Fig. 1: Distinction between quantum networks and untrusted quantum-classical hybrids.
From: Scalable determination of multipartite entanglement in quantum networks
Vertices and edges in a star topology represent an N-node entangled network equivalent to a GHZ state59, as illustrated in a for N = 4. The former stand for end nodes (qubits), and the latter describe node-node quantum interaction. b A classical-quantum hybrid consists of classical nodes of pre-existing data \({R}_{{m}_{k}}\) which constitute a fixed measurement set vk and nodes described by a density matrix of quantum mechanics. See Eq. (4). A variant can be found according to the number of classical (quantum) nodes, nc (N − nc), and the combination of classical (quantum) end nodes described by the node index set Vc (VQ), such as (c). For 0 < nc < 4, all possible hybrids are shown in b–f. We show detection of N-node star-topology quantum networks by ruling out all quantum-classical hybrids requires only N + 1 measurement settings.
