16
January 2003
Cryptography: Key step
No form of cryptography is of any use unless the key to unlock it can be securely transmitted. Conventional key distribution methods are vulnerable to interception by powerful computers, hence the interest in quantum key distribution. This maximizes security by exploiting a basic principle of quantum physics, that observation causes perturbation. Most current quantum key distribution techniques use single photon counting, but attention is switching to systems based on continuous variables. A new protocol, based on the transmission of laser pulses containing a few hundred photons, is described this week, and a proof-of-principle experiment shows its potential. Single photon detection has been the factor limiting the rate of key distribution, so this new approach may be a significant step towards practical quantum cryptography.
Quantum key distribution using gaussian-modulated coherent
states
FR�D�RIC GROSSHANS, GILLES VAN ASSCHE, J�RÔME
WENGER, ROSA BROURI, NICOLAS J. CERF & PHILIPPE GRANGIER
Nature
421, 238–241 (2003); doi:10.1038/nature01289
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Quantum cryptography: Code-breakers confounded
MARK HILLERY
Coherent-state quantum cryptography holds
the promise of efficient, secure communication. An experimental demonstration
shows that a secure key to the code can be exchanged, even if there is a large
transmission loss.
Nature 421, 224–225 (2003); doi:10.1038/421224a
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