Practical Cross-Domain Quantum Fair Exchange for Next-Generation Networks via Functional Decoupling

Abstract

Quantum Fair Exchange (QFE) is a critical primitive for secure multi-party cooperation in the emerging distributed Quantum Internet. However, extending QFE to cross-domain scenarios remains challenging. Existing schemes typically rely on centralized Bell State Measurements (BSM) during the fair-exchange phase, which impose stringent hardware and synchronization requirements and become difficult to deploy in wide-area settings due to transmission latency, quantum decoherence, and photon loss. To address these barriers, we propose a practical cross-domain QFE protocol based on Functional Decoupling and Reconstruction. Instead of performing demanding joint measurements on user-encoded quantum states, the proposed protocol decouples the required correlation-extraction functionality into distributed Z-basis measurements and classical result reconstruction. Thus, it obtains the information required by the fair-exchange rule without relying on centralized BSM in the fair-exchange phase, thereby simplifying physical implementation and improving cross-domain feasibility. We analyze the correctness, fairness, security, and efficiency of the proposed protocol under the stated assumptions, and compare its measurement requirements with those of conventional QFE designs. We further validate the core reconstruction logic on real superconducting and NMR quantum processors, and analyze the impact of representative noise models under different encoding strategies and noise regimes. The analytical, experimental, and simulation results show that the proposed scheme preserves the intended fair-exchange functionality while reducing engineering requirements, and that encoding selection affects protocol success under device-specific noise conditions.