Researchers from the Joint Quantum Institute, the National Institute of Standards and Technology and Qunnect sent entangled photons through 62 kilometers of commercial fiber between NIST’s campus in Gaithersburg and the University of Maryland in College Park.
The fiber was exposed to the ordinary changes of a working network, including temperature shifts, wind and movement on overhead lines. The team used reference light and real-time corrections to keep the photons’ fragile polarization states aligned.
Over 24 hours, the system distributed entangled photons 92.8 percent of the time and sent about 1,500 entangled photons per second. A statistical test confirmed that the photons remained entangled at both ends.
The experiment was not a distance record, and the transmission rate still needs to improve. Its value was showing that quantum networking can be tested on existing infrastructure instead of requiring entirely new fiber lines.
