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

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.

Automated summary

In this work, the differences between a common phenomenological model for the master equation and the more rigorous dressed-state master equation for optomechanical systems are investigated. An analytical method to obtain the absorption spectrum of the system for both models is provided, showing the breakdown of the phenomenological model in both the bad cavity and the ultra-strong coupling limit. The role of indirect dephasing of the optical cavity in both models and its impact on the predicted absorption spectra differences is discussed. This work offers a simple experimental test to determine whether the phenomenological model can accurately describe the system and is a step towards better understanding the role of coupling between subsystems for open-quantum-system dynamics.