Quantum networks provide unique possibilities for resolving open questions on
entanglement and promise innovative applications ranging from secure
communication to scalable computation. While two quantum nodes coupled by a
single channel are adequate for basic quantum communication tasks between two
parties, fully functional large-scale quantum networks require a web-like
architecture with multiply connected nodes. Efficient interfaces between
network nodes and channels can be implemented with optical cavities. Using two
optical fibre cavities coupled to one atom, we here realise a quantum network
node that connects to two quantum channels. It functions as a passive, heralded
and high-fidelity quantum memory that requires neither amplitude- and
phase-critical control fields nor error-prone feedback loops. Our node is
robust, fits naturally into larger fibre-based networks, can be scaled to more
cavities, and thus provides clear perspectives for a quantum internet including
qubit controlled quantum switches, routers, and repeaters.Comment: 12 pages, 8 figures (including Supplementary Information
