Bulletin of the American Physical Society
50th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 64, Number 4
Monday–Friday, May 27–31, 2019; Milwaukee, Wisconsin
Session K07: Spinor Gases and Magnetic Phenomena |
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Chair: Arne Schwettmann, University of Oklahoma Room: Wisconsin Center 103AB |
Wednesday, May 29, 2019 2:00PM - 2:12PM |
K07.00001: Dispersive imaging of antiferromagnetic Spinor Bose-Einstein Condensate Di Lao, Chandra Raman Non-equilibrium phenomena in quantum many-body systems can be explored by changing external fields dynamically. This provides a powerful platform to study spin dynamics such as Hanbury Brown-Twiss correlation (HBT) of different spin components that we have recently explored$^{[1]}$. We have studied antiferromagnetic spinor Bose-Einstein condensates (BECs) by dispersive imaging based on Faraday rotation. It provides a promising method to probe the dynamics of highly non-equilibrium spinor gases by a continuous series of measurements with only minimal disturbance. Using this technique, we can non-destructively probe the magnetization dynamics during a quench through the quantum phase transition. We will study the universality in the correlation of different spin components in real time during a strong quench in the vicinity of a continuous phase transition. [1]A. Vinit and C. Raman, New J. Phys. 20, 095003 (2018). [Preview Abstract] |
Wednesday, May 29, 2019 2:12PM - 2:24PM |
K07.00002: Efficient generation of many-body singlet state in an antiferromagnetic spinor Bose-Einstein condensate with 1000 atoms Peng Xu, Wenxian Zhang, S. Yi We propose a fast method utilizing multilevel oscillations to generate high-fidelity massively entangled states in an antiferromagnetic spin-1 Bose-Einstein condensate (BEC). Combining the multilevel oscillations with additional adiabatic drives, we greatly shorten the necessary evolution time and relax the requirement on the control accuracy of quadratic Zeeman splitting, from micro-Gauss to milli-Gauss, for a $^{23}$Na spinor BEC with 1000 atoms. The achieved high fidelities over $96\%$ show that two kinds of massively entangled states, the many-body singlet state and the twin-Fock state, are almost perfectly generated. The generalized spin squeezing parameter drops to a value far below the standard quantum limit even with the presence of atom number fluctuations and stray magnetic fields, illustrating the robustness of our protocol under real experimental conditions. The generated many-body entangled states can be employed to achieve the Heisenberg-limit quantum precision measurement and to attack nonclassical problems in quantum information science. [Preview Abstract] |
Wednesday, May 29, 2019 2:24PM - 2:36PM |
K07.00003: Observation of Dynamical Quantum Phase Transition in Antiferromagnetic Spinor Bose-Einstein Condensates Haoxiang Yang, Tian Tian, Liyuan Qiu, Haiyu Liang, Yanbin Yang, Ceren Burcak Dag, Anjun Chu, Yong Xu, Yingmei Liu, Luming Duan We experimentally study dynamical quantum phase transition (DQPT) in a many-body system with up to tens of thousands particles. We observe non-equilibrium dynamics after a sudden quench of the quadratic Zeeman energy using microwave dressing field. We chose a new observable as indictor of DQPT. The discontinuity of this observable near the transition point indicates the occurrence of DQPT in the system. The experimental result agrees well with theoretical prediction. Our experimental approach mainly overcomes challenges associated with long-time evolution after the quench. [Preview Abstract] |
Wednesday, May 29, 2019 2:36PM - 2:48PM |
K07.00004: Quantum quench and non-equilibrium dynamics in a spinor Mott-insulator Jared Austin, Zihe Chen, Tao Tang, Zachary Shaw, Lichao Zhao, Yingmei Liu We present an experimental study on the intricate non-equilibrium dynamics of a spinor Bose-Einstein condensate after it is quenched across a superfluid to Mott-insulator transition in a cubic optical lattice. Spin-mixing dynamics consisting of multiple frequencies are observed in time evolutions of the spinor condensate localized in deep lattices. The observed strong dependence of the non-equilibrium dynamics on the lattice potential provides a convenient method to precisely determine the spin-dependent interaction energy. We also confirm that the observed frequencies can be applied to detect atom number distributions of an inhomogeneous system in the Mott-insulator phase. [Preview Abstract] |
Wednesday, May 29, 2019 2:48PM - 3:00PM |
K07.00005: Spin synchronization in a finite temperature F=1 Bose-Einstein condensate Donald Fahey, Arne Schwettmann, Gil Summy, Jamie Luskin, Paul Lett The out-of-equilibrium spinor evolution of an ultracold spin-1 thermal Bose gas is characterized by population oscillations driven via coherent spin-mixing collisions. Despite its multi-spatial-mode nature, the thermal gas dynamics match those of a single-spatial-mode spinor BEC in the mean-field regime with a modified oscillation period resulting from lower density. But in a BEC at finite temperature, condensed and thermal components coexist and are coupled through collisions. We report on the synchronization of spin oscillations between these components in a harmonic trapping potential and discuss approaches to modelling this system. [Preview Abstract] |
Wednesday, May 29, 2019 3:00PM - 3:12PM |
