Digital Engineering for Quantum Communication Networks: A Systematic Review of Models, Simulators, and Testbeds

Research on quantum communication networks has grown rapidly in recent years, driven by progress in quantum devices, simulators, and experimental testbeds. As these systems become more complex, there is increasing interest in digital methods that can support analysis, prediction, and performance assessment without relying exclusively on physical experimentation. Surveying articles from 1984 to 2025, this systematic literature review examines the current state of digitalisation in quantum communication networks. It evaluates how existing tools and studies contribute to the longer-term goal of creating digital twin technologies for quantum systems. Using PRISMA, a structured and transparent review process, the literature is grouped into three categories that reflect different levels of digital representation: digital models, digital shadows, and initial attempts that resemble early digital twin practices. The findings show that the community has developed sophisticated simulation platforms and a wide range of modelling approaches, and that several experimental testbeds already support partial data-driven integration. However, the review also shows that continuous synchronisation between physical quantum networks and their digital counterparts remains largely undeveloped. The study identifies the main technical gaps that prevent deeper cyber-physical integration and outlines research directions that could guide the development of future digital frameworks capable of supporting prediction, optimisation, and system-level evaluation across the full lifecycle of quantum communication networks.