Expanding the Quantum-Limited Gravitational-Wave Detection Horizon

We demonstrate the potential of new adaptive optical technology to expand the detection horizon of gravitational-wave observatories. Achieving greater quantum-noise-limited sensitivity to spacetime strain hinges on achieving higher circulating laser power, in excess of 1 MW, in conjunction with highly squeezed quantum states of light. The new technology will enable significantly higher levels of laser power and squeezing in gravitational-wave detectors, by providing high-precision, low-noise correction of limiting sources of thermal distortions directly to the core interferometer optics. In simulated projections for LIGO A+, assuming an input laser power of 125 W and an effective injected squeezing level of 9 dB entering the interferometer, an initial concept of this technology can reduce the noise floor of the detectors by up to 20% from 200 Hz to 5 kHz, corresponding to an increment of 4 Mpc in the sky-averaged detection range for binary neutron star mergers. This work lays the foundation for one of the key technology improvements essential to fully utilize the scientific potential of the existing 4-km LIGO facilities, to observe black hole merger events past a redshift of 5, and opens a realistic pathway towards a next-generation 40-km gravitational-wave observatory in the U.S., Cosmic Explorer.