  We present a simple yet rigorous field theoretic demonstration of the
nonlocality of a single-photon field. The formalism used allows us to calculate
the electric field of a single-photon light beam sent through a beam splitter,
which directly demonstrates that it is the light field, rather than the photon
itself regarded as a particle, that exhibits nonlocality. Our results are
obtained without using either inequalities or specific measurement apparatuses,
so that they have perfectly general validity.
