Quantum theory of measurement

Abstract

Inspite of its abstract mathematical structure quantum mechanics is above all the pragmatic theory which enables to predict the results of the experiments. The weakness of classical physics to explain the behavior of microsystems initialized the revolution in physics at the beginning of this century. The experiments, both “gedanken” or feasible, are playing the primary role in development of quantum mechanics. Quantum measurement represents therefore an extraordinarily important part of quantum theory which links the fundamental phenomena in microworld to those which can be classically detected and recognized according to the rules of classical physics. Of course, this treatment implicitly assumes that such a separation of the Universe to the classical and quantum parts is possible. This point represents a contra-verse issue, which is unsatisfactory mainly from the philosophical viewpoint. Moreover, the border between the classical and quantum worlds seems to be fuzzy. Quantum observation theory linking hypothetical quantum features to the classical phenomenon of everydays life is considered from this reason as uncomplete and there are live discussions concerning this topic in existing literarure. In spite of the existence of conceptual problems, any future explanation should take into account the agreement of the pragmatic Copenhagen interpretation of quantum mechanics with existing experiments. In our treatment we will therefore focus on the operational aspects of the quantum measurement taking the existence of quantum and classical worlds as granted by experience.