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That queer experiment; what is its limit?

  1. Jan 21, 2006 #1
    Some of you may have heard of this experiment:

    http://www.cs.caltech.edu/~westside/quantum-intro.html


    I'm thinking of the experiment at the top of the page where the light beem seems to take two paths.

    Does anyone know whether there is a limit for how far you can let this beem "travel in both directions". E.g. we might try to let the beem travel 1km.
     
  2. jcsd
  3. Jan 23, 2006 #2
    come on, someone please help me out!
     
  4. Jan 23, 2006 #3
    IIRC there have been entanglement experiments with distances of that order. Don't quote me on this though.
     
  5. Jan 23, 2006 #4

    JesseM

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    Science Advisor

    No, theoretically there shouldn't be any upper limit. In the context of something called the "delayed choice experiment", I've often seen the suggestion that an astronomer could, depending on her choice of measurement, determine whether a photon emitted millions of years ago behaves as though it took a single path around a galaxy or whether it behaves as though it took both paths at once--see the section entitled 'Does our choice "change the past"?' from this page on the delayed-choice experiment. I don't know whether an experiment of this type has actually been performed, though.
     
  6. Jan 23, 2006 #5
    got link?

    Thx. If anyone´s got a link or reference to such a "long distance" experiment I´d be very thankful.
     
  7. Jan 23, 2006 #6
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