Method for generating heralded single-photons

It is claimed a method for the generation of heralded single photons with a heralded-photon frequency-mode fh comprising the stepsi) generation of correlated photon pairs, whereas each photon pair comprises a signal photon ps with a signal frequency-mode fs and an idler photon pi with an idler frequency-mode fi, whereas the signal photon ps and the idler photon pi of each photon pair are correlated in the frequency-mode,ii) frequency-to-time multiplexing of the signal photon ps, in order to delay the signal photon ps by a time τ depending on the signal frequency-mode fs,iii) detection of the time τ of the signal photon ps by a detection means,iv) frequency shift of the idler-frequency-mode fi according to the time τ, in order to shift the idler-frequency mode fi of the idler photon pi into the heralded-photon frequency-mode fh, preferably by a frequency shift means.