Spin ensemble-based AC magnetometry using concatenated dynamical decoupling at low temperatures

TL;DR

This study compares various dynamical decoupling protocols for NV center-based AC magnetometry at different temperatures and frequencies, highlighting the effectiveness of concatenated XY sequences at low temperatures for high-frequency fields.

Contribution

It demonstrates that concatenated XY-based dynamical decoupling enhances sensitivity for high-frequency AC magnetic field measurements at low temperatures.

Findings

Concatenated XY sequences improve high-frequency sensitivity.

CPMG protocol is less effective due to pulse imperfections.

Cooling enhances low-frequency measurement performance.

Abstract

Ensembles of nitrogen-vacancy (NV) centers in diamond are widely used as AC magnetometers. While such measurements are usually performed using standard (XY) dynamical decoupling (DD) protocols at room temperature, we study the sensitivities achieved by utilizing various DD protocols, for measuring magnetic AC fields at frequencies in the 10-250 kHz range, at room temperature and 77 K. By performing measurements on an isotopically pure $^{12}$C sample, we find that the Carr-Purcell-Meiboom-Gill (CPMG) protocol, which is not robust against pulse imperfections, is less efficient for magnetometry than robust XY-based sequences. The concatenation of a standard XY-based protocol may enhance the sensitivities only for measuring high-frequency fields, for which many ($> 500$) DD pulses are necessary and the robustness against pulse imperfections is critical. Moreover, we show that cooling is effective only for measuring low-frequency fields (~10 kHz), for which the experiment time apporaches $T_1$ at a small number of applied DD pulses.