Gravitational wave antenna with QND speed meter

Abstract. Rapid experimental progress has recently allowed the use of light to prepare macroscopic mechanical objects into nearly pure quantum states. This research field of quantum optomechanics opens new doors toward testing quantum mechanics, and possibly other laws of physics, in new regimes. In the first part of this paper, I will review a set of techniques of quantum measurement theory that are often used to analyze quantum optomechanical systems. Some of these techniques were originally designed to analyze how a classical driving force passes through a quantum system, and can eventually be detected with optimal signal-to-noise ratio -while others focus more on the quantum state evolution of a mechanical object under continuous monitoring. In the second part of this paper, I will review a set of experimental concepts that will demonstrate quantum mechanical behavior of macroscopic objects -quantum entanglement, quantum teleportation, and the quantum Zeno effect. Taking the interplay between gravity and quantum mechanics as an example, I will review a set of speculations on how quantum mechanics can be modified for macroscopic objects, and how these speculations -and their generalizations -might be tested by optomechanics.

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“…Some of these schemes [68,69,70,71] were "speed meters", motivated by the fact that momentum of a free mass is a QND observable [72].…”

Section: 4mentioning

confidence: 99%

Macroscopic quantum mechanics: theory and experimental concepts of optomechanics

Chen¹

2013

J. Phys. B: At. Mol. Opt. Phys.

276

302

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“…Radiation pressure noise is expected to dominate at low frequencies and is a kind of measurement back action that limits the sensitivity of the instrument. Various schemes have been investigated with the express aim of circumvent the SQL [2][3][4][5][6][7][8].…”

Section: Gravitational-wave (Gw) Detectors Such As Advanced Ligo Armentioning

confidence: 99%

Polarization speed meter for gravitational-wave detection

et al. 2012

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We propose a modified configuration of an advanced gravitational-wave detector that is a speed meter type interferometer 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 in earlier work of Purdue and Chen [P. Purdue and Y. Chen. PRD 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 Limit over a broad range of frequencies for Advanced LIGO-like parameters. The benefits and possible difficulties of implementing such a scheme are outlined. We also present results for tuning of the speed meter by adjusting the degree of polarization coupling, a novel possibility that does not exist in previously proposed designs, showing that there is a smooth transition from speed meter operation to that of a signal recycling Michelson behavior.

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“…12 We have chosen to use the curvature instead of the radius of curvature because in this region the wavefronts are very flat.…”

Section: Appendix C: Effects Due To Mode Mismatchingmentioning

confidence: 99%

Practical speed meter designs for quantum nondemolition gravitational-wave interferometers

2002

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In the quest to develop viable designs for third-generation optical interferometric gravitational-wave detectors ͑e.g., LIGO-III and EURO͒, 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 ͑SQL͒ 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 Ϫ2R Ӎ0.1) inserted into the output port so as to keep the circulating power down, the SQL can be beat by h/h SQL ϳͱW circ SQL e Ϫ2R /W circ at all frequencies below some chosen f opt Ӎ100 Hz.Here W circ SQL Ӎ800 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. 12͒; these losses are 10% or less over most of the frequency range of interest ( f տ10 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. 4͒.

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Gravitational wave antenna with QND speed meter

Cited by 108 publications

References 3 publications

Macroscopic quantum mechanics: theory and experimental concepts of optomechanics

Macroscopic quantum mechanics: theory and experimental concepts of optomechanics

Polarization speed meter for gravitational-wave detection

Practical speed meter designs for quantum nondemolition gravitational-wave interferometers

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