Multiparticle Quantum Superposition and Stimulated Entanglement by   Parity Selective Amplification of Entangled States
  A multiparticle quantum superposition state has been generated by a novel phase-selective parametric amplifier of an entangled two-photon state. This realization is expected to open a new field of investigations on the persistence of the validity of the standard quantum theory for systems of increasing complexity, in a quasi decoherence-free environment. Because of its nonlocal structure the new system is expected to play a relevant role in the modern endeavor on quantum information and in the basic physics of entanglement. 
Francesco De Martini and Giovanni Di Giuseppe