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arXiv:quant-ph/9907073 · Physical Review A

Continuous variable quantum cryptography

Timothy C. Ralph

Published Dec 8, 1999• 644 citations
arXivHTMLPDF

Abstract

We propose a quantum cryptographic scheme in which small phase and amplitude modulations of cw light beams carry the key information. The presence of Einstein-Podolsky-Rosen type correlations provides the quantum protection.
DOI
10.1103/physreva.61.010303

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Correlations of the type discussed by EPR in their original 1935 paradox for continuous variables exist for the quadrature phase amplitudes of two spatially separated fields. These correlations were first experimentally reported in 1992. We propose to use such EPR beams in quantum cryptography, to transmit with high efficiency messages in such a way that the receiver and sender may later determine whether eavesdropping has occurred. The merit of the new proposal is in the possibility of transmitting a reasonably secure yet predetermined key. This would allow relay of a cryptographic key over long distances in the presence of lossy channels.
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