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Single Electron D-slit Interference Experiment

  1. May 10, 2012 #1
    In the two well referenced experiments [1, 2] that claimed to have observed double slit interference pattern of SINGLE electron, the central claim is that there could not have been more than ONE electron present at the same time in the apparatus (or such probability is negligible).

    However, can anyone explain their rational for that claim? I read the original paper [2], and a commentary on paper [1], but I cannot get a good understanding on how the experimenters made sure (or reasoned) that the electrons passed through the apparatus ONE by ONE (a concept to me even contradictory to the very implication claimed by them - the wave nature of electrons).

    If the presence of more than ONE electron at the same time is excluded with a high probability but not absolute certainty, how is this probability computed?

    1. Merli, P. G., Missiroli, G. F., and Pozzi, G. [1974]: `Electron Interferometry with the Elmiskop 101 Electron Microscope', Journal of Physics E: Scientic Instruments, 7, pp. 729–732.

    2. Tonomura, A., Endo, J., Matsuda, T., Kawasaki, T., and Ezawa, H. [1989]: `Demonstration of Single-Electron Buildup of an Interference Pattern', American Journal of Physics, 57, pp. 117–120.
  2. jcsd
  3. May 11, 2012 #2


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    See if this link will get you the article:


    They mention in the article that the electrons were fired at the rate of 1000 per second. The distance from the source to the detector was 1.5 meters. And at the speed the electron travels, the average interval between successive electrons was 100 times more than the time each is in the apparatus.
  4. May 24, 2012 #3
    Yes, but that works only if they can control the electrons to be fired ONE by ONE every 1000th of a second. How did they do that? I did not find any clue from the original paper.

    My understanding of the argument is that all they did was to control the electrons at a current ~1muA, so roughly 1000 electrons/sec by definition. However, why does that imply that the electrons are fired into the apparatus SUCCESSIVELY? The current intensity is a CLASSIC macroscopic quantity on the collective movement of the electrons. It seems that the authors used a very classic interpretation of electron current, that a current is made up by electrons that are lined up in a single file and are fired by one by one. How can such a interpretation be consistent with the interpretation they made on the result of the experiment?

    Can you offer me your view on that?
    Last edited: May 24, 2012
  5. May 24, 2012 #4


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    Sure. They noted that on the average, electrons arrived too far apart to be in the apparatus at the same time. It doesn't need to get any more complicated. If you are asking whether ANY of the electrons arrived too close on the heels of its predecessor: I guess that is *possible* given their description, although it really wouldn't make any sense. And certainly wouldn't affect the results in a manner which would produce this kind of interference. If 2 arrived too closely, they would repel rather than interfere.

    As to the idea that there are classical electrons lined up to be fired: All they need is some kind of source that gets them out one at a time.
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