Mechanical Spin Control of Nitrogen-Vacancy Centers in Diamond

We demonstrate direct coupling between phonons and diamond nitrogen-vacancy (NV) center spins by driving spin transitions with mechanically generated harmonic strain at room temperature. The amplitude of the mechanically driven spin signal varies with the spatial periodicity of the stress standing wave within the diamond substrate, verifying that we drive NV center spins mechanically. These spin-phonon interactions could offer a route to quantum spin control of magnetically forbidden transitions, which would enhance NV-based quantum metrology, grant access to direct transitions between all of the spin-1 quantum states of the NV center, and provide a platform to study spin-phonon interactions at the level of a few interacting spins.

Figure 1

(a) Schematic of an NV center. The $z$ axis corresponds to the symmetry axis of the NV center. (b) Levels of an NV center ground-state spin. Magnetic driving enables $\Delta m_s=\pm 1$ transitions, whereas mechanical driving can produce $\Delta m_s=\pm 2$ transitions. (c) Reflected microwave power ($S_{11}$) as a function of frequency from the MEMS device measured using a network analyzer. Standing wave resonances have $Q\mathrm{s}$ as high as 437. (d) Device schematic. A loop antenna produces gigahertz-frequency magnetic fields for magnetic control while an HBAR produces gigahertz-frequency stress standing waves within the diamond.

Figure 2

(a) Pulse sequence used for ODMSR measurements. (b) Population driven into the $|+1⟩$ state by the mechanical driving field as a function of the axial magnetic field $B_{\parallel }$ for ${\omega }_{\mathrm{HBAR}}=2\pi \times 1.076\mathrm{GHz}$ at room temperature. (c) NV hyperfine structure labeled with the experimentally observed transitions. Each arrow corresponds with the resonance condition ${\omega }_{\pm 1}={\omega }_{\mathrm{HBAR}}$ for each of the three nuclear spin sublevels.

Figure 3

(a) Normalized PSF of our confocal microscope plotted at a node and an antinode of the stress standing wave. (b) Peak ODMSR signal as a function of depth inside the diamond. The oscillations as a function of focal depth correspond to oscillations in stress along the standing wave used to drive spin transitions.