  We experimentally demonstrate a long-distance quantum communication at 143 km
between the city of Kazan and the urban-type village of Apastovo in the
Republic of Tatarstan by using quantum key distribution prototype providing
high noise-immunity of network lines and nodes due to phase coding in
subcarrier wave. Average secret key generation rate was 12 bits per second with
losses in the line of 37 decibels for a distance of 143 km during 16.5 hours of
continuous field test. The commercialization perspectives of the demonstrated
long-range QKD system are discussed.
