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Q & A: entangled particles

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Most recent answer: 05/23/2018
Q:
HiI am not an expert (not even a novice), but one thing that really confuses me is entangled particles.You can not change the state of a an entangled particle. As this would mean faster than light communication.When I see documentaries, they show a pack of cards. when they measure one particle, its the same measurement as the other entangled particle. (both the same card 3 of clubs for example)How do they know they are communicating with each other?surely it makes more sense that when you entangle particles you force them to act in the same random state.like shuffling the two decks in the exact same random way. Therefore whenever one is measured it would produce the same reading.this seems a lot more logical. I never get this answered watching documentaries.maybe I am missing something.kind regards Gavin Osborn.
- GAVIN OSBORN (age 42)
RAINHAM
A:

Your idea certainly makes more "sense" to all of us, so that's why it  has been tested experimentally. It's wrong.

That idea is in the broad class of "local realist" models. In those models, observables with predictable values have something that causes that value to occur. In this case, measuring one particle (or card) allows a reliable prediction of what will be seen wth the second. All such local realist pictures share certain properties, including obeying some mathematical inequalities discovered by John Bell. Many, many experiments now show that entangled particles violate the Bell Inequalities.

So whatever is going on doesn't make sense to us in the way local realist pictures do. There are many arguments and unsatisfactory ideas about what's happening.

Mike W.


(published on 05/23/2018)

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