Sagnac Interferometer as a Speed-Meter-Type, Quantum-Nondemolition Gravitational-Wave Detector

According to quantum measurement theory, "speed meters" -- devices that measure the momentum, or speed, of free test masses -- are immune to the standard quantum limit (SQL). It is shown that a Sagnac-interferometer gravitational-wave detector is a speed meter and therefore in principle it can beat the SQL by large amounts over a wide band of frequencies. It is shown, further, that, when one ignores optical losses, a signal-recycled Sagnac interferometer with Fabry-Perot arm cavities has precisely the same performance, for the same circulating light power, as the Michelson speed-meter interferometer recently invented and studied by P. Purdue and the author. The influence of optical losses is not studied, but it is plausible that they be fairly unimportant for the Sagnac, as for other speed meters. With squeezed vacuum (squeeze factor $e^{-2R} = 0.1$) injected into its dark port, the recycled Sagnac can beat the SQL by a factor $\sqrt{10} \simeq 3$ over the frequency band 10 {\rm Hz} \alt f \alt 150 {\rm Hz} using the same circulating power $I_c\sim 820$ kW as is used by the (quantum limited) second-generation Advanced LIGO interferometers -- if other noise sources are made sufficiently small. It is concluded that the Sagnac optical configuration, with signal recycling and squeezed-vacuum injection, is an attractive candidate for third-generation interferometric gravitational-wave detectors (LIGO-III and EURO).Comment: 12 pages, 6 figure

Quantum noise in laser-interferometer gravitational-wave detectors with a heterodyne readout scheme

We analyze and discuss the quantum noise in signal-recycled laser interferometer gravitational-wave detectors, such as Advanced LIGO, using a heterodyne readout scheme and taking into account the optomechanical dynamics. Contrary to homodyne detection, a heterodyne readout scheme can simultaneously measure more than one quadrature of the output field, providing an additional way of optimizing the interferometer sensitivity, but at the price of additional noise. Our analysis provides the framework needed to evaluate whether a homodyne or heterodyne readout scheme is more optimal for second generation interferometers from an astrophysical point of view. As a more theoretical outcome of our analysis, we show that as a consequence of the Heisenberg uncertainty principle the heterodyne scheme cannot convert conventional interferometers into (broadband) quantum non-demolition interferometers.Comment: 16 pages, 8 figure

The gravitational wave detector VIRGO

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The Virgo data acquisition system

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Search for non-Gaussian events in the data of the VIRGO E4 engineering run

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Erratum - Recycling interferometric antennas for periodic gravitational waves

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Thermal noise reduction in interferometric gravitational wave antennas: using high order TEM modes

We compute the low-frequency tail of the power spectral density of thermal noise in the case of an optical Fabry–Perot resonant cavity operating with Laguerre–Gauss modes of orders higher than (0, 0). We show a significant reduction of the thermal noise as the order of the mode increases. We discuss the diffraction losses

Lisa amplitude modulation: A study of the angular resolution of LISA for monochromatic gravitational waves

We present formulae for the amplitude modulation of the X,Y and Z TDI combinations for monochromatic gravitational waves and use these to study the LISA angular resolution in the case of large SNR. The angular resolution, Δθ/(0.1 * SNR), is found to lie between 2° and 5° and is somewhat dependent on the ecliptic colatitude angle (β), on the polarisation (h+,hx) and much less on the ecliptic longitude angle (λ). Comparisons with other studies are presented. Future studies will treat the case of small SNR

Virtual gravitational wave interferometer with actual mirrors

Phys. Rev. D, vol. 67, n. 102006, pp. , 2003, 2003International audienc