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Determining wether consciousness is required in the double-slit experiment

  1. Feb 24, 2009 #1
    Considering the double-slit-experiment version whereby only one electron is fired at once, and a measuring device is placed by one of the slits, which can determine through which slit te electron travels.

    My question would be: Which case is sufficient to qualify as an observation that will collapse the wavefunction of the observed electrons, thereby destroying the interference-pattern?
    1) The presence of a measuring device that is switched on and measuring by one of the slits, or
    2) The observation of the results of the measurement from this device by a human being,
    3) Otherwise?

    This experiment could be relatively easy to do. Just place a measuring device by one of the slits, turn it on, totally discard the measuring results, and watch the surface behind the slits for an interference pattern to emerge or not. In my opinion, it will reveal wether consciousness is required to make an observation in the QM sense.
     
    Last edited: Feb 24, 2009
  2. jcsd
  3. Feb 24, 2009 #2
    As far as I can tell (at the risk of making some concrete assertion about the problem of measurement!) it would. But to be honest, I don't think consciousness causing collapse is really an idea anyone takes seriously any more. Most people are quite happy to write it off as an ugly sollipsism.
     
  4. Feb 25, 2009 #3

    Demystifier

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    Such experiments have already been done. 1) turns out to be the correct answer. There will be no interference pattern even if you do not look at the result of the measuring device on the slit. The mere presence of this device turns out to be sufficient.
     
  5. Feb 25, 2009 #4
    Does anyone have reference(s) to research on this?
     
  6. Feb 25, 2009 #5

    Demystifier

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    It is so trivial that it does not really need a reference.
     
  7. Feb 25, 2009 #6
    No, if the device is isolated from the environment (which is really difficult to achieve, there decoherence leaks even thru the thermal radiation) and is dropped into a black hole then there is no path information
     
  8. Feb 25, 2009 #7

    Demystifier

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    First, if the device is isolated from the environment, then it is not even justified to call it a "measurement device".
    Second, if the device is in the black hole, than the hole through which the wave function should pass is also in the black hole, so the wave function will not be able to escape from the hole, implying that there will be no interference pattern again.
     
  9. Feb 25, 2009 #8
    1
    It can be an ordinary measurement device, just far enough so it can not interact - FOR SOME TIME. After it enters out lightcone we can get a result of a measurement.

    2
    Nope... Wavefunction is non local so it can pass thru the event horizon.
    For example imagine a Bell experiment with 2 electons, but 1 electorns is directed into a black hole...
     
  10. Feb 25, 2009 #9

    Demystifier

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    I don't get a picture. Far enough from WHAT? Lightcone of WHAT?

    Are you talking about experiments of the type of
    http://xxx.lanl.gov/abs/quant-ph/9903047
    where interference in encoded in the coincidences between two entangled particles? If you do please let me know, because this is something very different from which we were talking about so far.
     
  11. Feb 25, 2009 #10
    My bad, it is just double slit experiment... You're right.
     
  12. Feb 25, 2009 #11

    Demystifier

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    It is a pleasure to discuss with you because we arrive at a consensus very soon. :smile:
     
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