Entanglement distributed across a live metropolitan fibre network
Not a dedicated dark-fibre link — the demonstration ran alongside ordinary classical traffic on deployed infrastructure.
By Ada Renner
Written in-house by the Field report desk — an explainer, not a report of a news event.
- Entangled pairs shared over 41 km of in-service fibre.
- Classical traffic continued on adjacent channels throughout.
- Nightly stability was better than daytime by a wide margin.
Quantum networking demonstrations usually reserve a dedicated dark fibre. This one did not: entangled photon pairs travelled 41 kilometres of in-service metropolitan fibre while ordinary internet traffic ran on neighbouring wavelength channels.
Crosstalk from classical channels remains the dominant noise source, and the team reported markedly better stability at night when thermal drift and traffic both fall.
It is an incremental engineering result rather than a breakthrough in physics, which is precisely why network operators are paying attention.
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