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Detectors used for the electron double slit experiment

  1. Jan 8, 2014 #1
    I recently learned about the electron double slit experiment, and I'd like to know more about the detectors used to track which slit the electron passes through.

    When the detector is turn on, the electron acts like a particle, and when it's turned off, the electron acts like a wave. I'm wondering how the detector interacts with the electron. Somehow, the electron is changed when it is detected. How does it sense the electron has passed through?
     
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  3. Jan 8, 2014 #2

    Bobbywhy

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    Here is the paper describing the experiment:

    "Controlled double-slit electron diffraction"
    Roger Bach1, Damian Pope2, Sy-Hwang Liou1 and
    Herman Batelaan

    “The resulting patterns were magnified by an electrostatic quadrupole lens and imaged
    on a two-dimensional microchannel plate and phosphorus screen, then recorded with a
    charge-coupled device camera.”

    http://arxiv.org/abs/1210.6243v1
     
  4. Jan 9, 2014 #3

    rude man

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    It's not the detector, it's the light source. Replace 'detector' with 'light source'.

    If you had no detector then you wouldn't know that the electron behaved like a wave.

    The detector does not interact with the electron. It emits a pulse or whatever when an electron strikes it, end of story. A typical detector would be an electron multiplier tube.
     
  5. Jan 9, 2014 #4

    sophiecentaur

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    Actually, there is a half way house in this. It is possible to have a detector that is affected but does not stop a passing electron nor does it catch all of them. But when a passing electron 'brushes past' without being stopped in its path, the information about its passing is 'out' and the quantum decision has been made at the detector and not between the two slits and screen. The electron will just carry on and arrive at the screen (having been diffracted by the small aperture of the slot, as usual), forming a separate little pile of electrons which do not form part of the two slit diffraction pattern. There will be a similar pile in the straight through path through the other slit.

    How sensitive could the detector be made? Could it be made sensitive enough to spot the electron without affecting it in any way? Nope. One question I'm not sure about is, what if there were a detector in each slit and they both detected the 'same' electron (in its two possible selves) going past at exactly the same time. What would the result for the interference pattern? Would the two detectors come to some mutual decision as to which of them would clock the electron?
     
  6. Jan 9, 2014 #5

    ZapperZ

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    Wait, has this EVER happened before with dealing with single-electron sources?

    Zz.
     
  7. Jan 9, 2014 #6

    sophiecentaur

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    HAHA
    Well, when are you going to detect that? What timing difference would be near enough zero?
    Trouble is that single electron sources are dealing with such small numbers, it would take a long time to establish that it could never happen. Also, a detector that would take so little energy out of the electron would, necessarily, I think, have a very slow response time (i.e. the energy would be tiny so the frequency of the photon would be low) and simultaneity would be even harder to establish.
    I'm sure this must have been discussed and discarded years ago.
     
  8. Jan 9, 2014 #7

    Bobbywhy

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    The OP asked about detecting electrons, so this may be relevant. We are learning new techniques in double-slit interference experiments. Here is an analogous experiment using photons:

    “Physicists have seen a single particle of light and then let it go on its way. The feat was possible thanks to a new technique that, for the first time, detects optical photons without destroying them.”

    https://www.sciencenews.org/article/single-photon-detected-not-destroyed
     
  9. Jan 9, 2014 #8

    ZapperZ

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    As long as the timing difference is LESS than the timing between successive electrons, that good enough.

    The problem here is that there's a fundamental issue related to what you are suggesting, that we CAN detect the SAME, single electron going through BOTH slits. I can tell you that if this actually can happen, us experimentalists will find a way to detect that. Electrons are some of the easiest particles to detect, and we already have instruments sensitive enough to detect single electrons easily! And since you claim that there can be instances that the single electron hits both slits, I don't even have to make a non-destructive measurement. I can just put my detector to block each slit, and look at the timing profile. I have detectors that have picosecond resolution, which is orders of magnitude smaller than the time between single electron emission, which I can easily gate!

    So no, the detection part is a done deal! It is the physics part here that I want to see, such as where in QM is this the scenario when you have detectors at BOTH slits.

    Zz.
     
  10. Jan 9, 2014 #9

    sophiecentaur

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    That's not what I was proposing. We 'all' know the result of that experiment. We learned it at our mothers' knees. My suggestion is along much softer lines. The electron still has to have the option of including both slits in its journey as it makes its way to the screen. There is one extreme situation - which is what you propose (above) and the other extreme, when the electron's path / wave function includes both slits because it is left alone on its journey. You could still let electrons pass through the slits and have a chance of producing an interference pattern but subtly be aware of their passage without disturbing the wave enough to spoil the pattern.
    I guess it would be asking the question of 'how binary' is the distinction between the two situations. Conventionally, it is assumed that the two are totally different.
     
  11. Mar 30, 2014 #10
    Double Slit Experiment using a "Which-Way" Detector

    I've been searching for the same thing myself, and I think I've found the paper that demonstrates the destruction of the interference pattern using a "which-way" detector (atom interferometer) to determine the particle's path (with thanks to UltrafastPED). "Origin of quantum-mechanical complementarity probed by a 'which-way' experiment in an atom interferometer": Nature 395, 33-37 (3 September 1998) | doi:10.1038/25653; (1998).

    http://www.atomwave.org/rmparticle/a...nce%201998.pdf [Broken]

    Also see this list of "which way" experiments (thanks again to UltrafastPED):
    http://web.mit.edu/redingtn/www/netadv/Xafshar.html
     
    Last edited by a moderator: May 6, 2017
  12. Feb 7, 2016 #11

    drl

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    Try this.When an electron is in its bound form to an atom and given enough energy to overcome its electromagnetic attraction to the atom(work function) it becomes a free electron which rapidly changes to a wave. Hence, a bound electron + work energy =wave and a wave- work energy=bound electron. Got it. Now in the 2 slit we start with an electron wave which passes thru an electromagnetic field generated by the detector and in doing so loses its work function energy and reverts back to a bound type of electron. If you don't like this see if the consciousness of the observer or 2 worlds makes more sense.
     
  13. Feb 7, 2016 #12

    ZapperZ

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    But all of these seem to think that the "slit" is the ONLY set up that electron interference can occur. This is false.

    What is the interaction with the "slit" in a superconducting quantum interference device (SQUID)? After all, we detect the SAME interference pattern there, but look ma, no slits! Or what about the interference patterns we detect from LEED or RHEED devices?

    The ONLY common factor in all of these phenomena is that the electron is given more than one possible path to go from the source to the detector/screen. These paths could be the paths from multiple slits, the current paths through one branch of a superconductor, or the paths through a crystal lattice. In none of these are there any interaction with the different paths. Otherwise, and especially in the SQUID, you would have detected such interaction when it is THAT sensitive as to detect a single magnetic quantum flux.

    BTW, you are replying to a thread that's 2 years old.

    Zz.
     
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