Researchers at Shanghai Jiao Tong University demonstrated continuous-variable quantum key distribution (QKD) across a network combining different communication channels. The experiment utilized a setup with both fiber optic cables and free-space links, extending QKD beyond isolated laboratory conditions. This work, published on September 9, 2026, in Quantum Science and Technology, tested a basis-encoding QKD protocol alongside traditional methods to improve performance in complex access networks. The demonstration included four users and verifies the feasibility of this scheme in a hybrid-channel environment.
QPSK-BE-QKD Protocol Demonstrated in Heterogeneous Access Network
The demonstrated network successfully integrated both free-space and fiber optic channels, a configuration reflecting the complexities of real-world deployments and moving beyond the limitations of single-medium quantum communication tests. This experimental setup, detailed in Quantum Science and Technology, utilized a quadrature phase shift keying (QPSK) modulation scheme within a basis-encoding quantum key distribution (BE-QKD) protocol to achieve secure communication. The team’s work addresses a gap in current CVQKD systems, which often struggle with performance in networks featuring hybrid channels and multiple users.
The experiment’s design incorporated a heterogeneous network with four users connected via two free-space links and two fiber optic channels, allowing assessment of the QPSK-BE-QKD protocol’s resilience across varying transmission conditions. Traditional CVQKD protocols often face performance limitations when applied to such complex, multi-user environments, making this configuration significant. The researchers specifically focused on demonstrating the compatibility of the QPSK-BE-QKD protocol with the more established QPSK-CVQKD protocol.
The results confirmed this compatibility, suggesting a smoother transition for networks seeking to adopt the new protocol. Performance metrics revealed the QPSK-BE-QKD protocol’s ability to mitigate channel loss and maintain secure key rates, critical factors for long-distance quantum communication. This resilience is particularly important for building large-scale quantum networks capable of supporting numerous users and diverse applications, and the study highlights the protocol’s potential advantages in quantum access networks where signal degradation is a significant challenge.
The research team, affiliated with the State Key Laboratory of Photonics and Communications at Shanghai Jiao Tong University, also included collaborators from the Shanghai Research Center for Quantum Sciences and Hefei National Laboratory. Shanghai XunTai Quantech Co., Ltd. also contributed to the work.
The acceptance of the paper on August 28, 2026, indicates a recent advancement in the field, suggesting the technology is nearing a stage of potential deployment. The demonstrated scheme is designed for easy integration into existing CVQKD access networks, reducing the barriers to adoption and accelerating the development of large-scale quantum communication infrastructure.
The findings suggest a new implementation paradigm for CVQKD networks operating in complex and hybrid channel environments, offering a pathway toward more robust and scalable quantum communication systems. The researchers believe this approach will be instrumental in building the next generation of secure communication networks capable of safeguarding sensitive data in an increasingly interconnected world.
Shanghai Research Center for Quantum Sciences is a collaborative initiative established in 2018 to coordinate quantum research across Shanghai’s leading universities, including Fudan University and Shanghai Jiao Tong University. Headquartered in Shanghai, China, the center functions as a consortium, bringing together multiple institutions to advance shared goals in quantum science. Its core activities involve providing shared research infrastructure and facilitating collaboration between researchers, with a long-term aim to develop quantum talent and establish Shanghai as a leading global research hub.
This work by researchers at Shanghai Jiao Tong University builds on the broader objectives of the Shanghai Research Center for Quantum Sciences by demonstrating progress in practical quantum communication. The center’s support for collaborative projects allows teams to tackle complex challenges in the field, such as extending quantum communication beyond isolated laboratory settings and into more realistic network configurations. As of August 2nd, 2026, the consortium continues to support research aimed at developing the infrastructure and expertise needed for future quantum technologies.
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