Professor Berge Englert
Quantum Information Technology Group
National University of Singapore

"The Singapore Protocol for Quantum Cryptography"

A minimal scheme for qubit tomography enables one to realize a novel qubit protocol for quantum key distribution -- the Singapore Protocol, which is fully tomographic and more efficient than other tomographic protocols. Under ideal circumstances the efficiency is log_2(4/3)=0.415 key bits per qubit sent, which is 25% more than the efficiency of 1/3=0.333 for the standard 6-state protocol. One can extract 0.4 key bits per qubit by a simple two-way communication scheme, and can so get close to the informationtheoretical limit.

I'll discuss the noise thresholds for secure key bit generation in the presence of unbiased noise.