Back-Action Evading Measurement in Gravitational Wave Detectors to Overcome Standard Quantum Limit, Using Negative Radiation Pressure

TL;DR

This paper proposes a novel opto-mechanical scheme with negative radiation pressure coupling to perform back-action evading measurements, significantly reducing quantum and thermal noise in gravitational wave detection beyond previous methods.

Contribution

The scheme introduces a double cavity with interlocked end mirrors and uses two-mode squeezed vacuum, achieving greater noise suppression than prior hybrid negative mass systems.

Findings

Back action noise suppressed by nearly two orders of magnitude.

Output noise squeezed below the standard quantum limit.

Thermal noise significantly reduced.

Abstract

Aiming at application for gravitational wave (GW) detection, we propose a novel scheme how to obtain quantum back action evading measurements performed on an opto-mechanical cavity, by introducing a negative radiation pressure coupling between the cavity field and the end mirror. The scheme consists of introducing a double cavity with end mirrors interlocked by a pivot and moving in opposite directions. The measurement is performed by sending a two-mode squeezed vacuum to both cavities and detecting the output through the heterodyne detection. Compared to the previously proposed hybrid negative mass spin-optomechanical system in Phys. Rev. Lett. 121, 031101 (2018), we see that our scheme is capable to suppress back action noise by nearly two orders of magnitude more in the lower frequency region. Overall, the setup has been able to squeeze the output noise below the standard quantum limit, with more efficiency. In addition, the scheme has also proven to be beneficial for reducing thermal noise by a significant amount. We confirm our result by a numerical analysis and compared it with the previous proposal Phys. Rev. Lett. 121, 031101 (2018).