  Classically, electromagnetic pulses are described by real fields that couple
to charged matter and propagate causally. We will show here that real fields of
the form used in standard classical electromagnetic theory have a quantum
mechanical interpretation in which the probability density for a photon to be
at x is positive definite and operators representing all of the standard
physical observables exist. A covariant alternative to the {\omega}_{k}^{1/2}
dependence that appears in most (but not all) presentations of quantum optics
and quantum field theory is presented and real scalar one photon advanced and
retarded potentials are derived.
