Covariance approach to the free photon field

We introduce photon theory following the same principles as for introduction of the quantum theory of a single particle, using a C*-algebraic approach based on covariance systems. The basic symmetries are additivity of the fields and additivity of test functions. We write down in explicit form a state of this covariance system. It turns out to reproduce the traditional Fock representation of the free photon field, with a Lorentz invariant vacuum. Properties of smeared-out photons are discussed.Comment: Latex, 24 pages, to appear in: "Probing the structure of Quantum Mechanics: nonlinearity, nonlocality, computation and axiomatics", eds. D. Aerts, M. Czachor, and T. Durt (World Scientific, 2002