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A wave that can only be detected in one location

  1. May 24, 2010 #1
    A detector is a device that once it absorbs a minimum amount of energy changes its state and returns data to an observer.

    The energy in a wave is proportional to the wave number, or momentum, and is continuous.

    A wave packet of total energy equal to the minimum detection energy could interfere with itself while only being detected when the interference is constructive, as any amount of destructive interference would result in a wave below the minimum detection energy.

    It could never be detected in more than one location. The constructive energy of two locations, being above the minimum detection energy, would be higher than the initial energy of the packet.

    Does the double slit experiment for a photon seem so mysterious now?
     
  2. jcsd
  3. May 24, 2010 #2

    DrChinese

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    I fail to see how this explains anything about the double slit.

    Were your description accurate, the implication would be that the energy of the wave is itself spreading out. It would decrease with time (distance). Yet that does not happen.
     
  4. May 24, 2010 #3
    When they setup these photon guns, they decrease the intensity until only a single detection is made at a time. Could it be that the energy at the emitter is higher than the minimum detection energy, but just the right amount that by the time it reaches the detector it is the minimum detection energy.

    A photon emitter wouldn't work so well if you pointed it at two slits on the moon without re-adjustment right?
     
  5. May 24, 2010 #4

    Cthugha

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    No, this is completely ruled out by experiments showing antibunching for single photon sources.
     
  6. May 24, 2010 #5
    Yes, but does this explain how the particle is at two places, in one moment of time. I think we need more facts to explain this amazing experiment. What do you think?
     
  7. May 24, 2010 #6

    Doc Al

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    Where do you see the particle in two places at once?
     
  8. May 24, 2010 #7
    The particle went through both slits at once. When they were observed, they acted as a particle. Here is a video from you tube
     
    Last edited by a moderator: Sep 25, 2014
  9. May 24, 2010 #8
    If something can be detected, then this means that it must necessarily exist in more than one location. Mathematically speaking, a location is simply a non-dimensional geometric point. In a three-dimensional universe such as ours, any object that occupies any less that three full dimensions occupies precisely zero space, and therefore fails to exist.

    The purpose for field/continuum theories is to gain a theoretical handle on the logically necessary concept of, for want of a better phrase, "spatial occupancy."

    Wave theories (which deal in modulations of fields) are therefore perfectly well equipped to deal with the problem of how it is that integral volumes of space may be involved in our so-called "localistic" experiences of physical reality.
     
  10. May 25, 2010 #9

    DrChinese

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    It was not observed at 2 places. Just 1. The inference was that it traveled through both slits. This does not relate to the OP's comment that the doubli slit was "solved" somehow by considering it as a wave in 2 places. The mystery is how a wave in different spots collapses to be in just one.
     
  11. May 25, 2010 #10
    In the book I am reading it states " We fired an atom one at a time. The atom acted differently and our detectors picked up the data that the atom went through both slits at once." (Jim Al-Khalili 14) What a mystery this is.
     
  12. May 25, 2010 #11

    DrChinese

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    This is a curious statement.
     
  13. May 25, 2010 #12
    In order to be detected it must have some momentum, and in order to define momentum you must have 2 locations to take the difference of. So I guess that is a true statement.
     
  14. May 25, 2010 #13
    Quoted out of context it is. Reading further, I was trying to show that the only rigorously mathematical concept of location is that of the geometric point. Since a point occupies precisely no part of any spatial volume, it cannot be said to have anything to do with the phenomena of our universe. If we think of the smallest of spaces as necessarily being "more than" a single location (or even an infinity of them: 0+0+0...=0), then the curiosity factor of the statement will hopefully be minimized.
     
  15. May 26, 2010 #14

    Doc Al

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    You seem to be saying, to use an analogy with baseballs: Since a baseball, to exist, must occupy space, it must of necessity be in more than one place at the same time. (Or at least parts of it must occupy different points of space.)

    I don't see the relevance of this to the double slit experiment, where the analogy would be closer to the baseball being at first base and at third base at the same time.
     
  16. May 26, 2010 #15

    DrChinese

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    I guess that makes sense. That an infinitely precise point location means not observable, and is therefore all objects must exhibit some size; and therefore occupy 2 points.
     
  17. May 26, 2010 #16
  18. May 26, 2010 #17

    DrChinese

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    If an atom could be considered a point particle, then yes. But it can't, that is what the experiment proves. As it is acting as a wave, instead of a particle, it exhibits interference effects. Particles don't do that.
     
  19. May 26, 2010 #18
    Right, that is the question is how did matter have a wave function that allowed it to be in two places at once. What is your thinking on this subject?
     
  20. May 26, 2010 #19

    Doc Al

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    A wavefunction going through both slits is not quite the same thing as a particle going through both slits. Often the latter statement is made as an interpretation of the formalism, but it is not demanded. We never detect a particle being in two places.
     
  21. May 26, 2010 #20
    My attempt was to remove the need for the word particle by describing a wave that can only be detected in one place. Is it not possible?
     
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