Tests of Basic Quantum Mechanics in Oscillation Experiments

While quantum theory works remarkably well and there is no evidence to date that its validity may be limited, there have been attempts at modifying its structure both in order to resolve some conceptual problems or in order to establish its limits of validity. In particular, modifications of quantum theory have been considered in order to resolve the problem of transition to classical theory (the problem of “decoherence”). Briefly, it has to be made sure that if two states are macroscopically different, then there is no definite phase relation between them and thus, their superposition is not a physically admissible state. (Sometimes this is dubbed as the “problem of Schrödinger’s cat”, see for instance D’Espagnat [1].) It is generally thought that decoherence is a consequence of some kind of an interaction with the environment in