Effective description of cooling and thermal shifts in quantum systems coupled to bosonic modes

Recently, an effective Lindblad master equation for quantum systems whose dynamics are coupled to dissipative bosonic modes was introduced [Jager et al., Phys. Rev. Lett. 129, 063601 (2022)]. In this approach, the bosonic modes are adiabatically eliminated, and one can effectively describe the dynamics of the quantum systems. Here, we demonstrate that this effective master equation can also be used to describe cooling in systems with light-matter interactions. We provide two examples: sideband cooling of an optomechanical oscillator in the unresolved as well as resolved sideband regime and cooling of an interacting quantum system, the transverse-field Ising model. We compare our effective description with a full numerical simulation of the composite formed by the quantum system plus bosonic mode and find excellent agreement. In addition, we present how the effective master equation can be extended to the case of nonvanishing mean thermal occupations of the bosonic mode. We use this approach to calculate modifications of the linewidth and frequency for a two-level system coupled to a dissipative thermal bosonic mode. Here, we highlight that our approach allows for a massive reduction of the underlying Liouville-space dimension.

Automated summary

Recently, an effective Lindblad master equation was introduced for quantum systems coupled to dissipative bosonic modes. This equation allows for an adiabatic elimination of the bosonic modes and effectively describes the dynamics of the quantum systems. The authors demonstrate that this effective master equation can also describe cooling in systems with light-matter interactions and provide examples of sideband cooling and cooling of an interacting quantum system. They compare their effective description with numerical simulations and highlight the reduction of the Liouville-space dimension achieved with this approach.