arXiv:0709.1335 · New Journal of Physics
Interference of spontaneous emission of light from two solid-state atomic ensembles
Mikael Afzelius, M. U. Staudt, Hugues de Riedmatten, Christoph Simon, Sara R. Hastings-Simon, Raimund Ricken, H. Suche, W. Sohler, Nicolas Gisin
Abstract
We report an interference experiment of spontaneous emission of light from two distant solid-state ensembles of atoms that are coherently excited by a short laser pulse. The ensembles are erbium ions doped into two LiNbO 3 crystals with channel waveguides, which are placed in the two arms of a Mach–Zehnder interferometer. The light that is spontaneously emitted after the excitation pulse shows first-order interference. By a strong collective enhancement of the emission, the atoms behave as ideal two-level quantum systems and no which-path information is left in the atomic ensembles after emission of a photon. This results in a high fringe visibility of 95%, which implies that the observed spontaneous emission is highly coherent.