title: Realization and characterization of a two-photon four-qubit linear cluster state.
abstract: We report on the experimental realization of a four-qubit linear cluster state via two photons entangled both in polarization and linear momentum. This state was investigated by performing tomographic measurements and by evaluating an entanglement witness. By use of this state we carried out a novel nonlocality proof, the so-called "stronger two observer all-versus-nothing" test of quantum nonlocality.
authors.affiliation: Dipartimento di Fisica dell'Universitá La Sapienza and Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, Roma, 00185 Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Vallone
authors.forename: Enrico
authors.initials: E
authors.lastname: Pomarico
authors.forename: Paolo
authors.initials: P
authors.lastname: Mataloni
authors.forename: Francesco
authors.initials: F
authors.lastname: De Martini
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Berardi