PHILADELPHIA, Sept. 11, 2025 — A recent experiment demonstrated a way to run quantum networking on commercial fiber-optic cables using the same Internet Protocol (IP) that runs the web. University of Pennsylvania researchers developed a quantum chip that they called ‘Q-Chip’ (Quantum-Classical Hybrid Internet by Photonics), which coordinates quantum and classical data using the same language as the web. Their work, tested on Verizon’s campus fiber-optic network, showed that the chip can send fragile quantum signals on the same infrastructure that carries everyday online traffic.

“By showing an integrated chip can manage quantum signals on a live commercial network like Verizon’s and do so using the same protocols that run the classical internet, we’ve taken a key step toward larger-scale experiments and a practical quantum internet,” said Liang Feng, senior author of the research paper describing the advancement.

The work showed that the chip can not only send quantum signals, but also automatically correct for noise, bundle quantum and classical data into standard internet-style packets, and route them using the same addressing system and management tools that connect everyday devices online. 

“Normal networks measure data to guide it towards the ultimate destination,” said Robert Broberg, a doctoral student in electrical and systems engineering and co-author of the paper. “With purely quantum networks, you can’t do that, because measuring the particles destroys the quantum state.”

The Q-Chip measures classical signals for routing, while leaving the quantum signal intact. The classical signal travels ahead of the signal; thus, the researchers call it the classical header. With the classical header able to be measured, the entire system can follow the same IP as the web.

In essence, the new system works like a railway, pairing regular light locomotives with quantum cargo. “The classical ‘header’ acts like the train’s engine, while the quantum information rides behind in sealed containers,” said Yichi Zhang, a doctoral student in electrical and systems engineering. “You can’t open the containers without destroying what’s inside, but the engine ensures the whole train gets where it needs to go.”

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Yichi Zhang with the equipment used to generate and send the quantum signal over Verizon fiber optic cables. Courtesy of the University of Pennsylvania

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Because the classical header can be measured, the entire system can follow the same IP governing today's internet traffic.

“By embedding quantum information in the familiar IP framework, we showed that a quantum internet could literally speak the same language as the classical one,” said Zhang. “That compatibility is key to scaling using existing infrastructure.”

A major problem in transmitting quantum particles on commercial infrastructure is the variability of real-world transmission lines. Commercial networks encounter weather, vibration from human activities like construction and transportation, and seismic activity, which aren’t ideal conditions for maintaining quantum states.

To handle these conditions, the researchers developed an error-correction method that takes advantage of the fact that interference with the classical header will affect the quantum signal similarly.

“Because we can measure the classical signal without damaging the quantum one,” said Feng, “we can infer what corrections need to be made to the quantum signal without ever measuring it, preserving the quantum state.”

During tests, transmission fidelities remained above 97%, showing that it could overcome the noise and instability that usually destroy quantum signals outside the lab. And because the chip is made of silicon and fabricated using established techniques, it could be mass-produced, making the approach easy to scale.

“Our network has just one server and one node, connecting two buildings, with about a kilometer of fiber-optic cable installed by Verizon between them,” said Feng. “But all you need to do to expand the network is fabricate more chips and connect them to Philadelphia’s existing fiber-optic cables.”

The main barrier to scaling quantum networks beyond a metro area is that quantum signals cannot yet be amplified without destroying their entanglement. Although some teams have shown that quantum keys can travel long distances over ordinary fiber, those systems use weak coherent light to generate random numbers that cannot be copied, a technique highly effective for security applications, but not sufficient to link actual quantum processors. 

Overcoming this challenge will require new devices, but the current study provides an important early step: showing how a chip can run quantum signals over existing commercial fiber using internet-style packet routing, dynamic switching, and on-chip error mitigation that work with the same protocols that manage today's networks. 

“This feels like the early days of the classical internet in the 1990s, when universities first connected their networks,” said Broberg. “That opened the door to transformations no one could have predicted. A quantum internet has the same potential.”

This research was published in Science (www.doi.org/10.1126/science.adx6176).