Quantum effects are pressing on us all the time, and we now have observational evidence for this somewhat puzzling fact.
Researchers with the Gravitational Wave Laser Interferometer Observatory (LIGO) Scientific collaboration has measured the small kick imparted to its exquisitely sensitive team by quantum fluctuations, a new study reports.
And that kick is really small, moving the 88 pounds of LIGO. (40 kilograms) reflects only 10 ^ -20 meters, the scientists found.
Related: Hunting gravitational waves: the LIGO project in photos
“A hydrogen atom measures 10 ^ -10 meters, so this mirror shift is to a hydrogen atom what a hydrogen atom is to us, and we measure it,” study co-author Lee McCuller, research scientist from the Massachusetts Institute. from the Kavli Institute of Technology (MIT) for Space Astrophysics and Research, he said in a statement.
Other research groups have measured such quantum effects before, but never on this scale. LIGO mirrors are about a billion times heavier than previously observed “kicked” objects, study team members said.
The LIGO project seeks gravitational waves – waves in space-time caused by the acceleration of massive objects – using two detectors, one in Livingston, Louisiana and the other in Hanford, Washington.
Each detector is an L-shaped installation with legs 2.5 miles (4 kilometers) long. A laser at the crucial point of the “L” illuminates these legs and weighs 88 pounds. The mirrors at the end of each return the beams. If the reflected rays return to the crucial point at slightly different times, it is potential evidence of a gravitational wave distorting the space-time structure in the legs.
The LIGO team has used this strategy to great effect. The collaboration now has around a dozen confirmed gravitational wave detections under its belt, including the first such finding, made in september 2015. Most of these events involve merging black holes, but two were caused by the collision of super-dense, city-sized stellar corpses known as neutron stars.
LIGO detectors are incredibly sensitive and deeply protected from noise; they have to be, or else they would be unable to pick up gravitational waves. Doing the groundbreaking 2015 detection, for example, required measuring a change in distance 1,000 times smaller than the width of a proton, the team members have said.
The new study takes advantage of that sensitivity and takes it to another level. The researchers, led by MIT physics graduate student Haocun Yu, used a “quantum juicer,” an additional instrument they recently built that allows them to “tune in” to quantum noise inside the detectors. That noise is created by tiny particles that go in and out of existence, a constant crackling noise that permeates the universe.
“We think of quantum noise as being distributed along different axes, and we try to reduce noise in some specific way,” Yu said in the same statement.
The study team measured the total noise, both quantum and “classical,” which is caused by ordinary vibrations, inside the detector. Then, with the help of the juicer, they subtracted the classic noise during the data analysis. This work revealed that quantum fluctuations Only with laser light can you move the detector’s mirrors, which hang from the pendulums in a quadruple suspension configuration, by 10 ^ -20 meters.
That number is in line with predictions made by theorists, team members said.
the new study, which was published Wednesday (July 1) in the journal Nature, has more than just a gee-whiz appeal. The quantum juicer allows the LIGO team to “manipulate the detector’s quantum noise and reduce its kicks towards the mirrors, in a way that could ultimately improve LIGO’s sensitivity in detecting gravitational waves,” Yu said.
Mike Wall is the author of “Out There” (Grand Central Publishing, 2018; illustrated by Karl Tate), a book on the search for extraterrestrial life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook.
