Resource-efficient quantum key distribution with integrated silicon photonics

Integrated photonics provides a promising platform for quantum key distribution(QKD)system in terms of miniaturization,robustness,and scalability.Tremendous QKD works based on integrated photonics have been reported.Nonetheless,most current chip-based QKD implementations require additional off-chip hardware to demodulate quantum states or perform auxiliary tasks such as time synchronization and polarization basis tracking.Here,we report a demonstration of resource-efficient chip-based BB84 QKD with a silicon-based encoder and a decoder.In our scheme,the time synchronization and polarization compensation are implemented relying on the preparation and measurement of the quantum states generated by on-chip devices;thus,we need no additional hardware.The experimental tests show that our scheme is highly stable with a low intrinsic quantum bit error rate of 0.50%±0.02%in a 6 h continuous run.Furthermore,over a commercial fiber channel up to150 km,the system enables the realization of secure key distribution at a rate of 866 bit/s.Our demonstration paves the way for a low-cost,wafer-scale manufactured QKD system.

Silicon-based decoder for polarization-encoding quantum key distribution

Silicon-based polarization-encoding quantum key distribution(QKD)has been extensively studied due to its advantageous characteris-tics of its low cost and robustness.However,given the difficulty of fabricating polarized independent components on the chip,previ-ous studies have only adopted off-chip devices to demodulate the quantum states or perform polarization compensation.In the cur-rent work,a fully chip-based decoder for polarization-encoding QKD was proposed.The chip realized a polarization state analyzer and compensated for the BB84 protocol without the requirement of additional hardware,which was based on a polarization-to-path conversion method utilizing a polarization splitter-rotator.The chip was fabricated adopting a standard silicon photonics foundry,which was of a compact design and suitable for mass production.In the experimental stability test,an average quantum bit error rate of 0.59%was achieved through continuous operation for 10 h with-out any polarization feedback.Furthermore,the chip enabled the automatic compensation of the fiber polarization drift when utiliz-ing the developed feedback algorithm,which was emulated by a ran-dom fiber polarization scrambler.Moreover,a finite-key secret rate of 240 bps over a fiber spool of 100 km was achieved in the case of the QKD demonstration.This study marks an important step to-ward the integrated,practical,and large-scale deployment of QKD systems.