Entanglement topography of large-scale quantum networks

Large-scale quantum networks, necessary for distributed quantum information processing, are posited to have quantum entangled systems between distant network nodes. The extent and quality of distributed entanglement in a quantum network, that is its functionality, depends on its topology, edge-parameter distributions and the distribution protocol. We uncover the parametric entanglement topography and introduce the notion of typical and maximal viable regions for entanglement-enabled tasks in a general model of large-scale quantum networks. We show that such a topographical analysis, in terms of viability regions, reveals important functional information about quantum networks, provides experimental targets for the edge parameters and can guide efficient quantum network design. Applied to a photonic quantum network, such a topographical analysis shows that in a network with radius 10³ kms and 1500 nodes, arbitrary pairs of nodes can establish quantum secure keys at a rate of R_sec=1 kHz using 1 MHz entanglement generation sources on the edges and as few as 3 entanglement swappings at intermediate nodes along network paths.