Researchers have broken a distance record in quantum communication by sending a secret encryption key nearly 13,000 km from China to South Africa, using a cheap, lightweight ‘microsatellite’.

The satellite was able to send pulses of laser light, put into special quantum states, from a rooftop in Beijing to another at Stellenbosch University near Cape Town. The pulses formed a quantum key that was used to encrypt two images — one of China’s Great Wall and one showing part of Stellenbosch’s campus. The feat, a kind of encryption known as quantum key distribution (QKD), is a step towards being able to send ultra-secure messages between any two locations, however distant. It was described in Nature on 19 March1.