Quantum squeezed light in gravitational-wave detectors

The field of squeezed states for gravitational-wave (GW) detector enhancement is rapidly maturing. In this review paper, we provide an analysis of the field circa 2013. We begin by outlining the concept and description of quantum squeezed states. This is followed by an overview of how quantum squeezed states can improve GW detection, and the requirements on squeezed states to achieve such enhancement. Next, an overview of current technology for producing squeezed states, using atoms, optomechanical methods and nonlinear crystals, is provided. We finally highlight the milestone squeezing implementation experiments at the GEO600 and LIGO GW detectors.