Dissipation and thermal noise in hybrid quantum systems in the ultrastrong-coupling regime

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. Photonic ReservoirMatter Reservoir Photonic Reservoir Matter Reservoir LightMatter Light-Matter system

Ultrastrong coupling regimes of light-matter interaction

“…The spectrum of the system could be used in this way to probe dephasing noise (Beaudoin et al, 2011). A more general treatment has been used to describe open systems in the USC regime at finite temperatures (Settineri et al, 2018).…”

Simple preparation of Bell and Greenberger-Horne-Zeilinger states using ultrastrong-coupling circuit QED

“…In writing the master equation, we have assumed that the environment that the system interacts with is at zero temperature, T = 0. If needed to better model experiments, the master equation can be extended to account for non-zero temperatures [106].…”

Conversion of mechanical noise into correlated photon pairs: Dynamical Casimir effect from an incoherent mechanical drive

“…For ultra-strongly coupled hybrid quantum systems [64][65][66][67][68], the standard quantum-optical master equation breaks down, and a dressed master equation approach is needed [54,69,70]. Furthermore, if the energy level spectrum displays a quasi-harmonic behaviour [49], like in optomechanical systems, a new dressed master equation [71,72] not involving the usual secular approximation is required.…”

“…In Sec. IV we apply the generalized master equation [72] to calculate the dynamics of the system at finite temperatures and, using the quantum regression theorem, we present the power spectra in the weak and strong light-matter Noise Source Figure 1. Schematic of a generic optomechanical system.…”