  A general procedure for constructing conserved electromagnetic current
operators, for both finite and infinite degree of freedom systems, is given. A
four-momentum operator consisting of matter, photon, and electromagnetic
interactions is assumed to be polynomial in photon creation and annihilation
operators. Commutators of the four-momentum operator with the four-vector
potential operator at the space-time point zero give the electromagnetic field
tensor and current operator at the space-time point zero. In this construction
there are no equations of motion to be satisfied and field operators at an
arbitrary space-time point-defined as the four-momentum translates of the
corresponding operators at the space-time point zero-are not local operators.
Several examples are given to show how the construction is carried out.
