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Two slit experiment - variable detector

  1. Dec 1, 2009 #1
    I have a question about the situation with the two slit experiment where detectors are placed by the two slits to determine which slit the particle has gone through (and destroy the diffraction pattern).

    Okay, so what I'm wondering is what happens if the detectors' accuracy is not fixed, but can be tuned. As you alter the accuracy of the detectors would you then get patterns midway between the full diffraction pattern and the full particle-like pattern? By accuracy I mean the ability to determine the particles position (I realize that in QM the particle doesn't actually have a position).
  2. jcsd
  3. Dec 1, 2009 #2


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    Sure, if you vary the amount of knowledge you get, you vary the amount of diffraction.
  4. Dec 1, 2009 #3
    If you vary the amount of information that is lost to the environment, you vary the amount of interference. Note that you are not only observing the detectors, you are also observing the screen (and interference pattern).
  5. Dec 1, 2009 #4
    Would it matter how the accuracy of the detector is reduced? Lets say you reduce the amount of knowledge by just adding a circuit to the detector that adds electrical noise to the results. Would that decrease in knowledge work as well to adjust the diffraction?
  6. Dec 1, 2009 #5
    No. Adding the electric circuit would not change the interference pattern. The amount of knowledge that you get from observing the detectors does not matter. What matters is the amount of information that you get from observing the screen. That amount would be less if you place which-path detectors on the way.
    Last edited: Dec 2, 2009
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