Distributing graph states with a photon-weaving quantum server

Abstract

One of the key aims of quantum networks is the efficient distribution of multipartite entangled states among end users. While various architectures have been proposed, each comes with distinct advantages and limitations. Many designs depend on long-lived quantum memories and deterministic gates, which, while powerful, introduce considerable cost and technical challenges. Experimentally cheaper alternatives that circumvent these constraints are often limited to specific types of entanglement and a specific number of users. Here, we present an experiment-friendly quantum server that relies only on linear optical elements, offering a flexible approach to multipartite entanglement distribution. Our so-called photon-weaving quantum server can generate and distribute one of several locally nonequivalent graph states, including Greenberger-Horne-Zeilinger (GHZ) states, as well as path, cycle, and caterpillar graph states. This is achieved through two distinct fusion protocols, i.e., multiphoton graph-state fusion (graph-state weaving) and multiphoton GHZ-state fusion (GHZ-state weaving), and can readily be implemented.