A speck of metal with 10,000 atoms was held in two places at once

Physicists have put a metal particle made of up to 10,000 atoms into a state where it occupied two slightly separated positions at the same time. The cluster is barely visible at all — about eight nanometres across — but it is far larger and far heavier than anything previously held in a verified quantum superposition. For the first time, the textbook strangeness usually reserved for single atoms and small molecules has been shown to extend to a real piece of solid metal.

A quantum superposition is the situation in which a particle behaves, for as long as it stays isolated from its surroundings, as if it were in more than one place at once. The famous thought experiment of Schrödinger’s cat is the popular cartoon, but the laboratory version is more sober and more revealing: send a particle through a precise arrangement of obstacles and look at the pattern of where it lands. If it interferes with itself, it was in two places along the way. If it does not, it behaved like a classical object.

The sodium clusters used here weigh more than 170,000 atomic mass units, which puts the particle roughly an order of magnitude beyond the previous heaviest object placed in such a state. The spread of the superposition was dozens of times wider than the particles themselves, a regime physicists describe with a quantitative score called macroscopicity, where the new result reaches μ = 15.5.

The experiment was done by groups at the University of Vienna and the University of Duisburg-Essen, with doctoral researcher Sebastian Pedalino as lead author and Markus Arndt, Stefan Gerlich and Klaus Hornberger as the principal investigators. The technique they used is called near-field matter-wave interferometry. Three diffraction gratings made of ultraviolet laser light act as the obstacles. The clusters cross them in sequence, and the way they pile up on the detector tells the team whether each one travelled as a wave through the apparatus, in two places at once, or as an ordinary particle.

The point of the experiment is not to enable a new technology. The point is to keep pushing the boundary where quantum mechanics has been tested and where it might break. Every prediction of the theory has held in every region probed so far, but the theory says nothing about why classical objects in everyday life never seem to be in two places at once. Stretching the regime to heavier and more complex objects sharpens that question, and any future failure of interference at a particular mass scale would amount to direct evidence of new physics.

The result is constrained. The interference signal lives only at deeply ultracold temperatures and only for about a hundredth of a second of free flight through the apparatus, after which residual gas, radiation and thermal motion destroy the coherence. The cluster sizes are still microscopic by ordinary standards. And the experiment relies on assumptions about the laser-light gratings and the cluster source that the team must defend against alternative explanations, which is part of what peer review tested.

Compared to where the field stood a couple of decades ago, when interference was first shown for the 60-atom carbon molecule known as a buckyball, the current result is dramatic. The mass jump is roughly two orders of magnitude beyond those early demonstrations, and the macroscopicity score is comparably higher. Each step closer to objects the size and complexity of viruses or living cells is also a step closer to where intuition stops being a useful guide.

The work appeared in May 2026 in Nature. The Vienna and Duisburg-Essen teams have stated their next phase will target still larger particles and different material compositions, the natural ladder upward in this line of experiments, and will explore whether the matter-wave technique can be used as a precision sensor for forces and properties at the nanoscale.