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I I say that this experiment confirms Schrodinger's Cat...

  1. Mar 14, 2017 #1
    I'm having a fun little argument with my wife, about an article posted on www.sciencedaily.com. I say that the article CONFIRMS that Schrodinger was RIGHT. My WIFE says that this confirms that Schrodinger is WRONG.

    The article concerns the quantum techniques used creating the shortest pulse of light possible so far (femtosecond). And please, excuse my mis-spelled words. But this article definitely states, that something is in two states simultaneously, and I think I'm right! Forgive the selfish motive, but I want to understand why I'm wrong, if in fact I am. Then that would be a physics-reading-comprehension error on my part :(

    Can someone please help us out here and help me either win (or lose) this argument? Thanks.
    You can search the article immediately, ON the web page with: An electron is small enough that it behaves like a wave as well as a particle

    Here's the article's URL:
    https://www.sciencedaily.com/releases/2017/03/170313135050.htm
     
  2. jcsd
  3. Mar 14, 2017 #2

    PeterDonis

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    Both of you are incorrect. The article doesn't say Schrodinger was right or wrong, because Schrodinger in that thought experiment was talking about macroscopic objects like cats, and the article only talks about microscopic objects (ultrashort pulses of light and electrons).
     
  4. Mar 14, 2017 #3

    phinds

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    I've not read either of the links that you provided, but here's the deal. Schrodinger developed his "dead/alive" cat exposition NOT to show that you could really have a cat that was both dead and alive but to expose the silliness of some of the incorrect statements made based on misunderstandings of the Copenhagen interpretation of QM (e.g. the moon isn't there if no one is looking). The cat is always either alive or dead, never both at the same time.
     
  5. Mar 14, 2017 #4

    vanhees71

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    It's also wrong to claim anything is in two states at once. In standard quantum theory a system is in a state (described by an statistical operator), and that's it. Forget about the hopeless attempt of popular-science writers to make things simpler than possible (something, Einstein famously warned about). Usually they confuse the issue more than helping to make it understandable. There is not other way to talk about quantum theory in a non-confusing manner than to use the adequate mathematics!
     
  6. Mar 14, 2017 #5
    Ok, but isn't this the quintessential example of that thought experiment, that is, an object being in two states simultaneously, the confirmation of that thought experiment regardless of it being a macroscopic object? After all, he was just using an example to describe a quantum effect, or quantum super-position? If I'm not mistaken, this is the The Copenhagen interpretation of quantum mechanics. The macro cat's just a metaphor this quantum fact of simultaneity. I'm not even talking about what happens when it's observed. That's a different, but related topic.
     
  7. Mar 14, 2017 #6

    vanhees71

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    Again: According to quantum theory a system is in one and only one state. The claim that Schrödinger said otherwise, doesn't help. I don't know, in which sense the above cited article about femtosec light pulses refers to it, but I guess what you have in mind is Schrödingers famous cat experiment. In this setup, the state is given as a superposition of two other states according to the rules of quantum theory. To establish und keep such a coherent superposition with macroscopic objects is very difficult if not practically impossible. However, the analogous situation is realized zillions of times with various microscopic setups (entangled-photon states, states of single atoms, particles in traps, etc. etc.), and all confirm quantum theory.
     
  8. Mar 14, 2017 #7
    Why is that? In 2005, the National Institute of Standards and Technology successfully created six atoms that were simultaneously in spin-up and spin-down states. To me that sounds like two states at once. Here's the link to that article. http://gizmodo.com/new-quantum-cat-state-can-be-in-two-places-at-once-1779243935

    Actually, this isn't about the atoms being in two places at the same time. It's about their spin-states. But, I have to keep an open mind here, point out the error of my ways. Thanks
     
  9. Mar 14, 2017 #8
    That's what I'm talking about (of course), superposition. Two states simultaneously (on a quantum level). That's all I'm saying'. And this experiment exploited that. BTW, the cat wasn't meant to say anything about this being possible macroscopically. I also give a quick-search link to the line in the article where they start talking about this.

    Thanks for your reply.
     
  10. Mar 14, 2017 #9

    PeroK

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    That's what they want you to think, but the article is nonsense.

    States are like vectors, they can be split up any way you like. If you know some physics this is analogous to splitting the gravity force vector into two vectors in different directions. Gravity is a single force in a single direction, but it can be expressed as the combination of two forces in many ways.
     
  11. Mar 14, 2017 #10

    PeterDonis

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    No, they didn't. They created six atoms that were in a single quantum state that is a superposition of spin-up and spin-down.

    This is one of those areas where you really need to be careful about what sources you read. The abstract of the actual paper is here:

    No, that's not what superposition means. A superposition is a single state that, when written in terms of eigenstates of a particular operator, is a sum of multiple terms. Note that this means the property of a being a superposition depends on which set of eigenstates you choose to write the state in terms of; for any quantum state, there will be some operator that it is an eigenstate of, and if you write the state in terms of eigenstates of that operator, it will not be a superposition.
     
