Quantum Information metric for time-dependent quantum systems and higher-order corrections

TL;DR

This paper introduces a higher-order quantum information metric for time-dependent systems, exemplified by a two-level atom model, revealing long-lasting quantum noise and novel tensorial fidelity susceptibility.

Contribution

It derives the first higher-order rank-3 tensor fidelity susceptibility for time-dependent quantum systems, expanding the understanding of quantum information metrics.

Findings

Higher-order fidelity susceptibility tensor derived

Quantum noise persists long in the model

Information metric signals phase transitions without local order parameters

Abstract

It is well established that quantum criticality is one of the most intriguing phenomena which signals the presence of new states of matter. Without prior knowledge of the local order parameter, the quantum information metric (or fidelity susceptibility) can indicate the presence of a phase transition as well as it measures distance between quantum states. In this work, we calculate the distance between quantum states which is equal to the fidelity susceptibility in quantum model for a time-dependent system describing a two-level atom coupled to a time-driven external field. As inspired by the Landau-Zener quantum model, we find in the present work information metric induced by fidelity susceptibility. We, for the first time, derive a higher-order rank-3 tensor as a third-order fidelity susceptibility. Having computed quantum noise function in this simple time-dependent model we show that the noise function eternally lasts long in our model.