  Nitrogen-vacancy (NV) centers in diamond constitute a solid-state nanosensing
paradigm. Specifically for high-precision magnetometry, the so-called Ramsey
interferometry is the prevalent choice where the sensing signal is extracted
from time-resolved spin-state-dependent photoluminescence (PL) data. Its
sensitivity is ultimately limited by the photon shot noise, which cannot be
sufficiently removed by averaging or frequency filtering. Here, we propose
Ramsey DC magnetometry of a single NV center enhanced by a wavelet-denoising
scheme specifically tailored to suppress photon shot noise. It simply operates
as a classical post-processing applied on a collected PL time series. Our
implementation is based on a method that we named template margin thresholding
which enables not only frequency but also time-dependent denoising. We
computationally benchmark its DC magnetic field sensing signal-to-noise-ratio
improvement over the raw PL data around an order of magnitude.
