  Principles of discrete time mechanics are applied to the quantisation of
Maxwell's equations. Following an analysis of temporal node and link variables,
we review the classical discrete time equations in the Coulomb and Lorentz
gauges and conclude that electro-magneto duality does not occur in pure
discrete time electromagnetism. We discuss the role of boundary conditions in
our mechanics and how temporal discretisation should influence very early
universe dynamics. Quantisation of the Maxwell potentials is approached via the
discrete time Schwinger action principle and the Faddeev-Popov path integral.
We demonstrate complete agreement in the case of the Coulomb gauge, obtaining
the vacuum functional and the discrete time field commutators in that gauge.
Finally, we use the Faddeev-Popov method to construct the discrete time
analogues of the photon propagator in the Landau and Feynman gauges, which
casts light on the break with relativity and possible discrete time analogues
of the metric tensor.
