Polarization speed meter for gravitational-wave detection

摘要

We propose a modified configuration of an advanced gravitational-wave detector that is a speed-meter-typeudinterferometer with improved sensitivity with respect to quantum noise. With the addition of polarization-controlling components to the output of an arm cavity Michelson interferometer, an orthogonal polarization state of the interferometer can be used to store signal, returning it later with opposite phase to cancel position information below the storage bandwidth of the opposite mode. This modification provides an alternative to an external kilometer-scale Fabry-Pérot cavity, as presented inudearlier work of Purdue and Chen [Phys. Rev. D 66, 122004 (2002)]. The new configuration requires significantly less physical infrastructure to achieve speed meter operation. The quantity of length and alignment degrees of freedom is also reduced. We present theoretical calculations to show that such a speed meter detector is capable of beating the strain sensitivity imposed by the standard quantum limitudover a broad range of frequencies for Advanced Laser Interferometer Gravitational-wave Observatory-likeudparameters. The benefits and possible difficulties of implementing such a scheme are outlined. We alsoudpresent results for tuning of the speed meter by adjusting the degree of polarization coupling, a noveludpossibility that does not exist in previously proposed designs, showing that there is a smooth transitionudfrom speed meter operation to that of a signal-recycling Michelson behavior.