By Peter Weiss
Helium never ceases to amaze. Physicists have now heard a quantum-mechanical whistle emanating from two reservoirs of liquid helium-4 that were separated by a perforated membrane.
According to theory, when liquid helium is pushed through a tiny hole at ultracold temperatures, the substance oscillates at a frequency that, when amplified electronically, sounds like a whistle.
Other than confirming a quantum talent first predicted for helium-4 some 40 years ago, the new findings by Emile M. Hoskinson of the University of California, Berkeley and his colleagues may lead to ultraprecise devices that sense helium flow through a ring of punctured membranes to measure an object’s rotation. Those devices could prove useful for such tasks as measuring earthquakes and Earth’s spin, the scientists report in the Jan. 27 Nature.