Scientists have at last succeeded in creating a reliable stream of entangled photons — an advance that could boost quantum technologies.

Quantum-communication networks and quantum computers require ‘entangled’ photons, pairs of intrinsically linked light particles that can carry ultra-secure signals and help to process quantum computations. But these fragile photon pairs are tricky to manufacture, and for years researchers have sought a reliable method for producing a high-quality stream of them.

Xuehua Wang of Sun Yat-sen University in Guangzhou, China, and his colleagues enclosed a nanometre-scale semiconductor called a quantum dot in concentric rings made of an aluminium-gallium-arsenide compound. When the researchers shone a laser on the dot, it emitted entangled photons that were reflected multiple times by the rings and eventually guided to a lens that efficiently harvested the photons, amplifying the detected quantum signal.

This photon source, which could be easily integrated into a computer chip, produces a bright and steady flow of indistinguishable photons. A reliable supply of such photons will be crucial for relaying quantum signals over long distances and for building high-performing quantum computers.