  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.
