BB84 Quantum Key Distribution System based on Silica-Based Planar   Lightwave Circuits
  We constructed an optical interferometer for a Bennett-Brassard quantum key distribution system using integrated optics based on planar lightwave circuit technology, and tested its operation and stability. Experimental results show that this interferometer is useful in implementing a practical quantum key distribution system. 
Yoshihiro Nambu, Takaaki Hatanaka and Kazuo Nakamura