Quantum nondemolition measurement of optical field fluctuations by optomechanical interaction

TL;DR

This paper demonstrates a quantum nondemolition measurement of optical field fluctuations using an optomechanical system with a micro-mirror, reducing measurement uncertainty below shot-noise level.

Contribution

It presents an experimental implementation of quantum nondemolition measurement via optomechanical interaction with a micro-mirror, showing reduced measurement uncertainty.

Findings

Measured correlations between light intensity fluctuations and mirror motion.

Reduced uncertainty of light intensity fluctuations below shot-noise level.

Confirmed the feasibility of QND measurement in optomechanical systems.

Abstract

According to quantum mechanics, if we keep observing a continuous variable we generally disturb its evolution. For a class of observables, however, it is possible to implement a so-called quantum nondemolition measurement: by confining the perturbation to the conjugate variable, the observable is estimated with arbitrary accuracy, or prepared in a well-known state. For instance, when the light bounces on a movable mirror, its intensity is not perturbed (the effect is just seen on the phase of the radiation), but the radiation pressure allows to trace back its fluctuations by observing the mirror motion. In this work, we implement a cavity opto-mechanical experiment based on an oscillating micro-mirror, and we measure correlations between the output light intensity fluctuations and the mirror motion. We demonstrate that the uncertainty of the former is reduced below the shot-noise level determined by the corpuscular nature of light.