Quantum Scientists Put Metal Particles in Two Places at Once

Physicists have achieved a groundbreaking demonstration of quantum mechanics at an unprecedented scale, showing that tiny metallic particles composed of thousands of atoms can exist in multiple locations simultaneously. The experiment, conducted by researchers at the University of Vienna and University of Duisburg-Essen, represents one of the most ambitious tests of quantum theory ever attempted with large-scale objects, bringing quantum behavior closer to the everyday world than previously thought possible.

The research team, led by Markus Arndt and Stefan Gerlich, successfully demonstrated quantum interference using sodium nanoparticles measuring approximately 8 nanometers across and containing between 5,000 and 10,000 individual atoms. Each particle had a mass exceeding 170,000 atomic mass units, making them heavier than most biological proteins and similar in scale to components found in modern computer processors. Despite their relatively large size and mass, these metallic clusters still exhibited the wave-like behavior predicted by quantum mechanics.

To achieve this remarkable result, the scientists created ultracold sodium clusters and guided them through a sophisticated arrangement of three laser-generated diffraction gratings. The first ultraviolet laser beam positioned each cluster with nanometer precision while simultaneously placing the particles into quantum superposition states, allowing them to effectively travel multiple paths through the experimental apparatus at once. When these different quantum paths later overlapped, they produced measurable interference patterns that matched theoretical predictions.

"Intuitively, one would expect such a large lump of metal to behave like a classical particle," says lead author and doctoral student Sebastian Pedalino. "The fact that it still interferes shows that quantum mechanics is valid even on this scale and does not require alternative models." The results indicate that during their journey through the experiment, the particles did not occupy single, well-defined positions but instead existed in quantum states spread across regions dozens of times larger than the particles themselves.

The achievement represents what physicists describe as creating "Schrödinger cat states" with metallic matter, referencing the famous thought experiment about quantum superposition. The successful demonstration with such large particles pushes the boundaries of where quantum mechanics applies and could eventually inform the development of quantum technologies that operate with larger, more complex systems than current quantum devices.