Julius Römer

Advancements in quantum computing pose significant threats to the security of conventional encryption standards. Although quantum key distribution systems offer inherent security, they face challenges in achieving practical secret-key rates over long transmission distances (2). Multiplexing schemes can substantially enhance key rates, and integrated photonic chip technologies provide the necessary scalability and system efficiency for high key rates using wavelength-division time-bin protocols. We propose a hybrid sender module that employs on-chip lasers and fast modulators on the indium-phosphide platform for qubit state preparation. The multiplexer is fabricated on a low-loss silicon nitride chip, utilizing ring resonators and Bragg reflectors. We report progress in developing a sender module designed to achieve secret key rates in the gigabit per second range. Additionally, the system is compatible with a receiver that integrates waveguide-based superconducting nanowire single-photon detectors with on-chip de-multiplexing, ensuring high detection efficiency and key rates (1). This design supports the implementation of protocols such as the one-decoy state time-bin BB84 protocol and promises further scalability.