Spin-phonon decoherence in solid-state paramagnetic defects from first principles

TL;DR

This study uses first-principles simulations to understand spin-phonon decoherence in solid-state qubits, revealing the role of low-frequency vibrations and offering insights for designing more coherent quantum systems.

Contribution

It provides a quantitative ab initio analysis of spin-phonon relaxation, linking vibrational modes to decoherence in solid-state defect qubits, especially in 2D materials.

Findings

Low-frequency two-phonon processes cause spin relaxation.

Vibrations in 2D materials shorten coherence times.

Simulation results match experimental temperature dependence.

Abstract

Paramagnetic defects in diamond and hexagonal boron nitride possess a unique combination of spin and optical properties that make them prototypical solid-state qubits. Despite the coherence of these spin qubits being critically limited by spin-phonon relaxation, a full understanding of this process is not yet available. Here we apply ab initio spin dynamics simulations to this problem and quantitatively reproduce the experimental temperature dependence of spin relaxation time and spin coherence time. We demonstrate that low-frequency two-phonon modulations of the zero-field splitting are responsible for spin relaxation and decoherence, and point to the nature of vibrations in 2-dimensional materials as the culprit for their shorter coherence time. These results provide a novel interpretation to spin-phonon decoherence in solid-state paramagnetic defects, offer a new strategy to correctly interpret experimental results, and pave the way for the accelerated design of new spin qubits.