Operator fidelity susceptibility: an indicator of quantum criticality

TL;DR

This paper introduces operator fidelity susceptibility as a new tool to detect quantum critical points, demonstrating its effectiveness in models with and without degeneracy.

Contribution

It proposes the operator fidelity susceptibility as a universal indicator of quantum criticality applicable to various quantum systems.

Findings

Operator fidelity susceptibility signals quantum phase transitions.

It works effectively in models with degeneracy.

It is a robust indicator across different quantum systems.

Abstract

We introduce the operator fidelity and propose to use its susceptibility for characterizing the sensitivity of quantum systems to perturbations. Two typical models are addressed: one is the transverse Ising model exhibiting a quantum phase transition, and the other is the one dimensional Heisenberg spin chain with next-nearest-neighbor interactions, which has the degeneracy. It is revealed that the operator fidelity susceptibility is a good indicator of quantum criticality regardless of the system degeneracy.