Linear optical implementation of ancilla-free 1→3 optimal phase covariant quantum cloning machines for the equatorial qubits

We propose experimental schemes to implement ancilla-free 1→3 optimal phase covariant quantum cloning machines for x-y and x-z equatorial qubits by interfering a polarized photon, which we wish to clone, with different light resources at a six-port symmetric beam splitter. The scheme requires linear optical elements and three-photon coincidence detection, and is feasible with current experimental technology