Photonics is among the dew platforms that can reach very high levels of complexity in quantum communication, computation and sensing. This is made possible by the mobility of photons and the large variety of their controllable degrees of freedom. Scaling up optical quantum technologies requires efficient sinle-photon sources delivering no more than one photon per pulse with the highest repetition rate. For many applications the generated photons should be indistinguishable with a high level of fidelity.