APS: Squeezing More from Gravitational-Wave Detectors

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APS: Squeezing More from Gravitational-Wave Detectors

Post by bystander » Tue Dec 10, 2019 9:45 pm

Squeezing More from Gravitational-Wave Detectors
Physics Focus | American Physical Society | 2019 Dec 05

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%.

Since 2015, gravitational-wave detections have become routine in the two US-based Advanced LIGO instruments and in the Virgo detector in Italy, opening a new window in astronomy. The LIGO and Virgo collaborations have now demonstrated—in separate papers—a modification to their detectors that uses quantum physics to suppress random noise in the signal. The scheme improves the sensitivity of both instruments, which will boost the expected rate of detections by 20 to 50%.

Advanced LIGO and Virgo use interference of laser light bouncing back and forth along two perpendicular arms, 3–4 km long, to detect the spacetime ripples from a passing gravitational wave. The detector sensitivity — which corresponds to space distortions of close to 10−20m — is limited by the effects of so-called quantum noise in the photons. Each photon in the light beam experiences quantum fluctuations, which affects its time of arrival after a round trip along the arms. “The photons arrive ‘on time’ at the detector on average, but some are very early and some are very late, forming a wide bell curve,” says Maggie Tse ... The detectors are only sensitive to a gravitational wave if it changes the travel time in one arm by more than the width of this bell curve.

The LIGO and Virgo teams have reduced this noise using quantum squeezing—an idea first suggested nearly 40 years ago by quantum physicist Carlton Caves [1]. Quantum squeezing makes the arrival-time bell curve narrower, so that the photon fluctuations mask fewer of the gravitational-wave signals. A few prototype demonstrations have previously shown that squeezing can reduce noise in gravitational-wave detection [2, 3], and it has been used for several years at the GEO600 detector operated by the Albert Einstein Institute (AEI) in Germany [4]. ...

New Instrument Extends LIGO's Reach
Massachusetts Institute of Technology | 2019 Dec 05

Squeezed Light Success at Virgo
Albert Einstein Institute | 2019 Dec 05

Quantum-Enhanced Advanced LIGO Detectors in the Era of Gravitational-Wave Astronomy ~ M. Tse et al Increasing the Astrophysical Reach of the Advanced Virgo Detector
via the Application of Squeezed Vacuum States of Light
~ Virgo Collaboration, F. Acernese et al
Last edited by bystander on Fri Dec 13, 2019 7:59 pm, edited 1 time in total.
Reason: Added AEI link
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AEI: Squeezed Light Makes Virgo's Mirrors Jitter

Post by bystander » Wed Sep 23, 2020 4:35 pm

Squeezed Light Makes Virgo's Mirrors Jitter
Albert Einstein Institute | Max Planck Institute for Gravitational Physics | 2020 Sep 22

A quantum mechanical effect demonstrated for the first time in the Advanced Virgo gravitational-wave detector

Quantum mechanics does not only describe how the world works on its smallest scales, but also affects the motion of macroscopic objects. An international research team ... has shown how they can influence the motion of mirrors, each weighing more than 40 kg, in the Advanced Virgo gravitational-wave detector through the deliberate use of quantum mechanics. At the core of their experiment ... is a squeezed-light source, developed and built at the AEI in Hanover, which generates specially tuned laser radiation and improves the detector's measurement sensitivity during observing runs.

The quantum mechanical world of probabilities and uncertainties also governs the behavior of the kilometer-sized gravitational wave detectors Advanced LIGO, Advanced Virgo, and GEO600. The sensitivity of these high-precision instruments to gravitational waves – caused, for example, by distant black hole mergers – is currently limited by quantum mechanical background noise. ...

In gravitational wave detectors shot noise – the patter of the randomly and irregularly arriving light particles – is usually reduced. This trick is necessary because this quantum mechanical background noise limits the sensitivity of the detectors at high measuring frequencies with which they listen into the cosmos.

According to the uncertainty relation, however, reduced shot noise results in increased radiation pressure noise: The force with which the stream of light particles pushes on the mirrors fluctuates more strongly. As a result, the mirrors move back and forth more, simply because of the effects of quantum mechanics. ...

Massive Mirrors Feel Fluctuating Photon Forces
APS Physics Synopsis | 2020 Sep 22

Quantum Backaction on Kg-Scale Mirrors: Observation of Radiation Pressure
Noise in the Advanced Virgo Detector
~ F. Acernese et al (Virgo Collaboration)
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor