Minimal dissipation model for bipartite quantum systems at finite temperature

TL;DR

This paper introduces the 'depolarizing heat bath' as a minimal dissipation model for bipartite quantum systems at finite temperature, demonstrating its effectiveness and model-independence through numerical simulations.

Contribution

The paper proposes a new minimal dissipation model for bipartite quantum systems and provides numerical evidence supporting its universal applicability at strong dissipation.

Findings

The depolarizing heat bath accurately models dissipation in bipartite systems.

Model-independence of the dissipation dynamics at strong coupling.

Stabilization of coherence and populations under strong dissipation.

Abstract

We consider the reduced dynamics in a bipartite quantum system (consisting of a central system and an intermediate environment) coupled to a heat bath at finite temperature. To describe this situation, in the simplest possible -- yet physically meaningful way, we introduce the "depolarizing heat bath" as a new minimal dissipation model. We conjecture that at sufficiently strong dissipation, any other dissipation model implemented in the form of a Markovian quantum master equation will yield the same reduced dynamics of the central system, as the minimal model. To support this conjecture, we study a two-level system coupled to an oscillator mode. For the coupling between the two parts, we consider the Jaynes-Cummings or a dephasing coupling, while the coupling to the heat bath is modeled by the quantum optical or the Caldeira-Leggett master equation (neglecting any direct coupling between central system and heat bath). We then provide ample numerical evidence, for both, model-independence and accuracy of the depolarizing heat bath model. Alongside with our study, we investigate different regimes, where the strong coupling condition leads to coherence and/or population stabilization.