Gravitational-wave hunt restarts — with a quantum boost

The hunt for gravitational waves is on again — this time assisted by the quirks of quantum mechanics.

Three massive detectors — the two in the United States called LIGO and one in Italy known as Virgo — officially resumed collecting data on 1 April, after a 19-month shutdown for upgrades. Thanks in part to a quantum phenomenon known as light squeezing, the machines promise not only to spot more gravitational waves — ripples in space-time that can reveal a wealth of information about the cosmos — but also to make more detailed detections. Researchers hope to observe as-yet undetected events, such as a supernova or the merging of a black hole with a neutron star.

The run, which will last until next March, also marks a major change in how gravitational-wave astronomy is done. For the first time, LIGO and Virgo will send out public, real-time alerts on wave detections to tip off other observatories — and anyone with a telescope — on how to find the events, so that they can be studied with traditional techniques, from radio- to space-based X-ray telescopes. The alerts will also be available through a smartphone app. “Astronomers are really hungry,” says David Reitze, a physicist at the California Institute of Technology in Pasadena and director of the Laser Interferometer Gravitational-wave Observatory (LIGO), which made the first historic detection of gravitational waves in 2015.

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