  We address the implementation of the positive operator-valued measure (POVM)
describing the optimal M-outcomes discrimination of the polarization state of a
single photon. Initially, the POVM elements are extended to projective
operators by Naimark theorem, then the resulting projective measure is
implemented by a Knill-Laflamme-Milburn scheme involving an optical network and
photon counters. We find the analytical expression of the Naimark extension and
the detection scheme that realise it for an arbitrary number of outcomes M =
2^N.
