Scientists have observed an astonishing demonstration of classical physics that allows for quantum behavior and manipulates a liquid of ultra-cold sodium atoms into a distinct tornado-like formation.
Particles behave differently at the quantum level, in part because their interactions with each other at this point have more power over them than the energy from their motion.
Then, of course, there is the overwhelming fact that quantum particles do not exactly have a specific fixed location like you or I, which affects how they interact.
By cooling particles down to as close to absolute zero as possible and eliminating other interference, physicists can observe what happens when these strange interactions take hold, as a team from MIT has just done.
“It’s a breakthrough to be able to see these quantum effects directly,” says MIT physicist Martin Zwierlein.
The team captured and spun a cloud of about 1 million sodium atoms using lasers and electromagnets. In previous research, physicists demonstrated that this would turn the cloud into a long needle-like structure, a Bose-Einstein condensate, where the gas begins to behave as a single entity with common properties.
“In a classic liquid, like cigarette smoke, it would just get thinner,” says Zwierlein. “But in the quantum world, a liquid reaches a limit to how thin it can become.”
In the new study, MIT physicist Biswaroop Mukherjee and colleagues pushed beyond this stage, capturing a series of absorption images that reveal what happens after atoms have shifted from being predominantly controlled by classical to quantum physics.
The image below highlights the densities of ultracold atoms across microseconds.
(Mukherjee et al., Nature, 2022)
The atomic cloud evolved from the needle-like condensate (left), passed through snake-shaped instability (center), and formed small tornadoes (right).
There are even tiny dark spots between the adjacent crystals (see the ‘x’ marks below) where vortices with counter-current occur – just as we see in complex weather systems (think of the rushing adjacent storms on Jupiter).
(Mukherjee et al., Nature, 2022)
“Here we have quantum weather: The liquid, simply from its quantum instability, fragments into this crystalline structure of smaller clouds and vortices,” Zwierlein explains.
“This development is linked to the idea of how a butterfly in China can create a storm [in the US], due to instabilities that set off turbulence. Even in classical physics, this gives rise to exciting patterns, such as clouds wrapping around the Earth in beautiful spiral motions. And now we can study this in the quantum world. “
The team controlled the system so that nothing else exerted a force on the atomic issues. This meant that only the interaction of the particles and their rotation were at play. Their resulting behavior showed supersolid properties, a bit like what electrons produce in the form of Wigner crystals.
While traditional crystal solids are usually composed of atoms arranged in a stationary, repeating lattice structure, these structures continue to oscillate but remain within a definable pattern – like a liquid pretending to be a solid by holding and flowing through a solid form.
The team essentially caused the atoms to behave as if they were electrons in a magnetic field. Using atoms in this way makes the resulting quantum phenomena easier to both manipulate and observe – paving the way for even more discoveries about this mind-bending world.
“We can visualize what individual atoms do and see if they obey the same quantum mechanical physics,” Zwierlein says.
This study was published in Nature.
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