Quantum logic of sequential events and their objectivistic probabilities

A propositional calculus for quantum mechanical systems is presented which formalizes 'sequential' connectives 'and then' and 'or then' for yes-no experiments in the framework of complex Hilbert space. Properties of these connectives are compared with some well-known lattice-theoretical results in quantum logic. Probabilities and objectivization versus the Copenhagen interpretation are discussed in connection with Young's two-slit experiment. (author)