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(A bit for fun) Putting a Human in Superposition

  1. Jul 15, 2014 #1
    Putting a Human in Superposition

    I recognize the practical aspects of this would be absurd, but I must admit the premise of what it would take to put a human in a superposition of states is an amusing thought exercise and has some relevance towards me understanding actually in what scenarios QM is applicable and particularly a bit on the bride between classical and quantum. And surely this must be theoretical contrive-able, since we presume QM is the underlying framework of classical systems as well. So what would it take to put a whole human system in superposition of states?

    My intuition imagines an individual in a self-contained suit in the middle of a supervoid (or some similar isolation, maybe even throw the human in a Faraday cage) in space. Would this be sufficient assuming all mater and light so sparsely distributed as for there to be periods in which the human interacts with no external bodies? Or is there something fundamentally wrong with my understanding, and in what scenario could the entire human be in superposition (if possible)?

    Note that I'm resisting any questioning as to what said human would experience which might be a tad more debatable and philosophical.
     
    Last edited: Jul 15, 2014
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  3. Jul 15, 2014 #2

    atyy

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  4. Jul 15, 2014 #3
  5. Jul 16, 2014 #4
    Maybe we all could be in superposition without another to observe us, if being self aware doesn't count as an observation.
    In the early 1800s Thomas young created a double slit experiment, where light passed threw two slits and created an interference pattern. This ment light was both a particle and a wave. In 1961 Claus jonsson repeated the experiment with electrons. First he shot electrons threw one slit getting a pattern of .. one slit. Then he shot them threw two slits expecting to get two slits but instead he got an interference pattern. This means matter itself has the ability to act as both a particle and a wave. He wondered how this was possible and set up an electron detector to see how this was happening and repeated the experiment. This time he got two slits. Matter acted as a particle again just by being observed.
    Later this experiment was repeated with the same results with bucky balls made of 60 carbon atoms and much more recently they completed the same experiment with a 240 atom object.
    So who knows maybe next they'll use a cat :D
     
  6. Jul 16, 2014 #5
    I'm aware of the paper on putting a virus in superposition (of which I applaud that effort), and had heard a bit on that interesting single-photon vision test, so I'm glad to hear that's been experimented with. But even without these experimental proofs, do we not have a rigorous enough definition of superposition and decoherence within QM to acknowledge the implications for even larger objects (humans)? I.e. can we speak to whether the a scenario similar to what I proposed would be sufficient to need to consider the whole human system in superposition?
     
  7. Jul 16, 2014 #6

    kith

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    The question you need to think about is "a superposition of what?". Every quantum state is a superposition of basis states for some bases as well as a basis state for some other bases.

    The phrase of a system being "in superposition" makes only sense if something selects a preferred basis. Examples for this something are textbook measurements (which put the system in an eigenstate of the observable being measured) or decoherence during a quantum dynamical process (which puts the system in a statistical mixture of certain states).

    Also this arxiv-only article by Demystifier seems to be relevant to the topic at hand (I haven't read it).
     
  8. Jul 16, 2014 #7
    In our classical world it seems improbable for anything on a macroscopic scale to be in superposition. Reminds me of the old cliche, "If a tree falls in the woods and there is no one around to hear it does it make a sound?" If superposition on a mass scale was feasible the tree would be in all states possible from standing to on the
    ground at the same time, until next observed. The problem posed is the more mass the more fragile the quantum state, the object collapses and is reduced to only one location.
    On a microscopic scale an object in superposition's collapse is caused by observing or measuring. I assume the same would be true of larger objects plus the amount of mass itself would cause the collapse. Mass and energy can not be created or destroyed only altered. So to put a whole, living human body into superposition maybe you would need some sort of anti higgs field instrument to disguise your mass from gravity.
    What if our DNA and/or neurons in our brain could experience superposition in a way our bodies can not?
     
  9. Jul 16, 2014 #8
    Someone with more QM background than I should attack this - but I'll try.

    By some theories (ex, the Penrose Interpretation), the amount of time it takes for a wave function to collapse on its own is dependent on its mass.

    In the case of something as big as a person, this is less time than it would take for light to travel from the head to a foot.
     
  10. Jul 16, 2014 #9

    bhobba

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    Indeed.

    Superposition is simply a consequence of the vector space structure of pure states.

    States simply are a device to help us in calculating the expectation of the outcomes of observations - it can be viewed as entirely abstract - like probabilities. The fact such has a vector space structure means nothing - since its simply something we use in our calculations - it doesn't mean objects are literally in a superposition. Even probability theory can be put in a form with a vector space structure - but that doesn't mean objects we assign a probability to are partly in the possible outcomes. And since that superposition can be decomposed in many differing ways whose utility depends on what you want to observe its not objective anyway.

    Thanks
    Bill
     
    Last edited: Jul 16, 2014
  11. Jul 16, 2014 #10

    bhobba

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    Although its a common misconception, even with those who have studied the technical details, the above is NOT true.

