Northwestern Demonstrates Quantum Entanglement Over Live Telecom Fiber

Researchers in Prem Kumar's lab at Northwestern's McCormick School of Engineering, led by graduate student Gina Talcott, distributed entangled photon pairs across 24.4 km of installed fiber connecting Northwestern's Evanston campus to the StarLight facility in downtown Chicago — while the same fiber simultaneously carried roughly 36 terabits per second of live commercial internet traffic. By isolating quantum signals in the O-band while classical data used the C-band, with picosecond-level synchronization and filtering, the team preserved entanglement fidelity above 94%. Published in Optica Quantum, it is the first demonstration of entanglement distribution between remote nodes over a fiber carrying real-world commercial traffic, a key step toward a quantum internet that reuses existing telecom infrastructure.