US quantum communication breakthroughs

In late July 2026, researchers at Northwestern University demonstrated that entangled photon pairs could be transmitted over a 24.4-kilometre commercial fiber-optic link in Chicago while the same cable carried high-capacity internet traffic, preserving more than 94% entanglement fidelity. This was complemented by the use of a deep-learning adaptive-optics system to correct atmospheric turbulence, enabling free-space quantum key distribution (QKD) over 1.4 km and 7 km links even in daylight.

By mid-August 2026, the scope of these advancements expanded to include longer distances and improved data capacity. In Maryland, scientists from the National Institute of Standards and Technology and the University of Maryland successfully transmitted entangled photons across 62 kilometres of existing fiber-optic cable. To mitigate signal distortion caused by environmental stressors on above-ground cables, the team employed a real-time correction system to stabilize quantum states.

Simultaneously, researchers from the University of Geneva, alto University, and PSL University achieved a breakthrough in quantum memory. By using a rare-earth-ion ensemble, they demonstrated the storage of entanglement across 16,340 temporal modes—nearly doubling previous limits. This method, which utilized a 250MHz bandwidth to store photons for up to 63 microseconds over 5.66 km of metropolitan fiber, allows for significantly higher data transmission rates by exploiting multiple spectral channels. These cumulative developments suggest a path toward robust, high-capacity, and all-day hybrid quantum communication networks.