title: Ontological models predictively inequivalent to quantum theory.
abstract: Recently, it has been argued that no extension of quantum theory can have improved predictive power under a strong assumption of free choice of the experimental settings and validity of quantum mechanics. Here, under a different free choice assumption, we describe a model which violates this statement for almost all states of a bipartite two-level system, in a possibly experimentally testable way. From consistency with quantum mechanics and the nonsignaling principle, we derive a bound on the local averages for the family of deterministic ontological theories that our model belongs to.
authors.affiliation: Department of Physics, University of Trieste, and the Abdus Salam ICTP, 34151 Trieste, Italy. ghirardi@ictp.it
authors.forename: GianCarlo
authors.initials: G
authors.lastname: Ghirardi
authors.forename: Raffaele
authors.initials: R
authors.lastname: Romano