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Consciousness of Double Slit Observer

  1. Jun 17, 2008 #1
    Have any experiments been conducted that explore the state of consciousness of the observer in the double slit experiment?

    My understanding of the double slit experiment is this. Shoot one photon at a time through a slit and you get a line of light (particle model). Shoot single photons through double slits and you get an interference pattern (wave model). Shoot single photons through double slits while observing what passes through the slits and you get two lines of light (particles again). My wife likes to call this 'shy photons'. It doesn't matter if you observe the photons as they pass through the slits or long after the fact (delayed choice).

    Forgive me if my first-time post treads too far into the fringe, but a slight elaboration of my question might help folks understand what I am asking. There have been experiments attempting to demonstrate an impact of human consciousness on macro reality. I don't know if he qualifies as a scientist or a crank on this forum, but William Tiller's work would be an example. I am curious if any experiments have looked at whether the double slit experiment changes depending on who does the observing and what their state of consciousness is. Can meditating monks observe what slit(s) the photon passes through without losing the interference pattern?

  2. jcsd
  3. Jun 17, 2008 #2


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    It has nothing to do with consciousness. The observer doesn't have to be human. If information about which slit the photon passes through is collected by a piece of equipment, the interference pattern is destroyed.
  4. Jun 17, 2008 #3
    "The world is given to me only once, not one existing and one perceived. Subject and object are only one. The barrier between them cannot be said to have broken down as a result of recent experience in the physical sciences, for this barrier does not exist"
    Erwin Schrodinger, Mind and Matter 1958
    Thought that quote might be useful. I have also seen a quote by John Wheeler which I cant find now where he says that the laws of quantum mechanics cannot be established without the inclusion of consciousness at a fundamental level. Also look up Wigner's friend paradox which is in favour of the theory "consciousness causes collapse". I think many people would disagree that it has nothing to do with consciousness as dx said.
  5. Jun 17, 2008 #4
    Hi dx, are you sure about that? I heard that when the display screen is off (i.e. the thing that the observers look at) but the detectors are still in place and everything else is the same, the interference pattern remains. When they turn the screen on again (and change nothing else), it collapses. See this guy's lecture: http://www.youtube.com/watch?v=_OWQildwjKQ&feature=related
  6. Jun 17, 2008 #5
    I have never heard this exact claim made before, and the presenter in the video doesn't site a source. If one can get this clear result just by turning off a monitor I would expect to have seen a report of this before now. (I've read many different accounts of double slit results, and none of them say this. )
  7. Jun 18, 2008 #6
    Thanks for the replies. So far no example of anyone testing the state of consciousness of the observer, which is not surprising given its proximity to the fringe.

    This would also be a good experiment. It begs the question of what it means to be "collected by a piece of equipment". In the delayed choice quantum eraser version of the double slit, one could argue that the information is "in the equipment" and then removed. What if it were in the equipment in such a way as to make it impossible for a human to ever retrieve it? Maybe the possibility of observation by a human is sufficient. I don't know the answer to any of this.

    Thanks. That's my understanding. And it's this viewpoint that leads me to wonder about whether it is a property inherent in consciousness or perhaps a function of the state of consciousness. Is it possible for consciousness to act (metaphorically) like a quantum computer and observe without collapsing the wave function?
  8. Jun 19, 2008 #7
    The issue of the consciousness of the observer is not a fringe issue, and it has been considered by great minds such as Von Neumann, Wheeler, and Penrose.

    I personally am hopeful that some form of the decoherence process will eventually explain the collapse of the quantum state and destruction of the interference pattern. Here is a difficult but non-technical link to the concept of decoherence:


    If that is not fun to read then you can start with the wikipedia page, although wiki is weak for quantum topics. There is a good amount of empirical support for decoherence as a mechanism to move from quantum microworld to classical macroworld, although the evidence is not yet conclusive in the case of the measurement problem.
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