Quantum precision limits of displacement noise free interferometers

TL;DR

This paper derives quantum limits for displacement-noise free interferometers, proposing a new cavity scheme and analyzing how noise mitigation and squeezing can enhance gravitational wave detection sensitivity.

Contribution

It introduces a general framework for quantum precision limits in DFI schemes, including a novel triangular cavity configuration and optimal measurement strategies.

Findings

DFI schemes can surpass traditional noise limits in gravitational wave detection.

Squeezing enhances sensitivity in DFI configurations.

The triangular cavity DFI exhibits unique sensitivity profiles.

Abstract

Current laser-interferometric gravitational wave detectors suffer from a fundamental limit to their precision due to the displacement noise of optical elements contributed by various sources. Several schemes for Displacement-Noise Free Interferometers (DFI) have been proposed to mitigate their effects. The idea behind these schemes is similar to decoherence-free subspaces in quantum sensing i.e. certain modes contain information about the gravitational waves but are insensitive to the mirror motion (displacement noise). In this paper, we derive quantum precision limits for general DFI schemes, including optimal measurement basis and optimal squeezing schemes. We introduce a triangular cavity DFI scheme and apply our general bounds to it. Precision analysis of this scheme with different noise models shows that the DFI property leads to interesting sensitivity profiles and improved precision due to noise mitigation and larger gain from squeezing.