arXiv subjects

Guo-Qing Zhang

Publications and source records attributed to Guo-Qing Zhang.

22 records · Page 2Linked to original sources

arXiv2020

Simulating bosonic Chern insulators in one-dimensional optical superlattices

We study the topological properties of an extended Bose-Hubbard model with cyclically modulated hopping and on-site potential parameters, which can be realized with ultracold bosonic atoms in a one-dimensional optical superlattice. We show that the interacting bosonic chain at half filling and in the deep Mott insulating regime can simulate bosonic Chern insulators with a topological phase diagram similar to that of the Haldane model of noninteracting fermions. Furthermore, we explore the topological properties of the ground state by calculating the many-body Chern number, the quasiparticle energy spectrum with gapless edge modes, the topological pumping of the interacting bosons, and the topological phase transition from normal (trivial) to topological Mott insulators. We also present the global phase diagram of the many-body ground state, which contains a superfluid phase and two Mott insulating phases with trivial (a zero Chern number) and nontrivial topologies (a nonzero Chern number), respectively.

cond-mat.quant-gas↗

arXiv2018

Quantum evolution speed in the finite-temperature bosonic environment

We investigate the quantum evolution speed of a qubit in two kinds of finite-temperature environments. The first environment is a bosonic bath with Ohmic-like spectrum. It is found that the high temperature not only leads to the speed-up but also speed-down processes in the weak-coupling regime, which is different from the strong-coupling case where only exhibits speed-up process, and the effects of Ohmicity parameter of the bath on the quantum evolution speed are also different in the strong-coupling and weak-coupling regimes. Furthermore, we realize the controllable and stationary quantum evolution speed by applying the bang-bang pulse. For the second nonlinear bath, we study the quantum evolution speed of a qubit by resorting to the hierarchical equations of motion method beyond the Born-Markov approximation. It is shown that the performances of quantum evolution speed in weak-coupling and strong-coupling regimes are also different. In particular, the quantum evolution speed can be decelerated by the rise of temperature in the strong-coupling regime which is an anomalous phenomenon and contrary to the common recognition that quantum evolution speed always increases with the temperature.

quant-ph↗

arXiv2012

A universal assortativity measure for network analysis

Characterizing the connectivity tendency of a network is a fundamental problem in network science. The traditional and well-known assortativity coefficient is calculated on a per-network basis, which is of little use to partial connection tendency of a network. This paper proposes a universal assortativity coefficient(UAC), which is based on the unambiguous definition of each individual edge's contribution to the global assortativity coefficient (GAC). It is able to reveal the connection tendency of microscopic, mesoscopic, macroscopic structures and any given part of a network. Applying UAC to real world networks, we find that, contrary to the popular expectation, most networks (notably the AS-level Internet topology) have markedly more assortative edges/nodes than dissortaive ones despite their global dissortativity. Consequently, networks can be categorized along two dimensions--single global assortativity and local assortativity statistics. Detailed anatomy of the AS-level Internet topology further illustrates how UAC can be used to decipher the hidden patterns of connection tendencies on different scales.

physics.soc-ph↗

arXiv2006

Chinese Internet AS-level Topology

We present the first complete measurement of the Chinese Internet topology at the autonomous systems (AS) level based on traceroute data probed from servers of major ISPs in mainland China. We show that both the Chinese Internet AS graph and the global Internet AS graph can be accurately reproduced by the Positive-Feedback Preference (PFP) model with the same parameters. This result suggests that the Chinese Internet preserves well the topological characteristics of the global Internet. This is the first demonstration of the Internet's topological fractality, or self-similarity, performed at the level of topology evolution modeling.

cs.NI↗