Quantum superposition of multiple clones and the novel cloning machine

Abstract

We envisage a novel quantum cloning machine, which takes an input state and produces an output state whose success branch can exist in a linear superposition of multiple copies of the input state and the failure branch can exist in a superposition of composite states independent of the input state. We prove that unknown nonorthogonal states chosen from a set S can evolve into a linear superposition of multiple clones and failure branches by a unitary process if and only if the states are linearly independent. We derive a bound on the success probability of the novel cloning machine. We argue that the deterministic and probabilistic clonings are special cases of our novel cloning machine.