A gate-tunable, field-compatible fluxonium

TL;DR

This paper introduces a hybrid fluxonium circuit with a semiconducting nanowire that is compatible with magnetic fields up to 1T, enabling new studies of spin-polarized phenomena and topological qubits.

Contribution

It demonstrates a gate-tunable, field-compatible fluxonium circuit using a semiconducting nanowire, expanding capabilities for quantum information and condensed matter research.

Findings

Operates in magnetic fields up to 1 Tesla.

Observes the $oldsymbol{ heta}_0$-Josephson effect.

Enables exploration of spin-polarized phenomena.

Abstract

Circuit quantum electrodynamics, where photons are coherently coupled to artificial atoms built with superconducting circuits, has enabled the investigation and control of macroscopic quantum-mechanical phenomena in superconductors. Recently, hybrid circuits incorporating semiconducting nanowires and other electrostatically-gateable elements have provided new insights into mesoscopic superconductivity. Extending the capabilities of hybrid flux-based circuits to work in magnetic fields would be especially useful both as a probe of spin-polarized Andreev bound states and as a possible platform for topological qubits. The fluxonium is particularly suitable as a readout circuit for topological qubits due to its unique persistent-current based eigenstates. In this Letter, we present a magnetic-field compatible hybrid fluxonium with an electrostatically-tuned semiconducting nanowire as its non-linear element. We operate the fluxonium in magnetic fields up to 1T and use it to observe the $\varphi_0$-Josephson effect. This combination of gate-tunability and field-compatibility opens avenues for the exploration and control of spin-polarized phenomena using superconducting circuits and enables the use of the fluxonium as a readout device for topological qubits.