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I Like Schroedinger's Cat

  1. May 2, 2016 #1
    Can't we just put a human in the box, and do same thing except without the poison. Inside of the box, the human will either see the hammer smash a vial, he won't see the hammer smash the vial or he will feel like he saw both things happen.

    The time t' starts when the hammer is expected to drop or not to when the observer opens the box. We put a clock inside of box and tell the subject to remember what happens during time t'.

    Won't this at least rule out or conclude that he was in a superposition?
     
  2. jcsd
  3. May 2, 2016 #2

    Nugatory

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    We already know perfectly well that he won't be in a superposition of the sort that you're thinking about. Even Schrodinger wasn't trying to suggest otherwise - he proposed his thought experiment to expose a defect in the then-current understanding of quantum mechanics, namely that there was nothing in theory as it was understood early in the 20th century that explained the fact that the cat didn't end up in a superposition.

    Further work with the mathematical underpinnings of quantum mechanics over the next few decades has largely solved this problem. It turns out that QM in fact predicts that the cat ends up either alive or dead and you find out which it is by opening the box and looking; this is no different from tossing a classical coin and having to look at it to see whether it is heads or tails.

    You can Google for "quantum decoherence" (although I will caution you that the math is somewhat daunting) or you can give this https://www.amazon.com/Where-Does-Weirdness-Go-Mechanics/dp/0465067867 a try.
     
    Last edited by a moderator: May 7, 2017
  4. May 2, 2016 #3
    Yeah, okay, that makes sense.
     
  5. May 3, 2016 #4

    Demystifier

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  6. May 3, 2016 #5
    Human will be in a superposition of seeing the hammer drop and not seeing hammer drop. He will never see it "half-drop".

    Opening the box just entangles you with the human. Now you are in a superposition of hearing him saying "the hammer did drop" and hearing "no, it did not drop".
     
  7. May 3, 2016 #6

    bhobba

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    Human beings and hammers have definite position so can never be in superposition of seeing the hammer drop and not drop.

    The same with the cat - it can never be in a superposition of alive and dead - its constituent parts have definite position so can never be in a superposition of alive and dead eg a dead cats heart does not beat, it does not breathe etc.

    Thanks
    Bill
     
  8. May 4, 2016 #7
    Amazing that no one proposed this explanation before in all these decades of debate. Or did someone?
     
  9. May 4, 2016 #8
    Quantum mechanics is experimentally proven. Superposition is demonstrated in experiments for objects built of hundreds of atoms. When these objects are in superposition, everything works as it should - components of superposition "don't know" about mutual existence, can't "feel" it. Why humans should be different and not be able to be in a superposition?
     
  10. May 4, 2016 #9
    According to the paper in post #4, human beings can be in a superposition, but they can't experience or remember it afterwards. If they are perfectly "screened" to prevent them from perceiving which-path information, then you (the experimenter) will observe interference. If they are able to see (and therefore, remember) which path they took -- no interference!.
     
  11. May 4, 2016 #10
    Exactly my point.
     
  12. May 4, 2016 #11

    bhobba

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    Well first you need to understand what superposition is. Its simply that pure states form a vector space. This means any state is in superposition and in innumerable multiple ways. Obviously this applies to human beings. What a human being cant be is in a superposition of position. The reason is due to the radial nature of interactions generally found in the world out there objects decohere to have a definite position. You can find the detail here:
    https://www.amazon.com/Decoherence-Classical-Transition-Frontiers-Collection/dp/3540357734

    Human beings by the fact they breathe, stand on things etc etc is interacting with the environment so has a definite position. It impossible, utterly impossible for human beings, cats etc etc to be in a superposition of position.

    Thanks
    Bill
     
    Last edited by a moderator: May 7, 2017
  13. May 4, 2016 #12

    bhobba

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    If it says human beings can be in a superposition of position (which I doubt) its wrong - simple as that. Its impossible, utterly impossible, with 100% certainty, for a human being to be in a superposition of position. Of course since any state is a superposition of many many other states its always in superposition - but that is meaningless since objects having definite position at all times is pretty much what we mean by classical.

    Thanks
    Bill
     
  14. May 4, 2016 #13
    "Interaction with environment" entails having a bigger quantum system. You no longer can treat "human being" as an isolated system. The bigger quantum system can be in a superposition of states.
     
    Last edited by a moderator: May 7, 2017
  15. May 4, 2016 #14

    bhobba

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    A human being cant be an isolated system - they breath, need to stand on something, sweat evaporates etc etc. Its in the nature of human beings, cats etc etc and why they can never, ever be in a superposition of position.

    Thanks
    Bill
     
  16. May 4, 2016 #15
    Essentially, you are saying that electrons can experience quantum tunneling. Protons can. Entire atoms can. C60 fullerene molecules can. But humans can't. That's nonsense.
     
  17. May 4, 2016 #16

    bhobba

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    I am saying nothing of the sort. I am saying a human being cant be an isolated system and because of that is decohered to have definite position.

    Thanks
    Bill
     
  18. May 4, 2016 #17
    The experiment does not require a cat or human which is not interacting with anything. It requires a "box" which is not interacting with anything.
     
  19. May 4, 2016 #18

    bhobba

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    Your point being? The human being, cat, whatever, interacts with things in the box so has definite position.

    There is an issue with decoherence in that case, but it does not change the argument and needs a separate thread. Start one if you like so it can be explored - but it isn't germane to this.

    Thanks
    Bill
     
  20. May 4, 2016 #19
    The box as a whole can be in a superposition of states, with different positions of the cat (human) in those states. It's basics of quantum mechanics.
     
  21. May 4, 2016 #20

    Nugatory

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    We could put the discussion on firmer ground by asking:
    1) How would you prepare a system consisting of a cat (and as much of its environment as is needed to keep it alive) in a coherent superposition of position?
    2) Having done so, how long would the superposition last?
     
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