For nearly 80 years, physicists have relied on a thought experiment created by Richard Feynman to predict how quantum particles behave. For the first time, researchers in China have tested this trick directly in the lab.

Led by Shi-Liang Zhu at South China Normal University in Guangzhou, China, the team used single particles of light to show that Feynman’s idea holds up in practical experiments.

Their results are published in Science Advances.