    Collapse is very interpretation dependant with many interpretations such as the statistical interpretation not even having it. And in interpretations that do, it only applies to so called filtering type observations (in fact the modern view is to associate a state with such since its a state preparation procedure - but that is just bye the bye). The majority of observations that occur in practice destroy what is being observed.

    Thanks
    Bill
     
    Last edited: Jul 16, 2014
  12. Jul 16, 2014 #11

    bhobba

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    That's not what QM says at all.

    A tree, being a macroscopic object is in constant interaction with its environment, and that's what gives it its classical properties. In fact its a technological tour de force getting macroscopic objects to show quantum properties, but it has been done with very strange results.

    But a tree is not like that. Its part of the common-sense macro world Copenhagen, the Statistical interpretation and a host of others assumes exist and observations appear in. They, by definition, are not subject to quantum weirdness. Of course that raises the question how a theory that assumes such a world explains it but that is a discussion requiring its own thread.

    Thanks
    Bill
     
    Last edited: Jul 16, 2014
  13. Jul 16, 2014 #12
    Please help me to better understand, the way I thought it worked was matter in superposition exists partly in all its theoretically possible states simultaneously; but when measured or observed, it gives only one result.
    http://physicsworld.com/cws/article/news/2010/mar/18/quantum-effect-spotted-in-a-visible-object
    Where exactly is the boundary between our classical and the quantum world?
     
  14. Jul 17, 2014 #13

    bhobba

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    The theory is silent about what an unobserved system is. All it says it has is this thing called a state that tells you about statistical averages if you were to observe it.

    Here is it real conceptual core:
    http://www.scottaaronson.com/democritus/lec9.html

    Basically its an extension of probability theory that allows for continuous transformations between so called pure states. Here's why. Suppose we have a system in 2 states represented by the vectors [0,1] and [1,0]. These states are called pure. These can be randomly presented for observation and you get the vector [p1, p2] where p1 and p2 give the probabilities of observing the pure state. Such states are called mixed. Probability theory is basically the theory of such mixed states. Now consider the matrix A that say after 1 second transforms one pure state to another with rows [0, 1] and [1, 0]. But what happens when A is applied for half a second. Well that would be a matrix U^2 = A. You can work this out and low and behold U is complex. Apply it to a pure state and you get a complex vector. This is something new. Its not a mixed state - but you are forced to it if you want continuous transformations between pure states.

    QM is the theory that makes sense of such weird complex pure states (which are required to have continuous transformations between pure states) - it does so by means of the so called Born rule.

    Why the Born Rule? Basically its just how nature works but there is this theorem, Gleason's Theorem, that sheds light on it (non contextuality is it's essence):
    https://www.physicsforums.com/showthread.php?t=758125

    That is a difficult question requiring its own thread. Start it and myself and others will be only too happy to contribute.
     
    Last edited: Jul 17, 2014
  15. Jul 19, 2014 #14

    Demystifier

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    I think your intuition is right; isolation from the external environment is essential. But once you know it is isolated, it is not difficult to conclude what such a human would experience. He would experience nothing special, because he would not even know that he travels along one or more of the (interfering) paths. For details see
    http://lanl.arxiv.org/abs/1406.3221
     
  16. Jul 19, 2014 #15
    You will feel like twin in prespectiv
     
  17. Aug 4, 2014 #16
    Sorry for the belated reply, things got quite busy all of the sudden. Responding to a few points in brief:

    1) Demystifier, thanks. And I'm avoiding much speculation on what the human would experience. I suppose I should have made this question more streamlined by just supposing some large macroscopic object (like a desk chair) instead of a human (but the later was more catchy) :)

    2) Bhobba, this is a bit of a non-answer from myself, but I was intentionally leaving what we were looking to observe blank to leave an option of superposition for any logical state accessible by our system. I might throw out some examples such as whether the whole human moves a tiny bit in any direction, but the point generally being whether or not the situation would suffice to allow superposition on a very large macroscopic scale like that.
     
  18. Aug 4, 2014 #17

    bhobba

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    You hit a big issue right there,

    We are being observed all the time by the environment and it requires temperatures close to absolute zero, amongst other things, for that not to be the case.

    You even being concious let alone alive at absolute zero makes the whole thing pretty moot anyway.

    Thanks
    Bill
     
    Last edited: Aug 5, 2014
  19. Aug 4, 2014 #18
    It seems to me that to be in superposition a conscious entity would be isolated from its environment and would experience nothing. Seeing, touching, hearing all involve interaction with the environment. Without experience can we even think? If we can think can that cause decoherence?
     
  20. Aug 5, 2014 #19

    bhobba

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    You would not even have brain activity.

    Thanks
    Bill
     
  21. Aug 7, 2014 #20

    Demystifier

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    Not necessarily. As explained in
    http://lanl.arxiv.org/abs/1406.3221
    you may be closed in a box within which you have everything you need for a normal conscious life. But it is this box which must be isolated from the environment external to the box, while superposition and interference refers to the whole box together with you inside. In this way, you can e.g. read a book in the box, but you cannot experience a travel of the box through an interferometer.
     
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