Breakdown signatures of the phenomenological Lindblad master equation in the strong optomechanical coupling regime

TL;DR

This paper compares phenomenological and rigorous dressed-state master equations in optomechanical systems, revealing the breakdown of the simpler model in strong coupling regimes through analytical absorption spectrum analysis.

Contribution

It introduces an analytical method to compare the models and identifies conditions where the phenomenological approach fails, improving understanding of open-quantum-system dynamics.

Findings

Phenomenological model breaks down in ultra-strong coupling.

Absorption spectra differ significantly between models.

Experimental test proposed to validate model applicability.

Abstract

The Lindblad form of the master equation has proven to be one of the most convenient ways to describe the impact of an environment interacting with a quantum system of interest. For single systems the jump operators characterizing these interactions usually take simple forms with a clear interpretation. However, for coupled systems these operators take significantly different forms and the full dynamics cannot be described by jump operators acting on the individual subsystems only. In this work, we investigate the differences between a common phenomenological model for the master equation and the more rigorous dressed-state master equation for optomechanical systems. We provide an analytical method to obtain the absorption spectrum of the system for both models and show the breakdown of the phenomenological model in both the bad cavity and the ultra-strong coupling limit. We present a careful discussion of the indirect dephasing of the optical cavity in both models and its role in the differences of their predicted absorption spectra. Our work provides a simple experimental test to determine whether the simpler phenomenological model can be used to describe the system and is a step forward toward a better understanding of the role of the coupling between subsystems for open-quantum-system dynamics.