Nonlinear quantum Langevin equations for bosonic modes in solid-state systems

TL;DR

This paper develops nonlinear quantum Langevin equations to model how two-level systems affect bosonic modes in solid-state systems, providing insights into dissipation and parametric effects observed in experiments.

Contribution

It introduces a novel nonlinear Langevin framework incorporating two reservoirs, modeling impurity effects in solid-state quantum systems, and explains recent experimental phenomena.

Findings

Model captures impurity-induced dissipation effects.

Explains parametric effects in circuit-QED experiments.

Provides a unified description of open quantum systems with nonlinear dynamics.

Abstract

Based on the experimental evidence that impurities contribute to the dissipation properties of solid-state open quantum systems, we provide here a description in terms of nonlinear quantum Langevin equations of the role played by two-level systems in the dynamics of a bosonic degree of freedom. Our starting point is represented by the description of the system/environment coupling in terms of coupling to two separate reservoirs, modelling the interaction with external bosonic modes and two level systems, respectively. Furthermore, we show how this model represents a specific example of a class of open quantum systems that can be described by nonlinear quantum Langevin equations. Our analysis offers a potential explanation of the parametric effects recently observed in circuit-QED cavity optomechanics experiments.