  We propose an experimental setup that is capable of unambiguously
discriminating any pair of linearly independent single photon polarization
qubits, about which we don't have any knowledge except that an extra pair of
these unknown states are provided as the reference. This setup, which is
constructed with optical CNOT gates, weak cross Kerr non-linearities, Bell
state analysers and other linear optical elements, transforms the unknown
triple photon input states to the corresponding single photon states to be
deterministically processed by linear optics circuit. The optimal
discrimination of the unknown states is achieved by this setup.
