Aboobackkar Sidhique

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 the first fully photonic-integrated continuous-variable QKD (CVQKD) 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 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 the highest reported secure key rate to date, reaching 0.289 Gb/s and 0.246 Gb/s over a 20 km fiber link in the asymptotic and finite-size regimes, respectively. These results establish a record key rate and represent a critical step toward scalable, cost-effective, and mass-deployable quantum-secure communication using photonic-integrated CVQKD systems.

Continuous-variable quantum key distribution (CV-QKD) has attracted enormous attention in recent years due to its capability to achieve high secret key rates and ease of integration with existing telecom infrastructure. While squeezed-state CV-QKD offers significant advantages over coherent-state protocols, its practicality has remained limited by the bandwidth of traditional squeezers and bulk optical components. In this work, we demonstrate a high-speed squeezed-state CV-QKD system that employs a silicon-photonics integrated transmitter and a photonic–electronic integrated receiver based on a CMOS transimpedance amplifier, together with a broadband single-pass squeezed-light source. Operating at 500 MBaud, our system achieves a finite-size secret key rate of 2.3 Mbit/s over a 10 km fibre channel. This result demonstrates a clear path toward high-speed, scalable, and practical squeezed-state CV-QKD implementations.