LIGO Surpasses the Quantum Limit
Wikipedia defines LIGO as "a large-scale physics experiment and observatory designed to detect cosmic gravitational waves." (It stands for Laser Interferometer Gravitational-Wave Observatory - that is, measuring the interference caused by superimposed waves.) Now Science Alert reports:A technique for squeezing light in the arms of LIGO's interferometer has allowed its measurements to cross the quantum barrier. For LIGO, it's a bold new realm of sensitivity, giving the gravitational wave detector the ability to find 60% more dead star mergers than the rate of its previous run, which was around one or two detections every week or so... "Now that we have surpassed this quantum limit, we can do a lot more astronomy," says physicist Lee McCuller of Caltech... LIGO's sensitivity was already absolutely jaw-dropping. The interferometer works by detecting ripples in space-time that are generated by colliding black holes and neutron stars, millions of billions to light-years away. These cause gravitational waves, like ripples in a pond. We can't feel them; but they can be detected in miniscule deviations in the path of light down a long, long tunnel. These deviations are incredibly small, down to trillions of times smaller than a human hair. But once you get into subatomic scales - the quantum realm - LIGO's abilities are hobbled. That's because, on those unimaginably small scales, particles randomly pop in and out of space, creating a constant background hiss of quantum noise that's louder than any signal. Frequency-dependent squeezing is a way of amplifying the signals to be 'louder' than the quantum noise... If you pinch a property of light, such as amplitude (or power), other properties, such as frequency, can be measured more accurately... [T]he light can be squeezed in multiple ways to amplify the frequency of the gravitational waves the scientists are looking for... "We've known for a while how to write down the equations to make this work, but it was not clear that we could actually make it work until now. It's like science fiction," says physicist Rana Adhikari of Caltech... This means we're likely to see a significant uptick in the number of black hole and neutron star collisions we observe out there in the wider Universe.
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