Global Quantum Discord in Multipartite Systems

TL;DR

This paper introduces a symmetric global quantum discord measure for multipartite systems, capable of detecting complex quantum correlations and phase transitions, surpassing pairwise discord in characterizing quantum criticality.

Contribution

It presents a novel global quantum discord measure based on relative entropy, applicable to multipartite systems, and demonstrates its effectiveness in identifying quantum phase transitions.

Findings

Global quantum discord is non-negative for all states.

The measure detects infinite-order quantum phase transitions.

It outperforms pairwise discord in characterizing multipartite correlations.

Abstract

We propose a global measure for quantum correlations in multipartite systems, which is obtained by suitably recasting the quantum discord in terms of relative entropy and local von Neumann measurements. The measure is symmetric with respect to subsystem exchange and is shown to be non-negative for an arbitrary state. As an illustration, we consider tripartite correlations in the Werner-GHZ state and multipartite correlations at quantum criticality. In particular, in contrast with the pairwise quantum discord, we show that the global quantum discord is able to characterize the infinite-order quantum phase transition in the Ashkin-Teller spin chain.