Improved one-way rates for BB84 and 6-state protocols

TL;DR

This paper enhances quantum key distribution protocols by combining local randomization and structured block codes, improving error rate bounds for BB84 and 6-state protocols, and demonstrating benefits at small block lengths.

Contribution

It introduces a combined preprocessing scheme that improves error thresholds for BB84 and 6-state QKD protocols, extending previous results.

Findings

Lower bound on 6-state protocol error rate increased to 14.59%.

Iterating the combined preprocessing scheme yields further improvements.

Benefits observed at small block lengths.

Abstract

We study the advantages to be gained in quantum key distribution (QKD) protocols by combining the techniques of local randomization, or noisy preprocessing, and structured (nonrandom) block codes. Extending the results of [Smith, Renes, and Smolin, quant-ph/0607018] pertaining to BB84, we improve the best-known lower bound on the error rate for the 6-state protocol from 14.11% for local randomization alone to at least 14.59%. Additionally, we also study the effects of iterating the combined preprocessing scheme and find further improvements to the BB84 protocol already at small block lengths.