dc Magnetometry with Engineered Nitrogen-Vacancy Spin Ensembles in Diamond

Abstract

The exquisite optical and spin properties of nitrogenvacancy (NV) centers in diamond have made them a promising platform for quantum sensing. The prospect of NV-based sensors relies on the controlled production of these atomic-scale defects. Here we report on the fabrication of a preferentially oriented, shallow ensemble of NV centers and their applicability for sensing dc magnetic fields. For the present sample, the residual paramagnetic impurities are the dominant source of environmental noise, limiting the dephasing time (T 2 *) of the NVs. By controlling the P1 spin-bath, we achieve a 4-fold improvement in the T 2 * of the NV ensemble. Further, we show that combining spin-bath control and homonuclear decoupling sequence cancels NV−NV interactions and partially protects the sensors from a broader spin environment, thus extending the ensemble T 2 * up to 10 μs. With this decoupling protocol, we measure an improved dc magnetic field sensitivity of 1.2 nT μm 3/2 Hz −1/2 . Using engineered NVs and decoupling protocols, we demonstrate the prospects of harnessing the full potential of NV-based ensemble magnetometry.

Benchmark for Synthesized Diamond Sensors Based on Isotopically Engineered Nitrogen‐Vacancy Spin Ensembles for Magnetometry Applications

“…Studies show up to 99% orientational polarization of NVs in samples grown along Figure 1. a) Overview of created NV centers in comparison to the nitrogen present in the diamond layer n NV ∕n N D for different CVD growth processes from this work, related work, [13][14][15]18] and work covering electron irradiated and annealed ⟨100⟩ samples. [30,31] the ⟨111⟩ crystal direction.…”

“…[16,17] Compared to the lowenergy ion implantation technique, nitrogen incorporation (e.g., N doping) during diamond growth avoids the collateral damage of the crystal lattice, thus improving the spin environment of individual NV centers. Although some demonstration of enhanced magnetometry with preferentially aligned ensembles has been achieved, [18,19] the coherence time and the ensembles' density remain as critical limitations toward realistic applications. One of the primary reasons is the low N to NV creation efficiency in these samples.…”

“…The latter's estimation was performed using a pulsed detection scheme with a readout laser pulse of l = 300 ns, full spin contrast, and a count rate of a single NV center c R = 200 kcts s −1 as reported in ref. [1,18,32]. Conditions of the growth processes are microwave (MW) frequency f = 2.46 GHz, MW power P = 1.92 kW, pressure p = 52.5 mbar, methane concentration c M = 0.1 % with respect to hydrogen which was applied with a flow of 400 sccm.…”

Ultrasensitive Magnetic Field Sensors for Biomedical Applications

“…Currently, this magnetometer can achieve a detection limit of 10 pT/√Hz [152,153], but the predictable detection limit is of the order of 1 fT/√Hz [154]. There are several experimental protocols relying on the detection of luminescent light ((i)), and on the detection of the probe beam ((ii)) [155,156]. The geometries for and ((ii) and (iii)) are shown in panels (a) and (b) of Figure 10, respectively.…”

“…Hz [154]. There are several experimental protocols relying on the detection of luminescent light ((i)), and on the detection of the probe beam ((ii)) [155,156]. The geometries for and ((ii) and (iii)) are shown in panels (a) and (b) of Figure 10, respectively.…”