Key points are not available for this paper at this time.
Quantum cryptography over 23 km of installed telecommunications fibre using a novel interferometer with Faraday mirrors is presented. The interferometer needs no alignment nor polarisation control and features 99.8% fringe visibility. A secret key of 20 kbit length with an error rate of 1.35% for 0.1 photon per pulse was produced.
Zbinden et al. (1997) studied this question.