# Radiation Pressure Cooling as a Quantum Dynamical Process

## TL;DR

This paper models radiation pressure cooling as a dynamic process, revealing that the final phonon number depends on cooling speed and introduces an effective coupling parameter influencing cooling limits.

## Contribution

It presents a dynamical approach to optomechanical cooling, emphasizing the importance of cooling speed and an effective coupling parameter over traditional steady-state analyses.

## Key findings

- Cooling speed affects the final phonon number.
- Effective optomechanical coupling is crucial for cooling.
- Discontinuous jump in cooling limit at a critical parameter value.

## Abstract

One of the most fundamental problems in optomechanical cooling is how small the thermal phonon number of a mechanical oscillator can be achieved under the radiation pressure of a proper cavity field. Different from previous theoretical predictions, which were based on an optomechanical system's time-independent steady states, we treat such cooling as a dynamical process of driving the mechanical oscillator from its initial thermal state, due to its thermal equilibrium with the environment, to a stabilized quantum state of higher purity. We find that the stabilized thermal phonon number left in the end actually depends on how fast the cooling process could be. The cooling speed is decided by an effective optomechanical coupling intensity, which constitutes an essential parameter for cooling, in addition to the sideband resolution parameter that has been considered in other theoretical studies. The limiting thermal phonon number that any cooling process cannot surpass exhibits a discontinuous jump across a certain value of the parameter.