Quantum Physics2026-06-161 minarXiv:2606.17620expressSingle Photons in High HarmonicsIn very dim light, photons arrive one by one, like drops from a leaky faucet — never in pairs. This effect, predicted by Roy Glauber and confirmed by Leonard Mandel, directly proves that light is made of particles.Philipp Stammer·Javier Rivera-Dean·Maciej LewensteinHong–Ou–Mandel effectJeff KimbleLeonard Mandelcoherent statespectroscopy👍👎☆SimplePopularAdvanced