Fig. 1
Initialization and coherent control of a host 14N nuclear spin in a nanodiamond. a Illustration of an nitrogen-vacancy (NV) center in a nanodiamond, with applied magnetic field B0 along the NV axis. b Level diagram of the electronic-nuclear-spin system in the ground-state manifold in a magnetic field B0 = 250 mT. Relevant transitions are shown: microwave (MW) electronic-spin transitions (blue arrows), radio frequency (RF) nuclear-spin transitions (orange arrows), optical electronic-spin polarization (straight green arrows), and the optically induced spin nuclear-electronic flip-flop transitions (green wavy arrows) γ− (stronger transitions between the mS = 0 and −1 states, solid) and γ+ (weaker transitions between the mS = 0 and 1 states, dashed). c Optically detected magnetic resonance (ODMR) of the hyperfine electronic-spin transitions. See main text for discussion of the data. Inset: ODMR pulse sequence −532 nm laser pulses initialize and readout the electronic-spin state, a MW π-pulse drives transitions, and an avalanche photodiode (APD) collects photons. d Spin-flip probability in a single optical cycle for γ±. Near the excited state level avoided crossing (orange dashed line), γ− is much stronger than γ+. Inset: the shift of electronic-spin levels with magnetic field B0, showing the crystal field splitting parameter Des/h = 1.42 GHz in the excited state and the level anti-crossing (orange circle)
