# Observation of positronium diffraction

## TL;DR

Scientists observed the wave-like behavior of positronium through diffraction, confirming its quantum nature and opening new possibilities for precision experiments.

## Contribution

The first experimental observation of positronium diffraction, confirming its quantum wave behavior and single-entity nature.

## Key findings

- Positronium beams exhibit a 1st-order diffraction peak consistent with quantum wave predictions.
- The results confirm that positronium behaves as a single quantum entity rather than separate particles.
- This experiment marks a major advance in fundamental physics involving positronium.

## Abstract

Diffraction of matter waves is a fundamental consequence of quantum mechanics, directly illustrating the core principles of wave-particle duality, quantum superposition, and quantum interference. De Broglie’s proposal that particles exhibit wave-like properties has been experimentally confirmed for electrons, neutrons, and composite systems such as helium atoms, molecules and clusters. Here, we report the observation of positronium diffraction using a high-quality, energy-tunable positronium beam transmitted through graphene. Time-of-flight selection and spatially resolved detection reveal a distinct 1st-order diffraction peak at a position consistent with the prediction from matter-wave considerations for positronium. This work provides the direct and definitive evidence of quantum interference in positronium beams and confirms that it behaves as a single quantum entity rather than two independent interfering particles. This groundbreaking experimental milestone marks a major advance in fundamental physics, not only demonstrating positronium’s wave nature as a bound lepton-antilepton system but also opening pathways for precision measurements involving positronium.

Recent experiments with positronium are opening new avenues towards laser cooling and manipulation. Here, the authors experimentally demonstrate the matter wave nature of positronium by measuring diffraction of positronium beams.