2004/12/09 by Berthold-Georg Englert, Berthold‐Georg Englert, Englert, Berthold-Georg +10 · 1 citation
Computer Science · Physics and Astronomy · #FOS: Physical sciences #Quantum Computing Algorithms and Architecture #Quantum Information and Cryptography #Quantum Mechanics and Applications #Quantum Physics (quant-ph) #quant-ph
paper · pdf · doi:10.48550/arxiv.quant-ph/0412075
Title modified; 4 pages, 2 figures; v4 is the updated and much extended version of 18/05/08; this is Ref. [30] in quant-ph/0405084 v2
openalex publication_date 2004/12/09 · arxiv created 2008/05/19 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We introduce the Singapore protocol, a qubit protocol for quantum key distribution that is fully tomographic, more efficient than other tomographic protocols, and very robust. Under ideal circumstances the efficiency is log2(4/3)=0.415 key bits per qubit sent. This is 25% more than the efficiency of 1/3=0.333 for the standard six-state protocol, which sets the benchmark. We describe a simple two-way communication scheme that extracts 0.4 key bits per qubit and thus gets close to the information-theoretical limit. The noise thresholds that we report for a hierarchy of eavesdropping attacks demonstrate the robustness of the protocol: A secure key can be extracted if there is less than 38.9% noise.