Increasing the Astrophysical Reach of the Advanced Virgo Detector via the Application of Squeezed Vacuum States of Light

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Increasing the Astrophysical Reach of the Advanced Virgo Detector via the Application of Squeezed Vacuum States of Light

F. Acernese et al. (Virgo Collaboration)

Phys. Rev. Lett. 123, 231108 – Published 5 December 2019

See Focus story: Squeezing More from Gravitational-Wave Detectors

Abstract

Current interferometric gravitational-wave detectors are limited by quantum noise over a wide range of their measurement bandwidth. One method to overcome the quantum limit is the injection of squeezed vacuum states of light into the interferometer’s dark port. Here, we report on the successful application of this quantum technology to improve the shot noise limited sensitivity of the Advanced Virgo gravitational-wave detector. A sensitivity enhancement of up to $3.2 \pm 0.1 dB$ beyond the shot noise limit is achieved. This nonclassical improvement corresponds to a 5%–8% increase of the binary neutron star horizon. The squeezing injection was fully automated and over the first 5 months of the third joint LIGO-Virgo observation run O3 squeezing was applied for more than 99% of the science time. During this period several gravitational-wave candidates have been recorded.

Received 11 November 2019

DOI:https://doi.org/10.1103/PhysRevLett.123.231108

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Gravitational waves Nonlinear optics Quantum optics

Gravitational wave detection

Gravitation, Cosmology & AstrophysicsAtomic, Molecular & Optical

Focus

Squeezing More from Gravitational-Wave Detectors

Published 5 December 2019

New hardware installed in current gravitational-wave detectors uses quantum effects to boost sensitivity and increase the event detection rate by as much as 50%.

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Authors & Affiliations

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Quantum-Enhanced Advanced LIGO Detectors in the Era of Gravitational-Wave Astronomy

M. Tse et al.

Phys. Rev. Lett. 123, 231107 (2019)

Article Text

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References

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Issue

Vol. 123, Iss. 23 — 6 December 2019

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Images

Figure 1
Simplified layout of the quantum enhanced Advanced Virgo gravitational-wave detector. The Advanced Virgo detector is a power recycled Michelson interferometer using 3 km long Fabry-Perot cavities in the arms. Before being injected into the interferometer, the high power (18 W) input laser beam passes through a 143 m long triangular mode cleaner cavity. After the recombination at the central beam splitter, a fraction of the carrier light copropagates with the signal field to be used for a dc readout scheme. This output field is spatially filtered by an output mode cleaning stage and divided into two beams before detection. The sum of the two photo detectors is used to derive the gravitational-wave signal $h (t)$ . All the interferometer optics as well as the injection and the detection benches are suspended and operated in vacuum. Squeezed vacuum states of light are prepared externally on an optical bench (blue box). This in-air bench hosts the squeezed light source (yellow box), the reflective mode matching telescope, the Faraday isolators, and alignment steering mirrors. The bench is covered with an enclosure to protect the optics against acoustic noise and air turbulence and is passively suspended by means of elastomer attenuators. More sophisticated suspension stages are not required as below $\sim 30 Hz$ the squeezer backscattered light effect is dominated by the up-conversion of the low frequency ( $\sim 0.15 Hz$ ) microseismic peak [18, 19]. Finally, the squeezed beam is injected into the interferometer vacuum system through an antireflectively coated viewport. The path between the acoustic enclosure and this optical window is shielded by a tube from air turbulence.
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Figure 2
Measured spectral strain sensitivity of the Advanced Virgo detector in different conditions of squeezed light injection. The black trace corresponds to the reference sensitivity in the absence of squeezed light. The measured sensitivity with squeezing or antisqueezing are shown as the red and blue traces, respectively. Our analysis yields a detected squeezing level of $3.2 \pm 0.1 dB$ with the corresponding antisqueezing of $8.5 \pm 0.1 dB$ , normalized to the reference at 2.8 kHz. For this set of measurements, the injected squeezing level was about 10 dB.
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Figure 3
Long-term performance of the shot noise reduction during the first 5 months of the O3 science run (1 April to 9 September 2019). Values are derived from the band limited rms strain sensitivity between 2650 and 3140 Hz. The reference shot noise level in the absence of squeezing is calculated from the optical gain of the arm cavities (see text). Each point corresponds to an average over 100 s time. Data in red correspond to the time interval between 5 June and 8 July 2019. Data gaps are due to nonscience mode periods of the interferometer. Right: histogram of the collected data with bin width 0.036 dB.
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