  The fluctuations or disordered motion of the electromagnetic fields are
described by statistical properties rather than instantaneous values. This
statistical description of the optical fields is underlying in the
Stokes-Mueller formalism that applies to measurable intensities. However, the
fundamental concept of optical coherence, that is assessed by the ability of
waves to interfere, is not treatable by this formalism because it omits the
global phase. In this work we show that, using an analogy between deterministic
matrix states associated to optical media and quantum mechanical wavefunctions,
it is possible to construct a general formalism that accounts for the
additional terms resulting from the coherency effects that average out for
incoherent treatments. This method generalizes further the concept of coherent
superposition to describe how deterministic states of optical media can
superpose to generate another deterministic media state. Our formalism of
coherency is used to study the combined polarimetric response of interfering
plasmonic nanoantennas.
