The aim of this JRP is to develop deterministic, compact and efficient single-photon sources (SPS) for needs of cutting edge quantum optical technologies such as quantum communication, quantum computation and quantum metrology. Such a high-impact single-photon source would indeed be a new standard source for the whole quantum optical technology field. This project harness the excellence in quantum metrology at national metrology institutes and the technological and theoretical excellence of leading academic researchers to realise highly efficient single-photon sources far beyond the state of the art and to carry out high precision measurements exceeding classical limits. The sectors that would benefit most include academic institutions and companies working in fields closely related to quantum information processing, especially quantum communication.