QKD Post-Processing: Choosing Reconciliation Codes and a GUI to Validate Them

Quantum Key Distribution hardware is shrinking, but the post-processing stack still decides whether you get a usable key rate. This arXiv tutorial (2611.09182) surveys the four main information-reconciliation families — Cascade, Winnow, LDPC, and polar codes — and ties each to asymptotic and finite-size secret key rate (SKR) bounds. It also ships a server-client reference implementation with a GUI so you can sweep QBER, block size, and code parameters without touching FPGA firmware. What to try first Start with the GUI. Load the provided DV-QKD presets, set your expected channel QBER (typically 1–5% for deployed fiber), and compare SKR across the four algorithms at your target block length. Cascade and Winnow are interactive and easier to debug; LDPC and polar codes need careful degree-profile or frozen-bit selection but scale to higher throughput. The GUI outputs per-stage latency (sifting → reconciliation → privacy amplification → authentication), which is often