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B Does Schrödinger's paradox work with multiple boxes?

  1. May 26, 2016 #1

    ProfuselyQuarky

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    I just read an article (linked below) today and found it to be quite curious and interesting. In short, physicists have taken Schrödinger's cat paradox to a whole new level by adding a second box. I’m still very new to all the ideas of quantum physics, but apparently this addition of another box adds the concept of entanglement to Schrödinger's thought experiment. From what I understand (and please correct me if I’m wrong) entangled particles are completely dependent in each other so that the the state of one particle determines the state of another. Applying this to Schrödinger's paradox, this means that the cat is either alive or dead in both boxes at the same time. Now for my question: Can more boxes be added? Does quantum physics allow for there to more than two boxes? Can the thought experiment work with three boxes? Four? Five? Apologies if this is an obvious question; I don’t know much about this topic.

    http://phys.org/news/2016-05-schroumldinger-cat.html
     
    Last edited: May 26, 2016
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  3. May 26, 2016 #2

    phinds

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    The cat is never alive and dead at the same time, which in fact was exactly Schrödinger's POINT in showing how paradoxical it would be if you considered things to depend on a human observer.
     
  4. May 26, 2016 #3

    ProfuselyQuarky

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    Ah, that part was my own typographical error... sorry; I edited my post. From the link:
     
  5. May 27, 2016 #4

    phinds

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    The cat is either alive or dead and regardless of how complicated you make the way we look at it or think about it, the cat does not care.
     
  6. May 27, 2016 #5

    DrClaude

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    They are talking about Schrödinger cat states, not actual cats :wink:

    The article can be found here: http://science.sciencemag.org/content/352/6289/1087
    For those who don't have access, the preprint is http://arxiv.org/abs/1601.05505
     
  7. May 27, 2016 #6

    ProfuselyQuarky

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    Hm, okay, I was looking for clarification because when reading about entanglement, all I saw were descriptions of only two particles being entangled. I think that this scenario makes sense because you can measure the spin of one particle and then the second one has the opposite spin. I'm not so sure how that can work out with more than two particles/boxes, though. How?
     
    Last edited: May 27, 2016
  8. May 27, 2016 #7

    phinds

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    I'm an engineer. These complicated quantum scenarios are beyond me. I'm just rooting for the cat :smile:
     
  9. May 27, 2016 #8

    ProfuselyQuarky

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    Sure, phinds, stick to the cat :smile: Hopefully somebody else can elaborate.
     
  10. May 27, 2016 #9

    Nugatory

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    No matter how many particles make up an isolated quantum system, it is still a single quantum system with a single quantum state and various measurements that you can make on it. When the quantum state is such that determining the value of one of these observables tells us what the value of another one will be, we say that those properties are entangled.

    When one of the possible measurements is "spin of the particle at detector A" and another possible measurement is "spin of the particle at detector B" we can't help but think as if we're dealing with two separate particles, and we say that we have an entangled pair - but as far as the mathematical formalism of QM is concerned we're looking at different aspects of a single system. A more complicated entangled system just means more observables that we can choose to categorize as properties of this particle/box or that particle/box, but it's still one quantum system.
     
  11. May 29, 2016 #10

    ProfuselyQuarky

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    Domo arigato! What a great explanation! Just a novice follow up inquiry, nonetheless:

    The definition I know of a basic quantum system is simply "a piece of the universe that is considered when working with quantum mechanics". Is there a more rigorous definition? If so (and if not, then this entire thought becomes complete rubbish), is it possible to look at two systems at the same time? Do these systems have unique properties that can help us distinguish one from another or are they just arbitrary things that help us manage whatever is studied in QM? Right now, I know that two or three entangled particles are within the same system. If there are solid characteristics or properties that help distinguish one system from another, can a particle from one system be entangled with a particle from another system?
     
  12. May 29, 2016 #11

    Nugatory

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    If the interaction between two parts of a quantum system is small enough, we can ignore that interaction and treat them as two independent systems. That's will be an approximation, but it can be a very good approximation - if you're studying an electron in a lab in Buenos Aires you won't bother calculating the effects of the interaction with a stray electron somewhere in Moscow. Thus, your choice of system boundary is somewhat arbitrary; as long as you've drawn it to include everything that matters for the problem at hand it's good.
     
  13. May 29, 2016 #12

    ProfuselyQuarky

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    Ah, this makes complete sense. Thank you, Nugatory!

    …and thanks phinds, and thanks cats :smile:
     
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