Identifying and harnessing dynamical phase transitions for quantum-enhanced sensing

TL;DR

This paper demonstrates how quantum Fisher information can diagnose dynamical phase transitions in quantum systems and proposes a protocol for quantum-enhanced sensing leveraging these transitions.

Contribution

It introduces a method to identify dynamical phase transitions using QFI and links it to excited-state quantum phase transitions, proposing a sensing protocol.

Findings

QFI peaks at dynamical phase transitions in the Lipkin-Meshkov-Glick model.

DPTs are connected to excited-state quantum phase transitions.

Proposed interferometric protocol enables quantum-enhanced sensing using DPTs.

Abstract

We use the quantum Fisher information (QFI) to diagnose a dynamical phase transition (DPT) in a closed quantum system, which is usually defined in terms of non-analytic behaviour of a time-averaged order parameter. Employing the Lipkin-Meshkov-Glick model as an illustrative example, we find that the DPT correlates with a peak in the QFI that can be explained by a generic connection to an underlying excited-state quantum phase transition that also enables us to also relate the scaling of the QFI with the behaviour of the order parameter. Motivated by the QFI as a quantifier of metrologically useful correlations and entanglement, we also present a robust interferometric protocol that can enable DPTs as a platform for quantum-enhanced sensing.