Using quantum encryption to send confidential information through entangled photons offers much better protection than today’s encryption, but several challenges remain. So far researchers have transmitted quantum information as far as a few hundred kilometers using fiber-optic cables and 1200 km using satellite arrays (see Physics Today, August 2017, page 14). But constructing a communication network connected by fiber is costly and prone to loss problems; and a network of satellites suffers from low transmission rates and is only usable at night. Now Zhenda Xie, Yan-Xiao Gong, and Shi-Ning Zhu of Nanjing University in China have accelerated an alternative approach: Their experiment successfully demonstrates the transmission of an entangled state through air from one drone to another.

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