Integrated silicon photonics chip fabricated by CMOS compatible technology for low-bit-error-rate quantum key distribution

Quantum communication has extremely high security and is a development direction of future communication networks. In this paper, an on-chip path, off-chip polarization encoded quantum key distribution (QKD) chip is designed and fabricated using advanced silicon photonics fabrication technology. Using a special two-dimensional grating, we can convert light of different path states into corresponding polarization states and propagate in fiber. The performance of the basic optics, waveguides, gratings, and Mach-Zehnder interferometers on the chip is characterized. In the demonstrated QKD experiment, the quantum bit error rate is as low as 1.08%. It provides an important device for the future development of advanced integrated quantum information.