Quantum discord and its asymptotic behaviors in a time-dependent XY spin chain

TL;DR

This paper investigates the dynamics and long-term behavior of quantum discord in a time-dependent XY spin chain, revealing non-ergodic evolution, temperature effects, and conditions for enhanced quantum correlations.

Contribution

It provides a detailed analysis of how quantum discord behaves in a time-dependent XY model, highlighting its asymptotic properties and robustness compared to entanglement.

Findings

Quantum discord shows non-ergodic dynamics but reaches a steady state.

Asymptotic quantum discord depends on coupling and magnetic field ratios.

Quantum discord is more robust than entanglement against temperature effects.

Abstract

We study the dynamics and the asymptotic behaviors of quantum discord in a one-dimensional XY model coupled through time-dependent nearest-neighbor interactions and in the presence of a time-dependent magnetic field. We find that the time evolution of the nearest-neighbor quantum discord in this system shows non-ergodic behaviors but is asymptotic to its steady value at the long-time limit. The zero-temperature asymptotic behaviors of quantum discord is only determined by the ratio between the coupling parameter and magnetic field, whereas the finite-temperature asymptotic behaviors determined by both of them. These asymptotic behaviors are sensitive not only to the initial values of the coupling parameter and magnetic field, but also to the final values. It is interesting to note that quantum discords are more robust than entanglement against the effect of temperature. We also find particular parameter regimes, where the nearest-neighbor quantum discord is enhanced significantly.