Sebastian Morris and colleagues at the University of Cambridge directly observed ultraquantum turbulence for the first time. This type of turbulence exists only in quantum systems and differs fundamentally from everyday turbulence in ordinary fluids.
The researchers cooled thousands of potassium atoms to near absolute zero using lasers and electromagnetic fields, creating a dilute quantum gas. They shaped the atoms into a cylinder a few dozen micrometers in size and used the same tools to introduce a disturbance that generated turbulence and vortices.
To image the vortices, the team used a sheet of laser light to capture a single cross-sectional slice through the cylinder. "As soon as I got the first pictures, I felt like, this is the one," Morris said. "You can see these holes, these imprints of the vortex lines as they wind in and out of this imaged cross-sectional slice."
The researchers tracked how vortices tangled, broke apart, connected into rings, or moved toward the cylinder's edge as the quantum fluid returned to equilibrium. They found this process resembled behavior previously observed in liquid helium, another quantum fluid that is denser with stronger atomic interactions.
Christoph Eigen, also at Cambridge, noted that while the order formation process resembles liquid helium's behavior, nothing else does. Zoran Hadzibabic at Cambridge said this exemplifies universal behavior for a whole class of quantum systems that should appear in other dissimilar settings.
Thomas Gasenzer at Heidelberg University in Germany said mathematical models for ultraquantum turbulence have existed for decades, but imaging vortices remains difficult. The new work provides precise experimental evidence supporting those models.
Davide Proment at the University of East Anglia called the measurement phenomenal and an advance over past ultraquantum turbulence investigations. Gasenzer suggested the universality of the process could help explain ultraquantum turbulence in distant environments like the dark matter halo around neutron stars.
The findings appeared in Physical Review Letters.