  One-loop calculations in quantum gravity coupled to U(1)-Abelian fields
(photon fields) are ultraviolet finite and cutoff-free in the framework of
causal perturbation theory. We compute the photon loop correction to the
graviton propagator and the photon self-energy in second order perturbation
theory. Perturbative gauge invariance to second order is shown and generates
the gravitational Slavnov-Ward identities.
