Scaling of macroscopic superpositions close to a quantum phase transition

TL;DR

This paper investigates how the effective size of macroscopic superpositions in a quantum system diverges near a quantum phase transition, revealing critical scaling behavior of quantum macroscopicity.

Contribution

It introduces a measure of quantum macroscopisity that captures the growth of superpositions near critical points, highlighting a new quantum property that diverges at phase transitions.

Findings

Effective size of macroscopic superpositions grows to system size near critical point

Derivative of superposition size shows singular behavior at transition

Scaling properties of superposition size are identified near quantum criticality

Abstract

It is well known that in a quantum phase transition (QPT), entanglement remains short ranged [Osterloh et al., Nature 416 608-610 (2005)]. We ask if there is a quantum property entailing the whole system which diverges near this point. Using the recently proposed measures of quantum macroscopisity, we show that near a quantum critical point, it is the effective size of macroscopic superposition between the two symmetry breaking states which grows to the scale of system size and its derivative with respect to the coupling shows both singular behavior and scaling properties.