Breakthrough experimental demonstration of technologies for future gravitational-wave detectors

Researchers at AEI Hannover have reached a milestone on the road towards third-generation gravitational-wave detectors such as the Einstein Telescope and Cosmic Explorer.

For their breakthrough the team successfully implemented several technologies required for future groundbased detectors in a single table-top experiment. For the laser beam shape used in current detectors, their table-top prototype was able to reduce quantum noise by 10 dB with squeezed light – a record breaking premiere. They also implemented the balanced homodyne detection scheme which is the planned signal readout for third generation detectors. For differently shaped laser beams – called higher-order Hermite-Gaussian modes – they showed between 7.5 dB and 9 dB of quantum noise reduction with squeezing. These “higher-order modes” are currently being investigated for their use in future gravitational-wave detectors. The results are an important demonstration for the planned detectors and for the efficient use of squeezed light in higher-order modes for gravitational-wave detection and other precision measurements.

Paper abstract

Future generations of gravitational-wave detectors (GWD) are targeting an effective quantum noise reduction of 10 dB via the application of squeezed states of light. In the last joint observation run O3, the advanced large-scale GWDs LIGO and Virgo already used the squeezing technology, albeit with a moderate efficiency. Here, we report on the first successful 10 dB sensitivity enhancement of a shot-noise limited tabletop Michelson interferometer via squeezed light in the fundamental Gaussian laser mode, where we also implement the balanced homodyne detection scheme that is planned for the third GWD generation. In addition, we achieved a similarly strong quantum noise reduction when the interferometer was operated in higher-order Hermite-Gaussian modes, which are discussed for the GWD thermal noise mitigation. Our results are an important step toward the targeted quantum noise level in future GWDs and, moreover, represent significant progress in the application of nonclassical states in higher-order modes for interferometry, increased spatial resolution, and multichannel sensing.