Dissipation and Thermal Noise in Hybrid Quantum Systems in the Ultrastrong Coupling Regime

TL;DR

This paper develops a general master equation framework for hybrid quantum systems in the ultrastrong coupling regime, accounting for environmental interactions and temperature effects, improving accuracy over previous models.

Contribution

It introduces a comprehensive master equation approach applicable to various hybrid quantum systems, extending beyond prior specific models to include thermal reservoirs and complex transitions.

Findings

Temperature significantly affects multiphoton Rabi oscillations in circuit QED.

Thermal effects alter energy conversion efficiency in optomechanical systems.

Previous models may overestimate decoherence and underestimate excited-state populations.

Abstract

The interaction among the components of a hybrid quantum system is often neglected when considering the coupling of these components to an environment. However, if the interaction strength is large, this approximation leads to unphysical predictions, as has been shown for cavity-QED and optomechanical systems in the ultrastrong-coupling regime. To deal with these cases, master equations with dissipators retaining the interaction between these components have been derived for the quantum Rabi model and for the standard optomechanical Hamiltonian. In this article, we go beyond these previous derivations and present a general master equation approach for arbitrary hybrid quantum systems interacting with thermal reservoirs. Specifically, our approach can be applied to describe the dynamics of open hybrid systems with harmonic, quasi-harmonic, and anharmonic transitions. We apply our approach to study the influence of temperature on multiphoton vacuum Rabi oscillations in circuit QED. We also analyze the influence of temperature on the conversion of mechanical energy into photon pairs in an optomechanical system, which has been recently described at zero temperature. We compare our results with previous approaches, finding that these sometimes overestimate decoherence rates and understimate excited-state populations.