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It is explained how, in quantum mechanics, information about a physical system is acquired through direct (von Neumann) and indirect (Kraus) measurements/observations. In a first part, a new theory of direct (projective, or von Neumann) measurements is developed, using methods and results from functional analysis. In a second part, the theory of indirect measurements is sketched, and it is shown how various theorems from probability theory and statistics can be used for this purpose. Many of the general ideas are explained in the context of a simple model system. Time permitting, I will outline tentative applications of the main ideas presented in this talk to a theory of perception.

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Jürg Fröhlich, ETH Zürich
Seminar Room TP 0.03
Contact: Martin Zirnbauer