2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/94111The phenomenological Maxwell field is quantized for arbitrarily space- and frequency-dependent complex permittivity. The formalism takes account of the Kramers--Kronig relation and the dissipation-fluctuation theorem and yields the fundamental equal-time commutation relations of QED. Applications to the quantum-state transformation at absorbing and amplifying four-port devices and to the spontaneous decay of an excited atom in the presence of absorbing dielectric bodies are discussed.4 pages, LaTeX, contribution to the Sixth International Conference on Squeezed states and Uncertainty relations ICSSUR VI, Naples 24-29 May 1999Quantum Physicstext