Increasing the sensitivity of future gravitational-wave detectors with double squeezed-input

Abstract

We consider improving the sensitivity of future interferometric gravitational-wave detectors by simultaneously injecting two squeezed vacuums (light), filtered through a resonant Fabry-Perot cavity, into the dark port of the interferometer. The same scheme with single squeezed vacuum was first proposed and analyzed by Corbitt et al.[1]. Here we show that the extra squeezed vacuum, together with an additional homodyne detection suggested previously by one of the authors [2], allows reduction of quantum noise over the entire detection band. To motivate future implementations, we take into account a realistic technical noise budget for Advanced LIGO (AdvLIGO) and numerically optimize the parameters of both the filter and the interferometer for detecting gravitational-wave signals from two important astrophysics sources, namely NeutronStar-Neutron-Star (NSNS) binaries and Bursts. Assuming the optical loss of the ∼ 30m filter cavity to be 10ppm per bounce and 10dB squeezing injection, the corresponding quantum noise with optimal parameters lowers by a factor of 10 at high frequencies and goes below the technical noise at low and intermediate frequencies.

Rotation of the noise ellipse for squeezed vacuum light generated via four-wave mixing

“…Several papers have discussed this proposal [20,21] and experimental demonstrations have been achieved [22]. Different techniques have been proposed to implement a frequency dependent noise ellipse [23][24][25] Most of these techniques are based on pre-filtering cavities as initially proposed in [22], and they can all introduce losses and mode-matching problems. More recently, Horrom et al have demonstrated an example of angle rotation of the quantum noise quadratures using the frequency-dependent absorption of the EIT window [26].…”

The third generation of gravitational wave observatories and their science reach

“…At the same time as the shot noise is reduced, the radiation pressure contribution will increase. By appropriately rotating the phase angle of the squeezing as a function of frequency, which can be achieved by sending the squeezed state through filter cavities [114,102,103], the shot noise (at high frequencies) and the radiation pressure noise (at low frequencies) can be simultaneously reduced. In case of using squeezing together with a detuned interferometer (i.e.…”

Optimal configurations of filter cavity in future gravitational-wave detectors

“…Namely, (i) we suppose that the main interferometer is tuned in resonance. In the absence of squeezing and filter cavities, the interferometer detuning can provide some moderate sensitivity gain [38,39], but it destructively interferes with other advanced technologies (see, e.g., [30]). Also, (ii) we suppose the squeeze angle I ¼ =2 À ; this tuning provides a minimum of the shot noise.…”

“…In order to evade this effect, an additional homodyne detection (AHD) capturing this information has to be used. This scheme was further developed in [30], where injecting additional squeezed vaccuum though the filter cavity end mirror and thus also suppressing the low-frequencies' radiationpressure noise was proposed .…”