QUANTUM CRYPTOGRAPHY WITH POLARIZED PHOTONS IN OPTICAL FIBERS - EXPERIMENT AND PRACTICAL LIMITS

An all-fibre quantum cryptography set-up based on the polarization of single photon pulses is described. The feasibility of establishing a k ey over more than 1 km has been experimentally demonstrated. The limit s due to the topological effects, the birefringence, and the polarizat ion mode dispersion of fibres are discussed. A set-up using only two n on-orthogonal polarization states and polarizers instead of analysers is proposed.