Physicists Achieve Large-Scale Atomic Cluster Superposition in Quantum Test

Physicists at the University of Vienna have advanced the experimental testing of quantum superposition, a core concept famously illustrated by Erwin Schrödinger's 1935 thought experiment concerning a cat simultaneously existing in multiple states until observed. This research directly probes the boundary between the quantum and classical realms using increasingly massive physical systems. The findings, published in the journal Nature on January 21, 2026, establish a new benchmark in experimental physics by demonstrating quantum behavior in a cluster of approximately 7,000 sodium metal atoms, each about 8 nanometers in diameter.

The team successfully induced these atomic clusters to exist in a superposition of distinct trajectories, exhibiting wave-like properties that resulted in a detectable interference pattern across their separated paths. Quantum theory suggests no inherent size limit for superposition, but environmental interactions typically cause decoherence, forcing the system into a singular, classical state. The significance of this 2026 work is measured by its 'macroscopicity,' a metric that accounts for both the object's mass and the duration of the quantum state maintenance.

According to the University of Vienna announcement, this new superposition state represents an order of magnitude greater than the previous record in this specific experimental context. However, the prior record for the heaviest mass placed in superposition was set in 2023 by researchers at the Swiss Federal Institute of Technology in Zurich (ETH Zurich). The ETH Zurich experiment utilized a sapphire crystal resonator involving ten thousand trillion atoms, cooled near absolute zero to minimize thermal fluctuations, demonstrating quantum effects in an object visible to the unaided eye.

Stefan Gerlich, an author from the University of Vienna, acknowledged that scaling these experiments further presents increasing complexity, as larger objects have shorter associated wavelengths, making the differentiation between quantum mechanical predictions and classical behavior more challenging. Decoherence remains the primary obstacle to achieving larger superpositions. Despite these limitations, the research team has articulated a future objective to subject biological matter to similar quantum experiments, underscoring the rapid progress in bridging the quantum-classical divide.

Schrödinger's original paradox was intended to highlight the perceived absurdity of extending quantum principles to macroscopic objects. Modern experiments, such as this latest demonstration with thousands of atoms, provide fundamental data for theories attempting to reconcile quantum mechanics with classical reality, offering insight into the transition zone where quantum phenomena yield to the predictable physics of the macroscopic world.