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Quantum Cryptography

Dr. Ping Koy Lam

Reader in Physics, Faculty of Science, The Australian National University

11:30am, Wednesday 6 October 2004, EN318, Engineering Building, Swinburne University

Cryptography is the science of covert communication between parties. Historically there are many dramatic accounts of the battles between cryptographers and cryptanalysts. One group tries to hide a message and the other tries to decipher its meaning. This war has finally ended after the invention of quantum cryptography with the cryptographer winning. Quantum cryptography relies on the use of quantum theory to ensure ABSOLUTE security. In most schemes, the main goal is to remotely generate a "one-time pad" between two communicating parties. Once this one-time pad is generated, absolutely secure communication can be facilitated. In this talk, I will briefly discuss our new Quantum Cryptography Program in the Quantum Optics Group of the Australian National University. Rather than using single photon sources and photon counters, we implement Quantum Key-Distribution using bright laser beams that have coherent state statistics. Work is still in progress but we have seen results hinting at successful generation of one-time pad even when transmission line loss is as high as 90%. One advantage of our system over single photon cryptography is in its orders of magnitude larger communication bandwidth.

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