Gabor-Hofer Szabo (Hungarian Academy of Science): “Two concepts of noncontextuality in quantum mechanics”

Abstract: There are two different and logically independent concepts of noncontextuality in quantum mechanics. First, an ontological (hidden variable) model for quantum mechanics is called noncontextual if every ontic (hidden) state determines the probability of the outcomes of every measurement independently of what other measurements are simultaneously performed. Second, an ontological model is noncontextual if any two measurements which are represented by the same self-adjoint operator, or equivalently, which have the same probability distribution of outcomes in every quantum state also have the same probability distribution of outcomes in every ontic state. In the talk I will argue that the Kochen-Specker arguments provide a state-independent proof only against noncontextual ontological models of the second type.