Concurrent sensing of vector magnetic field based on diamond nitrogen-vacancy ensemble using a time-divided hardware-synchronized protocol.

A diamond nitrogen-vacancy (NV) ensemble has been developed as a vector magnetometry platform for sensing external time-varying magnetic fields. However, due to the complexity of manipulating electron spins along different directions, a current vector NV magnetometer often needs a large amount of supporting equipment, preventing its applications in a compact circumstance. Here, we develop a hardware-level protocol to realize a multi-axis NV magnetometer using only a single channel of microwave generation and signal detection resources. This mechanism is to monitor each resonance serialized in a sequence and measure the electron-spin frequency shifts concurrently in real time. The functionality is realized by a home-made control system with an on-chip direct digital synthesis generator and signal processor. We finally achieve a vector sensitivity of around 14 nT/Hz on four different axes at the same time. We also analyze the phase delay of the sensing signal between different axes induced by the protocol. This protocol is compatible with other schemes to further improve the performance, such as hyperfine driving, balanced detection, and high-efficiency photon collection methods.