An experiment is performed where a single rubidium atom trapped within a high-finesse optical cavity emits two independently triggered entangled photons. The entanglement is mediated by the atom and is characterized both by a Bell inequality violation of S=2.5, as well as full quantum-state tomography, resulting in a fidelity exceeding F=90%. The combination of cavity-QED and trapped atom techniques makes our protocol inherently deterministic - an essential step for the generation of scalable entanglement between the nodes of a distributed quantum network.
@article{arxiv.0811.3612,
title = {Photon-Photon Entanglement with a Single Trapped Atom},
author = {B. Weber and H. P. Specht and T. Mueller and J. Bochmann and M. Muecke and D. L. Moehring and G. Rempe},
journal= {arXiv preprint arXiv:0811.3612},
year = {2009}
}