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I have questions: you describe the change of states of particle as

    "a smooth transition between being in one energy state to
    being in a superposition of two energy states to being
    entirely in the second energy state."
At the terminus of this transition, is the particle no longer in a superposition? IE there is now a 100% chance it's in the second state and 0% chance that it's in the original state?

If so, does that imply that the function of the particle's state (with respect to time) is discontinuous? Since there's a point at which it goes from being a superposition to exactly 0%.



That's a very good question. It has two answers.

The first answer is that a system is never 100% in any particular state because that would violate the uncertainty principle. When we speak of a system "definitely" being in a particular state that's an approximation/simplification. It actually means that the system is in a superposition of some range of states that for all intents and purposes we can treat as being the same, and the probability of it being in a state that cannot be treated the same for all intents and purposes is so close to zero we can ignore that.

The second answer is that whether or not a system is in a superposition depends on your point of view. A system can only ever be in a "single state" (according to the above approximation) with respect to some observable, and if it is in a single state with respect to that observable then it is necessarily in a superposition with respect to the complementary observable, e.g. a particle that is in a definite state with respect to position is necessarily in a superposition with respect to velocity.

So the whole process is everywhere and always continuous.




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