ANU developed ‘squeezing’ enhances gravitational wave detection

Gravitational wave detection resumed on the 1st of April after a year of upgrades, where the reduction of quantum noise has produced a major improvement in the detector range. This increase in range has, in one month of operation, lead to the detection of four binary black holes, a binary neutron star and the detection of a possible black hole neutron star inspiral. Instrumental to the reduction of quantum noise is the installation of the squeezed light source. This squeezed light source is engineered to have lower fluctuations in the phase quadrature than the electromagnetic fluctuations of the vacuum field. By replacing the quantum vacuum fluctuations entering the interferometer with squeezed light, the quantum noise impact on the gravitational wave detector is reduced and the signal to noise ratio is therefore enhanced. Squeezing levels of 3 dB below the shot noise of the detector are achieved which is equivalent to a 50% increase in the laser power used to measure the gravitational wave signal. This is especially significant as laser power is currently limited by the instabilities it causes in the interferometer.

Significant innovations in squeezer design from ANU include audio-band vacuum squeezing, the bow-tie geometry to reduce backscatter, improved mechanical stability and vacuum implementation technologies.

K. McKenzie, “Squeezing in the audio gravitational wave detection band“ Phys. Rev. Lett. 93, 161105 (2004). https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.93.161105 S. S. Y. Chua et. al. “Backscatter tolerant squeezed light source for advanced gravitational-wave detectors “ Opt. Lett. 36 23 (2011). https://www.osapublishing.org/ol/abstract.cfm?uri=ol-36-23-4680

A. R. Wade et. al. “A squeezed light source operated under high vacuum” Scientific Reports 5 (2015) https://www.nature.com/articles/srep18052

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