Laser cooling, a technique to slow down atoms using photons, has revolutionized atomic physics. This paper demonstrates, for the first time, laser cooling of antihydrogen, the antimatter counterpart of hydrogen. By exciting the 1s–2p transition with a pulsed Lyman-α laser, researchers Doppler-cooled magnetically trapped antihydrogen, achieving a significant reduction in energy. This breakthrough has substantial implications for antimatter studies, enabling more precise spectroscopy and gravitational measurements, and opening possibilities for future experiments like anti-atomic fountains and anti-atom interferometry.

C. J. Baker, W. Bertsche, A. Capra, C. Carruth, C. L. César, M. Charlton, A. Christensen, R. Collier, A. Cridland Mathad, S. Eriksson, A. Evans, N. Evetts, J. Fajans, T. Friesen, M. C. Fujiyama, R. D. Gilt, P. Grandemange, P. Grann, J. S. Hangs, V. N. Hardy, M. E. Hayden, D. Hodgjkinson, E. Hunter, C. A. Isaac, M. A. Johnson, J. M. Jones, S. A. Jones, S. Jonsell, A. Kharamov, R. Knapp, L. Kurchanov, N. Madsen, D. Maxwell, J. T. K. McKenna, S. Menary, J. M. Michal, T. Momose, P. S. Mullard, J. J. Munich, K. Olchanski, A. Olin, J. Pszka, A. Powell, P. Pusa, C. O. Rasmussen, F. Robicheaux, R. L. Sacramonte, M. Sameed, E. Sarid, D. M. Silveira, D. M. Starko, C. S. O. Sutter, A. Thibeault, R. I. Thompson, D. P. van der Werf, J. S. Wurtzele