The success story of squeezed light

TL;DR

This paper reviews the development and application of squeezed light, highlighting its theoretical origins, experimental progress, and crucial role in enhancing gravitational-wave detectors through quantum correlations.

Contribution

It summarizes the historical evolution, key experimental milestones, and the practical implementation of squeezed light in gravitational-wave observatories.

Findings

Squeezed states exhibit sub-Poissonian photon statistics.

Squeezed light is now used in all gravitational-wave observatories.

Development of squeezed light was crucial between 2002 and 2010.

Abstract

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.