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I Perceiving superpositions

  1. Mar 22, 2016 #1
    I was reading a M. Schlosshauer paper on decoherence and he does an effort in explaining perception by decoherence, in a example od an observer perceiving a spatial superposition. Here is the link of the paper:
    http://arxiv.org/abs/quant-ph/0506199

    Now my question is wouldnt the decoherence occur even before the light hit the observers eye unlike Schlosshauers example where he states that the retinal cells are in a superposition


    Thanks in advance.
     
  2. jcsd
  3. Mar 22, 2016 #2
    Isn't it rather that the perception is one cause of the decoherence? Perhaps I am reading it differently!
     
  4. Mar 22, 2016 #3

    bhobba

    Staff: Mentor

    As I have explained many many times objects in the everyday common-sense world are decohered to have an actual position regardless of perception by an observer.

    Thanks
    Bill
     
  5. Mar 23, 2016 #4
    I understand that. I was wondering about a hypotethical where we actually achieved the spatial superposition and after the light hit the object which is in two locations where would the decoherence regarding our perception happen? Or our perception practically wouldnt even work because it would be too cold to keep us alive?
     
  6. Mar 23, 2016 #5

    bhobba

    Staff: Mentor

    Its got nothing to do with perception. The photons would decohere it and give it an actual position.

    Thanks
    Bill
     
  7. Mar 23, 2016 #6
    Then why did Schlosshauer give that particular example? Can you please check the document I posted (maybe you already have since I know you're a huge fan of his).
    I don't really understand what he is refering to since he mentions superpositions of retina cells etc.

    Thanks
     
  8. Mar 23, 2016 #7

    bhobba

    Staff: Mentor

    One can place the classical quantum cut anywhere. Decoherence says you place it just after decoherence. He is looking at what happens if you don't and place it in the brain. Its interesting but IMHO just that - it leads to a very weird view of the world if you do.

    I suggest before delving into such exotica you learn some of the formalism of QM.

    Thanks
    Bill
     
    Last edited: Mar 23, 2016
  9. Mar 23, 2016 #8
    So the light that reflects of the object would actually transmit information to our eyes about the decohered stated of the object that is in one position rather than the past state of the object that was in two locations?
     
  10. Mar 23, 2016 #9

    bhobba

    Staff: Mentor

    You need to learn some QM. Things are not in two locations.

    Light that reflects of the object interacts with it decohering it so it has an actual position.

    Thanks
    Bill
     
  11. Mar 23, 2016 #10
    I know I need to learn it, we agreed on that. I was refering to the example of Schlosshauer where he clearly (but hypotethically) mention an object in two spots. So the light interacts with it giving it a definite position and then the light transmits information about the decohered object about it to our eyes. Right?
     
  12. Mar 23, 2016 #11

    bhobba

    Staff: Mentor

    If he said that he is wrong.

    Its what I said before. If that isnt clear then I cant explain it better.

    Thanks
    Bill
     
  13. Mar 24, 2016 #12

    The part you mentioned is clear, of course. The part I don't understand is the issue can we detect a superposition with our senses. And yes, I know, that in ou everyday common sense world there are no quantum effects but if we went to the lab and put an object in an excited state would the light transmit the information about the interference to our eyes before it decoheres the object our would the propagation of light to our eyes occur after the object decoheres? Thats my question.
     
  14. Mar 24, 2016 #13

    bhobba

    Staff: Mentor

    Again you are misunderstanding what a superpoition is - every state is in superposition.

    Hopefully you mean a superposition of position. No we cant.

    Thanks
    Bill
     
  15. Mar 24, 2016 #14
    Misuse of terms on my side, I apologize. I meant interference. Why we can't, physically speaking?
     
  16. Mar 24, 2016 #15

    bhobba

    Staff: Mentor

    Your eyes are like the screen in a double slit - it registers a definite position.

    Thanks
    Bill
     
  17. Mar 24, 2016 #16
    Ok, thanks, that's a great analogy. But of course that doesn't change the fact that the object will decohere to a definite outcome long before we even have a chance to observe it and that the photons will send the information not about the interference, but about the decohered object, right? So as you say, after decoherence everything is classical, and in an attempt to see interference we neccessarily need to interact with light and that light would 'collapse' the object and it wouldnt send any information about the interference. Please correct my reasoning if I am wrong
     
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