title: Nonlinear Bell Inequalities Tailored for Quantum Networks.
abstract: In a quantum network, distant observers sharing physical resources emitted by independent sources can establish strong correlations, which defy any classical explanation in terms of local variables. We discuss the characterization of nonlocal correlations in such a situation, when compared to those that can be generated in networks distributing independent local variables. We present an iterative procedure for constructing Bell inequalities tailored for networks: starting from a given network, and a corresponding Bell inequality, our technique provides new Bell inequalities for a more complex network, involving one additional source and one additional observer. We illustrate the relevance of our method on a variety of networks, demonstrating significant quantum violations, which could not have been detected using standard Bell inequalities.
authors.affiliation: Group of Applied Physics, Université de Genève, 1211 Genève, Switzerland.
authors.forename: Denis
authors.initials: D
authors.lastname: Rosset
authors.affiliation: Institut Néel, CNRS and Université Grenoble Alpes, 38042 Grenoble Cedex 9, France.
authors.forename: Cyril
authors.initials: C
authors.lastname: Branciard
authors.affiliation: Group of Applied Physics, Université de Genève, 1211 Genève, Switzerland.
authors.forename: Tomer Jack
authors.initials: TJ
authors.lastname: Barnea
authors.affiliation: Group of Applied Physics, Université de Genève, 1211 Genève, Switzerland.
authors.forename: Gilles
authors.initials: G
authors.lastname: Pütz
authors.affiliation: Département de Physique Théorique, Université de Genève, 1211 Genève, Switzerland.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Brunner
authors.affiliation: Group of Applied Physics, Université de Genève, 1211 Genève, Switzerland.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Gisin