Scientists Put Metal Particles in Two Places at Once in Record-Breaking Quantum Experiment

Physicists have achieved a mind-bending quantum experiment that demonstrates even tiny chunks of metal can exist in multiple places simultaneously, according to new research published in Nature. Scientists from the University of Vienna and University of Duisburg-Essen showed that metallic nanoparticles made of thousands of sodium atoms still display quantum behavior despite being far larger and heavier than particles typically used in such experiments. The achievement represents one of the strongest tests yet of quantum mechanics on scales approaching the macroscopic world.

The research team, led by Markus Arndt and Stefan Gerlich, extended quantum effects to metallic nanoparticles measuring roughly 8 nanometers across, similar in scale to modern transistor components. Each cluster contained more than 170,000 atomic mass units, making them heavier than most proteins. Even at this unprecedented scale, the particles still produced measurable quantum interference, challenging our understanding of where quantum mechanics gives way to classical physics.

Lead author and doctoral student Sebastian Pedalino explained the counterintuitive nature of the findings: "Intuitively, one would expect such a large lump of metal to behave like a classical particle. The fact that it still interferes shows that quantum mechanics is valid even on this scale and does not require alternative models." The experiment essentially created what physicists describe as "Schrödinger's metal lump," referencing the famous thought experiment about a cat existing in multiple states simultaneously.

To achieve these results, researchers created ultracold sodium clusters containing between 5,000 and 10,000 atoms, then directed them through three diffraction gratings generated by ultraviolet laser beams. The first laser beam established each cluster's position with 10-nanometer accuracy and placed the particles into quantum superposition, allowing them to follow multiple paths simultaneously through the apparatus. When these possible paths overlapped later in the experiment, they produced a detectable striped interference pattern matching quantum theory predictions.

The results indicate that the metal particles did not occupy fixed positions during their flight but instead existed in quantum states spread over regions dozens of times larger than the particles themselves. This demonstration of quantum behavior in relatively large metallic objects opens new possibilities for understanding the boundary between quantum and classical physics, while potentially advancing quantum technologies that could harness such effects in larger, more practical systems.