Rateless Protograph LDPC Codes for Quantum Key Distribution
Alberto Tarable, Rudi Paolo Paganelli, Marco Ferrari · IEEE Transactions on Quantum Engineering · 2024
Information Reconciliation (IR) is a key step in Quantum key distribution (QKD). In recent years, blind reconciliation based on low-density parity-check (LDPC) codes has replaced Cascade as a standardde facto, since it guarantees efficient information reconciliation without a priori quantum bit error rate estimation and with limited interactivity between the parties, which is essential in high key-rate and long distance QKD links. In this paper, a novel blind reconciliation scheme based on rateless protograph LDPC codes is proposed. The rate adaptivity, essential for blind reconciliation, is obtained by progressively splitting LDPC check nodes, which ensures a number of degrees of freedom larger than puncturing in code design. The protograph nature of the LDPC codes allows to use the same designed codes with a large variety of sifted-key lengths, enabling a blocklength flexibility, which is important in largely varying key-rate link conditions. The code design is based on a new protograph Discretized Density Evolution tool.