# Was quantum metrology important for gravitational-wave astronomy?

This article from 2010 titled Quantum metrology for gravitational wave astronomy, 6 years before the announcement of the first direct detection of gravitational waves from a binary black hole merger, states that:

Recent advances in quantum metrology may now contribute to provide the required sensitivity boost. The so-called squeezed light is able to quantum entangle the high-power laser fields in the interferometer arms, and could have a key role in the realization of GW astronomy.

My question: is that what happened? Are squeezed states of light used in the LIGO laser cavities? If so, did they lead to a boost in detector sensitivity that allowed for the ensuing detections?... or is it instead likely that the detections might have occurred without this application of squeezed light states?

The initial detections were made without using squeezed light.

Squeezed light was introduced in early 2019. It has the effect of increasing the detection sensitivity by about 15% above 50 Hz (Tse et al. 2019). Since gravitational wave strain scales inversely with distance, this expands the surveyed volume by about 50%.

• Though the performance improvement is not astronomical, the upgrade in the underlying technology sounds generational! :-)
– uhoh
Jul 14 '21 at 1:06