Accessible coherence in open quantum system dynamics

TL;DR

This paper characterizes quantum dynamics that preserve and reveal coherence over time, providing simplified conditions for detecting non-coherence-generating-and-detecting processes, especially in qubit systems.

Contribution

It reduces the conditions for non-coherence-generating-and-detecting dynamics to a finite set for time-independent generators, and extends these conditions to time-dependent cases.

Findings

Finite conditions for NCGD dynamics in d-dimensional systems

Application to qubit dynamics clarifies noise effects on coherence

Extended criteria for time-dependent quantum processes

Abstract

Quantum coherence generated in a physical process can only be cast as a potentially useful resource if its effects can be detected at a later time. Recently, the notion of non-coherence-generating-and-detecting (NCGD) dynamics has been introduced and related to the classicality of the statistics associated with sequential measurements at different times. However, in order for a dynamics to be NCGD, its propagators need to satisfy a given set of conditions for all triples of consecutive times. We reduce this to a finite set of $d(d-1)$ conditions, where $d$ is the dimension of the quantum system, provided that the generator is time-independent. Further conditions are derived for the more general time-dependent case. The application of this result to the case of a qubit dynamics allows us to elucidate which kind of noise gives rise to non-coherence-generation-and-detection.