Navegando por Autor "Santodonato, Luca"
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Artigo Experimental bilocality violation without shared reference frames(American Physical Society, 2017-06-09) Andreoli, Francesco; Carvacho, Gonzalo; Santodonato, Luca; Bentivegna, Marco; Araújo, Rafael Chaves Souto; Sciarrino, FábioNonclassical correlations arising in complex quantum networks are attracting growing interest, both from a fundamental perspective and for potential applications in information processing. In particular, in an entanglement swapping scenario a newkind of correlations arise, the so-called nonbilocal correlations that are incompatible with local realism augmented with the assumption that the sources of states used in the experiment are independent. In practice, however, bilocality tests impose strict constraints on the experimental setup and in particular to the presence of shared reference frames between the parties. Here, we experimentally address this point showing that false positive nonbilocal quantum correlations can be observed even though the sources of states are independent. To overcome this problem, we propose and demonstrate a scheme for the violation of bilocality that does not require shared reference frames and thus constitutes an important building block for future investigations of quantum correlations in complex networksArtigo Experimental violation of local causality in a quantum network(Nature Research, 2017-03-16) Carvacho, Gonzalo; Andreoli, Francesco; Santodonato, Luca; Bentivegna, Marco; Araújo, Rafael Chaves Souto; Sciarrino, FábioBell’s theorem plays a crucial role in quantum information processing and thus several experimental investigations of Bell inequalities violations have been carried out over the years. Despite their fundamental relevance, however, previous experiments did not consider an ingredient of relevance for quantum networks: the fact that correlations between distant parties are mediated by several, typically independent sources. Here, using a photonic setup, we investigate a quantum network consisting of three spatially separated nodes whose correlations are mediated by two distinct sources. This scenario allows for the emergence of the so-called non-bilocal correlations, incompatible with any local model involving two independent hidden variables. We experimentally witness the emergence of this kind of quantum correlations by violating a Bell-like inequality under the fair-sampling assumption. Our results provide a proof-of-principle experiment of generalizations of Bell’s theorem for networks, which could represent a potential resource for quantum communication protocolsArtigo Maximal qubit violation of n-locality inequalities in a star-shaped quantum network(IOP Publishing, 2017-11-14) Andreoli, Francesco; Carvacho, Gonzalo; Santodonato, Luca; Araújo, Rafael Chaves Souto; Sciarrino, FabioBellʼs theorem was a cornerstone for our understanding of quantum theory and the establishment of Bell non-locality played a crucial role in the development of quantum information. Recently, its extension to complex networks has been attracting growing attention, but a deep characterization of quantum behavior is still missing for this novel context. In this work we analyze quantum correlations arising in the bilocality scenario, that is a tripartite quantum network where the correlations between the parties are mediated by two independent sources of states. First, we prove that non-bilocal correlations witnessed through a Bell-state measurement in the central node of the network form a subset of those obtainable by means of a local projective measurement. This leads us to derive the maximal violation of the bilocality inequality that can be achieved by arbitrary two-qubit quantum states and arbitrary local projective measurements.Wethen analyze in details the relation between the violation of the bilocality inequality and theCHSHinequality. Finally, we show how our method can be extended to the n-locality scenario consisting of n two-qubit quantum states distributed among n + 1nodes of a star-shaped network