First demonstration of quantum teleportation over widely used Internet cables

Dec. 20 () –

The engineers of the University Northwestern (United States) are the first to successfully demonstrate quantum teleportation through a fiber optic cable that already carries Internet traffic. The discovery, which in the journal Optica, introduces the new possibility of combining quantum communication with existing Internet cables, greatly simplifying the infrastructure necessary for distributed sensing or quantum computing applications.

“This is incredibly exciting because no one thought it was possible“states Northwestern’s Prem Kumar, who led the study. “Our work shows a path toward next-generation quantum and classical networks that share a unified fiber optic infrastructure. Basically, it opens the door to take quantum communications to the next level“.

An expert in quantum communication, Kumar is a professor of electrical and computer engineering at Northwestern’s McCormick School of Engineering, where he directs the Center for Photonic Computing and Communication.

Quantum teleportation, limited only by the speed of light, could make communications nearly instantaneous. The process works by taking advantage of quantum entanglement, a technique in which two particles become linked, regardless of the distance between them. Instead of particles physically traveling to transmit information, entangled particles exchange information over long distances, without physically transporting it.

“In optical communications, all signals are converted into light” explains Kumar. “While conventional signals for classical communications are typically composed of millions of light particles, quantum information uses single photons.”

Before Kumar’s new study, conventional wisdom suggested that single photons would sink into wires filled with millions of light particles that carry classical communications. It would be like a flimsy bicycle trying to navigate a tunnel full of heavy trucks traveling at full speed. However, Kumar and his team found a way to help the delicate photons avoid heavy traffic.

After conducting in-depth studies on how light is scattered within fiber optic cables, the researchers found a less crowded wavelength of light in which to place their photons. Then, they added special filters to reduce the noise from regular Internet traffic.

“We carefully study how light scatters and place our photons at a point where that scattering mechanism is minimized”says Kumar. “We found that we could perform quantum communication without interference from classical channels that are present simultaneously.”

To test the new method, Kumar and his team installed a 30-kilometer-long fiber optic cable with a photon at each end. Then they simultaneously sent quantum information and normal Internet traffic through it.

Finally, they measured the quality of the quantum information at the receiving end while running the teleportation protocol by making quantum measurements at the midpoint. The researchers found that quantum information was transmitted successfully, even with heavy Internet traffic passing by at full speed.

Next, Kumar plans to extend the experiments to longer distances. It also plans to use two pairs of entangled photons (rather than one pair) to demonstrate entanglement exchange, another important milestone leading to distributed quantum applications. Finally, his team is exploring the possibility of conducting experiments on real-world underground optical cables instead of on spools in the lab. But even with more work to do, Kumar is optimistic.

“Quantum teleportation has the ability to securely provide quantum connectivity between geographically distant nodes“But many people have long assumed that no one would build specialized infrastructure to send light particles. If we choose the wavelengths correctly, we won’t have to build new infrastructure. “Classical communications and quantum communications can coexist.”