Quantum cryptography using continuous variable Einstein-Podolsky-Rosen correlations and quadrature phase amplitude measurements

Summary form only given. We show how such Einstein-Podolsky-Rosen (EPR) correlated beams may be used for quantum cryptography. The high detection efficiencies give a very much reduced overall loss factor, which may make it possible to transmit directly and efficiently a predetermined message, later checking providing a means to check security. In contrast photon-based proposals are limited by poor photon count detection efficiencies, and rely in practice on deciphering a sequence (key) a posteriori from infrequent detected photons.