Quantum-based Magnetic Field Sensing

In addition to the development of products in the defense sector (i.e. a sector that we at cronologic consciously refrain from serving), biomedicine in particular benefits from the new developments in quantum-based magnetic field sensing. The basic idea in biomedical quantum sensing is: as soon as magnetic or electric fields can be detected in living organisms, they can also be used for precise imaging. And if no suitable fields are available at the cell structures to be examined, medical biomarkers are used, e.g. in the form of magnetized nanoparticles, making imaging possible here as well.

Magnetometers based on quantum sensing basically offer significantly higher accuracy in the measurement of magnetic fields, since they characterize them at the atomic level.

Especially in cardiology and neurology, such new sensors for biomagnetism will certainly enable better diagnoses. They would be of advantage in magnetic resonance imaging (MRI), for example. While conventional MRI machines use conventional magnetometers to measure the magnetic fields generated by hydrogen atoms in the body's tissues, quantum-sensitive magnetometers could provide much greater sensitivity to measure these weak magnetic fields. It is already clear that the improvement in signal-to-noise ratio made possible by quantum technology will enable greater precision that will significantly improve image quality.

The core of such a quantum-sensitive magnetometer consists of quantum sensing detectors. Rubidium atoms are frequently used for this purpose, which is brought into a specific quantum state with the aid of laser beams as comparatively inexpensive laser diodes are available for the wavelengths relevant to the laser cooling of rubidium. This process is called "preparation" and ensures in the respective measurement environment that the quantum detectors are primarily sensitive to the external magnetic field. In the context of biological imaging, the external magnetic field interacts with the organic tissue under investigation and influences the quantum state of the detectors used. The changes in the respective quantum state are usually proportional to the strength and direction of the magnetic field. The detection of this interaction serves as the basis for the evaluation of the quantum states. In the course of data acquisition, the measurement results are converted into digital signals and forwarded to the imaging unit (e.g. one of the MRI machines).

Nitrogen vacancy magnetometry, for example, is based on optically detected magnetic resonance (ODMR). In this process, single nitrogen-vacancy centers (NV centers) in diamonds are used as quantum detectors to measure magnetic fields with high sensitivity and corresponding accuracy.
The quantum mechanical properties of a single nitrogen atom located at a vacancy in the diamond lattice make this atom sensitive to magnetic fields. More precisely, this measurement method takes advantage of the electron spin of the crystal defect to detect changes in the magnetic field by optical readout of photoemissions.

‍