Quantum frequency conversion of visible single photons from a quantum dot to a telecom band

The work demonstrates frequency downconversion of single photons from a quantum dot and prove the preservation of the single photon character. The authors were able to translate the frequency of single photons of a semiconductor quantum dot from the red spectral range to the telecom O-band. It was proven that this conversion process leaves the quantum properties of the photons untouched. The high over-all efficiency of 32% for this conversion interface makes it well suited for an application in long-range quantum transmission links.