Figure 1

(Color online) (a) Electronic-spin states of the NV center, showing the ESLAC near 510 G. Inset shows hyperfine levels and transitions for the ${}^{14}\text{N}$ isotope. (b)–(d) ESR for an NV center coupled to a proximal nuclear spin in $B=65\text{G}$ (top) and 509 G (bottom). (b) A third-shell ${}^{13}\text{C}$ [22, 25] exhibits $P=91\left(5\right)\%$ polarization at 509 G; parentheses indicate one standard deviation statistical error in the final digit. (c) ${}^{15}\text{N}$: $P=95\left(3\right)\%$. (d) ${}^{14}\text{N}$: $P=95\left(3\right)\%$.Reuse & Permissions

Figure 2

(Color online) (a) Pulse sequence. Following polarization, a MW $\pi$ pulse drives the system into the g.s. $m_s=-1$ state, where rf excites nuclear-spin transitions. A second MW $\pi$ pulse flips the electron spin back into $m_s=0$, and subsequent fluorescence detection reveals the average nuclear-spin projection. All data are taken in a magnetic field of $509\text{G}\parallel \widehat{z}$. Data for ${}^{13}\text{C}$, ${}^{15}\text{N}$, and ${}^{14}\text{N}$ are shown in (b,e,h), (c,f,i), and (d,g,j), respectively. (b)–(d) g.s. energy level diagrams for hyperfine levels; arrows indicate transitions driven by rf and MW; shading indicates the $m_s=-1$ manifold. (e)–(g) Fluorescence change [(signal-reference)/reference] vs rf frequency. Fitted resonance frequencies are given with one standard deviation statistical error. (h)–(j) Fluorescence vs rf pulse duration on resonance with a sinusoidal fit. Short-time data show contrast of electron-spin nutations for comparison.Reuse & Permissions

Figure 3

(Color online) (a) Energy levels for g.s. $m_s=0$ ${}^{14}\text{N}$ nuclear-spin manipulation. (b) Pulsed ESR spectra starting in $m_s=0$, $m_I=1$ (top) or $m_s=0$, $m_I=0$ (bottom). Dashed lines indicate expected ESR positions for the three hyperfine levels. (c) Nuclear Rabi nutations within the $m_s=0$ manifold. (d) NMR spectrum obtained using the pulse sequence illustrated. A fit to the expected square-pulse line shape yields resonant frequencies ${\omega }_1/\left(2\pi \right)=5.094\left(1\right)\text{MHz}$ and ${\omega }_2/\left(2\pi \right)=4.7908\left(7\right)\text{MHz}$, while the lower frequency line is deeper owing to the two-step polarization process for $m_I=-1$. (e) Nuclear Ramsey fringe experiment. The downward trend is likely due to electron-spin relaxation, which occurs at a rate $T_1\approx \text{few}$ ms at room temperature [14, 21].Reuse & Permissions

Figure 4

(Color online) (a) Theoretical transition probabilities and equilibrium polarization for ${}^{14}\text{N}$ with ${\mathbf{B}}_0=50\widehat{z}\text{G}$, $g{\mu }_B{\mathbf{B}}_1=20\widehat{z}\text{MHz}$, $\text{A}=50\text{MHz}$, $P=-5\text{MHz}$, $\text{D}=1.42\text{GHz}$, ${\gamma }_n=0.3077\text{kHz}/\text{G}$, ${\gamma }_e=2.8\text{MHz}/\text{G}$, $\gamma =2.5\Gamma$, and $k_{eq}={10}^{-5}\Gamma$. Resonances are indicated using the notation $|m_s,m_I⟩$. (b) Same as for (a), but with $g{\mu }_B{\mathbf{B}}_1=20\widehat{x}+20\widehat{z}\text{MHz}$ and ${\mathbf{B}}_0=40\widehat{x}+48\widehat{z}\text{G}$. The initial state in each resonance is $m_s=0$, $m_I=0$, $-1$, or $+1$; the final state in each resonance is noted as $|m_s,m_I⟩$. (c) Polarization of ${}^{14}\text{N}$ in ${\mathbf{B}}_0=40\widehat{x}+48\widehat{z}\text{G}$. Error bars indicate one standard deviation (statistical). Insets show ESR signal and fit for specific data points. (d) Polarization of ${}^{15}\text{N}$ under the same experimental conditions.Reuse & Permissions