Photons from macroscopic currents

Abstract Coherent states are a well-established tool of quantum optics to describe electromagnetic waves in terms of photons. However, they do not describe the near-field regime of macroscopic radiation sources. Instead, we generically use classical solutions of Maxwell’s equations to describe radiation in the near-field regime. The classical solutions provide linear relations between currents and emitted electromagnetic fields, whereas evolution of states at the quantum level involves photons. This begs the question how we can describe macroscopic fields from antennas or magnetic coils in terms of elementary photons. The present paper answers this question through the construction of generalized Glauber states for macroscopic radiation emitters.