Element base of quantum informatics II: Quantum communications with single photons

Quantum cryptography can provide almost complete security of the data transmitted in optical telecommunication systems by single photons based on the laws of quantum mechanics. The paper presents a brief overview of the element base and experimental investigations in the field of quantum cryptography and data transmission by single photons in atmospheric and optical fiber quantum communication lines. Two experimental setups for the single-photon quantum key distribution in the atmospheric and optical fiber quantum channels are described. The results of the quantum key distribution experiments performed on them are given.