A gravitational wave observatory operating beyond the quantum shot-noise limit: Squeezed light in application

TL;DR

This paper demonstrates the enhancement of the GEO600 gravitational wave detector's sensitivity using squeezed light, showcasing quantum technology's role in surpassing shot-noise limits for future GW observations.

Contribution

It provides the first practical application of squeezed light to improve a gravitational wave observatory's sensitivity, validating quantum entanglement techniques in GW detection.

Findings

GEO600's sensitivity was improved with squeezed light.

Quantum entanglement proves useful in GW astronomy.

Squeezed light is a key technology for future GW detectors.

Abstract

Around the globe several observatories are seeking the first direct detection of gravitational waves (GWs). These waves are predicted by Einstein's General Theory of Relativity [Einstein, A., Annalen der Physik 49, 769-822 (1916)] and are generated e.g. by black-hole binary systems [Sathyaprakash, B. S. and Schutz, B. F., Living Rev. Relativity 12, 2 (2009)]. Current GW detectors are Michelson-type kilometer-scale laser interferometers measuring the distance changes between in vacuum suspended mirrors. The sensitivity of these detectors at frequencies above several hundred hertz is limited by the vacuum (zero-point) fluctuations of the electromagnetic field. A quantum technology - the injection of squeezed light [Caves, C. M., Phys. Rev. D 23, 1693-1708 (1981)] - offers a solution to this problem. Here we demonstrate the squeezed-light enhancement of GEO600, which will be the GW observatory operated by the LIGO Scientific Collaboration in its search for GWs for the next 3-4 years. GEO600 now operates with its best ever sensitivity, which proves the usefulness of quantum entanglement and the qualification of squeezed light as a key technology for future GW astronomy.