Causality and entanglement in quantum field theory

In this paper, we discuss the Rafael Sorkin’s gedanken experiment of an impossible measurement in relativistic local quantum theory, which leads to an apparent violation of causality. Though we do not solve completely the Sorkin’s paradox, our discussion suggests that the mathematical structure of Algebraic Quantum Field Theory, namely its type [Formula: see text] local algebras of observables (via Connes-Stormer transitivity), is crucial for its understanding. Also the role of a type I factor as a “quantum mechanical” system needed to prepare an initial normal ([Formula: see text]physical) state is discussed.