An NV- center in magnesium oxide as a spin qubit for hybrid quantum technologies

TL;DR

This paper identifies a specific NV- defect in magnesium oxide with promising properties for quantum technology applications, supported by first-principles calculations of its electronic, optical, and spin characteristics.

Contribution

The study introduces a novel NV- center in MgO with detailed theoretical predictions of its properties, aiding experimental identification and potential quantum device integration.

Findings

Identified a stable NV- defect in MgO with favorable quantum properties.

Predicted optical and spin parameters including zero-phonon lines and hyperfine interactions.

Discussed strategies to enhance the defect's coherence by reducing vibronic coupling.

Abstract

Recent predictions suggest that oxides, such as MgO and CaO, could serve as hosts of spin defects with long coherence times and thus be promising materials for quantum applications. However, in most cases specific defects have not yet been identified. Here, by using a high-throughput first-principles framework and advanced electronic structure methods, we identify a negatively-charged complex between a nitrogen interstitial and a magnesium vacancy in MgO with favorable electronic and optical properties for hybrid quantum technologies. We show that this NV- center has stable triplet ground and excited states, with singlet shelving states enabling optical initialization and spin-dependent readout. We predict several properties, including absorption, emission, and zero-phonon line energies, as well as zero-field splitting tensor, and hyperfine interaction parameters, which can aid in the experimental identification of this defect. Our calculations show that due to a strong pseudo-Jahn Teller effect and low frequency phonon modes, the NV- center in MgO is subject to a substantial vibronic coupling. We discuss design strategies to reduce such coupling and increase the Debye-Waller factor, including the effect of strain and the localization of the defect states. We propose that the favorable properties of the NV- defect, along with the technological maturity of MgO, could enable hybrid classical-quantum applications, such as spintronic quantum sensors and single qubit gates.