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Practical speed meter designs for quantum nondemolition gravitational-wave interferometers

Purdue, Patricia and Chen, Yanbei (2002) Practical speed meter designs for quantum nondemolition gravitational-wave interferometers. Physical Review D, 66 (12). Art. 122004. ISSN 2470-0010. doi:10.1103/PhysRevD.66.122004.

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In the quest to develop viable designs for third-generation optical interferometric gravitational-wave detectors (e.g., LIGO-III and EURO), one strategy is to monitor the relative momentum or speed of the test-mass mirrors, rather than monitoring their relative position. A previous paper analyzed a straightforward but impractical design for a speed-meter interferometer that accomplishes this. This paper describes some practical variants of speed-meter interferometers. Like the original interferometric speed meter, these designs in principle can beat the gravitational-wave standard quantum limit (SQL) by an arbitrarily large amount, over an arbitrarily wide range of frequencies. These variants essentially consist of a Michelson interferometer plus an extra ``sloshing'' cavity that sends the signal back into the interferometer with opposite phase shift, thereby cancelling the position information and leaving a net phase shift proportional to the relative velocity. In practice, the sensitivity of these variants will be limited by the maximum light power W-circ circulating in the arm cavities that the mirrors can support and by the leakage of vacuum into the optical train at dissipation points. In the absence of dissipation and with squeezed vacuum (power squeeze factor e(-2R)similar or equal to0.1) inserted into the output port so as to keep the circulating power down, the SQL can be beat by h/h(SQL)similar torootW(circ)(SQL)e(-2R)/W-circ at all frequencies below some chosen f(opt)similar or equal to100 Hz. Here W(circ)(SQL)similar or equal to800 kW(f(opt)/100 Hz)(3) is the power required to reach the SQL in the absence of squeezing. (However, as the power increases in this expression, the speed meter becomes more narrow band; additional power and reoptimization of some parameters are required to maintain the wide band. See Sec. III B.) Estimates are given of the amount by which vacuum leakage at dissipation points will debilitate this sensitivity (see Fig. 12); these losses are 10% or less over most of the frequency range of interest (fgreater than or similar to10 Hz). The sensitivity can be improved, particularly at high freqencies, by using frequency-dependent homodyne detection, which unfortunately requires two 4-km-long filter cavities (see Fig. 4).

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Chen, Yanbei0000-0002-9730-9463
Additional Information:© 2002 The American Physical Society. Received 27 July 2002. Published 27 December 2002. We thank Kip Thorne for helpful advice about its solution and about the prose of this paper. We also thank Farid Khalili, Stan Whitcomb, Ken Strain, and Phil Willems for useful discussions. This research was supported in part by NSF grant PHY-0099568 and the David and Barbara Groce Fund at the San Diego Foundation.
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San Diego Foundation David and Barbara Groce FundUNSPECIFIED
Issue or Number:12
Record Number:CaltechAUTHORS:20140911-142222451
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49619
Deposited By: Katherine Johnson
Deposited On:11 Sep 2014 21:30
Last Modified:10 Nov 2021 18:46

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