Computers, smartphones, GPS: quantum physics has enabled many technological advances. It is now opening up new fields of research in cryptography (the art of coding messages) with the aim of developing ultra-secure telecommunications networks. There is one obstacle, however: after a few hundred kilometers within an optical fiber, the photons that carry the qubits or 'quantum bits' (the information) disappear. They therefore need 'repeaters', a kind of 'relay', which are partly based on a quantum memory. By managing to store a qubit in a crystal (a 'memory') for 20 milliseconds, a team has now taken a major step towards the development of long-distance quantum telecommunications networks.