Quantum interference can influence the probability of outcomes when measuring quantum states. See how it and entanglement are essential to quantum computers.

Researchers from Tokyo University of Science have achieved a significant milestone in quantum physics by observing wave-like interference in a beam of positronium for the first time. Positronium, an exotic and short-lived atom consisting of an electron and its antimatter counterpart, the positron, orbiting a common center of mass, demonstrated clear diffraction patterns when passed through a thin sheet of graphene. The team, led by Professor Yasuyuki Nagashima along with Associate Professor Yugo Nagata and Dr. Riki Mikami, created a high-quality, coherent positronium beam with energies up to 3.3 keV using negatively charged positronium ions and a precisely timed laser pulse to detach an extra electron. This neutral beam was directed at a graphene sheet whose atomic spacing matched the de Broglie wavelength of the positronium atoms, resulting in observable first-order diffraction peaks. The experiment confirms that positronium behaves as a single unified quantum object rather than two independent particles diffracting separately, reinforcing the principles of wave-particle duality. Conducted in ultra-high vacuum to maintain surface cleanliness, the setup provided clearer interference patterns than previous methods. This breakthrough not only strengthens our understanding of quantum mechanics in bound lepton-antilepton systems but also paves the way for future applications. Potential uses include non-destructive surface analysis of insulators and magnetic materials due to positronium's neutral charge. More importantly, it opens possibilities for precision experiments testing how antimatter interacts with gravity, a fundamental question that has yet to be directly measured. The findings were published in Nature Communications.

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