Bulletin of the American Physical Society
47th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 61, Number 8
Monday–Friday, May 23–27, 2016; Providence, Rhode Island
Session M2: Focus Session: Many-Body Physics in Quantum SimulationFocus
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Chair: Michael Wall, JILA Room: Ballroom B |
Thursday, May 26, 2016 8:00AM - 8:30AM |
M2.00001: Quantum thermalization and many-body Anderson localization Invited Speaker: David Huse The out-of-equilibrium dynamics of closed quantum many-body systems can now be explored in a variety of laboratories using a variety of different physical systems, and as a consequence have received a lot of recent theoretical attention. When such systems do go to thermal equilibrium under their own unitary time evolution, this is what is called thermalization. Thermalization is what happens at long times in many large interacting and closed quantum systems, and one way of understanding part of how this happens is via the eigenstate thermalization hypothesis (ETH). The main generic exception to thermalization is many-body localization (MBL), where the system fails to act as a bath to thermalize itself, in spite of being strongly interacting. Instead, the quantum state of a MBL system remains localized near its initial state. MBL is now understood as a new type of quantum integrability, with localized conserved operators. There is a new type of quantum phase transition between MBL and thermalization as one decreases the static randomness in the system; this phase transition remains poorly understood. [Preview Abstract] |
Thursday, May 26, 2016 8:30AM - 9:00AM |
M2.00002: Quantum Fisher information as efficient entanglement witness in many-body systems Invited Speaker: Philipp Hauke Large-scale entanglement in quantum many-body systems is typically difficult to quantify experimentally. Here, we discuss scenarios where many-body entanglement becomes accessible via the quantum Fisher information (QFI), a known witness for genuinely multipartite entanglement as a resource for quantum-enhanced metrology. First, we introduce a direct relation of the QFI in thermal states with linear response functions, which makes the QFI measurable with standard methods in optical-lattice and solid-state experiments [1]. Using this relationship, we show that close to continuous quantum phase transitions the QFI, and thus multipartite entanglement, is strongly divergent. Second, we demonstrate that the QFI can witness many-body localized phases, showing a characteristic growth of entanglement at long times after a quantum quench [2]. These results demonstrate that the quantum Fisher information represents a useful and efficiently measurable witness for entanglement in quantum many-body settings. [1] P. Hauke et al., arXiv:1509.01739 (2015). [2] J. Smith et al., arXiv: 1512.06172 (2015). [Preview Abstract] |
Thursday, May 26, 2016 9:00AM - 9:12AM |
M2.00003: Prethermalization and Many-body localization (MBL) in trapped ion spins. J. Zhang, J. Smith, A. Lee, P. W. Hess, B. Neyenhuis, P. Richerme, P. Hauke, M. Heyl, D. A. Huse, Z.X. Gong, A. Gorshkov, C. Monroe We present experimental investigations of quantum thermalization and equilibration dynamics in a precisely controlled, interacting, 171Yb+ spin chain, with up to 25 ions. We quench the trapped ion spins in a quantum many-body Hamiltonian with single-atom addressing techniques and measure the long-term dynamics with single-site resolution. With a long-range XY model spin Hamiltonian, we observe emergence of an exotic prethermal phase in the quench dynamics. This non-trivial prethermal phase arise from an inhomogeneous effective potential landscape, due to a combination of the long-range interactions and the open boundary condition. We also observe the absence of spin transport due to many-body localization (MBL) in the transverse-field Ising model with programmable disorder[1]. We measure the Hamming distance and verify the growth of entanglement through the Quantum Fisher Information (QFI) entanglement witness, consistent with expectations for the MBL state. [1] J. Smith et, al. arXiv: 1512.06172(2015). [Preview Abstract] |
Thursday, May 26, 2016 9:12AM - 9:24AM |
