Researchers at Leibniz University of Hanover have developed a technology for transmitting entangled photons via optical fibers that would enable the integration of the quantum and traditional Internet, promising increased security and efficient use of existing infrastructure.

A team of four researchers from the Institute of Photonics at Leibniz University Hannover has developed an innovative transmitter-receiver system for transmitting entangled photons via an optical fiber.

The breakthrough could allow the next generation of telecommunications technology, a quantum internet, to be routed over fiber. Quantum internet would secure critical infrastructure by promising tamper-proof encryption that even future quantum computers wouldn’t be able to crack.

“To make the quantum internet a reality, we need to transfer entangled photons via fiber-optic networks,” says Professor Dr. Michael Kues, head of the Institute of Photonics at the Leibniz University of Hannover and board member of the PhoenixD excellence cluster. “We also want to continue using optical fibers for conventional data transmission. Our research is an important step in combining the conventional internet with the quantum internet.”

In their experiments, the researchers showed that the entanglement of photons is preserved even when they are sent together with a laser pulse. “We can change the color of the laser pulse with a high-speed electrical signal so that it matches the color of the entangled photons,” explains Philipp Ruebeling, a postdoctoral researcher at the Institute of Photonics who researches the quantum internet. “This effect allows us to combine laser pulses and entangled photons of the same color in an optical fiber and then separate them again.”

Development of hybrid networks

This effect could combine the ordinary Internet with the quantum Internet. Until now, it was not possible to use both transmission methods for every color in an optical fiber. “Entangled photons block the data channel in the optical fiber, preventing it from being used for normal data transmission,” says Jan Heine, a postdoctoral researcher in Küss’s group.

Thanks to the concept, which was demonstrated for the first time in an experiment, photons can now be sent in the same color channel as laser light. This means that all color channels can be used for normal data transmission. “Our experiment shows how successful the practical application of hybrid networks can be,” says Professor Michael Kues.