General many-body entanglement swapping protocol (2506.22430v1)

Abstract: Sharing entangled pairs between non-signaling parties via entanglement swapping constitutes a striking demonstration of the nonlocality of quantum mechanics and a crucial building block for future quantum technologies. In this work, we generalize pair-swapping methods by introducing a many-body entanglement swapping protocol, which allows two non-signaling parties to share general many-body states along an arbitrary partitioning. The shared many-body state retains exactly the same Schmidt vectors as the target state and exhibits typically high fidelity, which approaches unity as the variance of the Schmidt coefficients vanishes. The cost of many-body swapping - arising from postselection in a third-party measurement - is determined by the 3rd R\'enyi entanglement entropy of the partitioning. We provide a proof of concept of the protocol on real quantum hardware and discuss how it enables new functionalities, such as flexible sharing of complex multi-qubit states and fault-tolerant entanglement swapping.