Quantum over existing fibre

A quantum network sends information with single particles of light, not ordinary data pulses, so any eavesdropping changes the signal and shows up immediately. NYU researchers said this week they ran those quantum signals over New York City’s existing telecom fiber instead of a custom-built line. (nyu.edu) The team worked with Brooklyn startup Qunnect and Cisco on a three-node test linking two nodes at the Brooklyn Navy Yard to a third at QTD Systems’ data center at 60 Hudson Street in Manhattan. NYU said the experiment is the first time entangled quantum signals were linked across multiple points on already-deployed telecom fiber. (nyu.edu) The key step is called entanglement swapping, which is a way to join short quantum links into a longer chain even when the particles at the ends never met. The preprint describing the work is titled *High-rate Scalable Entanglement Swapping Between Remote Entanglement Sources on Deployed New York City Fibers* and was posted to arXiv in February 2026. (arxiv.org) The route covered 17.6 kilometers, or about 10.9 miles, of installed fiber between Brooklyn and Manhattan. Qunnect said the system reached 5,400 swapped pairs per hour over deployed fiber and more than 1.7 million pairs per hour in a local setup. (qunnect.inc) Most quantum-network demos have relied on tightly controlled lab hardware or dedicated links, which keeps costs high and makes citywide deployment harder. This test used the same kind of telecom fiber already buried under New York streets, which shifts the problem from new construction to getting quantum hardware to tolerate real network noise. (nyu.edu) The setup also used a hub-and-spoke design, with more specialized cryogenic equipment concentrated at the central hub and room-temperature detectors at the edge nodes. Qunnect and Cisco said that architecture is meant to lower the cost of adding more sites to a metro-scale network. (qunnect.inc) NYU said the new result builds on a 2023 experiment in which NYU and Qunnect sent quantum information more than 10 miles over standard telecom fiber across New York City. The April 2026 result adds a third node and the swapping step needed to make separate links behave more like a network. (engineering.nyu.edu) (nyu.edu) The paper is still a preprint, not a peer-reviewed journal article, and the claims come from the research team and its partners. But NYU said doctoral student Tyler Cowan presented the findings at the American Physical Society’s annual meeting in March 2026, putting the result into the field’s main conference circuit. (arxiv.org) (nyu.edu) What happens next is less about proving quantum signals can survive a city fiber run and more about scale: more nodes, longer uptime, and hardware cheap enough for carriers and data centers to buy. New York is now serving as the test bed for that question on fiber that was already there. (nyu.edu) (qunnect.inc)