Scientists have sent quantum signals over standard fiber-optic cables using the same connectivity that powers today’s web, in what could be a major step towards a working quantum internet.
In a study published Aug. 28 in the journal Science, researchers used a custom-built quantum chip to package quantum data alongside a standard optical signal and transmit them over commercial infrastructure.
“Unlike earlier experiments that required isolated, lab-based setups or specialized infrastructure, this approach integrates quantum communication into real-world networks for the first time,” senior study author Liang Feng, professor of materials science and electrical engineering at the University of Pennsylvania, told Live Science in an email.
“Our Q‑Chip enables control of quantum signals and classical signals, so they travel together over the same fiber‑optic cables, using standard internet protocols.”
Why can’t the internet send quantum data?
Quantum data is carried by qubits — the basic units of quantum information. Unlike classical computer bits, which are represented as either 0 or 1, qubits can exist in a superposition of both states.
Qubits can also become entangled, meaning the state of one is symbiotically linked to the state of another, no matter how far apart they are. These properties enable quantum computers to perform calculations far beyond the reach of conventional computers — in parallel rather than in sequence.
However, these same properties also make quantum data notoriously fragile. Quantum states collapse when they’re observed or measured, making quantum information extremely difficult to work with. In classical internet, traffic is directed by routers that read and interpret information as it moves through the network. This can’t be done with quantum particles without destroying the very data being transmitted,because the superposition collapses as soon as it is observed.
How the Q-Chip works
The Q‑Chip, which stands for “quantum-classical hybrid internet by photonics”, tackles this challenge by pairing each quantum signal with a classical “header” — a data packet containing routing and timing information that’s encoded into a fiber-optic laser pulse.
As this information travels through the network, it’s inspected by routers — devices that direct internet traffic by reading packet information and forwarding it to the correct destination. Routers use the header to determine where the data should go and how to get it there.
By timing the classical and quantum signals to travel together in a synchronized pulse, the chip enables routers to read the header’s navigation information without interacting with or disrupting the quantum signal. This enables both to travel together via standard IP protocols.
While researchers have previously demonstrated that quantum data can be transmitted over standard fiber-optic cables, including alongside classical data in the same wavelength band, this latest study marks the first time that quantum signals have been transmitted using standard IP on live, real-world infrastructure.
This is crucial because it avoids the need for a separate quantum-only network, significantly lowering the barrier to deploying and scaling a quantum internet, said Feng.
“Using standard IP protocols means the Q‑Chip allows quantum communication to be managed like regular internet traffic with the already-developed tools for routing, addressing and coordination,” he told Live Science.
“By attaching classical ‘headers'” to quantum data, the Q‑Chip can route and manage quantum signals using the developed classical photonic devices, systems and infrastructure without disturbing the delicate quantum states, making this the first practical demonstration of quantum communication that fits within existing internet architecture.”
To test the system, the team built a simple connection between a server and a receiver node, using a 1-kilometer (0.6 miles) stretch of commercial fiber operated by telecommunications company Verizon.
Because the classical header and quantum signal respond to interference from the environment in similar ways, the team could use the classical signal to correct for noise without disturbing the quantum state. This ensured the data reached its destination intact.
While the pilot setup was small, the researchers believe it marks a foundational step toward a full-scale quantum internet that could link quantum devices — particularly as the Q-Chip is made of silicon and fabricated using existing processes, meaning it can be mass-produced.
“In the next 5-10 years, the early stages of a quantum internet will likely focus on local networks and/or metro-scale quantum internet,” Feng told Live Science. “Applications [could include] secure communication, interconnecting quantum computers and distributed quantum sensing such as ultra-precise navigation or timing.”