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atyy
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Sonderval said:I can calculate the evolution of teh ooperators once and for all and then apply them to different initial states) and that to actually calculate any measurable quantity I of course need to apply the operator to the initial state. Would you say that this interpretation/phrasing is incorrect?
If I understand what you mean by "once and for all", this isn't right. After a measurement, you still have to collapse either the wave function or the observables.
If you want a very shut up and calculate formula, you can try Eq 37 in Laloe's http://arxiv.org/abs/quant-ph/0209123. But the classical/quantum cut is fundamental in the traditional formulation of quantum mechanics, and it is natural to identify the state with the quantum side, and the operators with the classical side. But as with all observations, the physics is relative, and it is only the relative that is absolute (for example, the universe is absolutely expanding relative to a family of observers) , so one can imagine that the system is evolving relative to apparatus, or that the apparatus is evolving relative to the system.
More in this spirit is given in section 1.3 of Wiseman and Milburn's https://books.google.com/books?id=ZNjvHaH8qA4C&printsec=frontcover#v=onepage&q&f=false.
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