Single-photon source may meet the needs of quantum communication systems

This icon demonstrates the single photon source: When a laser beam (called Write, shown in green) hits the cold atomic cloud, a single spin excitation can be generated accompanying a Raman photon (shown in blue). Now the single spin excitation is ready for being retrieved to a single photon by another classical laser (called Read). The blue part at bottom right indicates the wavepacket of photons. Credit: Shuai Chen et al.