First demonstration of quantum teleportation over busy Internet cables


By Dr. Tim Sandle
December 24, 2024


A programmable photonic circuit has been developed that can execute various quantum algorithms and is potentially highly scalable. This device could pave the way for large-scale quantum computers based on photonic hardware. Image by 彭家杰. CC BY 2.5

Northwestern University engineers are the first to successfully demonstrate quantum teleportation over a fibreoptic cable already carrying Internet traffic.

The new research advance opens door for fast, secure quantum applications without specialized infrastructure. This is based on activity inside Internet cables. Internal to the cable, photons needed for teleportation are lost within the millions of light particles required for classical communications.

Now scientists have quantified light scattering to find exact areas to place photons to keep them safe from other particles. This approach has successfully worked in experiments carrying regular Internet traffic. The discovery introduces the new possibility of combining quantum communication with existing Internet cables — greatly simplifying the infrastructure required for distributed quantum sensing or computing applications.

Commenting on the research, Northwestern’s Prem Kumar, outlines why the research is important: “This is incredibly exciting because nobody thought it was possible…Our work shows a path towards next-generation quantum and classical networks sharing a unified fibreoptic infrastructure. Basically, it opens the door to pushing quantum communications to the next level.”

Only limited by the speed of light, quantum teleportation enables a new, ultra-fast, secure way to share information between distant network users, wherein direct transmission is not necessary. The process works by harnessing quantum entanglement, a technique in which two particles are linked, regardless of the distance between them. Instead of particles physically traveling to deliver information, entangled particles exchange information over great distances — without physically carrying it.

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

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. The photon itself does not have to be sent over long distances, but its state still ends up encoded onto the distant photon.

In other words, teleportation allows the exchange of information over great distances without requiring the information itself to travel that distance.

By examining how light scatters within fibreoptic cables, the researchers found a less crowded wavelength of light to place their photons. Then, they added special filters to reduce noise from regular Internet traffic.

To test the new method, the researchers set up a 30 kilometre-long fibreoptic cable with a photon at either end. Then, they simultaneously sent quantum information and high-speed Internet traffic through it. Finally, they measured the quality of the quantum information at the receiving end while executing the teleportation protocol by making quantum measurements at the mid-point. The researchers found the quantum information was successfully transmitted — even with busy Internet traffic whizzing by.

The study, “Quantum teleportation coexisting with classical communications in optical fiber,” appears in the journal Optica.