  Scaling current quantum communication demonstrations to a large-scale quantum
network will require not only advancements in quantum hardware capabilities,
but also robust control of such devices to bridge the gap to user demand.
Moreover, the abstraction of tasks and services offered by the quantum network
should enable platform-independent applications to be executed without
knowledge of the underlying physical implementation. Here we experimentally
demonstrate, using remote solid-state quantum network nodes, a link layer and a
physical layer protocol for entanglement-based quantum networks. The link layer
abstracts the physical-layer entanglement attempts into a robust,
platform-independent entanglement delivery service. The system is used to run
full state tomography of the delivered entangled states, as well as preparation
of a remote qubit state on a server by its client. Our results mark a clear
transition from physics experiments to quantum communication systems, which
will enable the development and testing of components of future quantum
networks.
