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Schrödinger cat´s from Rovelli Relational Quantum Mechanics viewpoint

  1. Jul 15, 2013 #1
    From RQM point of view, the Scrödinger cat appears 50 % times alive and 50 % times dead. From cat himself point of view he is 50 % times alive and 50 % times dead. But when it dies, he observe his reality like dead (non consciousness about external reality) or alive (conscious)-consciousness of course is not a itself observation ( no system can observe itself)-. Then the cat always see the experiment result when he survive, and for it the Born Rule is not correct (100 % times alive). ¿ How can it be explained from RQM point of view?
     
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  3. Jul 15, 2013 #2

    Simon Bridge

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    What is it you feel needs explaining?
    Did you understand that the point of the experiment is to connect a system that makes sense in classical statistics to a system that obeys quantum mechanical statistics - and so expose a problem with the Copenhagen interpretation? That's why the cat is not alone in the box.

    You can do all kinds of things with the physical description - the question is about the wave-function collapse and what we mean by "observation".
     
  4. Jul 15, 2013 #3
    Ok. Change the cat for a human (only mental experiment of course). The human would watch himself surviving all the time, violating for his relative point of view the Born rule, he would survive in his statistics 100 % of time, nor 50 %. This is an equivalent , I think, to the quantum suicide from many worlds. But I don´t know what it would be the solution in RQM. It is not for or against this interpretation. It is only about how RQM solve this question
     
  5. Jul 15, 2013 #4

    Simon Bridge

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    What is the observer in the box observing in the QM sense?
    Remember - the human/cat whatever, is not alone in the box.

    - you have just pointed out that a self-aware observer will only observe themselves in state "exists". RQM applies to the relation between the system under investigation and another system ... so what are the two systems? What is ti that need to be explained?
     
  6. Jul 16, 2013 #5
    Thinking about it, I suppose that we must consider that be dead is an observation state in a physical sense, no matter that in psychological sense a dead being can´t perceive anything. I suppose that is the solution. Like I said in the 2 post, that is the thing top be explained. Anyway, it is difficult to know what I wish somebody explains me if question is not read. Thanks anyway
     
  7. Jul 16, 2013 #6

    Simon Bridge

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    ... what is? You are incoherent.
    A dead being does not observe. What is wrong with that?
    A life form does not observe itself to be dead - why do you think this violates the Born rule?
    To find the RQM approach you must first specify the two systems to be related - you have not done this.

    I suspect you have misunderstood both schodingers cat and the relational interpretation.
     
    Last edited: Jul 16, 2013
  8. Jul 16, 2013 #7

    bhobba

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    There is no suppose about it - the dead cat is obviously and trivially different from the state of the live cat.

    Look - its simple really. In the relational interpretation all observers are considered equivalent and observers are not just conscious creatures like the cat or person that opens the box. The particle detector is also considered an 'observer' and if you use that view Schrodinger's cat is trivial. The issue with the Relational interpretation is all other observers are considered equally valid so reconciling them is an issue.

    I will leave it to those more expert in that particular interpretation to explain how it resolves that - to me its simply making a rod to break its own back by having all observations equivalent - but hey to each his/her own I suppose. I have no doubt it fixes issues with other interpretations - its like I say - they all suck in their own way - you simply pick the one that sucks the least for you.

    To me the right place to put the observation is just before the particle has been detected and decoherence has occurred (which happens very quickly) to localize the particle. I dont quite understand this need to place all observers on the same footing - yes it brings out everything must be treated quantum mechanically and probably fosters a information view of QM but I am not at all sure its complexity is needed.

    Thanks
    Bill
     
    Last edited: Jul 16, 2013
  9. Jul 16, 2013 #8

    Simon Bridge

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    There is no need to resolve differences in observation by different observers - RQM expects that different observers will measure different things. The R part is the relation between the observer and the system - which I why I'm trying to get OP to think about what is being observed in the context of the experiment.

    eg. If you treat the cat+poison+hammer as the detector of a change in state of the quantum system that is also in the box, then we can say that the detection of a change in state switches the detector off. But it does not actually help with the underlying issue that Schrodinger was trying to illustrate.
     
