Active stabilization of the optical part in fiber optic quantum cryptography

The method of active stabilization of the polarization and other parameters of the optical part of a two-pass fiber optic quantum cryptography has been proposed and implemented. The method allows the completely automated maintenance of the visibility of interference close to an ideal value (V ≥ 0.99) and the reduction of the instrumental contribution to the error in primary keys (QBER) to 0.5%.