Researchers at Northwestern transmitted entangled photons over a 24.4-kilometer fiber link between Evanston and downtown Chicago while the same cable carried commercial-style internet traffic, preserving entanglement above 94% fidelity.
The team protected the fragile quantum signals by placing them in the quieter O-band, keeping classical data in the C-band, and using filtering plus picosecond-level White Rabbit synchronization to identify photon pairs in real time.
The fiber simultaneously carried two 800-gigabit-per-second data channels and optical power representative of a fully loaded link—enough for a potential 36 terabits per second of classical traffic.
Published July 20 in Optica Quantum, the study is described as the first demonstration of entanglement distribution between remote nodes over fiber carrying modern telecommunications traffic, pointing to quantum networks built on existing infrastructure.
Next, the group aims to move beyond entanglement distribution to quantum teleportation between remote nodes across a metropolitan network under real-world traffic conditions.
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Quantum Teleportation Over Existing Internet Infrastructure: 30 km Milestone Signals Quantum Internet Future
Overview
In December 2024, engineers from Northwestern University achieved a major breakthrough by successfully demonstrating quantum teleportation over a 30.2-kilometer fiber optic cable that was already carrying high-speed classical internet traffic. This pioneering work, published in Optica, marks a crucial step toward integrating quantum networks with the existing global internet. By proving that quantum and classical signals can coexist on the same fiber, the team eliminated the need for dedicated 'dark fiber' for quantum applications. This achievement paves the way for more practical and widespread deployment of quantum communication technologies using current infrastructure.