Simultaneous wide-field imaging of phase and magnitude of AC magnetic signal using diamond quantum magnetometry

Abstract

Spectroscopic analysis of AC magnetic signal using diamond quantum magnetometry is a promising technique for inductive imaging. Conventional dynamic decoupling like XY8 provides a high sensitivity of an oscillating magnetic signal with intricate dependence on magnitude and phase, complicating high throughput detection of each parameter. In this study, a simple measurement scheme for independent and simultaneous detection of magnitude and phase is demonstrated by a sequential measurement protocol. Wide-field imaging experiment was performed for an oscillating magnetic field with approximately 100 µm-squared observation area. Single pixel phase precision was 2.1 • for 0.76 µT AC magnetic signal. Our method enables potential applications including inductive inspection and impedance imaging. A negatively charged nitrogen-vacancy (NV) center in diamond offers a promising material platform for quantum sensing 1,2. Spin-state manipulation with a state-selective microwave (MW) pulse, combined with spin-dependent fluorescence has been utilized for spectroscopic measurement of magnetic field. Fabrication of a dense ensemble of NV centers 3-6 allows these measurements to be applied in wide-field imaging modality 7-10 , and local current characterizations using NV center have been achieved 11-16. Wide-field imaging using NV center paves the way for inductive inspection 17,18 , which is still challenging with micron-scale resolution by established methods. Previous studies indicate that dynamical decoupling (DD) protocols like XY8 achieve magnetic field spectroscopy with high sensitivity for magnitude and phase of such a signa 19-22. Measuring magnitude and phase of oscillating magnetic signal is at the heart of Eddy-current inspection based upon inductive and impedance sensing, enabling conductivity measurement 23,24. Despite its high sensitivity, DD can only measure the output of fluorescence intensity with an intricate dependence on a magnitude and a phase of a signal. Therefore, a magnitude with a known phase or a phase with a known magnitude can only be measured with DD protocol 25. Independent and simultaneous measurements of magnitude and phase for magnetic field spectroscopy in wide-field open up new diamond applications such an accurate inductive sensing. In this study, we propose a stroboscopic measurement termed iQdyne 26 , a wide-field modality of Qdyne 27,28 enabled with lock-in detection, as a simple sensing scheme for magnitude b z and phase φ 0 of an oscillating magnetic field. The iQdyne provides an orthogonal measurement for magnitude and phase; it involves two input parameters (b z , φ 0) and time-series outputs I(b z)e iθ (φ 0) cos(2πft). Fourier analysis easily extracts two resulting parameters, magnitude I(b z) and phase θ(φ 0) , which are separated from each other and are readily interpretable. We implemented this stroboscopic protocol on a wide-field microscope and demonstrated an imaging experiment of an oscillating magnetic field generated from a current pattern fabricated on a diamond substrate. An ...

Non-invasive imaging of three-dimensional integrated circuit activity using quantum defects in diamond

“…Over the past decade, many efforts have been deployed to both improve the sensing capabilities of the NV centres [49][50][51][52][53] and to develop techniques to explore new regimes [54][55][56][57]. These combined advances led to remarkable achievements such as revealing electric fields associated with surface band bending in diamond [58] and probing Johnson noise in metals [59].…”

Optimized Planar Microwave Antenna for Nitrogen Vacancy Center based Sensing Applications

“…The radiated MW fields homogeneity on the scale of the aperture area enables higher coherence times for NV ensembles leading to enhanced sensitivities. Furthermore, simultaneous MW irradiation of high amplitude within a macroscopic area provides position independent high contrast and therefore improved signal-to-noise ratio making this antenna type promising for wide-field [21][22][23][24][25][26][27][28][29][30][31][32][33] as well as for scanning NV based sensing applications [13,[34][35][36][37][38][39][40][41].…”

“…Sensing with NVs can be typically divided into two approaches, either exploiting the atomic scale size of a single NV center to enable high resolution magnetometry or sacrificing the latter in favor of highly sensitive magnetometry with enhanced signal to noise ratio and sensitivity using an ensemble of NV centers. Sensing using ensembles requires highly homogeneous MW fields as any field inhomogeneity over the ensemble constitutes a dephasing and consequently reduces sensitivity [21][22][23][24][25][26][27][28][29][30][31][32][33]. Also for single NV-based schemes, spatially homogeneous fields are relevant especially, when scanning NV centers are used to image samples [13,[34][35][36][37][38][39][40][41].…”

Widefield quantum microscopy with nitrogen-vacancy centers in diamond: strengths, limitations, and prospects

“…Beside the measurement of static (DC) magnetic fields, NV microscopy has demonstrated utility in the detection of fluctuating magnetic fields at MHz and GHz frequencies, enabling electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectroscopy of liquid and solid samples. [23][24][25][26][27] Key advances include the reconstruction of two-dimensional (2D) current 28,29 and magnetization 30 distributions; mapping of electric fields 31 and strain [32][33][34] within the diamond; and operation at cryogenic temperatures. 35,36 The main applications of widefield NV microscopy considered so far are summarized in Figs.…”