Quantum state of light teleported over 30 kilometres of fibre optic cable amid internet traffic

In 2024, researchers managed to teleport a quantum state of light across more than 30 kilometres (about 18 miles) of fibre optic cable while it was carrying a heavy load of normal internet traffic - an engineering milestone many had previously written off as unachievable.

The US-based team’s result will not help you dematerialise on the way to work to dodge rush-hour queues, nor will it make your favourite cat videos download any quicker.

Even so, being able to teleport quantum states through today’s communications infrastructure is a major stride towards a quantum-connected computing network, stronger encryption, and new high-performance approaches to sensing.

"This is incredibly exciting because nobody thought it was possible," says Prem Kumar, a computing engineer at Northwestern University who led the study.

Watch the clip below for a summary of their research:

"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."

What was achieved in 2024

Quantum teleportation can sound a little like Star Trek’s transporters, which whisk passengers across space in an instant. In practice, it means taking the quantum possibilities describing an object in one place and, by deliberately eliminating that original state, imposing the same pattern of possibilities on a similar object somewhere else.

Although measurements on the two objects lock their outcomes together at the same moment, setting up their shared quantum identity still depends on sending a single wave of information between the two locations.

How quantum teleportation works in practice

A quantum state is fragile: like fairy floss in a spring shower, it is a blurred smear of possibilities that can collapse into everyday reality soon after it is created. Radiation in the form of electromagnetic waves, along with the heat-driven jostling of particles, can rapidly strip away the quantum features through decoherence unless the state is protected.

Keeping quantum states stable inside computers is one challenge. Sending a single photon through optical fibres that are already alive with bank transactions, cat videos, and text messages - and still preserving its quantum state - is considerably harder. It is akin to tossing your quantum fairy floss into the Mississippi and hoping it is just as sweet downstream.

Prem Kumar’s quantum teleportation over fibre optic cable

To keep their solitary photon’s delicate state intact amid a 400 gigabit-per-second flow of internet traffic, the researchers used multiple methods to constrain the photon’s channel and lower the risk that it would scatter and blend with other light waves.

"We carefully studied how light is scattered and placed our photons at a judicial point where that scattering mechanism is minimized," says Kumar.

"We found we could perform quantum communication without interference from the classical channels that are simultaneously present."

Other teams had previously shown, in internet-style simulations, that quantum information could be sent alongside classical data streams. Kumar’s group, however, was the first to teleport a quantum state while running it next to a real, live internet stream.

Each successful run adds weight to the idea that a quantum internet is unavoidable, offering computing engineers a new toolkit for measuring, monitoring, encrypting, and calculating in ways not previously possible - and doing so without having to rebuild the internet from scratch.

"Quantum teleportation has the ability to provide quantum connectivity securely between geographically distant nodes," says Kumar.

"But many people have long assumed that nobody would build specialized infrastructure to send particles of light. If we choose the wavelengths properly, we won't have to build new infrastructure. Classical communications and quantum communications can coexist."

This research was published in Optica.

An earlier version of this article was published in December 2024.