Force sensing in an optomechanical system with feedback-controlled in-loop light

TL;DR

This paper proposes a feedback-controlled optomechanical force sensor that significantly reduces measurement noise and enhances bandwidth, leveraging quantum control techniques for improved sensitivity in macroscopic systems.

Contribution

It introduces a novel feedback scheme that suppresses optically added noise and increases amplification bandwidth in optomechanical sensors, approaching quantum-limited performance.

Findings

Achieves extremely low optically added noise in force sensing.

Enhances mechanical response and amplification bandwidth with feedback.

System behaves like a quantum-limited optical parametric amplifier.

Abstract

Quantum control techniques applied at macroscopic scales provide us with opportunities in fundamental physics and practical applications. Among them, measurement-based feedback allows efficient control of optomechanical systems and quantum-enhanced sensing. In this paper, we propose a near-resonant narrow-band force sensor with extremely low optically added noise in an optomechanical system subject to a feedback-controlled in-loop light. The membrane's intrinsic motion consisting of zero-point motion and thermal motion is affected by the added noise of measurement due to the backaction noise and imprecision noise. We show that, in the optimal low-noise regime, the system is analogous to an optomechanical system containing a near quantum-limited optical parametric amplifier coupled to an engineered reservoir interacting with the cavity. Therefore, the feedback loop enhances the mechanical response of the system to the input while keeping the optically added noise of measurement below the standard quantum limit. Moreover, the system based on feedback offers a much larger amplification bandwidth than the same system with no feedback.