Back-action cancellation in interferometers by quantum locking

TL;DR

This paper demonstrates a method to completely cancel back-action noise in interferometers like gravitational-wave detectors using quantum locking, significantly enhancing measurement sensitivity by employing a local control and feedback loop.

Contribution

The authors introduce a novel quantum locking technique that suppresses back-action noise through local mirror control and optimized measurement, improving interferometric sensitivity without adding noise.

Findings

Back-action noise can be fully suppressed in interferometers.

The technique increases measurement sensitivity limited only by phase noise.

Back-action cancellation is robust against interferometer losses.

Abstract

We show that back-action noise in interferometric measurements such as gravitational-waves detectors can be completely suppressed by a local control of mirrors motion. An optomechanical sensor with an optimized measurement strategy is used to monitor mirror displacements. A feedback loop then eliminates radiation-pressure effects without adding noise. This very efficient technique leads to an increased sensitivity for the interferometric measurement, which becomes only limited by phase noise. Back-action cancellation is furthermore insensitive to losses in the interferometer.