People can perceive flashes of light as feeble as a single photon.

Alipasha Vaziri at the Rockefeller University in New York City and his colleagues asked three volunteers to stare into an optical system in the dark and listen to two sounds, one of which was sometimes accompanied by the emission of a photon. During more than 30,000 trials, the participants correctly identified a photon more frequently than would be expected if they had guessed at random.

Going forwards, the team plans to test how the human visual system responds to photons in various quantum states.

For more on this story, see go.nature.com/2anfrrf.

Nature Commun. 7, 12172 (2016)