  We create independent, synchronized single-photon sources with built-in
quantum memory based on two remote cold atomic ensembles. The synchronized
single photons are used to demonstrate efficient generation of entanglement.
The resulting entangled photon pairs violate a Bell's Inequality by 5 standard
deviations. Our synchronized single photons with their long coherence time of
25 ns and the efficient creation of entanglement serve as an ideal building
block for scalable linear optical quantum information processing.
