Lectures on History of Science – Lecture 23: Gravitational-wave detector: An instrument for macroscopic quantum effects

Summary

Gravitational wave offers a new access to exploring the universe. We examine Einstein’s General Theory of Relativity in strong gravitational field by detecting the merger of two black holes. Observations of gravitational waves and electromagnetic waves from binary neutron stars even spawned multi-messenger astronomy. Ground-based gravitational-wave detectors like LIGO, VIRGO and KAGRA are large laser interferometers with kilometers of length. These large interferometers have high sensitivity in order to detect weak signals of gravitational waves and unveil quantum effects that only significantly appears on the atomic scale. One of the main factors restricting the sensitivity of detectors is the quantum noise caused by quantum fluctuations of light. This lecture briefly recapitulates the discovery and detection of gravitational waves, introduces the quantum properties of the detectors and anticipates the future of gravitational-wave detection.