Correlations in star networks: from Bell inequalities to network inequalities. (7th July 2017)

• Record Type: Journal Article
• Authors: Tavakoli, Armin; Renou, Marc Olivier; Gisin, Nicolas; Brunner, Nicolas
• Is Part Of: New journal of physics. Volume 19:Number 7(2017:Jul.)
• Publication Date: 2017-07-07
• Subjects: quantum correlations -- quantum networks -- Bell inequalities; 03.67.Hk -- 03.67.-a -- 03.67.Dd; Physics -- Periodicals; Physics; Periodicals; 530.05
• DOI: 10.1088/1367-2630/aa7673
• Languages: English
• ISSNs: 1367-2630

Abstract

Abstract: The problem of characterizing classical and quantum correlations in networks is considered. Contrary to the usual Bell scenario, where distant observers share a physical system emitted by one common source, a network features several independent sources, each distributing a physical system to a subset of observers. In the quantum setting, the observers can perform joint measurements on initially independent systems, which may lead to strong correlations across the whole network. In this work, we introduce a technique to systematically map a Bell inequality to a family of Bell-type inequalities bounding classical correlations on networks in a star-configuration. Also, we show that whenever a given Bell inequality can be violated by some entangled state ρ, then all the corresponding network inequalities can be violated by considering many copies of ρ distributed in the star network. The relevance of these ideas is illustrated by applying our method to a specific multi-setting Bell inequality. We derive the corresponding network inequalities, and study their quantum violations.