Chip-based 16 GBaud continuous-variable quantum key distribution

Quantum key distribution (QKD) stands as the most successful application of quantum information science, providing information-theoretic security for key exchange. While it has evolved from proof-of-concept experiments to commercial products, widespread adoption requires chip-based integration to reduce costs, enable mass production, facilitate miniaturization, and enhance system performance. Here, we demonstrate a fully photonic-integrated continuous-variable QKD (CV-QKD) system operating at a classical telecom symbol rate of 16 GBaud. Our system integrates a silicon photonic transmitter circuit (excluding the laser source) and a 20 GHz shot-noise-limited photonic–electronic receiver, which features a phase-diverse silicon photonic integrated circuit and custom-designed GaAs pHEMT transimpedance amplifiers. Advanced digital signal processing allows our system to achieve a secure key rate for discrete-modulated coherent state CV-QKD that reaches 0.289 Gb/s and 0.246 Gb/s over a 20 km fiber link in the asymptotic regime and with finite-size parameter estimation, respectively. These results represent a critical step toward scalable, cost-effective, and mass-deployable quantum-secure communication using photonic-integrated CV-QKD systems.