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B Entangled or Synchronized

  1. May 1, 2017 #1
    Given a pair of entangled atoms, it's my understanding that the next measurements taken on each will correlate. If, after taking its measurement, before the other is measured, one of the pair is destroyed, it is my understanding that the remaining's initial measurement will be unaffected, as in still correlate to the deceased's original measurement. (If this were not the case then it would be easy to devise a scheme for "instantaneous" data transfers across any distance.) Therefore, it would seem there is no connection or entanglement or "spooky interaction" between these atoms. Rather they have only been configured or seeded to produce correlating results when next measured. So wouldn't atomic synchronization be a more accurate term than entanglement?
     
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  3. May 1, 2017 #2

    DrChinese

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    Certainly not. There is a shared state between entangled particles and they do not have an individual local/separate states. Keep in mind they are in a superposition of states.

    I am sure you have heard of Bell's Theorem, and that is what tells us that your description is not correct. There are no local hidden variables possible that would lead to the "atomic synchronization" you envision. You can work that out for yourself, or I might humbly suggest you look at a page I created for this purpose:

    http://drchinese.com/David/Bell_Theorem_Easy_Math.htm
     
  4. May 1, 2017 #3

    Nugatory

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    You are right that the correlations will only be present if the system has been prepared (you say "configured or seeded" instead of "prepared) in a particular way that gives it a particular property (formally, "non-factorizable", informally "entangled"). If you feel that it would be more natural to use "synchronized" instead of "entangled" to describe such states.... Well, all of this terminology is the result of various historical accidents, enforced only by habit and common usage.

    But I do worry that "synchronized" is an invitation to serious misunderstanding. Most people, I expect, would interpret "synchronized" as meaning something similar to how if take a pair of gloves, put each glove in its own box, and mail them to distant locations, then whoever opens one box knows immediately whether the glove in the other box is left-handed or right-handed. And as we know from Bell's theorem, that's not a good way of thinking about entanglement.
     
  5. May 2, 2017 #4
    Thanks for the feedback, Dr. Chinese, and for the link. I perused your article yesterday, and then reread again today carefully (after letting my subconscious digest). Very interesting. You had me at, "touches upon many of the fundamental philosophical issues that relate to modern physics." It gave me a better feel for some of the terms, like Hidden Variables. Googled "photon polarization" since this was the least clear term, and got quickly in over my head.

    The math is indeed simple. I played around with the table and see that no matter how many angles (whose +/- values can be expressed as binary bits, so the 3 angles have 23 or %1000 or 8 possible permutations, 8 angles 28 or %10000000 or 256, etc.), the probability of a pair's matching (assuming equal frequencies of occurrence) is always .5, though the minimum probability rises from 1/3 (in your example) toward 1/2 as the number of angles (bits) increases.

    I find it a little unsettling that, in a test to prove the validity of QM, quantum entanglement is used to measure pairs simultaneously. But what can you do, right? I also have a little difficulty with the assumption that the pairs sampled are representative of the pairs emitted by the source, and that this sampling could not have been influenced by Hidden Variables.

    But still a thought provoking, accessible and informative article. Very well written, too. Being a copy editor in the fiction world, I flagged a couple minor typos, if you care.

    its polarization at these 3 angles correspond
    corresponds

    In this case, if happen to select to test
    if we happen

    a measurement of B on Bob tell you indirectly about B on Alice.
    tells / will tell

    Philosophically, could you speculate on how a particle remains entangled with a particle that has been destroyed, and no longer exists? Or is my assumption that, entangling A and B, measuring B, destroying B, still predicts A's subsequent measurement, wrong? Also, can particles be entangled from different locations?
     
    Last edited: May 2, 2017
  6. May 2, 2017 #5
    Thanks again, Nugatory, for explaining and clarifying some of my vernacular. Yes, your glove analogy was kind of how I was thinking. That or maybe similarly loading a pair dice so that they each rolls 6'es half the time. I read Dr. Chinese's paper and understand better your reference to Bell's Theorem. And but which I'm still not sure asserts any sort of connectivity or cause/effect.
     
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