Force sensing beyond standard quantum limit with optomechanical `soft' mode induced by non-linear interaction

TL;DR

This paper demonstrates how an optomechanical system with a 'soft mode' induced by non-linear interactions can surpass the standard quantum limit in force sensing by reducing backaction noise.

Contribution

It introduces a novel approach using a soft mode in optomechanics to enhance force sensitivity beyond the standard quantum limit.

Findings

Achieves force sensitivity beyond the standard quantum limit.

Utilizes a soft mode to non-linearize backaction noise.

Operates in an unresolved side band limit with high-Q mechanical resonator.

Abstract

We consider an optomechanical system that is composed of a mechanical and an optical mode interacting through a linear and quadratic optomechanical dispersive couplings. The system is operated in an unresolved side band limit with a high quality factor mechanical resonator. Such a system then acts as parametrically driven oscillator, giving access to an intensity assisted tunability of the spring constant. This enables the operation of optomechanical system in its 'soft mode' wherein the mechanical spring softens and responds with a lower resonance frequency. We show that this soft mode can be exploited to non-linearize backaction noise which yields higher force sensitivity beyond the conventional standard quantum limit.