Breakdown of phenomenological Lindblad master equations in the strong 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 the quantum systems of interest. For single quantum systems, the jump operators that characterize this interaction usually take simple forms, with clear experimental/physical interpretation. However, for coupled quantum systems the jump operators can take significantly different forms and in general the total Lindbladian for the system cannot be described by separate Lindbladians acting on the individual quantum systems. In this talk we investigate the effects of such separate, phenomenological description in optomechanical and spin-boson systems, which are particularly pronounced in the strong coupling regime and compare the results with a more realistic microscopic derivation of the master equation. We show that these approaches, phenomenological and microscopic, lead to different solutions to the model and we explore the parameter regime and conditions where these differences manifest themselves in an experiment. We propose an experiment with superconducting systems to investigate these issues and the breakdown of the phenomenological approach with increasing coupling strength.