Spin Coherent Manipulation in Josephson Weak Links

TL;DR

This paper proposes a robust method combining spin polarization and Raman adiabatic passage to enable coherent spin manipulation in Josephson weak links, advancing the development of Andreev spin qubits despite noise and suppression issues.

Contribution

It introduces a novel protocol tailored for Josephson weak links that enhances coherent spin control, overcoming previous suppression and noise limitations.

Findings

The proposed method is robust across various design parameters.

It enables coherent spin manipulation within Andreev states.

The approach is effective even with current coherence time constraints.

Abstract

Novel designs of Josephson weak links based on semiconducting nanowires combined with circuit QED techniques have enabled the resolution of their fine structure due to spin-orbit interactions, opening a path towards Andreev spin qubits. Nevertheless, direct manipulation of the spin within a given Andreev state is in general suppressed compared to inter-doublet manipulation in the absence of Zeeman effects. In addition, noisy spin-flip mechanisms limit any coherent manipulation protocol to spin post-selection. We propose a combination of a spin polarization protocol analogous to sideband cooling with stimulated Raman adiabatic passage specifically tailored for these systems. We show this approach is robust for a large range of design parameters, including the currently rather stringent coherence times.