Positronium finally shows wave behavior in landmark quantum experiment

Researchers from Tokyo University of Science have, for the first time, directly observed wave-like behavior in positronium—a short-lived, neutral atom-like system composed of an electron and its antimatter counterpart, a positron. This achievement confirms matter-wave diffraction and wave-particle duality in positronium, a system that had previously eluded such experimental demonstration due to its unique properties and equal-mass constituents. The team, led by Professor Yasuyuki Nagashima, generated a high-quality positronium beam by creating negatively charged positronium ions and then using laser pulses to strip an extra electron, producing a fast, neutral beam suitable for interference experiments. The positronium beam was directed at a thin graphene target, whose atomic spacing matched the de Broglie wavelength of positronium at the energies used (up to 3.3 keV). The resulting diffraction pattern, detected with a position-sensitive detector, confirmed the wave nature of positronium. Importantly, the experiment