Vacuum-stimulated Raman transitions are driven between two magnetic substates of a rubidium-87 atom strongly coupled to an optical cavity. A magnetic field lifts the degeneracy of these states, and the atom is alternately exposed to laser pulses of two different frequencies. This produces a stream of single photons with alternating circular polarization in a predetermined spatio-temporal mode. MHz repetition rates are possible as no recycling of the atom between photon generations is required. Photon indistinguishability is tested by time-resolved two-photon interference.
@article{arxiv.quant-ph/0610227,
title = {Polarization-controlled single photons},
author = {T. Wilk and S. C. Webster and H. P. Specht and G. Rempe and A. Kuhn},
journal= {arXiv preprint arXiv:quant-ph/0610227},
year = {2007}
}