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Los Alamos National Labs Has Working Hub-and-Spoke Quantum Network
New submitter hutsell writes with this excerpt from MIT's Technology Review: "Richard Hughes and his associates at the Los Alamos National Laboratory in New Mexico announced today that they have been sending perfectly secure messages with their Quantum Internet that has been in operation for the last two and a half years."
Original paper. Unlike current quantum networks that only allow point-to-point networking, the system at Los Alamos combines traditional and quantum links to route messages through a hub while retaining the security advantages of quantum networking.
No, it doesn't assume the optical link can't be tapped. In fact, the quantum encoding is specifically a defense against the optical link being tapped. The data is sent one photon at a time. If a tapper captures the photon (even by leakage from evanescent waves), they destroy the information --- and are neither able to know for themselves, or reliably re-send to the receiver, the bit that was sent. If the tapper doesn't capture the photon, they they haven't tapped the line. At the receiving end, getting too high a dropped bit rate (or scrambled nonsense bits) lets you know the line is compromised, while the attacker still doesn't get any useful information.