Spin a vessel of water and, in time, the fluid will rotate as a rigid body, everywhere circling with the same angular velocity. Replace the water with a superfluid—a liquid chilled to a viscosity-free quantum state—and the flow instead spawns quantum tornadoes, vortices in which fluid circulates with quantized angular momentum.
First predicted more than a half century ago, quantized vortices have been studied extensively in experiments with rotating cryostats of liquid helium. They are thought to underlie such exotic phenomena as quantum turbulence (see the article by Joe Vinen and Russell Donnelly, Physics Today, April 2007, page 43), and they’ve been shown to reconnect in a fashion analogous to the magnetic reconnections that instigate solar flares.
When it comes to elucidating the underlying physics of rotating superfluids, however, cryostats have their limitations. Defects along the container’s surface inevitably disturb the flow in ways that can’t be neatly...
