Feb 2018

Feb 1- Feb 3 Jiansong Pan, Feb 4-Feb 8 Ahmet Keles, Feb 9-Feb 13 Max Aarzamazovs, Feb 14-Feb 18 Xuguang Yue, Feb 19-Feb 23 Huang Biao, Feb 24-Feb 28 Haiyuan Zou

Feb. 20

Measuring Electromagnetic and Gravitational Responses of Photonic Landau Levels

Nathan Schine, Michelle Chalupnik, Tankut Can, Andrey Gromov, Jonathan Simon

(Submitted on 13 Feb 2018)

The topology of an object describes global properties that are insensitive to local perturbations. Classic examples include string knots and the genus (number of handles) of a surface: no manipulation of a closed string short of cutting it changes its "knottedness"; and no deformation of a closed surface, short of puncturing it, changes how many handles it has. Topology has recently become an intense focus of condensed matter physics, where it arises in the context of the quantum Hall effect [1] and topological insulators [2]. In each case, topology is defined through invariants of the material's bulk [3-5], but experimentally measured through chiral/helical properties of the material's edges. In this work we measure topological invariants of a quantum Hall material through local response of the bulk: treating the material as a many-port circulator enables direct measurement of the Chern number as the spatial winding of the circulator phase; excess density accumulation near spatial curvature quantifies the curvature-analog of charge known as mean orbital spin, while the moment of inertia of this excess density reflects the chiral central charge. We observe that the topological invariants converge to their global values when probed over a few magnetic lengths lB, consistent with intuition that the bulk/edge distinction exists only for samples larger than a few lB. By performing these experiments in photonic Landau levels of a twisted resonator [6], we apply quantum-optics tools to topological matter. Combined with developments in Rydberg-mediated interactions between resonator photons [7], this work augurs an era of precision characterization of topological matter in strongly correlated fluids of light.



arXiv:1802.06704 [pdf, other]
Quantum simulation of lattice gauge theories using Wilson fermions
T. V. Zache, F. Hebenstreit, F. Jendrzejewski, M. K. Oberthaler, J. Berges, P. Hauke
Comments: 19 pages, 11 figures
Subjects: Quantum Gases (cond-mat.quant-gas); High Energy Physics - Lattice (hep-lat); High Energy Physics - Phenomenology (hep-ph); Quantum Physics (quant-ph)
Quantum simulators have the exciting prospect of giving access to real-time dynamics of lattice gauge theories, in particular in regimes that are difficult to compute on classical computers. Future progress towards scalable quantum simulation of lattice gauge theories, however, hinges crucially on the efficient use of experimental resources. As we argue in this work, due to the fundamental non-uniqueness of discretizing the relativistic Dirac Hamiltonian, the lattice representation of gauge theories allows for an optimization that up to now has been left unexplored. We exemplify our discussion with lattice quantum electrodynamics in two-dimensional space-time, where we show that the formulation through Wilson fermions provides several advantages over the previously considered staggered fermions. Notably, it enables a strongly simplified optical lattice setup and it reduces the number of degrees of freedom required to simulate dynamical gauge fields. Exploiting the optimal representation, we propose an experiment based on a mixture of ultracold atoms trapped in a tilted optical lattice. Using numerical benchmark simulations, we demonstrate that a state-of-the-art quantum simulator may access the Schwinger mechanism and map out its non-perturbative onset.



Strongly-correlated bosons on a dynamical lattice

Daniel González-Cuadra, Przemysław R. Grzybowski, Alexandre Dauphin, Maciej Lewenstein

(Submitted on 15 Feb 2018)

We study a one-dimensional system of strongly-correlated bosons interacting with a dynamical lattice. A minimal model describing the latter is provided by extending the standard Bose-Hubbard Hamiltonian to include extra degrees of freedom on the bonds of the lattice. We show that this model is capable of reproducing phenomena similar to those present in usual fermion-phonon models. In particular, we discover a bosonic analog of the Peierls transition, where the translational symmetry of the underlying lattice is spontaneously broken. The latter provides a dynamical mechanism to obtain a topological insulator in the presence of interactions, analogous to the Su-Schrieffer-Heeger (SSH) model for electrons. We numerically characterize the phase diagram of the model, which includes different types of bond order waves and topological solitons. Finally, we study the possibility of implementing the model experimentally using atomic systems.