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Single photon double slit, reset detector after each impact

  1. May 26, 2015 #1
    What is the experimental outcome of a single photon or electron double slit experiment under the constraint that after each detection the detector material is reset to the original state ie, in the limit it is substituted by another detector sheet, or photographic plate.

    Of course that the impact positions should be recorded in a computer to construct the accumulated final image.
     
  2. jcsd
  3. May 26, 2015 #2
    The result would be the same as if you pointed it at a constant medium. The individual location that the electron or photon strikes will appear random at first, but as you get more data you will see a wave-interference pattern.
     
  4. May 26, 2015 #3
    I want the experimental outcome. Can you provide a link to the actual experiment? Was it done?
     
  5. May 26, 2015 #4
    I would bet that almost all versions of this experiment done in the past 50 years have used a resetting detector. If they were using photons, the detector would almost certainly be a high precision CCD. I don't know if it would reset after every single photon, but they clear their frame buffer fairly often.
     
  6. May 26, 2015 #5

    Merlin3189

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    If you do that, does not the computer become the true detector and whatever material you are removing and replacing are just parts of the detector? Otherwise you could just use a CCD array or maybe even a single sheet of photographic emulsion cut into thousands of tiny pieces (or just count each halide grain as a separate detector.)

    (Not that I'm bothered how you do it, since each photon reaches every element of the detector before deciding which one to interact with. Maybe.)
     
  7. May 26, 2015 #6
    I want to remove any kind of memory in the detector after each detection.
     
  8. May 26, 2015 #7

    Nugatory

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    Then you should go with NewJerseyRunner's post #4 above - we haven't used screens or photographic film or other devices that "remember" where the particles landed for many decades now. You might also want to consider the way that the interference pattern is "observed" in this version of the delayed-choice quantum eraser experiment: We have five detectors, four fixed and one moving, and each detector just sends a timestamp to the computer when it detects a particle. The interference pattern is "observed" when we look at the timestamps after the fact and find that depending on where it is, the moving detector hits at the same time as one of the fixed detectors more or less often.
     
  9. May 26, 2015 #8
    What memoryless detectors are you saying are in use, please ?

    I'm almost sure that the detector, whatever the technology, is not resetted after each detection (or a few of them). I'm saying this because I never saw it mentioned (either explicit or implied).
    AFAIK the interference image we saw is acumulated from the begining thru the end of the experiment.
    In particular I'm thinking on the video of Hitachi Lab experiment double slit, single electron,
    I know that a CCD image can be read and resetted at will.
    The experiment I'm looking for is, for instance : a timed repeat of: read, acumulate, reset. And between each cycle only 0, 1, or few detections should exist, at most.
    A link to such experiment is what I'm asking.
     
  10. May 26, 2015 #9
    That's easy to design.

    Have a laser attached to a computer that can fire a single photon or electron.
    Fire said photon
    Wait for it's detection or a defined amount of time in case the photon is lost.
    Clear the CCD buffer completely.
    Don't fire the next photon until the buffer clear is complete.
     
  11. May 26, 2015 #10
    You are almost there:
    There is no need to link the laser to a computer. Before cleared the CCD must be read and stored to post-process, then: next cycle.

    I've never had news of such experiment, afaik.
     
  12. May 26, 2015 #11
    Right, the computer would control the laser and listen for the sensor. Wait for the sensor before firing the next photon. In computer science, that's a very very common thing, it's called procedural programming.
     
  13. May 26, 2015 #12

    Nugatory

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    Photons, however, are typically detected with photomultiplier devices - when a photon hits the front of one these, the device emits a flash of light out the back and returns to its original state. That's a cycle of reset/accumulate/read/reset with exactly zero or one detections per cycle.
     
