Implementing ancilla-free phase covariant quantum cloning with atoms trapped in cavities

Abstract

We propose a scheme to implement ancilla-free 1 to 2 optimal phase covariant quantum cloning with atoms trapped in cavities. In the scheme the W-class state of three atoms, which are individually trapped in three spatially separated cavities, is deterministically generated. Then by the use of this W-class state and detection of the atomic state, an optimal ancilla-free 1 to 2 phase-covariant quantum cloning between two spatially separated trapped atoms can be realized. The scheme is robust for atomic spontaneous decay, cavity decay and photon leakage out of the fiber. In principle, an M+1-atom W-class state can be generated by using such an approach. Thus this scheme also can be generalized to implement 1 to M ancilla-free phase-covariant quantum cloning.