Back-action evading impulse measurement with mechanical quantum sensors

TL;DR

This paper introduces a measurement protocol that significantly reduces quantum measurement noise by coupling optical fields to mechanical momentum, enabling measurements below the standard quantum limit across a broad frequency range.

Contribution

It develops a back-action evading measurement protocol using a double-ring optomechanical cavity, advancing quantum sensor precision beyond previous limits.

Findings

Achieves measurement noise below the standard quantum limit

Demonstrates feasibility with experimentally relevant parameters

Provides a continuous measurement protocol for back-action noise evasion

Abstract

The quantum measurement of any observable naturally leads to noise added by the act of measurement. Approaches to evade or reduce this noise can lead to substantial improvements in a wide variety of sensors, from laser interferometers to precision magnetometers and more. In this paper, we develop a measurement protocol based upon pioneering work by the gravitational wave community which allows for reduction of added noise from measurement by coupling an optical field to the momentum of a small mirror. As a specific implementation, we present a continuous measurement protocol using a double-ring optomechanical cavity. We demonstrate that with experimentally-relevant parameters, this protocol can lead to significant back-action noise evasion, yielding measurement noise below the standard quantum limit over many decades of frequency.