Silicon-based decoder for polarization-encoding quantum key distribution

Silicon-based polarization-encoding quantum key distribution (QKD) has been widely studied, owing to its low cost and robustness. However, prior studies have utilized off-chip devices demodulate the states or perform polarization compensation, given difficulty of fabricating polarized independent components on chip. In this paper we propose a fully chip-based decoder for QKD. The chip realizes state analyzer compensates BB84 protocol without requiring additional hardware. It is based polarization-to-path conversion method that uses splitter-rotator. was fabricated using standard silicon photonics foundry; it compact design suitable mass production. experimental stability test, an average bit error rate 0.59% achieved through continuous operation 10 h any feedback. Furthermore, developed feedback algorithm, enabled automatic compensation fiber drift, which emulated by random scrambler. case QKD demonstration, obtained finite-key secret 240 bps over spool 100 km. This study represents important step toward integrated, practical, large-scale deployment systems.