Curator's Take
This article provides the first systematic comparison of single‑qubit QKD protocols under a unified noise‑based metric, pinpointing exactly how much channel error each scheme can tolerate before secret‑key distillation fails. By showing that the six‑state protocol outperforms BB84, B92 and E91 in both noise threshold and post‑selection efficiency, it gives hardware designers a clear target for building more robust quantum communication links. The results also bridge the gap between theoretical security proofs and practical QBER limits, helping operators decide which protocol offers the best trade‑off between implementation complexity and real‑world resilience.
— Mark Eatherly
Summary
We investigate the resilience to noise of single-qubit quantum key distribution (QKD) protocols in the scenario of security against independent eavesdropping attacks and key distillation based on one-way classical communication. To this end, we introduce a noise-based metric that quantifies the efficiency of QKD protocols. Within this framework, we analyze the maximal noise levels that allow Alice and Bob to asymptotically establish a secure secret key. Using this assumption, we compare the noise tolerance of general single-qubit QKD protocols, in particular the BB84, B92, E91, and six-state protocols. Our main result determines the noise level threshold for QKD allowing one to distill an asymptotically secure secret key. Additionally, we demonstrate that the six-state protocol achieves the greatest resistance to noise while simultaneously yielding a higher post-selection efficiency than the other analyzed single-qubit protocols, confirming its robustness within the considered security model. Finally, we perform an analysis of the proposed noise-based metric and the conventional quantum bit error rate (QBER) metric.