Discovery of Atomic Clock-Like Spin Defects in Simple Oxides from First Principles

TL;DR

This paper predicts new spin defects in simple oxides, specifically calcium oxide, that exhibit atomic clock-like transitions with long coherence times, promising for quantum technology applications.

Contribution

The study introduces a new class of spin defects in calcium oxide with properties similar to NV centers, including clock-like transitions and telecommunication-range emission, identified through first-principles calculations.

Findings

Bi defect emits in the telecommunication range.

Coherence time exceeds seconds at clock-like transition.

Defects exhibit controllable quantum levels.

Abstract

Virtually noiseless due to the scarcity of spinful nuclei in the lattice, simple oxides hold promise as hosts of solid-state spin qubits. However, no suitable spin defect has yet been found in these systems. Using high-throughput first-principles calculations, we predict spin defects in calcium oxide with electronic properties remarkably similar to those of the NV center in diamond. These defects are charged complexes where a dopant atom -- Sb, Bi, or I -- occupies the volume vacated by adjacent cation and anion vacancies. The predicted zero phonon line shows that the Bi complex emits in the telecommunication range, and the computed many-body energy levels suggest a viable optical cycle required for qubit initialization. Notably, the high-spin nucleus of each dopant strongly couples to the electron spin, leading to many controllable quantum levels and the emergence of atomic clock-like transitions that are well protected from environmental noise. Specifically, the Hanh-echo coherence time increases beyond seconds at the clock-like transition in the defect with \ch{^{209}Bi}. Our results pave the way to designing quantum states with long coherence times in simple oxides, making them attractive platforms for quantum technologies.