Quantum information has just been transmitted across a busy fiber optic network, offering a glimpse into how future communication systems might run on existing infrastructure. Researchers at Northwestern University, led by Professor Prem Kumar, reported a successful demonstration of quantum teleportation across a 30-kilometer-long fiber optic cable that was also carrying high-speed Internet traffic. The group’s findings, published in the journal Optica, defy previous assumptions that delicate photons needed for quantum signaling would be lost among the millions of light particles used for classical communications.
Teleportation in this context involves sending information from one place to another without physically transporting it. Instead of relying on conventional data transfer, the team used quantum entanglement, which ties two photons together so they share information instantaneously over long distances. Experts believed that single photons — the crucial carriers in quantum work — could never squeeze through crowded traffic in a standard cable. But the Northwestern team proved otherwise by placing their photons at a “safe” wavelength and employing special filters to remove interference from everyday data signals.
During tests, Kumar and his team set up two photons at opposite ends of a fiber spool. After painstaking research into how light scatters within cables, they chose a wavelength zone where fewer classical signals overlap. As millions of particles zoomed through the same cable to simulate standard Internet traffic, the quantum bits still arrived at the far end intact. The result stunned many who long thought quantum teleportation required specialized, dedicated lines to avoid disruptions.
“This is incredibly exciting because nobody thought it was possible,” Kumar said. “It opens the door to taking quantum communications further without building new cables. Classical communications and quantum communications can function together.” That means companies and institutions hoping to secure data or leverage emerging quantum computing capabilities may not need to install expensive new hardware. Instead, they could eventually reconfigure existing networks with the right wavelength selection and filtering methods.
The benefits of teleporting information through entangled photons go beyond faster processing. Quantum systems hold promise for creating communications that are more secure than anything used today. Because any attempt to intercept data disrupts the entangled state, eavesdroppers could be detected instantly. While there is more work ahead before quantum networks become mainstream, Kumar’s experiment provides a strong indication that the same cables delivering our emails and streaming content might one day host unbreakable keys and near-instant updates between distant computing hubs.
“By performing a destructive measurement on two photons — one carrying a quantum state and one entangled with another photon — the quantum state is transferred onto the remaining photon, which can be very far away,” said the paper’s first author, Jordan Thomas, a Ph.D. candidate in Kumar’s laboratory. “The photon itself does not have to be sent over long distances, but its state still ends up encoded onto the distant photon. Teleportation allows the exchange of information over great distances without requiring the information itself to travel that distance.”
Next on the researchers’ agenda is stretching the distance to see how far quantum teleportation can travel on these standard cables. They also plan to experiment with entanglement swapping, which involves introducing extra pairs of photons to connect different segments of the network more reliably. Ultimately, the team hopes to conduct trials in everyday conditions, using cables buried underground rather than neatly coiled spools in a lab setting.
Looking ahead, this milestone sparks optimism that existing telecommunication pipelines can take on entirely new roles. Quantum teleportation might soon become more than a lab curiosity — it could form the backbone of an ultra-secure, entangled network, with no need to uproot or remodel our planet’s extensive cable infrastructure.
Citation: Jordan M. Thomas, Fei I. Yeh, Jim Hao Chen, Joe J. Mambretti, Scott J. Kohlert, Gregory S. Kanter, and Prem Kumar, “Quantum teleportation coexisting with classical communications in optical fiber,” Optica 11, 1700-1707 (2024)