Quantum networks at QCE26 met the weather

This guide follows 67 networking talks at IEEE Quantum Week 2026 in Toronto. Most of them built networks in software, and a few went out to measure what sun, wind and traffic do to real fibre. On the afternoon of Thursday 17 September, Thomas Gerrits of NIST showed what sunshine does to quantum networks. Their team’s link runs on fibre hung from poles on the way to the University of Maryland. As the cable warmed in the sun it grew a little longer, and the timing gap between the two ends rose to 180 trillionths of a second in a field where photons must meet within tens of them. Left alone, the link lost its entanglement within hours. A quantum network moves fragile quantum states from place to place. Most use single photons, sent down glass fibre or through the open air. The oldest use is quantum key distribution, or QKD, put forward by Charles Bennett and Gilles Brassard in 1984. Two people build a shared secret key from photons, and anyone who looks at the photons on the way leaves a trace. Fibre swallows light, losing about half of it every 15 km. A quantum state also cannot be…