In a first-of-its-kind experiment, engineers at Penn’s School of Engineering and Applied Science have brought quantum networking out of the lab and onto commercial fiber-optic cables using the same Internet Protocol (IP) that powers today’s web. Reported in Science, the work shows that fragile quantum signals can run on the same infrastructure that carries everyday online traffic. The team tested their approach on Verizon’s campus fiber-optic network.
Part of the equipment used to create a node of the quantum network, roughly one kilometer’s worth of Verizon commercial fiber optic cable away from its source.
(Image: Sylvia Zhang)
The Penn team’s tiny “Q-Chip” (quantum-classical hybrid internet by photonics) coordinates quantum and classical data and, crucially, speaks the same language as the modern web. This approach could pave the way for a future “quantum internet,” which scientists believe may one day be as transformative as the dawn of the online era.
“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,” says Liang Feng, professor in materials science and engineering (MSE) and in electrical and systems engineering (ESE), and the paper’s senior author.
Once quantum particles are measured, they lose their unusual properties, which makes scaling a quantum network extremely difficult.
“Normal networks measure data to guide it towards the ultimate destination,” says Robert Broberg, a doctoral student in ESE and coauthor of the paper. “With purely quantum networks, you can’t do that, because measuring the particles destroys the quantum state.”
To get around this obstacle, the team developed the “Q-Chip” to coordinate “classical” signals, made of regular streams of light, and quantum particles. “The classical signal travels just ahead of the quantum signal,” says Yichi Zhang, a doctoral student in MSE and the paper’s first author. “That allows us to measure the classical signal for routing, while leaving the quantum signal intact.”
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,” says Zhang. “You can’t open the containers without destroying what’s inside, but the engine ensures the whole train gets where it needs to go.”
Read more at Penn Engineering Today.