Decoherence, environment-induced superselection, and classicality of a macroscopic quantum superposition generated by quantum cloning

The high resilience to decoherence shown by a recently discovered macroscopic quantum superposition (MQS) generated by a quantum-injected optical parametric amplifier and involving a number of photons in excess of 5x104 motivates the present theoretical and numerical investigation. The results are analyzed in comparison with the properties of the MQS based on |α> and N-photon maximally entangled states (NOON), in the perspective of the comprehensive theory of the subject by Zurek. In that perspective the concepts of 'pointer state' and 'environment-induced superselection' are applied to the new scheme.