Entangled photons Artistic representation of quantum entanglement. Physicists in the US have shown how the phenomenon could be used to link optical telescopes over long distances. (Courtesy: iStock/Jian Fan)"> Entangled photons Artistic representation of quantum entanglement. Physicists in the US have shown how the phenomenon could be used to link optical telescopes over long distances. (Courtesy: iStock/Jian Fan)

Quantum-entangled sensors placed over a kilometre apart could allow interferometric measurements of optical light with single photon sensitivity, experiments in the US suggest. While this proof-of-principle demonstration of a theoretical proposal first made in 2012 is not yet practically useful for astronomy, it marks a significant step forward in quantum sensing.

Radio telescopes are often linked together to provide more detailed images with better angular resolution than would otherwise be possible.…