Spectral coherent-state quantum cryptography

A novel implementation of quantum-noise optical cryptography is proposed, which is based on a simplified architecture that allows long-haul, high-speed transmission in a fiber optical network. By using a single multiport encoder/decoder and 16 phase shifters, this new approach can provide the same confidentiality as other implementations of Yuen's encryption protocol, which use a larger number of phase or polarization coherent states. Data confidentiality and error probability for authorized and unauthorized receivers are carefully analyzed.