Multistage quantum swapping of vacuum-one-photon entanglement

Vacuum-one-photon entanglement can serve as an alternative to many protocols implemented by two-photon states, and also exhibits its own practical advantages. Quantum swapping plays a central role in both constructing photonic quantum computers and quantum networks. However, the phase-sensitivity in free space makes it very challenging to scale quantum swapping of vacuum-one-photon entanglement up to multistage, especially to large-scale quantum networks. Here, we implement multistage quantum swapping of vacuum-one-photon entanglement on a three-dimensional reconfigurable photonic chip. We also propose and experimentally demonstrate a prototype of a fully connected multipartite network based on multistage quantum swapping. Our results provide an integrated, scalable, and portable solution of multistage quantum swapping, showing the potential as a crucial element of the all-photonic quantum information processing.