Defects in solid-state semiconductors often introduce additional electronic states with energy lower than the band-gap, leading to color centers. Tens of different color centers are known for only diamond and silicon carbide, and their presence often enriches the original material’s optical and magnetic properties, enabling interesting applications in the fields of sensing, photonics, and more. In particular, the negative nitrogen-vacancy (NV？) center in diamond and negative boron vacancies in hexagonal boron-nitride (VB？), possess a combination of spin and optical properties that make them prototypical solid-state qubits. Spin coherence is key for any quantum application and ultimately sets the limit of sensing accuracy or computation fidelity. Despite its central role in the physics of paramagnetic defects, the contribution of spin-phonon interaction to relaxation and decoherence has not yet been fully understood and experiments are invariably interpreted by means of phenomenological models based on a simplistic Debye picture of phonons. Such a state of affairs effectively prevents the establishment of a rigorous understanding of spin dynamics in solid-state qubits and several outstanding questions are left unanswered. In this work, Sourav Mondal et al from the School of Physics, Trinity College in Ireland, applied ab initio spin dynamics simulations to address this problem and quantitatively reproduced the experimental temperature dependence of spin relaxation time and spin coherence time. They demonstrated that low-frequency two-phonon modulations of the zero-field splitting are responsible for spin relaxation and decoherence, and pointed to the nature of vibrations in two-dimensional (2D) materials as the culprit for their shorter coherence time. Moreover, 2D material hetero-structures and tailored surface coating might also offer a rich playground to tune the vibrational properties of spin qubits’ host environment. Although alternative relaxation pathways might be operative in spin qubits with different spin multiplicities or low-lying excited electronic states, these results are likely exportable to all spin qubits exhibiting zero-field splitting. This work provides an interpretation to spin-phonon decoherence in solid-state paramagnetic defects, offers a strategy to correctly interpret experimental results, and paves the way for the accelerated design of spin qubits.