Toshiba Europe Limited and Quantum Bridge Technologies (QBT) have demonstrated an international network capable of quantum-safe data transmission. The project combines Toshiba’s Quantum Key Distribution (QKD) technology with QBT’s Distributed Symmetric Key Establishment (DSKE) platform and was implemented on existing field-installed fibre infrastructure.
The demonstration, presented at the Optical Fiber Communication Conference 2026, shows how metropolitan QKD networks can be connected across continents using DSKE. The approach uses carrier-grade infrastructure and emerging interoperability standards to enable communication across long distances with a focus on maintaining security in the context of quantum computing developments.
The network is based on information-theoretic security (ITS), also known as provable security. This approach is designed to protect sensitive data regardless of an attacker’s computational resources, including future advances in supercomputing and quantum computing.
While QKD is deployed in metropolitan networks worldwide, extending it across continents presents challenges, including the lack of ultra-long-distance fibre QKD systems and limited availability of satellite-based QKD.
One approach to linking geographically separated QKD networks is post-quantum cryptography (PQC), which uses algorithms designed to resist quantum computing attacks. PQC is based on computational assumptions that may evolve over time.
QBT’s DSKE technology provides an alternative approach for long-distance connections. It uses symmetric cryptography, secret sharing, and pre-shared entropy to establish keys without relying on public-key infrastructure. This enables long-haul links designed to maintain a level of security comparable to QKD networks.
For the demonstration, a QKD network in Cambridge was connected to a QKD network in Toronto. The systems were hosted in Telehouse Canada data centres and connected using existing fibre infrastructure, demonstrating operation within carrier-grade environments.
The project also incorporated interoperability standards from the European Telecommunications Standards Institute (ETSI) Industry Specification Group on QKD. It used the ETSI GS QKD 020 Interoperable Key Management Specification to enable communication between key-management systems in QKD and DSKE platforms, supporting interoperability between different vendors.
