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Real Time Entanglement from the Zeilinger Group

  1. May 29, 2013 #1
    Last edited by a moderator: Sep 25, 2014
  2. jcsd
  3. May 29, 2013 #2


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    Freaking ey! I almost fell of the chair!! :surprised


    Thanks CW!! [Broken]

    P.S: Doesn’t the correlations look a bit like ‘electron clouds’...?? :bugeye:
    Last edited by a moderator: May 6, 2017
  4. May 29, 2013 #3


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    More info:

    Quantum entanglement for the first time live on camera [Google translate]

  5. May 29, 2013 #4
  6. May 29, 2013 #5
    That is real treat. It is one thing to study the theory and imagine, and other thing to watch it actually happening. Thank you for sharing this article.
  7. May 29, 2013 #6
    Thanks! What can I say? It's beautiful. But troublesome to me. I might have to change my understanding of entanglement. I've got to read that paper more than once, and I look forward to posts from more PF members about this. I'm feeling slightly dizzy about this thing :smile:. But it's beautiful.
  8. May 29, 2013 #7
    Last edited: May 29, 2013
  9. May 29, 2013 #8
    DennisN: It's all good. Same to DevilsAvocado. I am simply astounded by what people like Zeilinger and his group are doing. I'm enough of a dyslexsh...dyzlecx...dyslƩ≈... can't-see-the-forest-for-the-trees person that I appreciate any listing of new material on this.

  10. May 30, 2013 #9


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    ... I’m still stunned ... couldn’t sleep last night ... :smile:

    Where is the coincidence counting!? :bugeye:

    [my bolding]

    Unless I’m totally lost – blockbuster #2 is the real-time coincidence scheme!

    But how is it done!? “If no polarizer is put in the path of the trigger photon” must mean that they can tell from the polarization of only the “trigger photon” when the entangled pair is present in the system??? If this is correct it’s just amazing...

    And what happens if one day we could produce entangled pair in a controlled way, and thus no need for the trigger cable?? (FTL!? :O)
    Last edited by a moderator: May 6, 2017
  11. May 30, 2013 #10
    I think I have digested it better now (I hope :smile:).

    Polarizer A works like a selection device which ideally transmits 50% of the incoming photons and blocks the remaining 50%.

    The arrival of a transmitted photon A triggers the camera (there is only one camera catching photons from stream B).

    When polarizer A gets rotated, different selections of photonstream B get caught by the camera.

    Remove polarizer A, and all of photonstream B would be caught, showing no signs of entanglement.

    I think the setup also is a good demonstration that no real "FTL" information can be transmitted; both streams are needed as input to the camera in order to reveal the entanglement. The ICCD camera is obviously in one and the same location - disconnect/block any of the streams going into it, and: no sign of entanglement.

    Anyway, it's a beautiful experiment.
  12. May 30, 2013 #11


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    No entanglement experiment can give FTL without a violation of quantum mechanics. To transmit information, you always need some non-superluminal signal. This can be a trigger signal, it can be a measurement result, or anything else, depending on the setup. But you need something.
  13. May 30, 2013 #12


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    It is that long cable between the detecor and the ICCD. The ICCD is triggered. It is only registering data when the other detector tells it to which is equivalent to coincidence counting.

    Well, the "if no polarizer is present"-part just gives you the picture in the lower right corner. It just gives you a Laguerre-Gaussian mode which does not tell you anything about whether entanglement is present or not. You just know that ta photon has been detected at the other side and the quite short gating time of the ICCD is used to keep the noise at bay.
  14. May 30, 2013 #13


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    So little time and so much to say (including PM:s), I have to come back tomorrow...
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