# Enhancing sideband cooling by feedback--controlled light

## TL;DR

This paper demonstrates that feedback-controlled light can significantly enhance sideband cooling of an optomechanical system, achieving a 7.5 dB improvement and potentially surpassing quantum backaction limits.

## Contribution

The authors introduce a phase-sensitive feedback scheme that improves optomechanical cooling by manipulating pump field fluctuations, a novel approach in the field.

## Key findings

- Achieved 7.5 dB improvement in sideband cooling with feedback.
- Operating in the anti-squashing regime enhances cooling performance.
- Potential to surpass quantum backaction cooling limits.

## Abstract

We realise a phase-sensitive closed-loop control scheme to engineer the fluctuations of the pump field which drives an optomechanical system, and show that the corresponding cooling dynamics can be significantly improved. In particular, operating in the counter-intuitive "anti-squashing" regime of positive feedback and increased field fluctuations, sideband cooling of a nanomechanical membrane within an optical cavity can be improved by 7.5~dB with respect to the case without feedback. Close to the quantum regime of reduced thermal noise, such feedback-controlled light would allow going well below the quantum backaction cooling limit.