Analysis of a rate-adaptive reconciliation protocol and the effect of the leakage on the secret key rate

TL;DR

This paper analyzes a rate-adaptive reconciliation protocol in quantum key distribution, demonstrating that despite increased message length, it limits information leakage and enhances the secret key rate in fluctuating channels.

Contribution

It provides a theoretical and simulation-based analysis of a rate-adaptive protocol, showing limited entropy reduction and improved secret key rates under channel fluctuations.

Findings

Limited min-entropy reduction despite larger message exchanges

Increased secret key rate in fluctuating channels

Effective adaptation improves key distillation

Abstract

Quantum key distribution performs the trick of growing a secret key in two distant places connected by a quantum channel. The main reason is that the legitimate users can bound the information gathered by the eavesdropper. In practical systems, whether because of finite resources or external conditions, the quantum channel is subject to fluctuations. A rate adaptive information reconciliation protocol, that adapts to the changes in the communication channel, is then required to minimize the leakage of information in the classical postprocessing. We consider here the leakage of a rate-adaptive information reconciliation protocol. The length of the exchanged messages is larger than that of an optimal protocol; however, we prove that the min-entropy reduction is limited. The simulation results, both on the asymptotic and in the finite-length regime, show that this protocol allows to increase the amount of distillable secret key.