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Evidence for entanglement

  1. Nov 30, 2011 #1
    Hello all,

    I know "quantum entanglement" is real, in some sense. I know that if we entangle two particles their spin, for instance, is closely related. Especially spin entanglement has enough evidence, yet it is also easy to explain using a hidden variable.
    Hence I wonder: what other experimental evidence is there for entanglement? Which properties have been shown to be entangled, and in what way?

    Thanks in advance,
  2. jcsd
  3. Dec 1, 2011 #2


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    Once you read Bell's Theorem, I would hope you would revise your comment about "easy to explain using a hidden variable". A non-local hidden variable is theoretically feasible, but not with local ones. Are you familiar with Bell?

    As to things that can be entangled: there are many things which have been experimentally entangled besides photons. I don't keep track of them specifically, but you can get an idea of papers published this year by scanning some of these:


    Here is an older paper you may like:

    Hyper-entanglement (more than just spin):
  4. Dec 1, 2011 #3
    Thank you for your answer. I'm not saying it is easy to introduce a local variable theorem for all of entanglement, only for the entanglement of spin.

    I wasn't asking about what kind of particles have been entangled, I know it's not about the particles. But rather, which properties of particles have been tested to be entangled and in what way this test was done.
    The only one I am aware of is spin, where the test is "up-spin" or "down-spin" for two distinct axis. But I know others have been tested as well, I just don't know of any such experiments.

    I will read the links you posted now.

  5. Dec 1, 2011 #4


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    Bell's Theorem shows that is not possible. See below for a proof (from my website, and I will be glad to answer any questions).

    Bell's Theorem with Easy Math
  6. Dec 1, 2011 #5
    Hmm very interesting link... Maybe I was wrong, but I'm going to have to let it sink in a bit more.

    Thanks for your replies!
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