Metal nanoparticles exist in two places at once, study finds

Researchers from the University of Vienna and the University of Duisburg-Essen have demonstrated that metallic nanoparticles composed of thousands of sodium atoms still exhibit quantum mechanical behavior, specifically quantum interference. These nanoparticles, about 8 nanometers in size and weighing over 170,000 atomic mass units, are significantly larger than typical quantum objects like electrons or small molecules. Despite their size—comparable to components in modern electronics—they form interference patterns when passed through ultraviolet laser diffraction gratings, indicating they exist in a superposition of states, akin to Schrödinger cat states where the particles are simultaneously in multiple locations. This experiment marks a significant advancement in testing quantum mechanics at macroscopic scales, achieving a macroscopicity value of μ = 15.5, roughly ten times greater than previous experiments. The researchers created cold sodium clusters containing 5,000 to 10,000 atoms and used laser light to precisely control and measure their quantum states. The setup not only pushes the boundaries of quantum theory but also functions as