Imagine trying to float a soap bubble through a sandstorm without it popping. This is a rough analogy for the extraordinary achievement of Northwestern University researchers in the field of quantum communications. Instead of a delicate soap bubble, these scientists have successfully protected individual particles of light—carrying quantum information—from being overwhelmed by conventional internet traffic.
For years, experts believed that quantum communications would require a completely separate infrastructure, isolated from the busy highways of traditional internet traffic. However, these researchers have proven otherwise, demonstrating that quantum and classical signals can coexist on the same fiber optic cables without disrupting each other. This breakthrough is poised to accelerate the development of quantum networks, offering a more practical and cost-effective route for the future of communication.
Until now, many in the field thought that quantum signals, due to their fragile nature, would be drowned out by the heavy traffic of conventional internet data. “This is incredibly exciting because nobody thought it was possible,” says Prem Kumar, the study’s lead researcher from Northwestern’s McCormick School of Engineering. “Our work shows a path towards next-generation quantum and classical networks sharing a unified fiber optic infrastructure, opening the door to push quantum communications to the next level.”
Quantum signals are extremely sensitive, akin to trying to hear a whisper in a room full of rock concert noise. While classical internet signals are made up of millions of particles of light, quantum communications rely on individual photons—single particles that carry the information. Protecting these fragile quantum signals from the noisy environment of traditional internet traffic seemed an insurmountable challenge.
Kumar and his team at the Center for Photonic Communication and Computing found a clever solution by targeting less congested “lanes” of light waves and installing specialized filters to shield quantum signals from the surrounding noise. “We carefully studied how light is scattered and placed our photons at a strategic point where scattering is minimized,” Kumar explains. “We found that we could perform quantum communication without interference from the classical channels that were simultaneously present.”
A key part of the breakthrough involved demonstrating quantum teleportation, a vital process for quantum networks. Quantum teleportation harnesses quantum entanglement, a phenomenon where particles remain linked regardless of the distance between them. Instead of sending particles physically across a network, entangled particles can exchange information over vast distances, instantly transmitting data.
The team conducted this experiment over a 30.2-kilometer (19-mile) fiber optic cable, simultaneously transmitting conventional internet data at 400 gigabits per second. The setup featured three key participants: Alice (the sender), Bob (the receiver), and Charlie (the middleman). Alice prepared the quantum states she wanted to send to Bob, while Bob generated pairs of entangled photons, sending one to Charlie. When Charlie performed a special measurement involving both Alice’s photon and Bob’s entangled photon, Bob’s remaining photon instantly adopted the properties of Alice’s original state—effectively “teleporting” the information.
Remarkably, the team achieved high-quality quantum teleportation even with classical signals 150 times stronger than needed for error-free 400-Gbps communication. This achievement suggests that quantum and classical communications could easily coexist on the same fiber optic infrastructure, simplifying the future development of quantum networks.
Published in Optica, this research opens up exciting new possibilities for quantum-enhanced cryptography, sensing technologies, and networked quantum computing. The idea of integrating quantum networks with existing internet infrastructure could make these applications more practical and scalable. However, significant further research and development will be necessary before this becomes a reality. As Kumar notes, “Many people have long assumed that nobody would build specialized infrastructure to send particles of light. If we choose the wavelengths properly, classical and quantum communications can coexist without requiring new infrastructure.”
Looking ahead, the team plans to extend their experiments over longer distances and attempt more advanced experiments, such as entanglement swapping using two pairs of entangled photons. They also aim to move beyond laboratory settings to test their method in real-world underground optical cables, a critical step toward making quantum communication a practical tool for global networks.
By Impact Lab
