https://www.sciencedaily.com/releases/2018/11/181105105216.htm

Published in Nature Communications, the work saw the Griffith team, led by Professor Geoff Pryde, working with photons (single particles of light) and using them to measure the extra distance travelled by the light beam, compared to its partner reference beam, as it went through the sample being measured -- a thin crystal.

The researchers combined three techniques -- entanglement - (a kind of quantum connection that can exist between the photons), passing the beams back and forth along the measurement path, and a specially-designed detection technique.