Long-distance entanglement distribution with single-photon sources

We present an efficient architecture for quantum repeaters based on single-photon sources in combination with quantum memories for photons. Errors inherent to previous repeater protocols using photon-pair sources are eliminated, leading to a significant gain in efficiency. The requirements on the single-photon sources and on the photon detectors are within reach of current technology.

Figure 1

(Color online) Schematic architecture of an elementary link connecting two locations $A$ and $B$ for (a) the ${\mathrm{P}}^2{\mathrm{M}}^3$ protocol that uses photon-pair sources [3] and (b) the new single-photon source protocol. Sources, memories, and detectors are represented by circles, squares, and half-circles, respectively. Vertical bars labeled BS denote beam splitters. For both (a) and (b), the detection of a single photon behind the central beam splitter projects the two memories into an entangled state.