The goal of this note is to explain the reconciliation problem for continuous-variable quantum key distribution protocols with a discrete modulation. Such modulation formats are attractive since they significantly simplify experimental implementations compared to protocols with a Gaussian modulation. Previous security proofs that relied crucially on the Gaussian distribution of the input states are rendered inapplicable, and new proofs based on the entropy accumulation theorem have emerged. Unfortunately, these proofs are not compatible with existing reconciliation procedures, and necessitate a reevaluation of the reconciliation problem. We argue that this problem is nontrivial and deserves further attention. In particular, assuming it can be solved with optimal efficiency leads to overly optimistic predictions for the performance of the key distribution protocol, in particular for long distances.

翻译：本文旨在阐述离散调制连续变量量子密钥分发协议中的协商问题。此类调制格式具有吸引力，因为与高斯调制协议相比，它们能显著简化实验实现。以往严重依赖输入态高斯分布的安全性证明已不再适用，而基于熵累积定理的新证明方法应运而生。然而，这些新证明与现有的协商流程并不兼容，因此需要重新评估协商问题。我们认为该问题具有非平凡性，值得进一步关注。特别地，若假设该问题能以最优效率解决，将会导致对密钥分发协议性能（尤其是长距离场景下）过于乐观的预测。