Analysis of Research Trends in Distance Extension for QKD Network

In QKD (Quantum Key Distribution) network deployments, the inherent quantum characteristics impose distance limitations due to the difficulty in storing quantum information and the lack of intermediate network devices like classical routers or switches. This paper introduces these limitations and examines international efforts to overcome them. While China and Singapore are utilizing satellites to extend QKD transmission range, European countries and Japan are researching hybrid relay methods using post quantum cryptography (PQC) or digital key relay nodes