Quantum whistling in superfluid 4He

TL;DR

This paper reports the observation of Josephson oscillations in superfluid helium-4 through nanometer-sized apertures at 2K, demonstrating macroscopic quantum coherence that could lead to advanced rotation sensors.

Contribution

First experimental observation of Josephson oscillations in superfluid helium-4 at relatively high temperature, showing coherence across multiple apertures.

Findings

Oscillations obey the Josephson frequency equation.

Oscillations are coherent among all apertures.

Phenomenon observed at 2K, much higher than similar effects in helium-3.

Abstract

Fundamental considerations predict that macroscopic quantum systems such as superfluids and the electrons in superconductors will exhibit oscillatory motion when pushed through a small constriction. Here we report the observation of these oscillations between two reservoirs of superfluid 4He partitioned by an array of nanometer-sized apertures. They obey the Josephson frequency equation and are coherent amongst all the apertures. This discovery at the relatively high temperature of 2K (2000 times higher than related phenomena in 3He) may pave the way for a new class of practical rotation sensors of unprecedented precision.