Minimizing Quantum Decoherence in Gravitational-Wave Detectors

This award supports the development of instrumentation aimed at extending the astrophysical reach of gravitational-wave detectors. Since their first detection by Advanced LIGO in 2015, gravitational waves have opened a new observational window on the Universe. These faint disturbances in distant space-time carry new and complementary information to the light observed by telescopes.

In the coming decade, gravitational-wave detections will reveal new insights into extreme gravity, ultra-dense states of matter inside neutron stars, and the nature of black holes. The LIGO detectors employ high-power laser beams over 4-kilometer distances to measure passing gravitational waves. This project will develop novel adaptive optics capable of significantly reducing the optical losses inside LIGO and future detectors, enabling higher laser power and greater sensitivity to gravitational waves.

In addition to its astrophysical impact, this new technology will provide a general means of achieving lower loss in complex laser systems, with potential to accelerate discoveries in many fields including atomic, molecular, and optical physics and optical quantum computing.

Quantum noise limits the sensitivity of gravitational-wave detectors at high frequencies, where some of the most compelling observations—black hole ringdowns and binary neutron star mergers—stand to be made. The use of squeezed coherent states of light and higher laser power directly reduce this noise, extending the astrophysical reach of the detectors.

To support higher levels of squeezing and laser power, this project will develop novel low-noise adaptive optics for dynamic control of the laser wavefront at higher spatial-frequencies, endowing gravitational-wave detectors with critical new corrective capabilities. Higher-order optical aberrations induce decoherence of the squeezed state and degrade the optical gain of the laser cavities—and currently limit the operating power of Advanced LIGO.

Through the optical loss reduction it will afford, this new technology seeks to enable a quantum noise reduction factor of 1.7 from reaching the 750 kW Advanced-era design power, as well as greater squeezed-light enhancement. This will both extend the astrophysical range of the detectors, increasing detection rates, and enable higher-precision measurements of individual waveforms.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.