Scheme for implementing economical phase-covariant quantum cloning machine of distant atomic qubits with single-photon interference

By means of the cavity-assisted photon interference, a simple scheme is proposed to implement symmetric economical phase-covariant quantum cloning machine of two remote qubits, with each in a separate cavity. With our present scheme, a high-fidelity cloning machine is realized. Our scheme may be quite useful in terms of the distributed quantum information processing.