Exploitation of quantum physics for information processing offers solutions to some tasks which cannot be solved in classical information science. An important example is the secure distribution of a cryptographic key via a quantum channel. Modern quantum-optic technologies find significant use in quantum communication and quantum information processing. In this paper we will review the principle of quantum key distribution, briefly mention security of real quantum cryptographic devices, side channels, and give examples of particular applications., Miloslav Dušek., and Obsahuje seznam literatury