Thermalization of finite many-body systems by a collision model

TL;DR

This paper develops a collision model framework for understanding thermalization in finite many-body quantum systems, emphasizing the importance of timescales and resonance conditions, and demonstrating its effectiveness for classically correlated states.

Contribution

It introduces a collision model approach to thermalization in many-body systems, deriving a Lindblad master equation and analyzing conditions for effective thermalization.

Findings

Collision model thermalization depends on system-bath timescales and resonance conditions.

Effective for classically correlated systems, less so for entangled states.

Provides a framework for analyzing thermalization in finite quantum systems.

Abstract

We construct a collision model description of the thermalization of a finite many-body system by using careful derivation of the corresponding Lindblad-type master equation in the weak coupling regime. Using the example of two level target system, we show that collision model thermalization is crucially dependent on the various relevant system and bath timescales and on ensuring that the environment is composed of ancillae which are resonant with the system transition frequencies. Using this we extend our analysis to show that our collision model can lead to thermalisation for certain classes of many-body systems. We establish that for classically correlated systems our approach is effective, while we also highlight its shortcomings, in particular with regards to reaching entangled thermal states.