Quantum drones under development in China could lead to nigh unhackable airborne quantum communication networks, a new study finds. Quantum mechanics makes possible a strange phenomenon known as entanglement. Essentially, two or more particles such as photons that get linked or “entangled” can, in theory, influence each other no matter the distance between them. Entanglement is essential to the workings of quantum computers, the networks that would connect them, and the most sophisticated kinds of quantum cryptography—a means of information exchange that is impervious to hacking. A key problem with developing ground-based quantum networks is how fragile entanglement is; when sending photonsover existing fiber-optic networks, this limitstransmission distance and data rates. With that in mind, scientists have, in recent years, increasingly investigated quantum networks involving photons transmitted overopen air. Scientists in China and Europe are currently developing satellite-based quantum networks, enabling long-distance satellite-to-ground links. However, quantum satellites have a number of drawbacks. Among these: Satellites in low orbit can communicate with certain ground locations onlywithin limited windows of time;and the costs of space launch makes setting up a quantum satellite network quite expensive. Scientists at Nanjing University in China,noting the recent explosive advances in drone technology,have designed a “quantum drone”to serve as an airborne node in a quantum network.The researchers detailedtheir findingson 23 May in the ArXiV online preprint server.