Abstract
Magnetic resonance imaging (MRI) has revolutionized biomedical science by providing non-invasive, three-dimensional biological imaging. However, spatial resolution in conventional MRI systems is limited to tens of micrometres, which is insufficient for imaging on molecular scales. Here, we demonstrate an MRI technique that provides subnanometre spatial resolution in three dimensions, with single electron-spin sensitivity. Our imaging method works under ambient conditions and can measure ubiquitous 'dark' spins, which constitute nearly all spin targets of interest. In this technique, the magnetic quantum-projection noise of dark spins is measured using a single nitrogen-vacancy (NV) magnetometer located near the surface of a diamond chip. The distribution of spins surrounding the NV magnetometer is imaged with a scanning magnetic-field gradient. To evaluate the performance of the NV-MRI technique, we image the three-dimensional landscape of electronic spins at the diamond surface and achieve an unprecedented combination of resolution (0.8 nm laterally and 1.5 nm vertically) and single-spin sensitivity. Our measurements uncover electronic spins on the diamond surface that can potentially be used as resources for improved magnetic imaging. This NV-MRI technique is immediately applicable to diverse systems including imaging spin chains, readout of spin-based quantum bits, and determining the location of spin labels in biological systems.
Highlights
Green Laser no signal readoutCrowave (MW) pulsing on the NV spin prepares a coherent superposition of NV-spin states with phase φNV that evolves with evolution time τNV in proportion to the local magnetic field (projected along the NV quantization axis) from the target dark spins (BDark)
Magnetic resonance imaging (MRI) has revolutionized biomedical science by providing noninvasive, three-dimensional biological imaging [1]
Spatial resolution in conventional MRI systems is limited to tens of microns [2], which is insufficient for imaging on molecular and atomic scales
Summary
Crowave (MW) pulsing on the NV spin prepares a coherent superposition of NV-spin states with phase φNV that evolves with evolution time τNV in proportion to the local magnetic field (projected along the NV quantization axis) from the target dark spins (BDark). For NV-MRI of dark spins with static tip gradients, the target-spin interrogation time is limited the target spin T2∗ ( 150 ns), enabling sub-nanometer 3D NV-MRI resolution To demonstrate such sub-nanometer NV-MRI performance, we spatially mapped the spin environment of individual NV centers near a diamond surface. To achieve high-precision spinlocalization in the lateral dimensions, we fit the center of mass of the measured dark-spin PSF and compared this PSF to the center of the response circle, yielding the lateral offset ∆x = 4.0 ± 0.4 nm
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