First demonstration of 6 dB quantum noise reduction in a kilometer scale gravitational wave observatory

• Main Authors: Lough, James, Schreiber, Emil, Bergamin, Fabio, Grote, Hartmut, Mehmet, Moritz, Vahlbruch, Henning, Affeldt, Christoph, Brinkmann, Marc, Bisht, Aparna, Kringel, Volker, Lück, Harald, Mukund, Nikhil, Nadji, Séverin, Sorazu, Borja, Strain, Kenneth, Weinert, Michael, Danzmann, Karsten
• Format: Journal Article
• Language: English
• Published: 20-05-2020
• Subjects: Physics - Instrumentation and Detectors
• DOI: 10.48550/arxiv.2005.10292

Phys. Rev. Lett. 126, 041102 (2021) Photon shot noise, arising from the quantum-mechanical nature of the light,
currently limits the sensitivity of all the gravitational wave observatories at
frequencies above one kilohertz. We report a successful application of squeezed
vacuum states of light at the GEO\,600 observatory and demonstrate for the
first time a reduction of quantum noise up to $6.03 \pm 0.02$ dB in a
kilometer-scale interferometer. This is equivalent at high frequencies to
increasing the laser power circulating in the interferometer by a factor of
four. Achieving this milestone, a key goal for the upgrades of the advanced
detectors, required a better understanding of the noise sources and losses, and
implementation of robust control schemes to mitigate their contributions. In
particular, we address the optical losses from beam propagation, phase noise
from the squeezing ellipse, and backscattered light from the squeezed light
source. The expertise gained from this work carried out at GEO 600 provides
insight towards the implementation of 10 dB of squeezing envisioned for
third-generation gravitational wave detectors.