Tobias Fritz, Workshop on: QUANTUM INFORMATION AND FOUNDATIONS OF QUANTUM MECHANICS

Workshop on: QUANTUM INFORMATION AND FOUNDATIONS OF QUANTUM MECHANICS
Quantum Mechanics: Axiomatics and connections with Computing and Information Theory Violating Bell inequalities in no-signaling theories with repeatable measurements
aula DOTTORATO - 5 luglio ore 11.00
	Tobias Fritz, Institute of Photonic Science, Barcelona
>PRESENTATION:Tobias Fritz is a postdoctoral researcher at the Institute of Photonic Sciences in Barcelona. He works on mathematical methods of fundamental physics.
Abstract
	Bell inequalities are inequalities for the correlations between observables located at spatially separated sites, which are satisfied for classical systems with local interactions, but can be violated by quantum theory. They prove that quantum theory is not compatible with a description in terms of local hidden variables (Bell's theorem). Here, we consider the class of theories which have repeatable measurements and do not allow signaling, and ask whether Bell inequalities can be violated by any of these. We answer this in the positive by finding a simple example of such a theory where the correlations are those of the Popescu-Rohrlich box. The main idea in the construction is that the first party's measurement may change the state of the system in such a way that the second party's subsequent measurement reveals the correlations, while guaranteeing the repeatability of measurements and the impossibility of signaling. There will be plenty of time for discussion with the audience.