Quantum distribution of Gaussian keys using squeezed states -: art. no. 052311

A continuous key-distribution scheme is proposed that relies on a pair of conjugate quautum variables. It allows two remote Parties to share a secret Gaussian key try encoding it into one of the two quadrature components of a single-mode electromagnetic field. The resulting quantum cryptographic information versus disturbance trade-off is investigated for an individual attack based on the optimal continuous cloning machine. It is shown that the information gained by the eavesdropper then simply equals the information lost by the receiver.