Minimal dissipation model for bipartite quantum systems at finite temperature

摘要

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 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 our study, we investigate different regimes, where the strong-coupling condition leads to coherence and/or population stabilization.