# Service for Deploying Digital Twins of QKD Networks
## 6 Conclusions and Future Work  
Quantum networks are a novel research topic expected to change and evolve significantly in the next years, bringing many scientific and security-related advantages. Awaiting the hardware to be good enough for feasible and accessible deployment of QKD networks, emulation services are a valuable option for testing and experimenting with QKD-related subjects. In this context, we have designed, implemented, and validated a solution that allows the automatic deployment of QKD networks digital twins [12]. The service virtualizes the sites of a QKD network in virtual machines, offering a cost-effective solution to the problem of physically building a QKD network. A QKD protocol is implemented using an open-source quantum emulator, SimulaOron, and a standardized API, the ETSI GS QKD 004 [27], is included to enable the communication between clients and networks, making the digital twin environment very similar to a real QKD network. The tests that have been carried out show that the service is capable of building QKD network digital twins and making it operational in a reduced time frame that scales linearly with the number of nodes, achieving the deployment of an 8-node network in about 7 min (Figure 12a). The current implementation of the service provides a solid software base on which to build applications that make use of the QKD network digital twin environment, this implementation will be extended with different features to help create more specific applications. The emulated digital twin environment could be a useful tool not only for the development of QKD network technologies but also for the research on the integration of Quantum Communications in the current network since it can potentially be used on larger experiments leveraging on its orchestration features. The presented service is, in summary, a novel solution that allows experimentation over a digital twin, a virtual replica, of a QKD network. This opens the door to many diverse research lines, from the study of the integration of QKD on current infrastructures to the analysis of different strategies for quantum key exchange in multi-domain environments, i.e., environments where there may be networks from different providers. Some updates of the service are expected to be available soon, enabling features such as eavesdropping detection or hybrid deployments. Our work in the short term will include the implementation of the complete E91 protocol, to ensure the realization of tests of the CHSH inequality, and thus enable eavesdropping verification in the communication processes. Other lines of research, such as the support of a backend that takes into account different quantum parameters, like decoherence or quality of entanglement, are already being developed. The deployment of hybrid environments where real and virtualized quantum equipment work together is also being explored. Although the authentication of the channels is not addressed in this first version, the exploration of some options to solve that matter, such as Post-Quantum Cryptography (PQC) algorithms in the IPsec protocol [53] or methods rooted at physical properties [54] like Physical Unclonable Functions (PUFs) [55], is also a line of research that we intend to explore. **Author Contributions:** Software, R.M., B.N. and B.L. ; Validation, R.M. and B.N. ; Investigation, R.M., B.L., I.V., F.V. and B.N. ; Writing--Original Draft Preparation, B.L., R.M., I.V. and B.N. ; Writing--Review and Editing, B.L., I.V., F.V. and B.N. ; Visualization, B.L. ; Supervision, I.V. and F.V. All authors have read and agreed to the published version of the manuscript. **Funding:** The work of [PERSON] has partially been supported by the MCIN with funding from European Union NextGenerationEU (PRTR-C17.II) and funding from the Comunidad de Madrid--Programa de Acciones Complementarias, Madrid Quantum. This publication is also part of the project 6 GINSPIRE PID2022-1373290B-C42, funded by MCIN/AEI/10.13039/501100011033/.