M2.00004: Density-dependent light-assisted tunneling in fermionic optical lattices Wenchao Xu, William Morong, Brian DeMarco Many recent theoretical proposals have discussed the possibility to realize density-dependent tunneling in optical lattices via external periodic driving. These methods enable the simulation of novel many-body quantum phases. Here we present experimental progress on realizing density-dependent tunneling for ultracold 40K atoms trapped in a cubic optical lattice via stimulated Raman transitions. After preparing a spin-polarized gas in the Mott insulator regime of the Hubbard model, a pair of Raman beams is applied to flip the spin of atoms. The Raman beams also introduce an effective density-dependent tunneling that can be tuned by the Raman frequency difference and Rabi rate. The Mott gap inferred from measurements of the fraction of atoms transferred between spin states as the Raman frequency difference is adjusted matches the prediction based on a tight-binding model. We also observe the interaction-dependent tunneling by measuring the fraction of doubly-occupied sites created by the Raman driving. This method allows the engineering of density-dependent tunneling and effective nearest-neighbor interactions in fermionic optical lattices. [Preview Abstract] |
Thursday, May 26, 2016 9:24AM - 9:36AM |
M2.00005: Collective phases of strongly interacting cavity photons Ryan M. Wilson, Khan W. Mahmud, Anzi Hu, Alexey V. Gorshkov, Mohammad Hafezi, Michael Foss-Feig We study a coupled array of coherently driven photonic cavities, which maps onto a driven-dissipative XY spin-$\frac{1}{2}$ model with ferromagnetic couplings in the limit of strong optical nonlinearities. Using a site-decoupled mean-field approximation, we identify steady state phases with canted antiferromagnetic order, in addition to limit cycle phases, where oscillatory dynamics persist indefinitely. We also identify collective bistable phases, where the system supports two steady states among spatially uniform, antiferromagnetic, and limit cycle phases. We compare these mean-field results to exact quantum trajectories simulations for finite one-dimensional arrays. The exact results exhibit short-range antiferromagnetic order for parameters that have significant overlap with the mean-field phase diagram. In the mean-field bistable regime, the exact quantum dynamics exhibits real-time collective switching between macroscopically distinguishable states. We present a clear physical picture for this dynamics, and establish a simple relationship between the switching times and properties of the quantum Liouvillian. [Preview Abstract] |
Thursday, May 26, 2016 9:36AM - 9:48AM |
M2.00006: Quantum magnetism of alkali Rydberg atoms Svetlana Malinovskaya, Gengyuan Liu We discuss a method to control dynamics in many-body spin states of $^{87}Rb$ Rydberg atoms. The method permits excitation of cold gases and form ordered structures of alkali atoms. It makes use of a two-photon excitation scheme with circularly polarized and linearly chirped pulses. The method aims for controlled quantum state preparation in large ensembles. It is actual for experiments studding the spin hopping dynamics and realization of quantum random walks. [Preview Abstract] |
Thursday, May 26, 2016 9:48AM - 10:00AM |
M2.00007: Towards a photonic Mott insulator in superconducting circuits Ruichao Ma, John C Owen, David Schuster, Jonathan Simon Recent developments in circuit QED provide superconducting circuits as a unique platform for exploring quantum many-body phenomena with light. The absence of particle number conservation, however, makes creating and understanding of many-body photonic states challenging. Here we make a one-dimensional lattice of coupled superconducting qubits with an additional pumping site and a lossy site incorporated at the end of the chain, which serves as an effective chemical potential for photons. When driven on the pumping site, the photons can spontaneously thermalize into the ground state of the lattice while the excess energy is dissipated via the lossy site. In the presence of strong photon-photon interaction via the qubit non-linearity, we expect the creation of a Mott insulator state of light, which we probe with temporal- and spatially-resolved measurements. These experiments will give insights to the microscopic investigation of non-equilibrium thermodynamics in strongly-interacting quantum system, including the interplay between external driving and dissipation. [Preview Abstract] |
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