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MON: Monday Contributed Sessions

MON 20: Quantum Sensing and Decoherence: Contributed Session to Symposium II

MON 20.3: Talk

Monday, September 8, 2025, 17:00–17:15, ZHG009

Coherent feedback for quantum expander in gravitational wave observatories — •Niels Böttner, Joe Bentley, Roman Schnabel, and Mikhail Korobko — Institut für Quantenphysik und Zentrum für Optische Quantentechnologien, Universität Hamburg

The observation of gravitational waves from binary neutron star mergers offers insights into properties of extreme nuclear matter. However, their high-frequency signals in the kHz range are often masked by quantum noise of the laser light used. We propose the “quantum expander with coherent feedback”, a new detector design that features an additional optical cavity in the detector output and an internal squeeze operation. This approach allows to boost the sensitivity at high frequencies, at the same time providing a compact and tunable design for signal extraction. It allows to tailor the sensitivity of the detector to the specific signal frequency range. We demonstrate that our design allows to improve the sensitivity of the high-frequency detector concept NEMO (neutron star extreme matter observatory), increasing the detection rates by around 14%. Our approach promises new level of flexibility in designing the detectors aiming at high-frequency signals.

Keywords: Quantum noise; Squeezed light; Interferometry; Gravitational wave detection; Neutron star mergers