Conventional continuous-variable quantum key distribution systems typically rely on discrete optical components, which have limited integration, are bulky and expensive. To overcome these drawbacks, photonic integrated circuit technology is a viable alternative that promises to increase the system integration. However, variable optical attenuators compatible with established photonic integration processes have stability difficulties that limit the performance of the system. This work provides a chip-based variable optical attenuator based on Mach-Zehnder interferometer structure. By using an unbalanced interferometer arm, the sensitivity of the optical attenuation coefficient to environmental fluctuations can be reduced, ensuring the high-precision control required for continuous-variable quantum key distribution systems. Our scheme will facilitate the implementation of a reliable and highly stable chip-based continuous-variable quantum key distribution system.
Conventional continuous-variable quantum key distribution systems typically rely on discrete optical components, which have limited integration, are bulky and expensive. To overcome these drawbacks, photonic integrated circuit technology is a viable alternative that promises to increase the system integration. However, variable optical attenuators compatible with established photonic integration processes have stability difficulties that limit the performance of the system. This work provides a chip-based variable optical attenuator based on Mach-Zehnder interferometer structure. By using an unbalanced interferometer arm, the sensitivity of the optical attenuation coefficient to environmental fluctuations can be reduced, ensuring the high-precision control required for continuous-variable quantum key distribution systems. Our scheme will facilitate the implementation of a reliable and highly stable chip-based continuous-variable quantum key distribution system.
Quantum key distribution allows secret key generation with information theoretical security. It can be realized with photonic integrated circuits to benefit the tiny footprints and the large-scale manufacturing capacity. Continuous-variable quantum key distribution is suitable for chip-based integration due to its compatibility with mature optical communication devices. However, the quantum signal power control compatible with the mature photonic integration process faces difficulties on stability, which limits the system performance and causes the overestimation of a secret key rate that opens practical security loopholes. Here, a highly stable chip-based quantum signal power control scheme based on a biased Mach-Zehnder interferometer structure is proposed, theoretically analyzed, and experimentally implemented with standard silicon photonic techniques. Simulations and experimental results show that the proposed scheme significantly improves the system stability, where the standard deviation of the secret key rate is suppressed by an order of magnitude compared with the system using traditional designs, showing a promising and practicable way to realize a highly stable continuous-variable quantum key distribution system on chip.
Quantum key distribution (QKD) is a quantum communication technology that offers absolute security. Among its various implementations, continuous-variable (CV) QKD has garnered significant attention due to its high secret key generation rates and compatibility with conventional optical telecommunication infrastructure, which operates under ambient conditions. However, chip-based integration is crucial for realizing practical and scalable CV-QKD networks, and photonic integrated circuit technology is a potential solution, leveraging the on-chip integration of essential optical components onto silicon photonic circuits. Therefore, this work presents a compact, stable, and cost-effective quantum photonic CV-QKD system on a chip. Our architecture combines time- and polarization-multiplexing with high-extinction-ratio pulse generation to mitigate excess noise. At the same time, a real-time feedback control mechanism compensates for polarization drift, ensuring robust system performance. Fiber-based evaluations reveal secret key generation rates of 2.55 Mbps over 25 km and 0.737 Mbps over 50 km with 12 h stable operation, establishing, to our knowledge, a new benchmark for integrated photonic CV-QKD systems with both the transmitter and receiver on-chip. These results mark a significant milestone in on-chip quantum communication, paving the way for widespread adoption of photonic integrated circuits in future metropolitan quantum-secure networks.
Quantum key distribution, which ensures information-theoretically secret key generation, is currently advancing through photonic integration to achieve high performance, cost reduction, and compact size, thereby facilitating the large-scale deployment. Continuous-variable quantum key distribution is an attractive approach for photonic integrations due to its compatibility with off-the-shelf optical communication devices. However, its chip-based systems have encountered significant limitations primarily related to the shot-noise-limited receiver design, which demands low noise, wide bandwidth, high clearance, and well stability. Here, we report the implementation of a real local oscillator continuous-variable quantum key distribution system with an integrated silicon photonic receiver chip. Thanks to the well-designed chip-based homodyne detectors with a bandwidth up to 1.5 GHz and a clearance up to 7.42 dB, the transmission distance of the system has been extended to 28.6 km, achieving a secret key generation rate of Mbps level. This technological advancement enables the quantum key distribution systems with photonic integrated receivers to achieve the coverage in both access network scenarios and short-distance metropolitan interconnections, paving the way for the development of the next-generation quantum key distribution networks on a large scale.
Continuous-variable quantum key distribution (CV-QKD) technology has the characteristics of high channel capacity and well compatibility with existing optical communication infrastructures, and has become an important implementation method of quantum secure communication. Quantum photonics technology provides a promising solution for the construction of low-cost, miniaturized, portable, scalable and highly stable CV-QKD systems that can be deployed at large scale [1]. Therefore, it is of great significance to research and build a chip-based CV-QKD system with higher integration, higher system performance and higher practical security for the development of high-performance and practical quantum secure communication technology. This paper mainly reports the latest progress of the research of on-chip CV-QKD system in terms of system practical security [2] and integration of high-performance light sources [3].
Continuous-variable quantum key distribution (CV-QKD) enables secure communication over standard telecom infrastructure, but scaling is stalled by bulky, discrete optical hardware. We address this bottleneck by demonstrating a real-time CV-QKD system driven by a chip-scale hybrid transmitter using commercial telecom components. Combining a micro-optic external-cavity laser with a monolithic photonic integrated IQ modulator we enable secure secret-key generation over 102 km of optical fiber while reducing optical volume by 95% relative to the commercial discrete-component counterpart. Moreover, real-time operation overcomes offline post-processing bottlenecks of experimental setups. This work bridges laboratory demonstrations and field-deployable technology for cost-effective quantum networks.
Integrated quantum key distribution (QKD) systems based on photonic chips have high scalability and stability, and are promising for further construction of global quantum communications networks. On-chip quantum light sources are a critical component of a fully integrated QKD system; especially a continuous-variable QKD (CV-QKD) system based on coherent detection, which has extremely high requirements for the light sources. Here, for what we believe is the first time, we designed and fabricated two on-chip tunable lasers for CV-QKD, and demonstrated a high-performance system based on these sources. Because of the high output power, fine tunability, and narrow linewidth, the involved on-chip lasers guarantee the accurate shot-noise-limited detection of quantum signals, center wavelength alignment of nonhomologous lasers, and suppression of untrusted excess noise. The system’s secret key rate can reach 0.75 Mb/s at a 50 km fiber distance, and the secure transmission distance can exceed 100 km. Our results mark a breakthrough toward building a fully integrated CV-QKD, and pave the way for a reliable and efficient terrestrial quantum-secure metropolitan area network.