Arxiv Selection Nov 2019

Nov 1-Nov 7 Zehan Li, Nov 8- Nov 14 Jiansong Pan, Nov 15- Nov 21 Ahmet Keles, Nov 22 - Nov 28 Haiping Hu

Nov 5

arXiv:1911.01345 [pdf, other]

High-precision numerical solution of the Fermi polaron problem and large-order behavior of its diagrammatic series

K. Van Houcke, F. Werner, R. Rossi

Subjects: Quantum Gases (cond-mat.quant-gas); Strongly Correlated Electrons (cond-mat.str-el)

We introduce a simple determinant diagrammatic Monte Carlo algorithm to compute the groundstate properties of a particle interacting with a Fermi sea through a zero-range interaction. The fermionic sign does not cause any fundamental problem when going to high diagram orders, and we reach order N = 30. The data reveal that the diagrammatic series diverges exponentially as (−1/R) N with a radius of convergence R < 1. Furthermore, on the polaron side of the polarondimeron transition, the value of R is determined by a special class of three-body diagrams, corresponding to repeated scattering of the impurity between two particles of the Fermi sea. A powercounting argument explains why finite R is possible for zero-range interactions in three dimensions. Resumming the divergent series through a conformal mapping yields the polaron energy with record accuracy

Nov 4

arXiv:1911.00003 (cross-list from quant-ph) [pdf, other]

Simulating Lattice Gauge Theories within Quantum Technologies

M.C. Bañuls, R. Blatt, J. Catani, A. Celi, J.I. Cirac, M. Dalmonte, L. Fallani, K. Jansen, M. Lewenstein, S. Montangero, C.A. Muschik, B. Reznik, E. Rico, L. Tagliacozzo, K. Van Acoleyen, F. Verstraete, U.-J. Wiese, M. Wingate, J. Zakrzewski, P. Zoller

Comments: 45 pages, 38 figures, review article

Subjects: Quantum Physics (quant-ph); Quantum Gases (cond-mat.quant-gas); High Energy Physics - Lattice (hep-lat); High Energy Physics - Theory (hep-th)

Lattice gauge theories, which originated from particle physics in the context of Quantum Chromodynamics (QCD), provide an important intellectual stimulus to further develop quantum information technologies. While one long-term goal is the reliable quantum simulation of currently intractable aspects of QCD itself, lattice gauge theories also play an important role in condensed matter physics and in quantum information science. In this way, lattice gauge theories provide both motivation and a framework for interdisciplinary research towards the development of special purpose digital and analog quantum simulators, and ultimately of scalable universal quantum computers. In this manuscript, recent results and new tools from a quantum science approach to study lattice gauge theories are reviewed. Two new complementary approaches are discussed: first, tensor network methods are presented - a classical simulation approach - applied to the study of lattice gauge theories together with some results on Abelian and non-Abelian lattice gauge theories. Then, recent proposals for the implementation of lattice gauge theory quantum simulators in different quantum hardware are reported, e.g., trapped ions, Rydberg atoms, and superconducting circuits. Finally, the first proof-of-principle trapped ions experimental quantum simulations of the Schwinger model are reviewed.

Nov 1

arXiv:1910.14606 (cross-list from cond-mat.mes-hall) [pdf, other]

Non-Hermitian topological phase transitions for quantum spin Hall insulators

Junpeng Hou, Ya-Jie Wu, Chuanwei Zhang

Comments: 10 pages, 9 figures

Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Quantum Gases (cond-mat.quant-gas); Optics (physics.optics)

The interplay between non-Hermiticity and topology opens an exciting avenue for engineering novel topological matter with unprecedented properties. While previous studies have mainly focused on one-dimensional systems or Chern insulators, here we investigate topological phase transitions to/from quantum spin Hall (QSH) insulators driven by non-Hermiticity. We show that a trivial to QSH insulator phase transition can be induced by solely varying non-Hermitian terms, and there exists exceptional edge arcs in QSH phases. We establish two topological invariants for characterizing the non-Hermitian phase transitions: i) with time-reversal symmetry, the biorthogonal Z2 invariant based on non-Hermitian Wilson loops, and ii) without time-reversal symmetry, a biorthogonal spin Chern number through biorthogonal decompositions of the Bloch bundle of the occupied bands. These topological invariants can be applied to a wide class of non-Hermitian topological phases beyond Chern classes, and provides a powerful tool for exploring novel non-Hermitian topological matter and their device applications.