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There is a temptation to put in 'gee-whizz' items. In particular, I refer to the claim implicit in one example here that viruses are living things. And now we have as another example a proposal to put a bacterium into a state that has a wave function. At best, such a state would be one of suspended animation. I have not bothered to struggle with the editor who passionately claims that viruses are alive, apparently because they are complex, while avoiding the fact that they don't metabolize. The new proposal about bacteria, in its cited text source, says they would be alive. The key physical fact is that for superposition, one needs a wave function, as stated clearly by Willis Lamb (see just above). This is so obvious that not many writers would bother to say it explicitly, and yet it does seem to escape the attention of too many. The present use of two such examples, without note that they rely on at least suspended animation, puts us in near 'gee-whizz' territory. I would prefer to see both removed because of their dodgy form, but I don't intend to struggle over it.Chjoaygame (talk) 00:49, 22 September 2015 (UTC)
Most of the material in the "Concept" section needs either a complete rewrite, or should simply be removed. For example the term "pure state" has a very specific meaning in quantum mechanics, and has little to do with anything described there. For a specific example, "pure with respect to the filter" is gibberish - a quantum state is either pure or mixed, there's nothing relative about it. The reference given (Messiah) says nothing that supports what is written. Another example: "For perfect superposition it is essential that the intermediate beams are mutually coherent." Again, this is gibberish - superposition is an exact principle, it's never "imperfect", nor is it necessary for beams to be "coherent" for their corresponding quantum states to be superpose-able. Given the major problems with these sections and the lack of sources that support what is written, the content there now detracts significantly from the article and from the understanding of anyone seeking to learn from the article. Therefore I am deleting the entire section. Hopefully it can be replaced later with a correct version. Waleswatcher (talk) 23:08, 5 November 2015 (UTC)
Something to add - there is really no reason to discuss "beams" at all, especially not in a "concept" section that is supposed to gently introduce the idea of quantum superposition. Superposition is a totally general concept in QM that applies to everything from individual isolated particles to macroscopic systems (assuming QM applies to them). It's far more general than "beams". Also, a minor note on English usage. "Quantal" is really not a common word, either among professionals or lay-people. Best to avoid it. Waleswatcher (talk) 23:13, 5 November 2015 (UTC)
Dirac 4th edition (1958), p. 14: "It is important to remember, however, that the superposition that occurs in quantum mechanics is of an essentially different nature from any occurring in the classical theory, as is shown by the fact that the quantum superposition principle demands indeterminacy in the results of observations in order to be capable of a sensible physical interpretation."
Dirac 4th edition (1958), p. 17: "The assumption just made shows up very clearly the fundamental difference between the superposition of the quantum theory and any kind of classical superposition."
The second sentence of the lead of the present article currently reads "... much like waves in classical physics, any two (or more) quantum states can be added together ..." How much like?Chjoaygame (talk) 15:31, 21 November 2015 (UTC)
Maybe we could eliminate the whole section Experiments and applications. Of course these are some examples, but isn't any QM experiment a demonstration of quantum superposition? All QM experiments are under the assumption they follow somehow Schrodinger equation or some version of Dirac-von Neumann axioms. I agree we could leave some examples but not as experimental evidence and only if it is argued why is a good example of Q superposition, like the slit and the qubit in the lead. --MaoGo (talk) 16:38, 14 May 2018 (UTC)