On Order, Disorder and Coherence

TL;DR

This paper surveys quantum statistical measures of order, disorder, and coherence, highlighting their interconnections and extending classical concepts to quantum systems, emphasizing the relationship between signals and noise.

Contribution

It introduces a unified perspective on quantum order, disorder, and coherence, linking symmetry, entropy, and complexity in a comprehensive survey.

Findings

Order and coherence relate to symmetry breaking.

Disorder involves entropy and algorithmic complexity.

Quantum concepts extend classical interrelations between signals and noise.

Abstract

We provide a brief survey of quantum statistical characterisations of order, disorder and coherence in systems of many degrees of freedom. Here, order and coherence are described in terms of symmetry breakdown, while disorder is described in terms of entropy and algorithmic complexity, whose interconnection has been recently extended from the classical to the quantum domain. We see that, in the present physical context, the concepts of order and disorder are not mutually antithetical, but bear an interrelationship similar to that between signals and noise.