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An international research collaboration featuring scientists from the FAMU-FSU College of Engineering and the National High Magnetic Field Laboratory has discovered a fundamental universal principle that governs how microscopic whirlpools interact, collide and transform within quantum fluids, which also has implications for understanding fluids that behave according to classical physics.

The study, which was in the Proceedings of the National Academy of Sciences, revealed new insights into vortex dynamics within superfluid helium, a remarkable liquid that exhibits zero-resistance flow at temperatures approaching absolute zero. The research demonstrates that when these quantum vortices intersect and reconnect, they separate faster than their initial approach velocity, creating bursts of energy that characterize turbulence in both quantum and classical fluids.

"Superfluids offer a uniquely clear perspective on turbulence," said FAMU-FSU College of Engineering Professor Wei Guo, a study co-author. "We're beginning to understand the universal physics that connects quantum and classical worlds, and that's an exciting frontier for both science and technology."

Microscopic quantum tornadoes

Superfluid helium represents one of nature's most extraordinary states of matter. When cooled to near absolute zero temperatures, this unique substance transcends conventional fluid behavior, flowing without friction, defying gravity by climbing container walls and penetrating microscopic barriers with ease. Unlike ordinary liquids that can swirl freely, superfluid helium confines all rotational motion to quantized vortices, which are ultra-thin, hollow tubes that maintain precisely fixed circulation amounts dictated by quantum mechanical principles.

"These vortices are like microscopic tornadoes," Guo said. "Each one carries an exact amount of circulation, dictated by quantum mechanics. They are topologically protected, meaning they're remarkably stable and much easier to track than vortices in regular fluids."

This exceptional stability transforms these quantum structures into powerful investigative tools for exploring turbulence, one of the most complex and chaotic phenomena within physics, which influences everything from aircraft aerodynamics to oceanic current patterns.

Breakthrough discovery in vortex dynamics

Guo's team, together with collaborators in the UK and France, captured high-resolution imaging and conducted computational simulations that revealed the fundamental behavioral patterns of colliding quantum vortices. Their findings establish a universal physical law governing vortex interactions across multiple fluid types and temperature ranges.

The researchers injected tiny frozen particles of deuterium, an isotope of hydrogen, into superfluid helium to make invisible quantum vortices visible. They then used a laser sheet and a high-speed camera to capture how these vortices moved and reconnected.

"We found that after they reconnect, the vortices always move apart faster than they came together," Guo said. "This time-asymmetry, or irreversibility, turns out to be a fundamental property of how energy moves in fluids, whether they're quantum or classical."

Each reconnection event generated sudden energy bursts that propagated throughout the surrounding fluid medium, creating ripple-like effects comparable to cardiac rhythms sending waves through water. When multiple reconnections occur simultaneously within complex vortex networks, these coordinated energy releases can trigger distinctive forms of quantum turbulence with unique characteristics not observed in classical fluids.

Engineering and technology implications

While quantum vortices exist exclusively in exotic materials like superfluid helium, their behavioral patterns mirror fundamental principles governing vortices in everyday fluids, including air and water. This similarity enables quantum superfluid research to provide insights into classical mechanisms.

"By studying these well-behaved and easily observable quantum vortices, we gain valuable insight into the fundamental nature of turbulence," explains Yiming Xing, a postdoctoral researcher in Guo's group. "This understanding could one day help us design more efficient engines, optimize energy transfer in quantum systems, or even improve weather prediction models."

This transformative research exemplifies the power of international scientific collaboration, bringing together institutions including Newcastle University and Lancaster University in the UK, Côte d'Azur University in France and the Mauro Picone Institute for Computing Applications—National Research Council in Italy, alongside the research teams at FAMU-FSU.