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https://phys.org/news/2020-07-quantum-fluctuations-jiggle-human-scale.html
The universe, as seen through the lens of quantum mechanics, is a noisy, crackling space where particles blink constantly in and out of existence, creating a background of quantum noise whose effects are normally far too subtle to detect in everyday objects.
Now for the first time, a team led by researchers at MIT LIGO Laboratory has measured the effects of quantum fluctuations on objects at the human scale. In a paper published in Nature, the researchers report observing that quantum fluctuations, tiny as they may be, can nonetheless "kick" an object as large as the 40-kilogram mirrors of the National Science Foundation's Laser Interferometer Gravitational-wave Observatory (LIGO), causing them to move by a tiny degree, which the team was able to measure.
It turns out the quantum noise in LIGO's detectors is enough to move the large mirrors by 10-20 meters—a displacement that was predicted by quantum mechanics for an object of this size, but that had never before been measured.
Journal Reference:
Haocun Yu, L. McCuller, M. Tse, et al. Quantum correlations between light and the kilogram-mass mirrors of LIGO, Nature (DOI: 10.1038/s41586-020-2420-8)
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(Score: 3, Interesting) by Immerman on Thursday July 02 2020, @01:52PM (2 children)
Quantum fluctuations may not be deterministic, but they probably have recognizable bulk characteristics based on the method used to generate them. In fact, if you're using them to move a 40kg mirror, you're probably looking at the combined results of a truly mind-boggling number of individual fluctuations - and at such large scales the statistical properties may very well be deterministic, even though the individual fluctuations are not.
Rather like how those beautiful curtains of water caused by laminar flow are (fairly) deterministic and easy to predict, despite the fact that the motion of every water molecule within that flow is still chaotic. Or how social psychology can predict the behavior of large groups of people fairly accurately, despite the fact that predicting the behavior of a single person is essentially impossible. The behavior of large populations ends to average out the chaotic "noise" and reveal much simpler underlying trends. (e.g. water flows downhill, despite the fact that at any given instant roughly half of the molecules are moving upwards)
(Score: 2, Interesting) by shrewdsheep on Thursday July 02 2020, @03:43PM (1 child)
I understand and agree with your statements. Still it appears to me that additional modelling (i.e. assumptions) is necessary. Why was a given mirror movement due to QFs and not due to a gravitational wave? Or due to fluctuations in the cooling system?
(Score: 4, Informative) by Immerman on Thursday July 02 2020, @05:39PM
Easy - it reliably appears when the fluctuation-generating system is turned on, and disappears when turned off. So long as you isolate the fluctuation-generating system from the interferometer (in this case it sounds like they're transmitting the fluctuations via light?) that should be sufficient. For vibrations, etc. from cooling systems, etc - just don't turn those off so that they're a steady background noise.
Keep in mind we're talking about a system painstakingly designed specifically to filter out environmental noise - gravity waves only distort spacetime by a very tiny amount. A movement of 10^-20 meters is as small compared to an atom, as an atom is to us. If it wasn't aggressively isolated the vibrations in the ground from someone walking down the hall would likely drown out all the experimental signals.