Sensitive observables on infinite-dimensional Hilbert spaces

Abstract

Let Σ be a physical system consisting of two subsystems,S andT: We prove that there are, in the absence of superselection rules, quantum mechanical observables (called “sensitive”), whose expectation value depends on the type of state vector (first type or second type) describing Σ. This result generalizes a previous one obtained under the restriction that the Hilbert spaces ofS andT are two dimensional.