  12. Mar 14, 2017 #11

    PeroK

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    PS For example, what the article doesn't say is that this is a superposition of spin-up and spin-down for a given direction (about which the spin is to be measured). By convention, this is usually taken to be the z-direction.

    But, if you have a particle in the spin-up state (z-direction), then that state is a superposition of spin-up and spin-down in the x-direction; and, also a superposition of spin-up and spin-down in the y-direction; and, in fact, for any direction other than z.

    And if it's definitely spin-up in the x-direction, then it's a superposition of spin-up and spin-down in the z-direction.

    Every state, therefore, like a vector, is always a superposition of some other states.

    Superposition is, perhaps, the most misunderstood term in QM.
     
  13. Mar 14, 2017 #12

    Vanadium 50

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    While that is true, my advice is to tell your wife that she's right. Happy wife, happy life.
     
  14. Mar 14, 2017 #13
    I know that. Awe. come on. Of course not! Don't take me literally! All I am saying, is that this experiment, exploits super-position on a quantum level only (where phenomenon like that can only happen, and, all the time, every moment) That's all. I'm still probably wrong, as usual. heh heh.
     
  15. Mar 14, 2017 #14
    Gotcha. Thanks. But it turned out, that his equations were later confirmed on a quantum level? I think I asked the wrong question. All I'm asking, is if this experiment exploits quantum super-position. After all, if it wasn't possible, the creation of a Qubit wouldn't be possible?
     
  16. Mar 14, 2017 #15
    Thank you.
     
  17. Mar 14, 2017 #16

    Nugatory

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    Schrodinger developed his equation and it was confirmed at the quantum level years before he proposed the cat experiment. The concept of superposition was solidly established, and the mistaken notion that superposition meant that a quantum system could be "in two states at the same time" (or that the double-slit experiment showed a particle "going through both slits") was already taking root in the popular imagination.

    When Schrodinger proposed his cat thought experiment, he was not suggesting that the cat would be in a superposition of dead and alive. He was pointing out a flaw in the then-current understanding of the quantum mechanics of macroscopic systems like a cat - there was no satisfactory explanation for how we might end up with a box containg an angry cat or a cat's dead body. It took another few decades to work this out... And it is an interesting story, told in a layman-friendly form in David Lindley's book "Where does the weirdness go".
     
  18. Mar 14, 2017 #17
    Thank you. That's actually what I thought, I know that he wasn't talking about macro-sized objects. He used the example to actually clear up a common mistake made with the Copenhagen interpretation, as told to me from another poster and merely used the cat in a box example, as a very crude visualization of the goings-on at the quantum level (and only the quantum level).

    I should have been clearer in how I framed my question. My question is this: Recently an experiment was done, that uses super-position to achieve it's results. My wife, states that this proves that Schrodinger was wrong. I however, stated that the very fact that the apparatus used to create a femto-second light pulse using a quantum state of super-position ( embedded the science daily article in my first post question), proves that his IDEA was correct. Can you check this out please? The quantum methods are at the bottom of this article. All I'm saying, is that it does not PROVE him wrong. It proves that the Schrodinger Equations were RIGHT... I think! Though I'm not a physicist nor a mathematician, my understanding is obviously profoundly lacking, but I get the gist of it I think.

    Can I get a definitive answer on this from you? I'd really appreciate it. It's more towards the bottom of the article, stating - Because the electron was in two excited states at once

    You can search for that exactly, on the article, it'll bring you right to it as I'm sure you know, using Ctrl F in most browsers :). Here's the article.

    https://www.sciencedaily.com/releases/2017/03/170313135050.htm
     
  19. Mar 14, 2017 #18

    PeterDonis

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    Experiments have been done that "use superposition to achieve results" since the 1920s. If by "Schrodinger was right" you just mean "Schrodinger's equation is valid, at least within the non-relativistic domain", then that has been known for decades, and this recent experiment hasn't changed anything in that regard (it just re-confirms, for the umpteenth time, that Schrodinger's equation is valid in this domain).

    This article is not a good source if you are trying to find out the actual physics. The actual physics, as has been explained already, is that the electron was in a state that happens to be a superposition in a particular basis. That doesn't mean it's "in two states at once"; that is pop science language, not physics.
     
  20. Mar 14, 2017 #19

    Nugatory

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    Here you go....
    This experiment is one grain of sand in the mountain of experimental results that we have piled up in the past century, all confirming the correctness of the theory that Schrodinger, Heisenberg, Born, Dirac and many others collectively developed between 1925 and 1930.
     
  21. Mar 14, 2017 #20

    ftr

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    I heard Lubos say one time that the cat is either dead OR alive(not and) AND value is undefined before measurement yet somehow that is not a contradiction. I think that is the source of confusion, because others say that superposition is just that and it means AND.
     
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