In the 21st century, quantum technologies promise to have a significant impact on different aspects of human life. For example, quantum sensing protocols can be used to measure different physical quantities with high sensitivity and spatial resolution. One of such potential sensors is the so-called NV center in diamond, which can be optically addressed. This work demonstrates the magnetometry applications of the NV-based magnetic field sensor in the scanning probe configuration. At the same time, the investigations of the charge state conversion of the defects in the phosphorus-doped diamond at cryogenic temperatures are presented.weiterlesen