  10. Jul 16, 2013 #9

    bhobba

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    You beat me to it. I realized I didn't mention that in the relational view it doesn't matter - it accepts all views as equally valid. Don't quite like that way of looking at it since to me its a bit too subjectivist - like I say I put the observation as occurring just after decoherence. Of course my view has issues as well - no free lunch here.

    Thanks
    Bill
     
  11. Jul 16, 2013 #10

    bhobba

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    No it doesn't - and it is a very important one - but probably not what most think it is.

    It pointed to the fact interpretations like CI or the ensemble interpretation assume the existence of a classical world but really everything is quantum and you should be treated that way. It doesn't invalidate those interpretations, render them inconsistent or anything like that. But it does point out a defect. The relational interpretation by having all observers equally valid enforces everything must be quantum onto us - no escaping.

    Its just a bit too subjectivist for my taste.

    Thanks
    Bill
     
  12. Jul 16, 2013 #11
    Well, if the cat doesn´t survive then no observation?? Then the dead cat is it not then an observer?? The dead cat is a material system (not alive, not physcological observer, but a physical system, then a physical observator in RQM ( I am not sure, I suppose).. I would like your explanation/viewpoint. I am a graduate physics but I am not an expert in RQM, I only know the original arxiv from RQM (Rovelli, 1996) and a little references about it (not new things than the original article). I would thank your explanation. Resuming, I Would like the RQM solution to the quantum suicide though experiment.
     
  13. Jul 16, 2013 #12

    bhobba

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    I think you are getting confused between an 'observer' and a conscious observer. There is no requirement in the relational interpretation for an 'observer' (similar to CI and other interpretations it simply needs to be able to register an outcome here in the macro world) to be conscious eg the particle detector is also an observer and it most certainly is not conscious.

    What the relational interpretation requires is for all observations to be equivalent - not that observations require consciousness.

    Thanks
    Bill
     
  14. Jul 17, 2013 #13

    Simon Bridge

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    The observer is a role - the role is played by another quantum system.

    The idea is to make the process of measurement and recording explicit where the usual descriptions in introductory QM courses kinda waves hands over that part, as in: "a measurement of <whatever> has occurred", without discussing about how this happens.

    It's common enough that students come away with the impression that a consciousness is needed to "collapse the wavefunction".

    The RQM description of a quantum suicide thought-experiment goes the same way as the RQM description of anything ... 1st you have to describe the setup in relational terms. It's more of a discipline than anything.

    What's wrong with modelling the cat being a detector which gets switched off when a measurement yields a particular result? The cat may not consciously register the measurement, but it does register and record it physically - which is probably what you were thinking of earlier.

    I don't think RQM has anything much to add to the point being made by the thought experiment.
    The point of putting the cat + the rest of the apparatus "in a box" is so that the experimenter, the system playing the role of the observer, cannot see what's going on until some time after one usually presumes the decoherence has occurred. We can make sense of it by saying the cat is the detector/recorder and the experimenter just takes some time reading the record... but that's not the point is it?


    I tend to think of the concept of the wavefunction collapsing as a convenient metaphor ... it's a bit like when we teach conservation of momentum in collisions: we have a definite state before and after the collision obeying simple rules, but how the before state gets to the after state is sort-of hand-waved away. It's useful but is missing a big bit of the process.
     
  15. Jul 17, 2013 #14

    bhobba

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    Indeed. I learnt QM from Dirac - Principles of QM and Von Neumann - Mathematical Foundations. Dirac is very careful to use the term result of measurement and not observation, and of course Von Neumann analyses it very carefully.

    But from what I can see many people seem to be under the allusion an observation requires a conscious - and often human - observer. Most certainly popularization's like What The Bleep Do We Know promulgate it as if its accepted fact - which most certainly it isn't. In fact if you know the actual physics those popularization's are pretty sickening. I remember there was a backlash when Brian Cox in his A Night With The Stars made a bit of a goof regarding the Pauli Exclusion Principle - yea strictly speaking it was wrong and quite a few people pointed out what the issue was but its nothing compared to some of the other junk I have seen.

    Thanks
    Bill
     
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