Quantum weirdness: entanglement (Introduction)

by David Turell , Saturday, October 24, 2015, 15:08 (3319 days ago) @ David Turell

Another article on the Delft experiment which finally closes the door on 'hidden variables' that might confuse the issue of entanglement theory. This is the best test of entanglement yet. 'Spooky action at a distance' is real.-http://www.economist.com/news/science-and-technology/21676733-one-weirdest-bits-physics-proved-beyond-doubt-almost-hidden-no-more-"Plenty of experiments have closed one or the other of these loopholes, for example by detecting particles that are more reliably caught than photons, or by sending photons so far apart that no slower-than-light signal could flit between them in time to have an effect. By now, most physicists reckon the hidden-variable idea is flawed. But no test had closed both loopholes simultaneously—until this week, that is.-***-"Ronald Hanson of the University of Delft and his colleagues, writing in Nature, describe an experiment that starts with two electrons in laboratories separated by more than a kilometre. Each emits a photon that travels down a fibre to a third lab, where the two photons are entangled. That, in turn, entangles the electrons that generated the photons. The consequence is easily measured particles (the electrons) separated by a distance that precludes any shifty hidden-variable signalling.-"Over 18 days, the team measured how correlated the electron measurements were. Perhaps expectedly, yet also oddly, they were far more so than chance would allow—proving quantum mechanics is as spooky as Einstein had feared.-***-"There remains, alas, one hitch that could explain all these counterintuitive findings. Just maybe, every single event that will ever be, from experimenters' choices of the means of measurement to the choice of article you will read next, were all predetermined at the universe's birth, and all these experiments are playing out just as predetermined. That, however, is one for the metaphysicists.
" ( my bold, just to bug dhw!)