The success story of squeezed light

Squeezed states of the optical field were theoretically described in the early 1970s and first observed in the mid 1980s. The measured photon number of a squeezed state is correlated with the measured photon numbers of all other squeezed states of the same ensemble, providing sub-Poissonian statistics. Today all gravitational-wave observatories use squeezed light as the cost-efficient alternative to further scaling up the light power. This user application of quantum correlations was made possible through dedicated research and development of squeezed light between 2002 and 2010.Comment: Proceedings paper of the invited talk at the 56th Rencontres de Moriond 2022 on Gravitation in La Thuile, Aosta Valley, Italy, January 30 - February 6, 2022. https://moriond.in2p3.fr/download/proceedings_gravitation_2022new.pdf ; Full proceedings available at https://doi.org/10.58027/1e1n-797