Measurement-device-independent quantum key distribution for nonstandalone networks

Untrusted node networks initially implemented by measurement-device-independent quantum key distribution(MDI-QKD)protocol are a crucial step on the roadmap of the quantum Internet.Considering extensive QKD implementations of trusted node networks,a workable upgrading tactic of existing networks toward MDI networks needs to be explicit.Here,referring to the nonstandalone(NSA)network of 5G,we propose an NSA-MDI scheme as an evolutionary selection for existing phase-encoding BB84 networks.Our solution can upgrade the BB84 networks and terminals that employ various phase-encoding schemes to immediately support MDI without hardware changes.This cost-effective upgrade effectively promotes the deployment of MDI networks as a step of untrusted node networks while taking full advantage of existing networks.In addition,the diversified demands on security and bandwidth are satisfied,and network survivability is improved.