Impact of backscattered light in a squeezing-enhanced interferometric gravitational-wave detector

TL;DR

This paper investigates how backscattered light from a squeezed-light source affects the sensitivity of gravitational-wave detectors, providing measurements that inform the design of future quantum-enhanced observatories.

Contribution

It presents the first direct measurement of backscattered light impact in a large-scale gravitational-wave detector and guides the development of compatible squeezed light sources.

Findings

Backscattered light impacts detector sensitivity.

Measurements inform design of squeezed light sources.

Results aid future detector improvements.

Abstract

Squeezed states of light have been recently used to improve the sensitivity of laser interferometric gravitational-wave detectors beyond the quantum limit. To completely establish quantum engineering as a realistic option for the next generation of detectors, it is crucial to study and quantify the noise coupling mechanisms which injection of squeezed states could potentially introduce. We present a direct measurement of the impact of backscattered light from a squeezed-light source deployed on one of the 4 km long detectors of the Laser Interferometric Gravitational Wave Observatory (LIGO). We also show how our measurements inform the design of squeezed light sources compatible with the even more sensitive advanced detectors currently under construction, such as Advanced LIGO.