We present a protocol for performing entanglement connection between pairs of atomic ensembles in the single excitation regime. Two pairs are prepared in an asynchronous fashion and then connected via a Bell measurement. The resulting state of the two remaining ensembles is mapped to photonic modes and a reduced density matrix is then reconstructed. Our observations confirm for the first time the creation of coherence between atomic systems that never interacted, a first step towards entanglement connection, a critical requirement for quantum networking and long distance quantum communications.
@article{arxiv.0704.2246,
title = {Towards experimental entanglement connection with atomic ensembles in the single excitation regime},
author = {J. Laurat and C. W. Chou and H. Deng and K. S. Choi and D. Felinto and H. de Riedmatten and H. J. Kimble},
journal= {arXiv preprint arXiv:0704.2246},
year = {2009}
}