The measurement of weak continuous forces exerted on a mechanical oscillator is a fundamental problem in various physical experiments. It is fundamentally impeded by quantum back-action from the meter used to sense the displacement of the oscillator. In the context of interferometric displacement measurements, we here propose and demonstrate the working principle of a scheme for coherent back-action cancellation. By measuring the amplitude quadrature of the light reflected from a detuned optomechanical cavity inside which a stiff optical spring is generated, back-action can be cancelled in a narrow band of frequencies. This method provides a simple way to improve the sensitivity in experiments limited by quantum back-action without injection of squeezed light or stable homodyne readout.
@article{arxiv.2105.10510,
title = {Improving force sensitivity by amplitude measurement of light reflected from a detuned optomechanical cavity},
author = {Kentaro Komori and Takuya Kawasaki and Sotatsu Otabe and Yutaro Enomoto and Yuta Michimura and Masaki Ando},
journal= {arXiv preprint arXiv:2105.10510},
year = {2021}
}