Generation of frequency-multiplexed entangled single photons assisted by entanglement

We present a scheme to generate frequency-multiplexed entangled (FME) single photons based on the entanglement between two species in an atomic-mixture ensemble. The atomic ensemble driven by the write and read fields according to a certain timing sequence, the generation of FME single photons can be repeated until success is achieved. The source might have significant applications in wavelength-division-multiplexing quantum key distribution.