Subnanometre resolution in three-dimensional magnetic resonance imaging of individual dark spins

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.

High-efficiency resonant amplification of weak magnetic fields for single spin magnetometry at room temperature

“…Compared to the existing schemes that use the quantum nature of an intermediate spin for improving sensitivity, 18 we stress that our scheme is fully classical and thus should be easily realizable at room temperature-all the ingredients of our scheme are already demonstrated in separate experiments. 10,28,39,40 An alternative setup to achieve resonance between the qubit and FM is to place the NV-center and the FM on a cantilever 41 with resonance frequency in the GHz range. By driving the cantilever, we alleviate the necessity of driving the qubit at FMR frequency as the qubit field is modulated by the oscillations of the cantilever.…”

“…Ref. 10), consists of an NV-center near the target qubit and two distinct microwave sources that independently control the NV-center and qubit so that double electron-electron (electron-nuclear) resonance, DEER (DENR), can be performed.…”

“…10 These results are realizable due to the amazingly long decoherence times of NV-centers at room temperature and the ability to noninvasively engineer an NV-magnetometer very close to the magnetic sample. Although impressive, current state-of-the-art technology 15 is unable to detect a single nuclear spin; achieving such sensitivity would revolutionize magnetic imaging in chemical and biological systems by facilitating atomic resolution of molecules.…”

Magnetic Resonance Detection of Individual Proton Spins Using Quantum Reporters

“…1(a)] [12]. Clean (100) diamond surfaces in ambient conditions are known to host stable electron spins with S ¼ 1=2 and a g factor of 2 [13,14]. These spins have been considered to be deleterious because they are thought to cause decoherence of NV electronic spins within a few nanometers of the diamond surface [15,16].…”

Nanoscale nuclear magnetic imaging with chemical contrast

“…Second, exploiting advanced NMR techniques will provide a much greater variety of contrast mechanisms than simple isotope-labeling used in this study. In particular, J-couplings or chemical shifts will allow imaging of specific chemical bonds and substances, while Zeeman shifts in a magnetic field gradient could provide depth information with atomic resolution 26 . We therefore expect the technique to find applications in various fields of research.…”