Unveiling the limits in the coherence of spin qubits against magnetic noise

TL;DR

This paper introduces a first-principles model to evaluate decoherence in spin qubits caused by magnetic noise, revealing limits to coherence times in complex systems and improving understanding of magnetic qubit behavior.

Contribution

The paper presents a new general model for assessing spin bath effects on qubit coherence, applicable to complex magnetic molecules with high spin states.

Findings

The model accurately reproduces experimental phase memory times in simple systems.

It explains the coherence limits at clock transitions in high-spin magnetic molecules.

The approach surpasses previous models in complex, high-spin systems.

Abstract

The realization of spin-based logical gates crucially depends on magnetically-coupled spin qubits. Thus, understanding decoherence when spin qubits are in close proximity will become a roadblock to overcome. Herein, we provide a general first-principles model that straightforwardly evaluates the spin bath effect on the qubit phase memory time $T_m$ . The method is applied to a ground-spin $J=8$ magnetic molecule 1 displaying atomic clock transitions, which remarkably increase $T_m$ at unusually high spin concentrations. Besides reproducing experimental $T_m$ values calculated by recent models in simple spin-1/2 systems, our approach unveils the causes that limit the coherence reached at the clock transitions in more challenging systems such as 1, where these previous models fail.