Entropy production in open quantum systems: exactly solvable qubit models

TL;DR

This paper provides exact analytical solutions for the time-dependent entropy in two solvable qubit models, elucidating entropy production during decoherence and spontaneous decay processes in open quantum systems.

Contribution

It introduces exact solutions for entropy dynamics in two specific open quantum system models, enhancing understanding of entropy production mechanisms.

Findings

Entropy production analyzed in dephasing and decay models

Maximum entropy state occurs during spontaneous decay

Exact solutions clarify entropy behavior in open quantum systems

Abstract

We present analytical results for the time-dependent information entropy in exactly solvable two-state (qubit) models. The first model describes dephasing (decoherence) in a qubit coupled to a bath of harmonic oscillators. The entropy production for this model in the regimes of "complete" and "incomplete" decoherence is discussed. As another example, we consider the damped Jaynes-Cummings model describing a spontaneous decay of a two-level system into the field vacuum. It is shown that, for all strengths of coupling, the open system passes through the mixed state with the maximum information entropy.