Quantum Noise Engineering in Advanced LIGO

arXiv:2611.07074v1 Announce Type: new Abstract: Advanced LIGO is a gravitational-wave detector with extreme sensitivity, operating close to the quantum limits of optical measurement. The quantum noise in this system arises from vacuum fluctuations entering the interferometer readout port: phase-like fluctuations produce measurement imprecision, while amplitude-like fluctuations drive radiation-pressure back-action. In this review, we present an intuitive description in terms of complex fields and quadratures, and follow squeezed vacuum from its generation, through its interaction with the filter cavity and propagation through the interferometer, to the readout.