A Reconciliation Strategy for Real-Time Satellite-Based QKD

In practical Quantum Key Distribution (QKD) deployments we would like to design QKD solutions that provide for a target QKD key rate, in bits/pulse, at a specified upper-limit on the failure probability. However, in the finite-signalling setting, in which all real-world QKD systems exist, the common practice of achieving such a solution fails to deliver the maximum throughput rate of the classical decoder. This in turn means that the possibility that classical reconciliation becomes the bottleneck of the entire QKD protocol is not minimised. A design strategy that minimises this latter possibility, whilst achieving a target QKD rate with a target ceiling on the failure probability has not been developed - a situation we remedy here. Although our new design strategy detailed here is for LDPC codes and applied to two specific QKD protocols, the same strategy is generally applicable to all classical decoders and all QKD protocols. It is also deployable even in circumstances where the quantum bit error is variable, such as in satellite QKD systems.