SK Telecom (SKT) and the Korea Institute of Science and Technology Information (KISTI) developed a digital twin that lets operators test a quantum key distribution (QKD) network before installing equipment.

The system, which was unveiled at this year's ECOC optical communications conference, connects SKT’s quantum key manager to a KISTI-developed QKD simulator.

QKD uses quantum signals to establish shared cryptographic keys. Network performance depends partly on physical conditions, including the distance between sites and the amount of light lost along the fiber. Once a network is installed, changing those conditions is difficult, while the cost of QKD equipment makes it impractical to build multiple configurations simply to test them.

The digital twin moves that testing into a virtual environment. When SKT’s key manager requests a key, KISTI’s simulator models a specified QKD link and returns a simulated key along with performance and status information. The partners can then test the process from key generation through management and supply, rather than assessing the simulated link alone.

The simulator can vary transmission distance and optical loss, as well as equipment characteristics such as reception efficiency and post-processing algorithms. SKT says engineers could use the results to decide where to place equipment and how to configure it before deploying a physical network.

Ryu Takki, SKT’s head of network technology, noted in a translated statement that linking the key manager and simulator enables the partners to test “various network environments and key management functions," adding that SKT aims to use the work to develop a scalable operating environment for QKD networks.

SKT built its key manager as a containerized application and deploys it using Kubernetes. That lets it run across different computing environments and scale to accommodate the network conditions and key-management scenarios generated by the simulator. A network control system coordinates the interaction between the two components.

The components communicate through an interface compatible with specifications from the European Telecommunications Standards Institute (ETSI). SKT says the architecture could also connect its key manager to physical QKD equipment through a standards-compatible interface, potentially allowing the use of equipment from other suppliers.

The company describes the ECOC demonstration as the first public integration of a key manager and QKD simulator independently developed by different organizations. The demonstration establishes that those two systems can work together; SKT has not reported a test with another supplier’s physical QKD equipment or published results showing how closely the simulation predicts a deployed network’s performance.

Jungsuk Song, head of KISTI’s Network Future Technology Research Division, said the project provides a basis for testing different QKD environments with an operational key manager. South Korea’s Ministry of Science and ICT supported the work through projects focused on QKD network efficiency and national quantum communications infrastructure.