Northwestern University Demonstrates Quantum Entanglement on Chicago Fiber

Researchers at Northwestern University successfully transmitted entangled photon pairs over a 24.4‑kilometre commercial fiber‑optic cable linking Evanston and downtown Chicago. The same fiber simultaneously carried high‑capacity internet traffic, and the quantum signals retained more than 94 % entanglement fidelity.

The team used a quieter O‑band wavelength for the photons, applied advanced filtering, and employed the White Rabbit optical timing system to sync the two sites within a trillionth of a second. Lead author Professor Prem Kumar and graduate student Gina Talcott say the experiment shows quantum communication can coexist with existing telecom infrastructure, paving the way for practical quantum networks and future demonstrations of quantum teleportation across a metropolitan area. The work was published in Optica Quantum on 20 July 2024.