First demonstration of quantum teleportation over busy Internet cables

The discovery introduces new possibilities for integrating quantum communications with existing internet cables – greatly simplifying the infrastructure required for decentralized quantum sensing or computing applications.

The research will be published in the journal on Friday (December 20) Optics.

“This is very exciting because no one thought this was possible,” said Prem Kumar of Northwestern University, who led the research. “Our work demonstrates a path toward next-generation quantum computing with shared unified fiber optic infrastructure. And the path to classical networking basically opens the door to taking quantum communications to the next level.”

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

Limited only by the speed of light, quantum teleportation could make communication nearly instantaneous. This process is achieved by utilizing quantum entanglement, a technique that connects two particles regardless of the distance between them. Rather than physically moving to transmit information, entangled particles exchange information over long distances—without physically carrying the information.

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

Before Kumar’s new research, conventional wisdom held that a single photon would be drowned in a cable filled with millions of light particles that carry classical communications. It’s like a fragile bike trying to get through a crowded tunnel of speeding heavy trucks.

However, Kumar and his team found a way to help the delicate photons avoid heavy traffic. After an in-depth study of how light scatters within fiber optic cables, researchers have discovered a less crowded wavelength of light to place photons. Then, they added special filters to reduce the noise of regular network traffic.

“We carefully studied how light is scattered and placed our photons at a judicial point that minimized the scattering mechanism,” Kumar said. “We found that we could do this without interference from simultaneously existing classical channels. Make quantum communications possible.”

To test the new method, Kumar and his team set up a 30-kilometer-long fiber-optic cable with a photon at each end. They then sent both quantum information and regular network traffic through it. Finally, they measured the quality of the quantum information at the receiving end by performing quantum measurements at the midpoint while executing the teleportation protocol. Researchers have found that quantum information can be transmitted successfully even as heavy network traffic whizzes by.

Next, Kumar plans to expand the experiment to longer distances. He also plans to demonstrate entanglement swapping using two pairs of entangled photons instead of just one, another important milestone for decentralized quantum applications. Finally, his team is exploring the possibility of conducting experiments on real-world underground fiber optic cables rather than on spools in the lab. But while more work remains to be done, Kumar remains optimistic.

“Quantum teleportation can securely provide quantum connections between geographically distant nodes,” Kumar said. “But many have long believed that no one would build the dedicated infrastructure to send light particles. If we get it right wavelengths, we don’t have to build new infrastructure. Classical and quantum communications can coexist.”