It is planned that the next generation of laser interferometric gravitational-wave detectors will surpass the second-generation detectors in amplitude sensitivity in a broad range of frequencies by nearly tenfold. Since the sensitivity will be limited by quantum noise at all frequencies above ∼10 Hz at almost all frequencies, the development of new schemes for detectors that are able to provide the required lowered level of quantum fluctuations is very topical. A velocimeter based on the Sagnac interferometer, which is investigated in this study, is one such scheme and possibly is the most promising among them. We present a complete comparative analysis of the quantum noise of the signal-recycling Sagnac and Mickelson interferometers with frequency-dependent squeezing of the quantum state of light and demonstrate the substantial advantage of the former, both in sensitivity and from the viewpoint of its easier experimental implementation. In particular, we show that the Sagnac scheme is able to surpass even a xylophone configuration of two Michelson detectors in the level of quantum noises and is less tolerant to optical losses in the filter cavity when using frequency-dependent squeezing.
03.65.Ta Foundations of quantum mechanics; measurement theory
95.30.Sf Relativity and gravitation
95.85.Sz Gravitational radiation, magnetic fields, and other observations
$^1$Department of Physics, Moscow State University, Moscow, 119991, Russia
$^2$School of Physics, University of Western Australia, Crawley, 6009, Sterling Hwy, Australia
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