Sensitive AC and DC Magnetometry with Nitrogen-Vacancy Center Ensembles in Diamond

TL;DR

This paper demonstrates the most sensitive bulk NV-center magnetometer to date by combining advanced diamond growth, quantum sequences, and P1 driving, achieving near-DC and AC sensitivities of hundreds of femtotesla per root Hertz.

Contribution

It introduces a highly sensitive NV-based bulk magnetometer with optimized diamond growth and quantum control techniques, surpassing previous performance benchmarks.

Findings

Achieved near-DC sensitivity of ~460 fT/Hz^{1/2}.

Achieved narrowband AC sensitivity of ~210 fT/Hz^{1/2}.

Demonstrated the effectiveness of tailored diamond growth and quantum sequences.

Abstract

Quantum sensing with solid-state spins offers the promise of high spatial resolution, bandwidth, and dynamic range at sensitivities comparable to more mature quantum sensing technologies, such as atomic vapor cells and superconducting devices. However, despite comparable theoretical sensitivity limits, the performance of bulk solid-state quantum sensors has so far lagged behind these more mature alternatives. A recent review~\cite{barry2020sensitivity} suggests several paths to improve performance of magnetometers employing nitrogen-vacancy defects in diamond, the most-studied solid-state quantum sensing platform. Implementing several suggested techniques, we demonstrate the most sensitive nitrogen-vacancy-based bulk magnetometer reported to date. Our approach combines tailored diamond growth to achieve low strain and long intrinsic dephasing times, the use of double-quantum Ramsey and Hahn echo magnetometry sequences for broadband and narrowband magnetometry respectively, and P1 driving to further extend dephasing time. Notably, the device does not include a flux concentrator, preserving the fixed response of the NVs to magnetic field. The magnetometer realizes a broadband \textcolor{mhsnew}{near-}DC sensitivity $\sim 460$~fT$\cdot$s$^{1/2}$ and a narrowband AC sensitivity $\sim 210$~fT$\cdot$s$^{1/2}$. We describe the experimental setup in detail and highlight potential paths for future improvement.