  We demonstrate the fundamental links existing between two different
descriptions of quantum electrodynamics in inhomogeneous, lossy and dispersive
dielectric media which are based either on the Huttner-Barnett formalism for
polaritons [B. Huttner and S. M. Barnett, Phys.Rev. A 46, 4306 (1992)] or the
Langevin noise approach using fluctuating currents [T. Gruner and D.-G. Welsch,
Phys.Rev.A 53, 1818 (1996)]. In this work we demonstrate the practical
equivalence of the two descriptions by introducing the concept of effective
photon state associated with some specific noise current distribution. We study
the impact of these results on the calculation and interpretation of quantum
observables such as fluctuations, correlations, and Casimir forces.
