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.Comment: 9 pages, 5 figure
