Integrating conventional and quantum networks on the same optical fibers will advance quantum network technology. Quantum networking’s key function, quantum teleportation, has not yet been achieved over fibers used for high-power conventional optical data transmission.
However, a recent Northwestern University study has successfully demonstrated quantum teleportation over a fiber optic cable that also carries Internet traffic.
The research opens the door to simpler infrastructure to enhance sensing technologies and quantum computing by enabling new quantum communication methods over existing Internet connections.
Prem Kumar from Northwestern University, who led the study, expressed excitement, noting that the success demonstrates the possibility of combining quantum and classical networks on a shared fiber optic infrastructure, advancing quantum communications to the next level.
Before Kumar’s recent study, many doubted that quantum teleportation could occur through a fiber optic cable carrying classical communications, as entangled photons could easily be overwhelmed by the surrounding light particles—like a weak bicycle navigating a tunnel filled with speeding trucks.
However, Kumar and his team figured out how to overcome this challenge by studying how photons avoid interference. They discovered that by ensuring the quantum photons’ wavelength wasn’t overcrowded and installing specialized filters to reduce interference from regular Internet traffic, they could allow the delicate photons to travel successfully across the network.
Kumar said, “We carefully studied how light is scattered and placed our photons at a judicial point where that scattering mechanism is minimized. We found we could perform quantum communication without interference from the classical, simultaneously present channels.”
To test their method, Kumar’s team installed photon sources at both ends of a 30-kilometer fiber optic line, simultaneously transmitting both Internet traffic and quantum information.
They conducted quantum measurements from the middle of the line and assessed the quality of the quantum data received. The results showed that, despite the heavy Internet traffic, the quantum information was successfully transmitted, confirming the effectiveness of their teleportation protocol.
Jordan Thomas, a Ph.D. candidate in Kumar’s laboratory and the paper’s first author, said, “Although many groups have investigated the coexistence of quantum and classical communications in fiber, this work is the first to show quantum teleportation in this new scenario. This ability to send information without direct transmission opens the door for even more advanced quantum applications to be performed without dedicated fiber.”
To advance towards distributed quantum applications, Kumar plans to expand their tests to longer distances and use two pairs of entangled photons instead of just one, aiming to demonstrate entanglement swapping.
Additionally, his team is considering testing actual subterranean optical cables rather than relying on lab-based spools. Despite ongoing work, Kumar remains optimistic about the progress and potential of their research.
Kumar said, “Quantum teleportation can provide quantum connectivity securely between geographically distant nodes. However, many people have long assumed that nobody would build specialized infrastructure to send particles of light. We won’t have to build new infrastructure if we choose the wavelengths properly. Classical communications and quantum communications can coexist.”
Journal Reference:
- Jordan M. Thomas, Fei I. Yeh, Jim Hao Chen et al. Quantum teleportation coexists with classical communications in optical fiber. Optica. DOI: 10.1364/OPTICA.540362
