We report on the coherent quantum state transfer from a two-level atomic system to a single photon. Entanglement between a single photon (signal) and a two-component ensemble of cold rubidium atoms is used to project the quantum memory element (the atomic ensemble) onto any desired state by measuring the signal in a suitable basis. The atomic qubit is read out by stimulating directional emission of a single photon (idler) from the (entangled) collective state of the ensemble. Faithful atomic memory preparation and read-out are verified by the observed correlations between the signal and the idler photons. These results enable implementation of distributed quantum networking.
@article{arxiv.quant-ph/0410092,
title = {Quantum State Transfer Between Matter and Light},
author = {D. N. Matsukevich and A. Kuzmich},
journal= {arXiv preprint arXiv:quant-ph/0410092},
year = {2009}
}