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Understand the idea of superposition

  1. Sep 4, 2013 #1
    Forgive me if this post is too long and too full of misconceptions. I'll try to be clear and concise. And sorry for cramming too many questions into it, but they all sort of go together.

    I'm wondering if someone can help me understand the idea of superposition. Does it only have to do with a particle's position, or can the particle's other properties be in a state of superposition as well? (Strangely, I couldn't seem to find a definitive list of all of a particle's complementary properties) I am somehow under the impression that a particle can be in a superposition of its other properties as well, not just position. Am I misguided in this belief?

    If each of a particle's differing properties can have their own superposition, then does wave/particle duality depend only upon the particle's superposition as it relates to its position? Or is that simply our classical way of looking at it, since the effects of wave/particle duality are most noticeable when it comes to position? In a sense can wave/particle duality be extended to the particle's other properties?

    QM says that an unobserved particle exists in a superposition of all possible states, correct? While HUP says that complementary properties of a particle are inversely related, such that if one is known, then the other is unknown. Doesn't this mean that a particle is always in a state of superposition in regards to at least some of its properties?

    Are particles, in some sense, always in a state of flux as they interact with the environment, with properties popping in and out of superposition, depending upon the nature of their most recent interaction with the environment? People tend to think of a particle as having a fixed, definable state, but is that a bit naive as the particles are constantly changing with each interaction? Or am I the one who is naive here?

    Now when scientists interact with a particle they have the ability to choose which property they're going to measure, and to what degree of accuracy they're going to measure it, but what about the environment? Is the environment somewhat limited on how it interacts with a particle, and thus which properties, and how accurately it measures them? Or perhaps the opposite is true, that the environment's interactions with particles are more diverse and robust than ours, as we are in some way limited by our senses and instruments. Do people in their day to day lives actually make very poor observers, especially as far as the number of things that we consciously observe?

    It seems to me that reality is extremely dynamic, with particles constantly in a state of flux, and I have so many more questions than these. But I've asked enough of them for now. Any information or insights that anyone can provide would be appreciated.

    In some sense, is a particle always in a state of superposition?


    Thanks
     
  2. jcsd
  3. Sep 4, 2013 #2

    UltrafastPED

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    You appear to have many misconceptions. I suggest that you spend some time with John Polkinghorne's slim and easily understood book "Quantum Theory: A Very Short Introduction". The mathematical structure is provided in an appendix so that you can work out the fundamental details after you have read each section.
     
  4. Sep 4, 2013 #3
    Definitely too many questions all together let me try and answer what I can, others may answer the rest and correct any errors.

    First Question:
    Does it only have to do with a particle's position, or can the particle's other properties be in a state of superposition as well? (Strangely, I couldn't seem to find a definitive list of all of a particle's complementary properties) I am somehow under the impression that a particle can be in a superposition of its other properties as well, not just position. Am I misguided in this belief?

    No you are correct there are many properties that can be in superposition we sort of answer it in this thread (https://www.physicsforums.com/showthread.php?t=708326).

    Spin, polarization, position, particle number and energy have been proved to exist in a quantum superposition. As discussed there are probably more possible but I am not sure they have been conclusively observed.

    Second Question:
    If each of a particle's differing properties can have their own superposition, then does wave/particle duality depend only upon the particle's superposition as it relates to its position?

    No position has nothing to do with superposition of other properties extend the duality to the other properties is the correct view.

    Third Question:
    QM says that an unobserved particle exists in a superposition of all possible states, correct?

    Wrong ...

    "Exists partly in all its particular theoretically possible states (or, configuration of its properties) simultaneously"


    Fourth Question:
    Doesn't this mean that a particle is always in a state of superposition in regards to at least some of its properties?

    Yes and the word "partly" removes your conflict. There are deeper problems with this simplicity in that you don't really know anything about the state conditions at all so it carries no information. To be useful you need to control interactions to create useful superposition states. So an unobserved particle being in superposition is about as useful and meaningful as an unobserved particle in classic physics.

    That fixes up the real major problems I can see, others may have more to add ... now off and do more reading :smile:
     
    Last edited: Sep 4, 2013
  5. Sep 4, 2013 #4

    UltrafastPED

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    If you perform a measurement for spin you will receive a definite answer. If you measure again, you will get the same result.

    So you need not find superposition of states at all time.
     
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