Scientists have achieved device-independent distribution of a quantum key over a distance of more than 100 km using single atoms. The technology has been demonstrated on a city scale, representing an important step towards a secure quantum internet. The study was published in the journal Science, Volume 391, Number 6785, Pages 592-597, February 2026. They used optical methods to transmit quantum keys with high security. The experiment confirmed the functionality of the system at distances typical of an urban environment. The results were peer-reviewed and published with DOI 10.1126/science.aec6243.[2][3]