationary, narrow-linewidth 729 nm laser beam offset from the center of the rotating 2D array. Sub-Doppler cooling of 2D ion arrays in the compact trap will be described, and we will present a new compact Penning trap design utilizing printed circuit boards in place of extended electrodes. |
Wednesday, June 2, 2021 9:36AM - 9:48AM Live |
H10.00009: Optimal quantum control of mechanical motion at room temperature: ground-state cooling Lorenzo Magrini, Philipp Rosenzweig, Constanze Bach, Andreas Deutschmann-Olek, Sebastian Hofer, Sungkun Hong, Nikolai Kiesel, Andreas Kugi, Markus Aspelmeyer The ability to accurately control the dynamics of physical systems by measurement and feedback is a pillar of modern engineering. Today, the increasing demand for applied quantum technologies requires to adapt this level of control to individual quantum systems. Achieving this in an optimal way is a challenging task that relies on both quantum-limited measurements and specifically tailored algorithms for state estimation and feedback. Successful implementations thus far include experiments on the level of optical and atomic systems. Here we demonstrate real-time optimal control of the quantum trajectory of an optically trapped nanoparticle. We combine confocal position sensing close to the Heisenberg limit with optimal state estimation via Kalman filtering to track the particle motion in phase space in real time with a position uncertainty of 1.3 times the zero point fluctuation. Optimal feedback allows us to stabilize the quantum harmonic oscillator to a mean occupation of n=0.56±0.02 quanta, realizing quantum ground state cooling from room temperature. Our work establishes quantum Kalman filtering as a method to achieve quantum control of mechanical motion, with potential implications for sensing on all scales. |
Wednesday, June 2, 2021 9:48AM - 10:00AM Live |
H10.00010: Tunable Single-Ion Anisotropy in Spin-1 Models Realized with Ultracold Atoms Woo Chang Chung, Julius de Hond, Jinggang Xiang, Enid Cruz-Colón, Wolfgang Ketterle Mott insulator plateaus in optical lattices are a versatile platform to study spin physics. Using sites occupied by two bosons that possess an internal degree of freedom in the form of a hyperfine state, we realize a Hamiltonian with a uniaxial single-ion anisotropy term proportional to (Sz)2 which plays an important role in stabilizing magnetism for low-dimensional magnetic materials. The ground states of the Hamiltonian include a spin Mott insulating phase, which can be adiabatically connected to the correlated XY ferromagnet. We explore non-equilibrium spin dynamics after preparing a rotated spin state, which is quenched into a Hamiltonian with nonzero superexchange. We observe a resonant effect in the spin alignment as a function of lattice depth when the exchange coupling and on-site anisotropy are similar. Our results are supported by many-body numerical simulations, and the essential physics is captured by the analytical solution of a two-site model. |
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