An industrial-scale adoption of Quantum Key Distribution (QKD) requires the development of practical, stable, resilient and cost-effective hardware that can be manufactured at large scales. In this work we present a high-speed (1.25GHz), field-deployable QKD prototype based on integrated photonics, that is consolidated into standard 19-inch rack compatible units. Through integrated photonics, the system prioritizes autonomous long-term stability in metropolitan settings. The architecture is further simplified by removing the need for chromatic dispersion compensation over metropolitan distances (below 100km). We demonstrate continuous key exchange over more than 4 km of metropolitan optical fiber, where the prototype maintained stable, uninterrupted operation across a measurement spanning more than 12 day-night cycles without manual intervention.
An industrial-scale adoption of Quantum Key Distribution (QKD) requires the development of practical, stable, resilient and cost-effective hardware that can be manufactured at large scales. In this work we present a high-speed (1.25GHz), field-deployable QKD prototype based on integrated photonics, that is consolidated into standard 19-inch rack compatible units. Through integrated photonics, the system prioritizes autonomous long-term stability in metropolitan settings. The architecture is further simplified by removing the need for chromatic dispersion compensation over metropolitan distances (below 100km). We demonstrate continuous key exchange over more than 4 km of metropolitan optical fiber, where the prototype maintained stable, uninterrupted operation across a measurement spanning more than 12 day-night cycles without manual intervention.
As quantum key distribution (QKD) begins to move from laboratories into real-world use cases, some practical aspects need to be addressed before it can be widely adopted. Not least of which is the size and cost of the devices. The semiconductor industry, over the last 50 years, has provided a scalable platform for integrated electronics. Using the same fabrication processes, it is possible to create quantum photonic microchips to entirely replace the optical components needed for QKD. Using both indium phosphide and silicon devices, we can design and fabricate integrated devices to perform QKD with highly competitive speeds and error rates. At the same time, they offer dramatically reduced power requirements, size and costs while offering increased phase stability and inherent scalability. Other recent developments in the field include new protocols to remove the security assumptions about the physical devices used. One such protocol is measurement-device independent QKD (MDI-QKD) which removes all detector side-channels. Combining integrated devices with MDI-QKD, we are working towards developing a practical architecture for metropolitan QKD. Here, we provide a recap of QKD and discuss the current state of integrated QKD devices and their potential applications in metropolitan networks.
Quantum key distribution (QKD) provides information-theoretic security based on the laws of quantum mechanics, offering resistance to future computational threats, including quantum computers. While QKD technology shows great promise, its widespread adoption depends heavily on achieving both high performance and system-level practicality. In this work, we report an integrated silicon photonics-based QKD system that achieves a secret key rate of 1.213Gbits −1 , with composable security and finite-size analysis, over a metropolitan distance of 10 km with polarization multiplexing. Our contributions are twofold. First, at the quantum optical layer, we develop an on-chip quantum transmitter and receiver that operate at 40 Gbaud at room temperature, featuring high-performance balanced homodyne detection using low-noise amplifiers with off-the-shelf RF components. Second, we implement a discrete-modulated continuous variable (DM CV) QKD protocol that simplifies hardware requirements and leverages standard telecommunication components, and design a polar-code-based information reconciliation algorithm specifically optimized for DM CV QKD and amenable to real-time implementation. Our results demonstrate a cost-effective QKD solution that achieves high key rates through integrated photonics operating at room temperature with off-the-shelf RF components and digital signal processing for robust operation. We anticipate that this research will pave the way for large-scale quantum secure networks.
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 (QKD) is the fastest-growing and relatively mature technology in the field of quantum information, enabling information-theoretically secure key distribution between two remote users. Although QKD based on off-the-shelf telecom components has been validated in both laboratory and field tests, its high cost and large volume remain major obstacles to large-scale deployment. Photonic integration, featured by its compact size and low cost, offers an effective approach to addressing the above challenges faced by QKD. Here, we implement a high-performance, integrated local local oscillator continuous-variable (CV) QKD system based on an integrated silicon photonic transmitter and receiver. By employing a high-speed silicon photonic integrated in-phase and quadrature modulator, a low-noise and high-bandwidth silicon photonic integrated heterodyne detector, and digital signal processing, our CV-QKD system achieves a symbol rate of up to 1.5625 GBaud. Furthermore, the system achieves asymptotic secret key rates of 31.05 and 5.05 Mbps over 25.8 and 50.4 km standard single-mode fiber, respectively, using 8-phase-shift keying discrete modulation. Our integrated CV-QKD system with a high symbol rate and long transmission distance paves the way for the quantum secure communication network in metropolitan areas.
Quantum key distribution (QKD) provides information-theoretic security independent of computational assumptions, yet the bulk and cost of current systems hinder large-scale deployment. Although integrated photonic technologies have enabled highly integrated QKD chips, practical QKD transmitters are still predominantly implemented as rack-mounted systems. Here, we demonstrate a highly integrated standalone QKD transmitter that integrates all essential functionalities required for practical QKD operation within a compact platform built around a silicon photonic encoding chip. The transmitter occupies only 167×56×21mm3 (∼0.2dm3), comparable in size to a half-height, half-width PCIe card and more than 30 times smaller in volume than a conventional 1U rack-mounted system. Paired with a conventional discrete-component receiver, it achieves a secure key rate of 219.1 kbps over 51.3 km of standard single-mode fiber, with performance comparable to that of conventional discrete-component implementations. This work bridges the gap between photonic chip integration and deployable QKD hardware, marking an important step toward transitioning QKD transmitters from conventional rack-mounted equipment to compact board-level platforms.
We present a field-deployed quantum key distribution (QKD) link based on energy-time entanglement. Three nodes are connected, bridging the cities of Nice and Sophia Antipolis, by means of commercial grade optical fibers, spanning over a total distance of 50 km. We have built a packaged and resilient source of energy-time entangled photon pairs and implemented remote interferometer stabilization. Moreover, the clocks of the two end users are synchronized exploiting photon-counting techniques only, therefore requiring no dedicated channel. The system runs over the ITU 100-GHz standard telecom grid, through which a secure key rate of 7.0 kbit/s is extracted for one pair of channels. A homemade software performs all the necessary postprocessing procedures enabling to establish secret keys in real time. We present the first fully operational entanglement-based metropolitan QKD system being totally self-sufficient, i.e., requiring no additional overheads to be operated on a conventional metropolitan fiber network.