Coherence and quantum correlations measure sensitivity to dephasing channels

TL;DR

This paper introduces measures of quantum coherence based on the speed of evolution under decoherence, linking coherence to sensitivity in dephasing channels and exploring quantum discord's role in noise estimation.

Contribution

It proposes a new coherence measure using quantum Fisher information and analyzes the relationship between coherence and discord in dephasing sensitivity.

Findings

Quantum coherence can be quantified by the evolution speed under decoherence.

Quantum discord determines the minimum sensitivity to local dephasing.

The amount of discord generated by incoherent operations is limited by initial coherence.

Abstract

We introduce measures of quantum coherence as the speed of evolution of a system under decoherence. That is, coherence is the ability to estimate a dephasing channel, quantified by the quantum Fisher information. We extend the analysis to interferometric noise estimation, proving that quantum discord is the minimum sensitivity to local dephasing. A physically motivated set of free operations for discord is proposed. The amount of discord created by strictly incoherent operations is upper-bounded by the initial coherence.