A Recent Study on Frequency-dependent Squeezing Generation with EPR Entanglement

The sensitivity of gravitational wave interferometric detectors is ultimately limited by the quantum
noise, which arises from the quantum nature of light and it is driven by vacuum fluctuations of the
optical field entering from the dark port of the interferometer. One way to improve the sensitivity of
gravitational wave interferometers is to inject squeezed vacuum into the dark port. This has been
already demonstrated for the main gravitational wave detectors (GEO, Advanced LIGO and Advanced
VIRGO).We are studying tricks to produce a \frequency- dependent squeezing": a standard method is
to filter the squeezed optical field with one or more optical cavities (300 m long cavities). An
alternative method using a pair of squeezed EPR (Einstein-Podolsky-Rosen) entangled beams to
produce frequency-dependent squeezing by a non-degenerate OPO (Optical Parametric Oscillator)
will be discussed in this paper. This method promises to achieve a frequency-dependent optimization
of the injected squeezed light fields without the need for an external filter cavity. The improvement of
the GW interferometric detectors sensitivity will enhance the quality and quantity of GW observations,
allowing a deeper study of the sky and unexpected discoveries.