- The paper demonstrates a comprehensive field test of QKD in Tokyo, achieving secure key rates of up to 304 kbps over a 45 km fiber link.
- The paper details the integration of diverse QKD protocols within a three-layer network architecture that enables rapid rerouting upon eavesdropping detection.
- The paper underscores the operational resilience of quantum cryptography, showing long-term stability with systems operating continuously for months.
Overview of the Quantum Key Distribution Field Test in the Tokyo QKD Network
The paper presents a comprehensive field trial of Quantum Key Distribution (QKD) in a metropolitan area network, specifically the Tokyo QKD Network. This initiative integrated diverse QKD systems, showcasing a secure communication network capable of underpinning applications such as TV conferencing and secure mobile phones over a 45 km distance. The field test aims to exhibit the practical viability and operational stability of QKD in environments characterized by significant infrastructural constraints.
Composition of the Tokyo QKD Network
The Tokyo QKD Network leverages the Japan Giga Bit Network 2 plus (JGN2plus) as its backbone, incorporating four main access points: Koganei, Otemachi, Hakusan, and Hongo. Influencing factors such as high loss due to aerial fiber installations and environmental fluctuations were prominent challenges. The network successfully integrated several QKD approaches, forming a six-node logical mesh network, and demonstrated real-world operability of various QKD technologies and protocols.
Key Outcomes and Architectural Features
In a notable instance of applied QKD, the Mitsubishi link using a decoy-state BB84 protocol managed key distribution across a 24 km span and demonstrated robust and stable key generation for over three days. The ID Quantique (IDQ) system displayed resilience, operating continuously for over six months in a Plug & Play configuration, although requiring additional spectral filtering to mitigate inter-fiber crosstalk.
A standout attribute of the Tokyo QKD Network is its three-layer architecture: a quantum layer, a key management layer relying on trusted nodes for secure key relays, and a communication layer. The key management server (KMS) plays a pivotal role in ensuring an uninterrupted secure operation, as exemplified by the rapid rerouting of key distribution paths upon eavesdropping detection.
The NEC-NICT collaboration presented a decoy-state BB84 system equipped with superconducting single-photon detectors (SSPDs) for high-speed operation, achieving a secure key rate of 81.7 kbps despite a 14.5 dB channel loss over a 45 km stretch. Meanwhile, the TREL system noted an average secure bit rate of 304 kbps over the same distance, representing a significant leap in QKD performance compared to prior trials, attributable to innovations like gated photon detection.
Implications and Future Directions
This field trial signals a promising horizon for the deployment of QKD in metropolitan networks. The Tokyo QKD Network's success in facilitating real-time secure communication through QKD underlines the technology's readiness for high-security applications that have traditionally depended on physical courier exchanges for key management.
Further research is imperative to address real-world implementation challenges such as side-channel attacks. The need for standardized protocols can be addressed through collaborative efforts with global QKD testbeds, contributing to a unified framework for QKD deployment. Emphasis should also be placed on integrating QKD within broader photonic networks and exploring additional cryptographic functions, such as digital signatures backed by quantum security.
Conclusion
The Tokyo QKD Network field test stands as an illustrative benchmark in QKD application, showcasing both the operational feasibility and the obstacles inherent in large-scale deployment. The initiative's success sets a viable precedent for future research and standardization efforts directed toward the maturation of QKD technology, offering a secure foundation for a myriad of cryptographic services.