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Bell inequality tests questions

  1. Sep 8, 2009 #1
    1. Are there any tests done actually show Bell inequality is NOT violated?

    2. What are the different kinds of things the Bell inequality experiment test? I know most tests are testing spins of electrons, what are the other Bell tests, what they test?
  2. jcsd
  3. Sep 8, 2009 #2


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    1. Not so far. A test showing any kind of entanglement should always violate some kind of Bell Inequality (or other local realistic measure) in order to prove that such has been detected. To date, all setups which theoretically should show entanglement do show entanglement.

    2. There are a lot of different tests. There have been tests on electrons, photons and nuclei (ions). Most tests involve pairs of particles, but entanglement has been seen on 3, 4 and more particles.

    In addition, entanglement has been seen in different pairs of non-commuting observables: spin, position/momentum and time/energy are common. Sometimes, different pairs can be entangled at the same time.
  4. Sep 8, 2009 #3
    You can invariably NOT-violate it using defined sets of physically separate macro-objects with at least three specifiable common yes-or-no characteristics (it's easiest with a dozen or so keys or coins or books, food containers, people in a room ... or use Venn diagrams, letters in words from blocks of text etc. etc.) but some people find that less exciting than do others.

    But it reiterates the profundity of what Bell accomplished. Among everything else he actually defined, in a simple formulation, a way to measurably distinguish the domain of (seeming) local realism from the quantum world. He mathematized an ontological distinction.
    Last edited: Sep 8, 2009
  5. Sep 9, 2009 #4


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    In the narrow sense of this question - if there are some tests that violate predictions of QM entanglement? - the answer is no.
    In wider sense answer is somewhat trivial - in all other cases or aspects inequalities are not violated. "The exception proves the rule" in correct sense of this idiom namely "the exception confirms the rule in cases not excepted".
    Last edited: Sep 9, 2009
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