The quality of images that are obtained from ground-based telescopes has been revolutionized by the advent of adaptive optics. In this system, parts of the telescope mirror are continuously adjusted to compensate for the effect of atmospheric turbulence on the incoming signals. Researchers in Paris have proposed a similar adaptive system to cool the thermal motion of mirrors used in interferometers, such as the gravity wave hunters LIGO and VIRGO.

Researchers shone laser light onto a mirror and detected phase shifts in the reflected light, which were caused by the thermal motion of the mirror. By feeding this signal back into the system, the laser could be adjusted such that its radiation pressure cancelled the mirror's Brownian motion.

This cooling mechanism can reduce thermal noise by a factor of 20. This implies a spatial sensitivity of around 10-19 m for interferometer mirrors. AIP