Ultraviolet single-photons on demand and entanglement of photons with a large frequency difference

We investigate an efficient scheme for generating ultraviolet single-photons (similar to300 nm). The scheme combines the highly efficient single-photon four-wave mixing scheme and fast developing quantum dot single-photons on demand source technology. We show that near maximum, entanglement between two well matched ultraslowly propagating single-photon wave packets can be achieved. This study may lead to research and development opportunities in highly efficient entanglement schemes using photons of very large frequency difference, quantum information processing, and single-photon metrology and single-photon counting sensors in the uv spectra region.