Advance opens door for secure quantum applications without specialized infrastructure.

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

The discovery, published in the journal Optica, introduces the new possibility of combining quantum communication with existing Internet cables — greatly simplifying the infrastructure required for for advanced sensing technologies or quantum computing applications.

“This is incredibly exciting because nobody thought it was possible,” said Northwestern’s Prem Kumar, who led the study. “Our work shows a path towards next-generation quantum and classical networks sharing a unified fiber optic infrastructure. Basically, it opens the door to pushing 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 Communication and Computing.

How it works

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 explained. “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,” said Jordan Thomas, a Ph.D. candidate in Kumar’s laboratory and the paper’s first author. “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.”