Probing surface-mediated decoherence with nitrogen vacancy centers

Surface-mediated decoherence is a central obstacle to the development of quantum technologies. Quantitatively characterizing this decoherence requires attaining control over surface adsorbates coupled to a qubit-like degree of freedom. We have constructed an apparatus that allows reversible in-situ adsorption of indium atoms onto a diamond surface in UHV and direct measurement of adsorbate interactions with shallow subsurface nitrogen vacancy (NV) centers. Measuring NV spin properties at varying adsorbate densities, we observe adsorbate-induced decreases in T1, as well as a reduction in the contrast of Rabi oscillations. Exposure to a nanosecond pulsed laser partially reverses the effects. These results constitute progress toward reversible quantitative control over adsorbate-induced surface decoherence, and motivate the development of a cryogenic UHV “decoherence probe station” with in-situ surface preparation tools, the design of which we will briefly discuss.