fb-pixel

MIT says new instrument is allowing it to pick up more gravitational wave signals

Researchers install the new quantum squeezing device into one of LIGO’s gravitationa wave detectors.
Researchers install the new quantum squeezing device into one of LIGO’s gravitationa wave detectors.Lisa Barsotti for the Boston Globe

Researchers at MIT say a new instrument is allowing the detection of more gravitational wave signals at the groundbreaking Laser Interferometer Gravitational-Wave Observatory.

Since LIGO began its third operating run in April, the instrument has helped scientists pick out dozens of possible gravitational wave signals, MIT said.

The instrument, called a “quantum vacuum squeezer,” was designed, built, and integrated with LIGO by MIT researchers, along with collaborators from California Institute of Technology and the Australian National University, MIT said in a statement.

The instrument was described in a paper published Thursday by an international team of researchers in the journal Physical Review Letters.

Advertisement



In 2015, LIGO made the landmark discovery of gravitational waves, confirming a prediction that Albert Einstein made 100 years ago in his general theory of relativity. LIGO, which is supported by the National Science Foundation and operated by Caltech and MIT, consists of two enormous and intricate laser interferometers, one in Washington state and one in Louisiana.

Gravitational waves are ripples in the fabric of space-time that travel at the speed of light. They are extremely faint and cause infinitesimally small changes in distances that are measured by LIGO.

The new instrument is designed to reduce levels of quantum noise, which the study said, is “one of the fundamental limitations to the sensitivity of gravitational wave detectors.”

Quantum noise, which occurs due to random fluctuations of photons, leads to uncertainty and masking of fainter gravitational wave signals, according to the LIGO website.

“Where quantum mechanics comes in relates to the fact that LIGO’s laser is made of photons,” the new study’s lead author Maggie Tse, a graduate student at MIT, said in the MIT statement. “Instead of a continuous stream of laser light, if you look close enough it’s actually a noisy parade of individual photons, each under the influence of vacuum fluctuations. Whereas a continuous stream of light would create a constant hum in the detector, the individual photons each arrive at the detector with a little ‘pop.’”

Advertisement



“This quantum noise is like a popcorn crackle in the background that creeps into our interferometer, and is very difficult to measure,” Nergis Mavalvala, the Marble Professor of Astrophysics and associate head of the Department of Physics at MIT, said in the statement.

The detectors’ range with the new instrument has been extended by 15 percent. With an accompanying increase in the power of the lasers used, the detectors have extended their range to more than 400 million light years, allowing it to detect about one wave a week, the university said. Previously, about one wave was being detected per month.

“When the rate of detection goes up, not only do we understand more about the sources we know, because we have more to study, but our potential for discovering unknown things comes in,” says Mavalvala, a longtime member of the LIGO scientific team. “We’re casting a broader net.”


Martin Finucane can be reached at martin.finucane@globe.com