Secret key rate-adaptive inter-domain key service provisioning in heterogeneous protocol-based multi-domain quantum networks

Quantum key distribution (QKD), as one of the pivotal technologies for future-proof security, is progressing toward large-scale networking. Since different QKD protocols have their own potential advantages and shortcomings, the interconnection of metropolitan quantum networks based on heterogeneous protocols is an important step to realize a wide-area quantum network. In this scenario, the provision of inter-domain key services still faces challenges in terms of success probability, security level, and the balance between key supply and demand. Targeting these challenges, this work proposes four secret key rate (SKR) adaptive inter-domain key service provisioning policies based on the dynamic node bypass and elastic SKR slicing, namely, IrB-IaB (inter-domain bypass and intra-domain bypass), IrS-IaS (inter-domain slicing and intra-domain slicing), IrB-IaS (inter-domain bypass and intra-domain slicing), and IrS-IaB (inter-domain slicing and intra-domain bypass). The proposed policies are applicable to multi-domain quantum networks with heterogeneous protocols such as GG02-based metropolitan and BB84-based inter-domain connections, as well as BB84-based metropolitan and TF-based inter-domain connections. Furthermore, the inter-domain key service provisioning model is formulated, and four corresponding SKR-adaptive inter-domain key service provisioning algorithms are designed. Simulation results show that the IrS-IaS algorithm performs better in terms of success probability as well as the equilibrium degree between key supply and demand. The security level is quantitatively evaluated through the number of trusted relays. The IrB-IaB algorithm achieves the lowest number of trusted relays, which is more than 20% lower than the benchmark algorithm, resulting in a higher security level and lower cost. The key resource utilization efficiency is assessed via the equilibrium degree. Both the IrB-IaS and IrS-IaB algorithms have the potential to balance the effectiveness and reliability of quantum networks. In particular, the IrS-IaB algorithm is beneficial in achieving the best trade-off between key resource utilization efficiency and security level.