MIT’s Quantum Leap: First-Ever Images of Freely Interacting Atoms Unveiled

Physicists at MIT have successfully captured groundbreaking images of individual atoms interacting freely in space, revealing quantum correlations previously only theorized. Published in Physical Review Letters on May 5, 2025, these findings provide a new window into quantum phenomena, enabling scientists to observe atomic behaviors in unprecedented detail.

The team developed an innovative imaging method called “atom-resolved microscopy.” They begin by confining a cloud of atoms within a laser-based trap, allowing the atoms to move and interact naturally. A lattice of light is then activated to momentarily immobilize the atoms, followed by precisely calibrated laser pulses that illuminate them. This fluorescence captures the atoms’ exact positions before they disperse, producing a snapshot of their interactions.

Using this technique, the researchers imaged various atomic clouds, achieving several imaging milestones. They observed bosons—atoms like sodium that tend to cluster due to their quantum properties—forming a wave-like pattern known as a Bose-Einstein condensate. Additionally, they captured fermions, such as lithium atoms, pairing up in free space, a process critical to phenomena like superconductivity.

“This technique lets us see individual atoms and their interactions within these fascinating clouds, which is visually stunning and scientifically profound,” said Martin Zwierlein, Thomas A. Frank Professor of Physics at MIT.

Concurrently, two other research groups reported similar advances in the same journal issue. A team led by Nobel laureate Wolfgang Ketterle, also at MIT, imaged enhanced boson pair correlations, while a group from École Normale Supérieure in Paris, led by Tarik Yefsah, visualized noninteracting fermions.

Overcoming Imaging Challenges

Atoms, measuring about 0.1 nanometers in diameter, are governed by quantum mechanics, making their precise position and velocity inherently uncertain. Traditional methods, like absorption imaging, reveal only the general structure of atomic clouds, akin to seeing a cloud’s shape without discerning its constituent particles.

The MIT team’s approach diverges by enabling direct visualization of individual atoms. They trap atoms loosely with lasers, allowing free interactions, then use a light lattice to freeze them in place. A second laser induces fluorescence to map their positions. “Collecting light without disrupting the atoms was the biggest challenge,” Zwierlein explained. “We’ve refined techniques to gently illuminate them in situ, capturing their interactions at the moment of freezing.”

Observing Quantum Behaviors

The team applied their method to study bosons and fermions, distinguished by their spin. Bosons, with even total spin, attract each other, while fermions, with odd spin, repel their own kind but can pair with different fermion types. Imaging sodium bosons, the researchers visualized their tendency to “bunch” into a shared quantum wave, a phenomenon tied to the de Broglie hypothesis, which underpins modern quantum mechanics. This wave-like behavior, first observed directly by the team, confirms long-standing predictions.

For fermions, the team used lithium atoms to observe opposite types forming pairs, a mechanism foundational to superconductivity. “Seeing these pairs in a photograph makes abstract mathematical models tangible,” said co-author Richard Fletcher, assistant professor at MIT.

Future Applications

The team plans to use this imaging technique to explore complex quantum phenomena, such as quantum Hall states, where electrons exhibit novel behaviors under magnetic fields. These states, often depicted theoretically due to their complexity, can now be empirically verified. “Our microscope lets us test whether these theoretical sketches match reality,” Zwierlein noted.

The study, co-authored by MIT graduate students Ruixiao Yao, Sungjae Chi, Mingxuan Wang, and Richard Fletcher, was supported by the National Science Foundation, the MIT-Harvard Center for Ultracold Atoms, the Air Force Office of Scientific Research, the Army Research Office, the Department of Energy, the Defense Advanced Projects Research Agency, a Vannevar Bush Faculty Fellowship, and the David and Lucile Packard Foundation.