Quantum Decoding Integrated Chip for Quantum Key Distribution Based on Silica Planar Lightwave Circuit Technology

Silica-based planar lightwave circuit (PLC) devices can offer great potential for quantum key distribution (QKD) with the benefits of low-loss, low-cost, large-scale integration, miniaturization, stability and mass production. A quantum decoding integrated chip for QKD based on silica PLC technology was demonstrated, which consists of a variable optical splitter (VOS), an asymmetric Mach-Zehnder interferometer (AMZI) with a thermo-optic phase modulator (TOPM) and a delay line (DL) whose delay time is 400ps, and a variable directional coupler (VDC). The balanced pulse-pairs of double channels with measured delay times of 396ps and 398ps respectively were obtained in the conditions of both classical optics and single-photon transmissions. The chip has advantageous to achieve high interference visibilities of double channels simultaneously for BB84 phase and time-bin protocols.