Ehrenfest+R dynamics. I. A mixed quantum–classical electrodynamics simulation of spontaneous emission.

The dynamics of an electronic system interacting with an electromagnetic field is investigated within mixed quantum–classical theory. Beyond the classical path approximation (where we ignore all feedback from the electronic system on the photon field), we consider all electron–photon interactions explicitly according to Ehrenfest (i.e., mean-field) dynamics and a set of coupled Maxwell–Liouville equations. Because Ehrenfest dynamics cannot capture certain quantum features of the photon field correctly, we propose a new Ehrenfest+R method that can recover (by construction) spontaneous emission while also distinguishing between electromagnetic fluctuations and coherent emission. [ABSTRACT FROM AUTHOR]