Towards National Quantum Communication in Europe: Planning and Sizing Terrestrial QKD Networks

TL;DR

This paper presents a reproducible methodology for planning and sizing national terrestrial QKD networks in Europe, demonstrated through a case study of Austria, to support secure communication infrastructure development.

Contribution

It introduces a structured approach for estimating the size and components of national QKD networks based on explicit assumptions and a Monte Carlo simulation for Austria.

Findings

Provides first-order estimates for European QKD backbone sizes.

Derives scaling rules for other EU countries based on population and geography.

Offers planning-level references for infrastructure cost and size estimation.

Abstract

The European Union is developing the European Quantum Communication Infrastructure (EuroQCI) as a pan-European network to provide secure communication capabilities across Member States, including governmental and critical-infrastructure domains. While the strategic objective is defined at EU level, the required scale and structure of national quantum key distribution (QKD) networks remain largely unspecified. This work addresses the question of how to plan and size national terrestrial QKD networks to support critical infrastructure and public authorities. We propose a reproducible planning methodology that estimates network size, total fiber length, and the number of required QKD components based on a small set of explicit assumptions. The approach is demonstrated for Austria, where a synthetic but structured network model is constructed and evaluated using Monte Carlo simulation. The model focuses on terrestrial QKD infrastructure and explicitly excludes space-based segments. It estimates endpoint counts, trusted repeater node requirements, and hop-length distributions under realistic operational constraints. The Austrian case is then used as a baseline to derive scaling rules for other EU Member States based on population and geographic extent. The results provide first-order planning estimates for national QKD backbone sizes across Europe. These estimates are not intended as deployment designs but as planning-level references that support early-stage cost assessment and infrastructure dimensioning under the EuroQCI framework.