K07.00006: Atomic Interferometry in Antiferromagetic Spinor Bose-Einstein Condensates in the Regime of Long Evolution Time Shan Zhong, Qimin Zhang, Isaiah Morgenstern, Hio Giap Ooi, Arne Schwettmann We experimentally investigate nonlinear atom interferometry based on spin-exchange collisions in a F=1 Na spinor Bose-Einstein condensate in the long evolution time regime, $t\gg h/c$, where $hc$ is the spin-dependent interaction energy. Spin-exchange collisions can be precisely controlled by microwave dressing, and generate pairs of entangled atoms with magnetic quantum numbers $m_F$= +1 and $m_F$= -1 from pairs of $m_F$= 0 atoms. Spin squeezing created by the collisions can reduce the noise in an atom interferometer. We apply a microwave-dressing pulse during spin evolution to imprint a phase-shift. Using Stern-Gerlach absorption imaging, we then detect the interference fringes as the change of final $m_F$=0 population vs. phase-shift. For long evolution times, we observe non-sinusoidal interference fringes with significantly enhanced slope, useful for sensing applications, and signaling the breakdown of the Bogoliubov and truncated Wigner approximations. [Preview Abstract] |
Wednesday, May 29, 2019 3:12PM - 3:24PM |
K07.00007: Observation of spin-density wave propagation in a spinor Bose-Einstein condensate Joon Hyun Kim, DeokHwa Hong, Yong-il Shin We report the observation of spin-density wave propagation in a spin-1 antiferromagnetic spinor Bose-Einstein condensate. We develop a spin-dependent optical obstacle which is attractive for $m=1$ and repulsive for $m=-1$ with equal potential heights, by using a laser beam with its frequency tuned between the $D_1$ and $D_2$ transitions. By suddenly turning off the obstacle beam penetrating a condensate in an easy-plane polar phase, we observe that a magnetization pulse wave is generated. The pulse wave consists of a density dip of the $m=-1$ component and a density bump for $m=1$, and it propagates non-dispersively with a constant speed $v_s$, which demonstrates the linear dispersion of magnon mode of the spinor superfluid system. For comparison, we generate a mass-density wave in the same system, by using an ordinary spin-independent obstacle beam, and measure its propagation speed $v_m$. In our experiment, the ratio of $v_s/v_m$ is measured to be 0.20, which asserts that $c_2$ is twice larger than the conventional value from [PRL 99, 070403 (2007)]. Finally, we investigate a situation where the condensate is perturbed with an imbalanced potential for the two spin components, and observe that both mass and spin excitations are generated simultaneously but propagate separately. [Preview Abstract] |
Wednesday, May 29, 2019 3:24PM - 3:36PM |
K07.00008: Uniaxial dynamical decoupling for a spinor Bose-Einstein condensate Wenxian Zhang, Qi Yao, Jun Zhang, L. You Dynamical decoupling (DD) is an active and effective method for suppressing decoherence of a quantum system from its environment. In contrast to the nominal biaxial DD, we present a uniaxial decoupling protocol that requires a significantly reduced number of pulses and a much lower bias field satisfying the ``magic" condition. We show this uniaxial DD protocol works effectively in a number of model systems of practical interests, e.g., a spinor atomic Bose-Einstein condensate in stray magnetic fields (classical noise), or an electron spin coupled to nuclear spins (quantum noise) in a semiconductor quantum dot. It requires only half the number of control pulses and a 10-100 times lower bias field for decoupling as normally employed in the above mentioned illustrative examples, and the overall efficacy is robust against rotation errors of the control pulses. The uniaxial DD protocol we propose shines new light on coherent controls in quantum computing and quantum information processing, quantum metrology, and low field nuclear magnetic resonance. [Preview Abstract] |
Wednesday, May 29, 2019 3:36PM - 3:48PM |
K07.00009: Probing Ferromagnetic Order in Few-Fermion Correlated Spin-Flip Dynamics Georgios Koutentakis, Simeon Mistakidis, Peter Schmelcher We unravel the dynamical stability of a fully polarized one-dimensional ultracold few-fermion spin-1/2 gas subjected to inhomogeneous driving of the itinerant spins. Despite the unstable character of the total spin-polarization the existence of an interaction regime is demonstrated where the spin-correlations lead to almost maximally aligned spins throughout the dynamics. The resulting ferromagnetic order emerges from the build up of superpositions of states of maximal total spin. They comprise a decaying spin-polarization and a dynamical evolution towards an almost completely unpolarized NOON-like state. [Preview Abstract] |
Wednesday, May 29, 2019 3:48PM - 4:00PM |
K07.00010: Imaging magnetic polarons in the doped Fermi-Hubbard model Joannis Koepsell, Jayadev Vijayan, Pimonpan Sompet, Fabian Grusdt, Timon Hilker, Eugene Demler, Guillaume Salomon, Immanuel Bloch, Christian Gross Polarons are among the most fundamental quasiparticles emerging in interacting many-body systems, forming already at the level of a single mobile dopant. In the context of the two-dimensional Fermi-Hubbard model, such polarons are predicted to form around charged dopants in an antiferromagnetic background in the low doping regime close to the Mott insulating state. Here we report the first microscopic observation of magnetic polarons in a doped Fermi-Hubbard system, harnessing the full single-site spin and density resolution of our ultracold-atom quantum simulator. We reveal the dressing of mobile doublons by a local reduction and even sign reversal of magnetic correlations, originating from the competition between kinetic and magnetic energy in the system. The experimentally observed polaron signatures are found to be consistent with an effective string model at finite temperature. We demonstrate that delocalization of the doublon is a necessary condition for polaron formation by contrasting this mobile setting to a scenario where the doublon is pinned to a lattice site. [Preview Abstract] |
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