Orateur
Description
Gravitational-wave detectors use frequency-dependent quantum squeezing
to reduce the impact of quantum noise on the detector bandwidth. While a
single filter cavity (FC) is enough to achieve the frequency dependence for cur-
rent detectors, future generations such as Einstein Telescope Low-Frequency
(ETLF) will be operated with a detuned signal recycling cavity. This will re-
quire a complex rotation of the squeezing ellipse to achieve optimal quantum
noise reduction. For this complex rotation a single filter cavity is not suffi-
cient, two filter cavities (2FC) or one 3-mirrored coupled filter cavity (CFC)
have to be implemented. In this work, after having derived the equations of
quantum degradation for systems composed of more than one cavity, we com-
pare the feasibility and performances of these two systems (2FC and CFC) with
respect to various kinds of squeezing degradation sources: loss, mismatch and
phase noise. A special focus is also given to the impact of the middle mirror
in the coupled cavity configuration. This work extends previous analysis about
2FC and CFC in terms of squeezing degradation and uses new tools to derive
and compare quantum noise degradations using optimal readout schemes that
generalize homodyne detection.
