Experimental studies in quantum cryptography

A short survey on experimental works in quantum cryptography is presented. We describe experimental setups that were designed in the Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, for quantum key distribution through an air space and along a fiber-optic communication line. The results of the study of quantum efficiency parameters, probability of afterpulse appearance, and noise levels for different operation modes of InGaAs-InP avalanche photodiodes are presented.