Controlling a nuclear spin in a nanodiamond

The sensing capability of a single optically bright electronic spin in diamond can be enhanced by making use of proximal dark nuclei as ancillary spins. Such systems, so far realized only in bulk diamond, can provide orders of magnitude higher sensitivity and spectral resolution in the case of magnetic sensing, as well as improved readout fidelity and state storage time in quantum information schemes. Nanodiamonds offer opportunities for scanning and embedded nanoscale probes, yet electronic-nuclear spin complexes have so far remained inaccessible. Here, we demonstrate coherent control of a $¹³\mathrm{C}$ nuclear spin located 4 \AA{} from a nitrogen-vacancy center in a nanodiamond and show coherent exchange between the two components of this hybrid spin system. We extract a free precession time ${T}₂^*$ of $26 \ensuremath{\mu}\mathrm{s}$ for the nuclear spin, which exceeds the bare-electron free-precession time in nanodiamond by two orders of magnitude.