Northwestern Proves Quantum Internet Can Share Existing Telecom Fiber Over 15 Miles at 94% Fidelity

Researchers at Northwestern University successfully transmitted entangled photons across 15 miles of commercial fiber-optic cable while the same line carried 36 terabits per second of live internet traffic. This experiment, conducted between the university's Evanston campus and downtown Chicago, challenges the assumption that quantum signals require dedicated, private infrastructure to function.

The engineering team utilized spectral separation to protect the fragile quantum states. By placing entangled photon pairs in the O-band at 1,290 nanometers and restricting classical data to the standard C-band, they created a 270-nanometer gap. This separation, combined with high-precision filtering and the White Rabbit timing protocol, reduced background noise enough to achieve a 94.2% Bell state fidelity. This result is nearly identical to performance measurements taken on empty, isolated fiber cables.

For years, the necessity of leasing expensive dark fiber has stalled the practical deployment of quantum networks. This study demonstrates that existing telecommunications infrastructure can support both classical data and quantum communication simultaneously. Because commercial fiber is already installed worldwide, this finding suggests a path for integrating quantum security and distributed computing without the cost of laying new cables.

Led by professor Prem Kumar and graduate student Gina Talcott, the project represents a major shift from laboratory testing to real-world application. The team successfully navigated the noise generated by a Ciena Corporation optical line system operating at full capacity. While the experiment focused on entanglement distribution, the results confirm that the fundamental architecture for a quantum internet can exist within current network environments. The research team is now working toward the next goal: full quantum teleportation over similar production-grade links.