QUANTUM CRYPTOGRAPH USING POLARIZATION FEEDBACK

A system for quantum cryptography using polarization-preserving optica l fibre and a feedback loop to compensate for time-dependent changes i n the state of polarization has been implemented. Error rates of less than 0.5% have been demonstrated and much lower error rates can be exp ected in the future. An improved system that does not require the use of polarization-preserving fibre, and with expected data transmission rates of 100 kHz, is under construction.