Single-particle machine for quantum thermalization

TL;DR

This paper demonstrates how a single-particle reservoir can induce thermalization in a coupled quantum system, using a micromaser model, with potential experimental validation in circuit QED.

Contribution

It introduces a quantum thermalization mechanism driven by random single-particle actions and explores its effects using the micromaser model with experimental prospects.

Findings

Cavity reaches thermal equilibrium with reservoir temperature.

Atoms in different initial states can cool or heat the cavity.

Coherence in atoms can raise the cavity's temperature.

Abstract

The long time accumulation of the \textit{random} actions of a single particle "reservoir" on its coupled system can transfer some temperature information of its initial state to the coupled system. This dynamic process can be referred to as a quantum thermalization in the sense that the coupled system can reach a stable thermal equilibrium with a temperature equal to that of the reservoir. We illustrate this idea based on the usual micromaser model, in which a series of initially prepared two-level atoms randomly pass through an electromagnetic cavity. It is found that, when the randomly injected atoms are initially prepared in a thermal equilibrium state with a given temperature, the cavity field will reach a thermal equilibrium state with the same temperature as that of the injected atoms. As in two limit cases, the cavity field can be cooled and "coherently heated" as a maser process, respectively, when the injected atoms are initially prepared in ground and excited states. Especially, when the atoms in equilibrium are driven to possess some coherence, the cavity field may reach a higher temperature in comparison with the injected atoms. We also point out a possible experimental test for our theoretical prediction based on a superconducting circuit QED system.