Synopsis

Free Falling Matter Waves

A new experiment using matter-wave interferometry confirms that different atoms free fall in gravity at the same rate.

Dennis Schlippert/Institut für Quantenoptik and Centre for Quantum Engineering and Space-Time Research

Dennis Schlippert/Institut für Quantenoptik and Centre for Quantum Engineering and Space-Time Research ×

Objects of different masses—such as feathers and bowling balls—should fall at the same rate in the absence of friction forces. However, some quantum gravity theories predict that gravitational acceleration may depend on an object’s properties, like its atomic makeup. A new experiment, described in Physical Review Letters, looks for such an effect by comparing for the first time the free-fall accelerations of different atomic elements in the same matter-wave interferometer. The results confirm the universality of free fall and may constrain alternative gravity models.

Many experiments over the years have tested free fall with lunar laser ranging and torsion balances. More recently, physicists have used matter-wave interferometry to measure gravitational acceleration of quantum particles. Although not yet as precise as macroscopic tests, interferometer experiments offer the possibility to directly test how gravity depends on quantum properties such as atomic spin.