  14. May 26, 2015 #13
    Image intensifiers work that way - emitting light out the back - but photomultiplier tubes actually produce a cascade of electrons and thus a current pulse. The term photomultiplier is a bit misleading. But never mind. Once the pulse has gone off and been counted or whatever, the tube is reset. Just saying :)
     
  15. May 26, 2015 #14

    Nugatory

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    Ah - right - of course, and thanks for the correction.

    As far as the present discussion is concerned, the key point is that as you say, "the tube is reset."
     
  16. May 27, 2015 #15
    I'm not discussing, simply asking.
    I feel far from the initial topic. I'll be back when there is news of an experiment in OP conditions (pristine detector after each detection).
     
  17. May 27, 2015 #16

    zonde

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    I think C60 double slit experiment gives very good answer for massive particles.
    http://www.nature.com/nature/journal/v401/n6754/abs/401680a0.html (I found a copy by googling)
    Basically there is not much of a detector. C60 molecules at particular spot are brutally heated ap by laser and become ionized. And then any ionized molecule is detected.
    "At a further distance of 1.25 m behind the diffraction grating, the interference pattern was observed using a spatially resolving detector.It consisted of a beam from a visible argon-ion laser (24 W all lines), focused to a gaussian waist of 8 microm width (this is the size required for the light intensity to drop to 1/e^2 of that in the centre of the beam). The light beam was directed vertically, parallel both to the lines of the diffraction grating and to the collimation slits. By using a suitable mirror assembly, the focus could be scanned with micrometre resolution across the interference pattern. The absorbed light then ionized the C60 fullerenes via heating and subsequent thermal emission of electrons. ... The fullerene ions were then focused by an optimized ion lens system, and accelerated to a BeCu conversion electrode at −9 kV where they induced the emission of electrons which were subsequently amplified by a Channeltron detector."

    If we speak about photons then matters are way more complicated. For single photon detection nowadays you would use mostly avalanche photodiodes. And it is true that they are reset after each sucessful photon detection (significant current is flowing trough diode for some time after detection). But that is only after sucessful detection. If photon is reflected or absorbed without triggering avalanche detector is not reset.
     
  18. May 27, 2015 #17
    I get the impression that you think detector memory explains randomness - the Law of Averages or some such. Unfortunately there is no such law, random events do not adjust themselves in the light of past results to make averages come out right. If they did there would be some auto-correlation observable and there is not. You do not need to do your experiment, the fact that detectors do not remember their past is well established.
     
  19. May 27, 2015 #18
    [QUOTE/]If we speak about photons then matters are way more complicated. For single photon detection nowadays you would use mostly avalanche photodiodes. [/QUOTE]
    In the experiment you cited with C60 (free version) the emission is not one by one as required in the OP, and the detection is complicated.
    The detection in this 2013 exp (matter-wave interference) is very complicated (see Fig 2) .
    Avalanche photodiodes http://www.princetonlightwave.com/images/pli_content/pga-246-25%20v10.pdf [Broken] are not good for the purpose of detecting the impact position to form an image, imo.
    The description of the Hitachi exp is described here and they say "When a large number of electrons is accumulated,..." (in a modified photon detector. To our surprise, it could detect even a single electron with almost 100 % detection efficiency.).
    I dont like the accumulated in the detector. I want to see like 'detect, read position, reset detector, repeat...'
     
    Last edited by a moderator: May 7, 2017
  20. May 27, 2015 #19
    I will not try to convince anybody of nothing not even that a pristine detector is quite different of one with previous detections already imprinted.
    IMO the detectors do remember the past (take a photo) ccd, photograph plate.
    From the begining this is not about theory nor 'about what I think' and I do not need interpreters of what I think. Please keep the 'what you think of what I think' to yourself. Please.
    I'm starting to study QM and I can not afford to take for granted the neutrality of the detector, even if most of others apparently presume it as a fact.
    If it is, as you say, 'well established' then show me the experiment. I'm not asking for opinions.
     
  21. May 27, 2015 #20
    IMO . wrong place to that post.
     
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