Effective Formalism for Open Quantum System Dynamics: Time-coarse-graining Approach

TL;DR

This paper develops a time-coarse-graining method for open quantum systems that simplifies dynamics by removing high-frequency coherences, with validation on multi-level atoms driven by lasers.

Contribution

It extends the time-coarse-graining formalism to open quantum systems, providing an effective framework for low-energy dynamics analysis.

Findings

Good agreement between exact and coarse-grained dynamics under certain conditions

High-frequency coherences are effectively removed by the coarse-graining

Method's validity depends on laser strength and initial coherences

Abstract

We formulate an effective-description framework for the dynamics of open quantum systems by extending the time-coarse-graining formalism to open systems. Our coarse-graining procedure efficiently removes high-frequency processes which are responsible for coherences between lower- and upper-manifold states and are irrelevant when considering only low-energy dynamics. We investigate the regime of validity of the resulting coarse-grained master equation by applying it to multi-level atoms driven by far-detuned lasers. Except for such high-frequency coherences, we find good agreement between the exact and coarse-grained dynamics unless the driving lasers are too strong or the initial high-frequency coherences are sizable.