Groundbreaking discovery: MIT team sees individual atoms behaving like waves, proving 100-year-old quantum theory

In a landmark experiment that bridges a century of quantum theory and modern technology, physicists have, for the first time, directly observed individual free-range atoms interacting in open space. Published on May 5, 2025, in Physical Review Letters, the breakthrough confirms a foundational theory proposed by Louis de Broglie in 1924 — that certain particles behave like waves.

The work, led by MIT physicist Martin Zwierlein, signals a new era in quantum mechanics and showcases a laser-based technique that brings the invisible world of atoms into sharp focus.

Atoms, despite being the fundamental units of matter, are notoriously elusive under direct observation. Their quantum behavior — existing in multiple states at once — complicates efforts to capture them in isolation. “Seeing a cloud in the sky, but not the individual water molecules that make up the cloud,” is how Martin Zwierlein once described the challenge.

This new experiment zeroed in on bosons, particles that tend to cluster and act like waves — a property predicted over a century ago by French physicist Louis de Broglie. His theory suggested that bosons wouldn’t behave like discrete objects but would instead exhibit collective, wave-like traits.

Zwierlein’s team has now visually confirmed this phenomenon. Using a precision laser setup, they were able to freeze sodium atoms in place at ultracold temperatures, forming a loose trap with a lattice of laser light. Another laser then illuminated the atoms’ exact positions, revealing the predicted wave behavior in striking clarity. “We are able to see single atoms in these interesting clouds of atoms and what they are doing in relation to each other, which is beautiful,” said Zwierlein.

The technique, known as atom-resolved microscopy, also captured images of lithium fermions — a class of particles that, unlike bosons, repel each other and refuse to bunch up. This contrast offers new avenues to study how different particles behave in the quantum world.

Beyond confirming de Broglie’s vision, the breakthrough paves the way for exploring deeper quantum effects. The team is already setting its sights on phenomena like the quantum Hall effect, where electrons move in sync under intense magnetic fields.