Spin-orbit coupling fluctuations as a mechanism of spin decoherence

We discuss a general framework to address spin decoherence resulting from fluctuations in a spin Hamiltonian. We performed a systematic study on spin decoherence in the compound ${\mathrm{K}}₆[{\mathrm{V}}₁₅{\mathrm{As}}₆{\mathrm{O}}₄₂({\mathrm{D}}₂\mathrm{O})]\phantom{\rule{0.16em}{0ex}}\ifmmode\cdot\else\textperiodcentered\fi{}\phantom{\rule{4pt}{0ex}}8{\mathrm{D}}₂\mathrm{O}$, using high-field electron spin resonance. By analyzing the anisotropy of resonance linewidths as a function of orientation, temperature, and field, we find that the spin-orbit term is a major decoherence source. The demonstrated mechanism can alter the lifetime of any spin qubit and we discuss how to mitigate it by sample design and field orientation.