  Quantum key distribution (QKD) provides theoretic information security in
communications based on the laws of quantum physics. In this work, we report an
implementation of quantum-secured data transmission in the infrastructure of
Sberbank of Russia in standard communication lines in Moscow. The experiment is
realized on the basis of already deployed urban fiber-optics communication
channels with significant losses. We realize the decoy-state BB84 QKD protocol
using the one-way scheme with polarization encoding for generating keys.
Quantum-generated keys are then used for continuous key renewal in the hardware
devices for establishing a quantum-secured VPN Tunnel between two offices of
Sberbank. The hybrid approach used offers possibilities for long-term
protection of the transmitted data; it is promising for integrating into the
already existing information security infrastructure.

Quantum Physics;Cryptography and Security