Entanglement, EPR correlations and mesoscopic quantum superposition by   the high-gain quantum injected parametric amplification
  We investigate the multiparticle quantum superposition and the persistence of multipartite entanglement of the quantum superposition generated by the quantum injected high-gain optical parametric amplification of a single photon. The physical configuration based on the optimal universal quantum cloning has been adopted to investigate how the entanglement and the quantum coherence of the system persists for large values of the nonlinear parametric gain g. 
Marco Caminati, Francesco De Martini, Riccardo Perris, Fabio   Sciarrino, Veronica Secondi