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Delayed Choice Eraser with dispersion pattern controlled detectors

  1. Feb 20, 2014 #1
    Sorry if it's a silly question but I was trying to find such an experiment and wasn't successful.

    What I am thinking is, in the standard delayed choice quantum eraser, the dispersion pattern on the screen correlates to whether or not we can detect which path the electron took.

    What if the it's setup so that there is a very large delay after the signal photon impacts on the screen before the sensor array that might detect which path info from the idler photon. And let's say that calculations are made such that certain areas on the screen are known to only be possible if the photon acts as a particle and/or if the photon acts as a wave.

    Could it be done such that the screen, upon detecting a photon impact that MUST be wave form or MUST be particle form then turns on or off the sensors which would give us which path info to make such a result impossible before the entangled particle arrives to be detected?

    Perhaps this could be accomplished by putting the detector array close to the screen and forcing the idler photon to travel very far away and back again before being detected (similar to what was done on la palma but instead of detecting on the remote island, simply return the idler photon back from the remote island for detection near it's origin).

    I was thinking this might make an interesting situation where an already observed scenario would be forced to change after it has been observed (ie the signal photon impacts outside the range the lump pattern could conceivably cover meaning it displayed wave function, so we turn on the detector which forces it to take particle function and thus it must move it's impact site into the lump pattern area).

    Here is a basic image explaining the general a layout. http://i.imgur.com/Zx3jvfV.png and explaining how you could have the detector array controlled by the detector screen before the idler arrives.

    Thanks for any thoughts!
  2. jcsd
  3. Feb 21, 2014 #2


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    Before we start discussing complicated thought experiments: No, it does not!

    The pattern on the screen is always the same, no matter whether you have which-way info or not. It is only the coincidence count pattern between signal and idler which changes.
  4. Feb 24, 2014 #3
    So help me out here then... I thought the way it worked was that the the signal hits the screen and then the idler goes through the array of sensors, sometimes hitting ones that give which path info and sometimes ending up at ones that obfuscate the what path info.

    When reviewed the times the idler gives what path info, the entangled signal particle fell into an area that correlates with an interference patter and vice versa.

    So while I understand the overall pattern for the group of test particles is always the same, is it not the case that if you only look at the ones that correlate with an idler giving which path info, the result is a lump patter while looking at only signals that correlate with obfuscated info you get a diffusion pattern?

    Is that not how it works?

    EDIT: Never mind... I realize now that there is no point on the detection screen that is exclusive to lump or interference pattern participant particles.
    Last edited: Feb 24, 2014
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