Since its inception, quantum physics has been shrouded in mystery, challenging our understanding of reality. In this bizarre quantum world, particles can be in two places at once, act like both particles and waves, and even “spooky” actions can happen over vast distances instantly.
Put simply, quantum mechanics is so far removed from everyday life that to the uninitiated, it looks like a hoax. But it’s very much real — so real that British researchers have now managed to ‘touch it’.
In a new study, researchers at Lancaster University introduced a finger-sized probe into the superfluid helium-3. In the process, they grasped the sensation of “touching quantum physics.”
Probing the quantum world using superfluids
Superfluids are a unique state of matter. Imagine a fluid that flows without any resistance, almost like a magical liquid without friction. This is achieved when certain elements, like helium, are cooled to temperatures just above absolute zero (-273.15°C or -459.67°F). At these temperatures, helium’s atoms slow down, transforming it into a superfluid.
Physicists led by Samuli Autti carried out experiments at about a 10,000th of a degree above absolute zero in a special refrigerator and used a finger-sized mechanical resonator — which oscillates between kinetic and potential energy forms — to probe the very cold superfluid. The experiment’s results are groundbreaking not only for our knowledge of superfluids but also because they provide a feel for the intangible quantum world.
“In practical terms, we don’t know the answer to the question ‘How does it feel to touch quantum physics?,'” Alutti, a research fellow and lecturer at Lancaster, said. “These experimental conditions are extreme and the techniques complicated, but I can now tell you how it would feel if you could put your hand into this quantum system.”
Helium exists in different versions called isotopes, with helium-3 and helium-4 being two notable examples. Both can transform into superfluids, where the fluid flows without resistance. Helium-4 achieves this state when its particles, called bosons, become super-cold, causing them to act collectively as one giant “super-atom”.
On the other hand, helium-3 contains particles named fermions. Unlike bosons, fermions don’t naturally clump together. However, when helium-3 is cooled sufficiently, its fermions form “Cooper pairs” that mimic the behavior of bosons, allowing helium-3 also to achieve the superfluid state through this unique pairing mechanism.
Experiments conducted by Autti and his team with helium-3 superfluids led to intriguing findings. In particular, they discovered that inserting the rod into the superfluid did not harm the delicate Cooper pairs or otherwise alter the flow of the fluid.
The researchers observed that the superfluid’s surface appeared to develop an independent two-dimensional layer responsible for dissipating heat from the probe. The bulk of the superfluid underneath this layer displayed an almost vacuum-like quality. It seemed passive and practically imperceptible. Only the two-dimensional surface layer interacted with the probe, revealing that the superfluid’s thermomechanical properties were determined entirely by this layer.
“This liquid would feel two-dimensional if you could stick your finger into it,” Autti said. “The bulk of the superfluid feels empty, while heat flows in a two-dimensional subsystem along the edges of the bulk—in other words, along your finger.”
The implications of this research are far-reaching. Due to its rarity and purity, helium-3 superfluid has great scientific value for studying collective matter states. Understanding its two-dimensional layer dynamics may lead to new insights into quantum energy states, topological defects, and the behavior of quasiparticles.
After completing their study, the group emphasized the game-changing implications of their findings, writing “These research avenues have the potential to transform our understanding of this versatile macroscopic quantum system.”
This experiment, besides offering an almost tangible touch to quantum physics, might also light the way for future quantum research.
The findings appeared in the journal Nature Communications.