Integrating quantum key distribution (QKD) and classical optical communication for large-scale applications presents a significant challenge due to high cost and complexity. In this paper, we experimentally demonstrate the feasibility of simultaneous continuous-variable QKD (CV-QKD) and classical optical communication over a shared infrastructure. Through high-linearity modulators and detectors, we validated classical quadrature phase shift keying communication and CV-QKD protocol on a single platform by time-division multiplexing technology. Experimental results show that the classical communication achieved a bit rate of 200 Mbits/s, and the CV-QKD protocol achieved a secret key rate of 1.12 Mbits/s at 6 dB channel attenuation. This work reveals the feasibility of using a shared optical module to realize classical and quantum communication, leading to simplified integrating QKD and classical communication infrastructure.
Integrating quantum key distribution (QKD) and classical optical communication for large-scale applications presents a significant challenge due to high cost and complexity. In this paper, we experimentally demonstrate the feasibility of simultaneous continuous-variable QKD (CV-QKD) and classical optical communication over a shared infrastructure. Through high-linearity modulators and detectors, we validated classical quadrature phase shift keying communication and CV-QKD protocol on a single platform by time-division multiplexing technology. Experimental results show that the classical communication achieved a bit rate of 200 Mbits/s, and the CV-QKD protocol achieved a secret key rate of 1.12 Mbits/s at 6 dB channel attenuation. This work reveals the feasibility of using a shared optical module to realize classical and quantum communication, leading to simplified integrating QKD and classical communication infrastructure.
Since the working conditions of classical and quantum signals are very different, how to effectively integrate classical and quantum communication networks without affecting their respective performance has become a great challenge.In this paper, we proposed a scheme to realize classical communication and continuous-variable quantum key distribution (CV-QKD) based on frequency-division multiplexing (FDM), and we verified the feasibility of simultaneously realizing CV-QKD and classical optical communication data synchronous transmission scheme under the same infrastructure.We achieved a 0 bit error rate in 50 frames and a 20 Mb/s bit rate for the classical signal and an average secret key rate of around 5.86 × 10 5 bit/s for the quantum signal through a 4 dB fiber channel.This work provides a scheme to establish a QKD channel by only reserving a small passband in the entire optical communication instead of an entire wavelength, increasing efficiency and simplifying the integration of QKD and classical communication.
Integrating quantum key distribution (QKD) with classical data transmission over the same fiber is crucial for scalable quantum-secured communication. However, noise from classical channels limits QKD distance. We demonstrate the longest-distance continuous-variable QKD (CV-QKD) over 120 km (20 dB loss) in the asymptotic regime, and over 100 km (17 dB loss) in the finite-size regime, both coexisting with a fully populated coarse wavelength division multiplexing system. Natural mode filtering of the local oscillator and phase noise mitigation enabled this without additional filtering or wavelength reallocation. Benchmarking against a commercial discrete-variable QKD system and considering finite-size effects confirms the feasibility of CV-QKD as a plug-and-play solution for typical 80-100 km long-haul optical networks. Our results set a record fiber distance for CV-QKD, showing its potential for cost-effective, large-scale deployment in existing network infrastructure.
Future quantum communication infrastructures will need to serve heterogeneous users on shared physical channels: short-range, high-throughput links favor Continuous-Variable Quantum Key Distribution (CV-QKD), while long-reach, high-loss links remain the domain of Discrete-Variable QKD (DV-QKD). Wavelength-division multiplexing (WDM) of the two protocols on a common channel would address both regimes simultaneously, but their markedly different noise sensitivities make coexistence non-trivial and, to date, experimentally untested. Here we report the first simultaneous operation of two independent CV- and DV-QKD systems on a common optical channel, using standard C-band DWDM filters at 1550.12 nm (CV) and 1545.32 nm (DV). We demonstrate joint operation on both optical fiber and a 620 m urban daylight free-space link. On fiber, the two systems exhibit the expected complementarity, crossing over at 7.56 dB of channel loss where both deliver $\sim$1.43 Mbit/s; in daylight free-space, both sustain Mbit/s key rates under time-varying atmospheric attenuation. Across all configurations we observe no measurable multiplexing-induced penalty in QBER or excess noise. These results establish hybrid CV-DV WDM as a practical building block for heterogeneous quantum communication networks, where metropolitan high-throughput users and long-reach backbone links can be served on a single physical infrastructure.
Classical communication and quantum key distribution (QKD) share similarities in signal modulation, transmission, and reception, providing a foundation for their integration. This paper proposes a novel protocol for simultaneous quantum and classical communication in short-distance Continuous-Variable QKD (CV-QKD). The protocol employs polarization-state encoding of classical information with weak coherent states, allowing for the concurrent transmission of quantum and classical data without the need for classical optical pulses. A noise model is established to analyze the system’s excess noise under varying modulation variances, along with the performance of both classical and quantum communication. Simulation results indicate that our proposed protocol can achieve a secure key rate of no less than 1.05Mbps over a distance of 20km.
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.