title: Realization of an optimally distinguishable multiphoton quantum superposition.
abstract: We report the realization of an entangled quantum superposition of M approximately 12 photons by multiple universal cloning of a single-photon qubit via the high gain, quantum-injected optical parametric amplification. The system has been found extremely resilient to decoherence. By quantum tomography, the nonseparability and the quantum superposition are demonstrated for the mesoscopic output state of the dynamic "closed system."
authors.affiliation: Dipartimento di Fisica and Istituto Nazionale di Fisica per la Materia, Universitá La Sapienza, Roma 00185, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: De Martini
authors.forename: Fabio
authors.initials: F
authors.lastname: Sciarrino
authors.forename: Veronica
authors.initials: V
authors.lastname: Secondi