SCHEME FOR IMPLEMENTING ASSISTED CLONING OF AN UNKNOWN TWO-PARTICLE ENTANGLED STATE VIA CLUSTER STATE

We present a scheme that can realize quantum cloning of an unknown two-particle entangled state and its orthogonal-complement state with assistance offered by a state preparer, via entangled cluster state as quantum channel. The first stage of the scheme requires usual teleportation via a maximally four-particle entangled cluster state as quantum channel. In the second stage of the scheme, with the assistance (through a two-particle projective measurement) of the preparer, the perfect copies and complement copies of an unknown two-particle entangled state can be obtained. We also put forward a scheme for the teleportation by using nonmaximally entangled quantum channel. The clones and complement clones of unknown state can be produced with certain probability in the latter scheme.