Long-range quantum discord in critical spin systems

TL;DR

This paper demonstrates that quantum discord can effectively characterize quantum phase transitions in spin systems by showing long-range correlations and changes in decay rates across critical points, unlike entanglement.

Contribution

It reveals that quantum discord exhibits long-range decay and detects phase transitions, providing a new tool for studying quantum criticality in condensed matter systems.

Findings

Quantum discord shows long-range decay in critical spin systems.

Decay rate of quantum discord changes at quantum critical points.

Quantum discord can distinguish different types of quantum phase transitions.

Abstract

We show that quantum correlations as quantified by quantum discord can characterize quantum phase transitions by exhibiting nontrivial long-range decay as a function of distance in spin systems. This is rather different from the behavior of pairwise entanglement, which is typically short-ranged even in critical systems. In particular, we find a clear change in the decay rate of quantum discord as the system crosses a quantum critical point. We illustrate this phenomenon for first-order, second-order, and infinite-order quantum phase transitions, indicating that pairwise quantum discord is an appealing quantum correlation function for condensed matter systems.