Demonstration of vector magnetic field sensing by simultaneous control of nitrogen-vacancy centers in diamond using multi-frequency microwave pulses.

An ensemble of nitrogen-vacancy (NV) centers in diamond is a fascinating candidate to realize a sensitive magnetic field sensor. In particular, since the axes of the NV centers are distributed along four directions, a collection of measurement data from NV centers with different axes provides information on the vector components of a magnetic field. However, in the conventional approach, the low measurement contrast of NV centers limits the sensitivity of vector magnetic field sensing. Recently, to overcome this problem, multi-frequency control of the NV centers has been proposed. The key idea is that the four types of NV centers with different axes are simultaneously controlled by multi-frequency microwave pulses. Here, we demonstrate vector magnetic field sensing with an ensemble of NV centers in diamond via such multi-frequency control with pulsed-type measurements. We use Hahn echo pulses and extract information on the vector components of an applied AC magnetic field. We find that the sensitivity of diamond-based vector field sensing with multi-frequency control is better than that with single-frequency control for every vector component of a magnetic field.