Quantum Cryptography Using Polarization Feedback

Abstract

A system for quantum cryptography using polarization-preserving optical fibre and a feedback loop to compensate for time-dependent changes in the state of polarization has been implemented. Error rates of less than 0·5% have been demonstrated and much lower error rates can be expected 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.