Quantum Communication Breakthroughs Enable Daytime Free‑Space QKD and Urban Fiber Entanglement

Researchers have demonstrated a deep‑learning adaptive optics system that corrects strong atmospheric turbulence, allowing free‑space quantum key distribution (QKD) over 1.4 km and 7 km links even in daylight. The method directly estimates wave‑front phase from images, improving the Strehl ratio and key rates without complex wave‑front sensors, addressing a long‑standing limitation of nighttime‑only QKD.

In a separate study, a team led by Professor Prem Kumar at Northwestern University showed that entangled photons can travel more than 24 km through a busy metropolitan fiber network in Chicago while the same cable carries high‑capacity internet traffic. The quantum connection retained over 94 % fidelity, proving that delicate quantum signals can coexist with conventional data streams in existing infrastructure.

Together, these results point toward practical, all‑day quantum communication networks that can operate over both free‑space and existing fiber links, bringing global quantum networking closer to reality.