Quantum discord and related measures of quantum correlations in XY chains

TL;DR

This paper investigates quantum correlations in finite XY spin chains, analyzing quantum discord and related measures, highlighting parity effects, and their behavior near the critical and factorizing fields through analytical and numerical methods.

Contribution

It provides a comprehensive analysis of quantum discord and related measures in XY chains, emphasizing the role of parity effects and behavior near critical points.

Findings

Quantum discord reaches full range near the factorizing field.

Parity effects significantly influence quantum correlation measures.

Correlation measures become independent of separation and coupling range near the factorizing field.

Abstract

We examine the quantum correlations of spin pairs in the ground state of finite XY chains in a transverse field, by evaluating the quantum discord as well as other related entropic measures of quantum correlations. A brief review of the latter, based on generalized entropic forms, is also included. It is shown that parity effects are of crucial importance for describing the behavior of these measures below the critical field. It is also shown that these measures reach full range in the immediate vicinity of the factorizing field, where they become independent of separation and coupling range. Analytical and numerical results for the quantum discord, the geometric discord and other measures in spin chains with nearest neighbor coupling and in fully connected spin arrays are also provided.