Squeezed light states to improve measurement precision: application to the gravitational wave detector Virgo.

Virgo is a km-scale Michelson interferometer with suspended (i.e. free falling) end
mirrors located near Pisa: this detector is part of a network of observatories
aiming at the detection of gravitational wave (GW) signals from compact
astrophysical sources. The observations will soon be resumed in 2015-16 at
unprecendented sensitivity by upgraded detectors, Advanced Virgo and Advanced LIGOs.
The sensitivity will be limited nearly at all frequencies by quantum noise:
radiation pressure noise at low frequencies (10-100Hz) and shot noise at high
frequencies (100Hz-10kHz).
Within the Advanced Virgo (AdV) collaboration, we are developing a squeezed vacuum
source to be injected into the dark port of the interferometer that will allow AdV
to increase the sensitivity below the standard limit set by quantum fluctuations
(Standard Quantum Limit). The planned sensitivity improvement (6dB) will increase
the radius of the observed universe by a factor of two that makes a factor of 8 in
volume of observed universe.