Dissipative quantum systems modeled by a two level reservoir coupling

TL;DR

This paper analyzes how a quantum system interacts with a two-level reservoir using Feynman-Vernon theory, highlighting differences from oscillator baths and deriving a Langevin equation under specific spectral conditions.

Contribution

It introduces a model for dissipative quantum systems with a two-level reservoir and derives the Langevin equation considering a finite spectral distribution at zero frequency.

Findings

The two-level reservoir differs from oscillator baths in key ways.

A finite spectral distribution at zero frequency is necessary for the Langevin equation.

The model provides insights into quantum dissipation mechanisms.

Abstract

The coupling between a quantum dynamical system and a two-level system reservoir is analysed within the framework of the Feynman-Vernon theory. We stress the differences between this new reservoir and the well-known bath of oscillators and show that, in order to obtain the Langevin equation for the system of interest in the high temperature regime, we have to choose a spectral distribution function $J(\omega)$ which is finite for $\omega=0$.