Towards a micromechanical qubit based on quantized oscillations in superfluid helium

TL;DR

This paper proposes a novel superfluid helium-based qubit device leveraging quantized superfluid motion and mechanical elements, potentially achieving charge-neutral quantum computing with long coherence times.

Contribution

It introduces a new superfluid helium qubit concept using quantized oscillations and mechanical coupling, expanding quantum device architectures beyond superconducting circuits.

Findings

Quantized superfluid motion can be harnessed for qubit operation.

Device engineering can achieve the necessary nonlinearity for qubits.

Potential for micron-sized, long-coherence superfluid qubits.

Abstract

Superconducting circuits can exhibit quantized energy levels and long coherence times. Harnessing the anharmonicity offered by Josephson junctions, such circuits have been successfully employed as qubits, quantum limited amplifiers and sensors. Here, we consider superfluidity as the charge-neutral analogue of superconductivity. Both dissipationless mass flow and Josephson tunneling have been demonstrated in superfluid helium. We propose a quantum device, consisting of a superfluid weak link and a mechanical element. The superfluid motion in this device is quantized. The resulting discrete energy levels are resolvable at millikelvin temperatures essential to maintaining the superfluid state. Appropriate device engineering can yield the necessary nonlinearity to realize qubit functionality. Hence, this device can potentially operate as a charge-neutral, superfluid quantum bit with micron-sized dimensions and millisecond scale coherence time. We show that this quantum regime is within reach for a range of device designs.