Double-Quantum Spin-Relaxation Limits to Coherence of Near-Surface Nitrogen-Vacancy Centers

We probe the relaxation dynamics of the full three-level spin system of near-surface nitrogen-vacancy (NV) centers in diamond to define a T₁ relaxation time that sets the T₂≤2T₁ coherence limit of the NV's subset qubit superpositions. We find that double-quantum spin relaxation via electric field noise dominates T₁ of near-surface NVs at low applied magnetic fields. Furthermore, we differentiate 1/fα spectra of electric and magnetic field noise using a novel noise-spectroscopy technique, with broad applications in probing surface-induced decoherence at material interfaces.