Nitrogen Defect Centers

Nitrogen vacancy centers are defects of the diamond crystal structure: a nitrogen atom is present instead of one of the carbon atoms, and one of the neighboring positions in the lattice is vacant.

A specially prepared diamond is irradiated with a green laser, which puts the NV centers into an excited state. In this state, the NV centers can emit light and also change their quantum states when they interact with an external magnetic field. (Here, spontaneous parametric downconversion is used to create entangled signal photons with perpendicular polarization from pump photons. After data acquisition, the emitted light is analyzed using ADCs or TDCs to obtain information about the magnetic field that affected the NV centers. By evaluating the polarization & possibly the intensity of the light, the magnetic field strength and direction in the vicinity of the NV centers can be determined. Such measurements using quantum sensors based on NV centers are absolute, operate at room temperature, and require no separate calibration. Therefore, the methods are robust and reproducible. Consequently, current flows of micro- and nanoelectronic circuits can be imaged with high resolution in this way.

Advantages:

• High sensitivity precision, and long-term stability in magnetic and electric field measurements.
• Robust and easy to control.
• Operates at room temperature.

Disadvantages:

• Limited spatial resolution and frequency range.

Application areas: optical magnetometry, nitrogen defect magnetometry, nanotechnology, materials science, quality control in microelectronics, biomedical research, and quantum information technology.

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