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There might be no getting around what Albert Einstein called "spooky action at a distance." With an experiment described [February 7th] in Physical Review Letters — a feat that involved harnessing starlight to control measurements of particles shot between buildings in Vienna — some of the world's leading cosmologists and quantum physicists are closing the door on an intriguing alternative to "quantum entanglement."
[...] In the first of a planned series of "cosmic Bell test" experiments, the team sent pairs of photons from the roof of [Anton] Zeilinger's lab in Vienna through the open windows of two other buildings and into optical modulators, tallying coincident detections as usual. But this time, they attempted to lower the chance that the modulator settings might somehow become correlated with the states of the photons in the moments before each measurement. They pointed a telescope out of each window, trained each telescope on a bright and conveniently located (but otherwise random) star, and, before each measurement, used the color of an incoming photon from each star to set the angle of the associated modulator. The colors of these photons were decided hundreds of years ago, when they left their stars, increasing the chance that they (and therefore the measurement settings) were independent of the states of the photons being measured.
And yet, the scientists found that the measurement outcomes still violated Bell's upper limit, boosting their confidence that the polarized photons in the experiment exhibit spooky action at a distance after all.
Source: https://www.quantamagazine.org/20170207-bell-test-quantum-loophole/
(Score: 0) by Anonymous Coward on Tuesday February 14 2017, @01:02PM
Aren't these experiments just a form of NHST? By that I mean that they only test for zero correllation without deducing a prediction for how much correlation should be seen from QM. If so, I bet this has lead to all sorts of confusion and BS papers.
(Score: 2, Insightful) by Anonymous Coward on Tuesday February 14 2017, @02:51PM
No. There is a certain amount of correlation classical physics (or more exactly, any local realistic theory) allows, and the quantum correlation exceeds that amount. There's also an upper bound to correlations that quantum mechanics can produce, which is lower than the bound of correlations that would be possible with arbitrary theories, therefore in principle such an experiment could falsify both classical and quantum mechanics at the same time.
Basically there are three possibilities:
Or in short: We don't need any quantum strangeness.
Or in short: Quantum strangeness is needed.
Or in short: Reality is even weirder than quantum mechanics.
The experiments show values in the second range, so local realism is out, but quantum mechanics isn't.
(Score: 0) by Anonymous Coward on Tuesday February 14 2017, @03:00PM
Please quantify, correlation runs from -1 to 1.
For classical theory, apparently the data needs to be consistent with 0.
- Data is not consistent with 0, so either the theory is wrong or some auxiliary assumption is off.
- OK
For quantum theory, the data need to be consistent with ???
- What is this range?
(Score: 0) by Anonymous Coward on Tuesday February 14 2017, @03:09PM
It is not a simple correlation, but actually a linear combination of four correlations which are however not independent of each other (I assume they specifically measured the CHSH inequality, as this is the one usually used). Classical theory allows values between -2 and 2. Quantum mechanics allows values between -2sqrt(2) and 2sqrt(2). When making no restrictions (i.e. treating those correlations as if they were independent of each other), values can go between -4 and 4 (because it's four correlations, each one with a prefactor of either -1 or 1, and each one can range between -1 and 1).
(Score: 0) by Anonymous Coward on Tuesday February 14 2017, @03:56PM
Ok, interesting. So the speilraum goes from -4 to +4. Then 50% of the spielraum is consistent with classical theory (this is pretty vague already):
About 70% of the speilraum is consistent with QM (this is more vague):
Then the remaining 30% is inconsistent with any proposed theory? These don't seem like very strong experiments to me.
(Score: 0) by Anonymous Coward on Wednesday February 15 2017, @03:52AM
I wish some version of this was included in papers instead of (or at least in addition to) p-values.
(Score: 0) by Anonymous Coward on Wednesday February 15 2017, @10:10AM
A car with engine type C can go up to 50 mph. A car with engine type Q can go up to 70 mph. Possibly there could be cars that go to 100 mph, but we don't know an engine that does this.
We observed a car going faster than 50mph, but not faster than 70 mph. That is strong evidence that this car is not using engine C. It is consistent with the car using engine Q. I'd say that is a very strong experiment.
(Score: 0) by Anonymous Coward on Wednesday February 15 2017, @12:48PM
There is a bait and switch in this reasoning. Strong evidence against engine C does not correspond to strong evidence for engine Q, in this case it is weak evidence for engine Q. Also, engine C was already ruled out long ago for other reasons, so is just a strawman.
These experiments do not severely test QM, so shouldn't have much effect on our belief in that idea. Thats all. There have to be better ways of studying this quantum entanglement phenomenon.