Fig. 1: Schematics of the proposed protocol.

a The nitrogen-vacancy (NV) spin state is transferred through an intermediate electron at the diamond surface. b Schematics of the microwave pulse sequence on the NV and the electron spin for pulsed polarization transfer. c Comparison between the direct PulsePol scheme and the double-channel PulsePol. In the latter, the electron interacts coherently with the NV and the nearby nuclei to mediate the polarization process. The introduction of the electron as mediator allows for stronger interactions and thus faster protocols.