Quantitative nanoscale MRI with a wide field of view

Abstract

Novel magnetic sensing modalities using quantum sensors or nanoscale probes have drastically improved the sensitivity and hence spatial resolution of nuclear magnetic resonance imaging (MRI) down to the nanoscale. Recent demonstrations of nuclear magnetic resonance (NMR) with paramagnetic colour centres include single molecule sensitivity, and sub-part-per-million spectral resolution. Mostly, these results have been obtained using well-characterised single sensors, which only permit extended imaging by scanning-probe microscopy. Here, we enhance multiplexed MRI with a thin layer of ensemble spin sensors in an inhomogeneous control field by optimal control spin manipulation to improve ensemble sensitivity and field of view (FOV). We demonstrate MRI of fluorine in patterned thin films only 1.2 nm in thickness, corresponding to a net moment of 120 nuclear spins per sensor spin. With the aid of the NMR signal, we reconstruct the nanoscale depth distribution of the sensor spins within the substrate. In addition, we exploit inhomogeneous ensemble control to squeeze the point spread function of the imager to about 100 nm and show that localisation of a point-like NMR signal within 40 nm is feasible. These results pave the way to quantitive NMR ensemble sensing and magnetic resonance microscopy with a resolution of few ten nanometers.

Nonvanishing effect of detuning errors in dynamical-decoupling-based quantum sensing experiments

“…These findings show that detuning errors, which are often unavoidable in experiments, must not be neglected when extracting quantitative information from NMR data, such as the number of spins in the sample or the depth of the NV centre. While in this paper we focused on two of the simplest dynamical decoupling sequences, CPMG and XY8, it would be interesting to investigate the effect of detunings on quantitative NMR sensing based on more advanced protocols specifically designed to be more robust against pulse errors [41,60,61]. Another direction of interest is the study of different combinations of pulse errors in the NMR context, such as finite pulse-durations combined with a flip-angle error (i.e.…”

Surface NMR Using Quantum Sensors in Diamond

“…This results in a distribution of nearsurface NV-centers ∼ 5-12 nm below the surface [27]. For these implant conditions, we estimate an NV density of ∼ 50-100 NVs/µm 2 [28][29][30], corresponding to 2-4x10 5 NV-centers for the ∼ 4000 µm 2 spot used in our experiments as shown in Fig. 2 c (see Supplementary Note 3).…”

Principles and techniques of the quantum diamond microscope

“…As with broadband Ramsey spectroscopy, the pulse sequences used for narrowband AC magnetic imaging necessitate efficient temporal segmentation of NV fluorescence data at timescales of <1 microsecond, which is challenging for standard scientific imaging cameras. For this reason, there have been few reported demonstrations of NMR signal imaging using QDMs reported in the literature to date [122,123], and none with the spectral resolution required to distinguish molecular species. Nevertheless, we anticipate that ongoing work to integrate broadband Ramsey spectroscopy into the QDM platform can be directly extended to narrowband AC signal detection, and ultimately to high spectral-resolution NMR readout techniques [43,[132][133][134]].…”

“…(C) Imaging presence of 19 F on diamond surface through NMR signal. Panel reprinted with permission from[122] (D) High spatial resolution imaging of patterned19 F on diamond surface[123]…”