TOKYO, September 6, 2024 -- Toshiba Corporation, a leading innovator in technologies realizing quantum key distribution (QKD) for secure network communications, has announced two significant advances in essential technologies for establishing global-scale quantum networks: Large-Scale Quantum Key Distribution Network Control Technology, and High-Speed Quantum Key Distribution Technology.

A QKD network is structured into two layers: the Key Management Layer responsible for key management and key distribution route control, and the Quantum Layer, which manages the distribution of quantum keys. Large-Scale QKD Network Control Technology enhances key distribution efficiency in the Key Management Layer, while High-Speed Quantum Key Distribution Technology accelerates key distribution in the Quantum Layer. These technologies will realize faster distribution of keys with higher capacities, and more secure quantum cryptography communications over a wider area. These advances enable the transmission of larger volumes of keys at higher speeds, thereby expanding the reach and operability of quantum communications.

The QKD network is a platform that enables encrypted communications by securely sharing quantum keys across multiple sites in a network of QKD systems. The Key Management Layer ensures the efficient relay of quantum keys through designated sites, which enables secure communications between sites that are not directly linked by QKD systems.

Toshiba’s Large-Scale QKD Network Control Technology integrates an autonomous key data transfer control function at every site in the Key Management Layer, alongside an optimized control function of stored number of key data managed by a centralized server. This combination ensures efficient key distribution and optimal distribution of quantum keys shared throughout the network. Separately, in the Quantum Layer, High-Speed Quantum Key Distribution Technology uses a newly developed optical wavelength multiplexing device to distribute quantum keys from multiple QKD systems over a single optical fiber, which enhances speed and realizes distribution of higher capacity quantum keys.

In the development of Large-Scale QKD Network Control Technology, Toshiba used a simulated QKD network with 16 sites to successfully demonstrate optimal key distribution. For the High-Speed Quantum Key Distribution Technology, three QKD systems were bundled and operated in a laboratory environment using a 45 km fiber, a configuration that significantly improved key distribution speed: from approximately 0.9 Mbps with one system to approximately 2.3 Mbps with the multiplexed systems.