  We discuss the limits of the photon wavefunction (PWF) formalism, which is
experiencing a revival in these days from the new practical applications in
photonics and quantum optics. We build a Dirac-like equation for the PWF
written in a manifestly covariant form and show that, in presence of charged
matter fields, it reproduces the standard formulation of (classical)
Electrodinamics. This shows the inconsistency of the attempts to construct a
quantum theory of interacting photons, based on the so called photon
wavefunction approach, alternative to standard QED. PWF formalism can then be
used to provide an easier description of the propagation of free photons, when
the photon number remains fixed in time.

Quantum Physics