MIT Physicists Formed Quantum Tornadoes by Spinning Ultra-Cold Atoms

The experiment documented what happens when atoms cross from classical physics to quantum behaviors

An image of spinning sodium atoms entering a state of quantum physics after first being in a state of classical physics
Reseachers observed sodium atoms breaking up into crystal particles that resemble tornado-like structures after entering a quantum state. Mukherjee et al, Nature, 2022

MIT researchers have now observed peculiar and eerie quantum mechanics in a twirling, fluid column of ultra-cold sodium atoms, Science Alert's Tessa Koumoundouros reports. As the particles shifted from being influenced by classical physics to quantum physics, the particles were observed spinning in a tornado-like structure.

The study, published this month in Nature, is the first direct documentation of the evolution of a rapidly-rotating quantum gas, Jennifer Chu explains in an MIT statement. MIT physicist Martin Zwierlein explains it is sort of similar to the way Earth's rotation spins up weather patterns.

“The Coriolis effect that explains Earth’s rotational effect is similar to the Lorentz force that explains how charged particles behave in a magnetic field,” Zwierlein says in a statement. “Even in classical physics, this gives rise to intriguing pattern formation, like clouds wrapping around the Earth in beautiful spiral motions. And now we can study this in the quantum world.”

On a quantum level, atoms behave differently because their interactions with each other hold more influence and power than the energy of their movements, per Science Alert. Scientists observed the tornado-like behavior after trapping and spinning a cloud of one million sodium atoms using lasers and electromagnets at 100 rotations per second. The team also cooled the particles to near absolute zero and eliminated any other interference to see what happens when quantum effects overrule classical physics.

In previous experiments called Bose-Einstein condensates, physicists have observed gas spin into a long, thin, needle-like structure that could be described mathematically as a single quantum mechanical entity—despite being made up of many particles influencing each other's movement, Science Alert reports. As the gas continued to spin, the research team caught the moment when the needle-like structure gave in to quantum instability. 

In the quantum world, fluid reaches a limit of how thin it can get before reaching instability. But in classical physics, cigarette smoke, for example, gets thinner and thinner until appearing to vanish into nothingness, explains MIT physicist and study author Richard Fletcher in a statement. But Fletcher and his team demonstrated what happens when the limits of classical physics are suppressed and pushed beyond this state to see how the needle-like matter would behave once it entered a quantum state. The spinning needle started to waver, corkscrew, and then finally broke into even tinier tornadoes made of quantum crystals, the statement reports. 

"This evolution connects to the idea of how a butterfly in China can create a storm here, due to instabilities that set off turbulence," Zwierlein explains in a statement. "Here, we have quantum weather: The fluid, just from its quantum instabilities, fragments into this crystalline structure of smaller clouds and vortices. And it's a breakthrough to be able to see these quantum effects directly."

The crystallization indicated that the gas was undergoing evolution from being in a classical world of physics to a quantum one. How the spinning atoms changed is similar to how Earth's rotations spin up weather patterns, explains Zwierlein in a statement. In the image, dark spots between the crystals show where counterflow occurs, Science Alert reports. 

While crystal solids usually are composed of atoms arranged in a symmetrical, ridged, and repeating structure—similar to the types of crystals electrons produce known as Wigner crystals. These types of crystals can fluctuate and remain in a fixed shape, like water turning to ice. The teams' cloud of atoms was shaped into quantum mini tornadoes because they made the particles behave like electrons in a magnetic field. 

"We thought, let's get these cold atoms to behave as if they were electrons in a magnetic field, but that we could control precisely," Zwierlein said in a statement. "Then we can visualize what individual atoms are doing and see if they obey the same quantum mechanical physics."