  We have recently developed a quantized fluctuational electrodynamics (QFED)
formalism to describe the quantum aspects of local thermal balance formation
and to formulate the electromagnetic field ladder operators so that they no
longer exhibit the anomalies reported for resonant structures. Here we show how
the QFED can be used to resolve between the left and right propagating fields
to bridge the QFED and the quantum optical input-output relations commonly used
to describe selected quantum aspects of resonators. The generalized model
introduces a density of states concept describing interference effects, which
is instrumental in allowing an unambiguous separation of the fields and related
quantum operators into left and right propagating parts. In addition to
providing insight on the quantum treatment of interference, our results also
provide the conclusive resolution of the long-standing enigma of the anomalous
commutation relations of partially confined propagating fields.
