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Subatomic particles form a crazy world in which the rules are very different to what we know in the classical world. There, you can move one thing and the opposite at the same time or something being in two places at once or teleport, situations inasumibles to the physical with which we are all familiar with. But that kingdom is so small, however strange that seems to us, can influence our. Now, for the first time, a team led by researchers at the Laboratory MIT LIGO was able to measure their effects on objects at a human scale.
In an article published in the journal “Nature”, scientists have observed how the quantum fluctuations that exist in the universe, regardless of how small, can “kick” an object as large as the mirrors 40 kilograms of the Observatory the Laser Interferometer Gravitational Wave (LIGO), causing them to move minimally a distance of 10 to the minus 20 meters. This shift had been predicted by quantum mechanics for an object of that size, but it had never before been measured.
In particular, the mirrors have been moved by the noise of the quantum. The universe, seen through the lens of quantum mechanics, the space is noisy and crackling where the particles parpadéan constantly in and out of existence, creating a background noise quantum whose effects are normally too subtle to be detected in everyday objects. It occurs in ourselves, but we do not realize.
“Every nanosecond of our existence, we are being shaken, struck by these quantum fluctuations. It’s just that the nervousness of our existence, our thermal energy, which is too large for these fluctuations of the quantum vacuum affecting our movement in a way that is measurable”, says Nergis Mavalvala, the head of the department of physics at MIT. “The special thing about this experiment is that we have seen quantum effects in something as large as a human being,” he added.
To achieve this, the researchers isolated the mirrors in LIGO’s movement driven thermally and by other forces, so that they are now strong enough to be shaken by quantum fluctuations, and these “creepy popcorn in the universe”.
Kick quantum
LIGO is designed to detect gravitational waves (made the first detection in September 2015) that reach the Earth from sources cataclysmic millions or billions of light years away. It consists of two detectors identical twins, one in Hanford, Washington, and the other in Livingston, Louisiana. Each detector is an interferometer in L-shape formed by two tunnels 4 miles long, at the end of which hangs a mirror of 40 kilograms.
in order To detect a gravitational wave, a laser located at the entrance to the interferometer LIGO sends a beam of light for each tunnel of the detector, where it is reflected in the mirror at the far end, to get back to your starting point. In the absence of a gravitational wave, the lasers should be back at the exact same time. If you pass a gravitational wave, would disrupt briefly the position of the mirrors and, therefore, the times of arrival of the lasers.
The interferometer is protected from external noise, to have a better opportunity to detect the perturbations extremely subtle created by a gravitational wave incoming. But the researchers wondered if LIGO could also be sensitive enough to feel the effects more subtle, such as quantum fluctuations inside the interferometer and, specifically, the noise of the quantum generated between the photons in the laser LIGO.
“This quantum fluctuation in the laser light can cause a radiation pressure that can actually kick an object,” notes Lee McCuller, research scientist at the Kavli Institute for Astrophysics and space Research at MIT. “The object in our case is a mirror of 40 kilograms, which is a billion times heavier than objects at the nanoscale in the other groups have measured this quantum effect,” he says.
Juicer noise
For the experiment, the team used an instrument built recently as a complement of interferometers, called a squeezer quantum. With the juicer, the scientists can adjust the properties of the noise of the quantum within the interferometer of LIGO.
The team measured first, the total noise within the interferometer, including the noise of the quantum of fund, as well as the noise “classic” or the disruptions generated by the vibrations of everyday normal. Then they lit the juicer and set up in a specific state that altered the properties of the noise quantum. They then were able to subtract the noise classic during the data analysis, to isolate the noise purely quantum. As the detector constantly monitors the offset of the mirrors to any noise incoming, the researchers were able to observe that only the quantum was sufficient to move the mirrors slightly.
Mavalvala notes that the measurement is aligned exactly with what predicted by quantum mechanics. “But even so it is remarkable to see that is confirmed in something so big,” he stresses. “A hydrogen atom is 10 to the minus 10 meters, so that this displacement of the mirrors is to a hydrogen atom which a hydrogen atom is to us, and what we have measured”, adds McCuller.
The experiment can also lead to other results. When studying how to manipulate the noise of the quantum detector and to reduce their kicks towards the mirrors, the researchers may even improve the sensitivity of LIGO detection of gravitational waves, further enhancing the new field for astrophysics opened up in recent years. As they explain the physical Valeria Sequino, University of Naples Philip II, and Mateusz Bawaj, of the University of Perugia (Italy), in an article accompanying the study in “Nature”, “once you have developed a better sensitivity, we could detect gravitational waves of what is possible in the present. The future work on noise suppression, therefore, will take us back to an era of exciting performance.”
