Diamond quantum DC magnetometer with efficient digital signal processing*

Nitrogen-vacancy (NV) centers in diamond are promising solid-state quantum sensors. The sensor can potentially monitor the real-time magnetic field at room-temperature toward the brain-machine interface. One of the biggest challenges is to implement a highly sensitive sensor in a compact system. The sensor based on a digital signal processing with the Fourier transform has an advantage of its simpler system than an analog type, but it is hard to monitor the real-time magnetic field because the method needs many computational resources.
Here, we demonstrate an alternative method of digital signal processing with less computational resources than the Fourier transform. The method uses a digital filter that effectively becomes a sinc filter utilizing the orthogonality of trigonometric functions by multiplication of the acquired data by a trigonometric function. The computational time of the method to compute the signal from n points of data is O(n), whereas the time with Fourier transform is O(n log n). We confirm our method with a large detection volume of the ensemble NV centers. Consequently, we obtained a DC magnetic field sensitivity of 2.4 nT/√Hz.