Researchers Develop Highly Sensitive ­Optical Quantum Magnetometers that ­Reveal Deeply Buried Mineral Resources

Optical quantum magnetometers could make the search for raw materials more efficient and environmentally friendly. The Quantum Magnetometry group at Leibniz IPHT has developed a method that measures magnetic fields with high precision – without elaborate cooling. The technology could also open up new opportunities in medicine and industry.

Inside the silver-colored magnetically-shielded cylinder in the lab of the Quantum Systems research department, controlled conditions prevail. The cylinder blocks external magnetic fields – from Earth’s magnetic field to interference from lab equipment – and thus enables precise measurements. A Halbach cylinder inside generates a homogeneous magnetic field. Here, Dr. Thomas Schönau and Prof. Dr. Ronny Stolz are testing an optically pumped vector magnetometer. A tiny cesium vapor cell responds to the weakest changes in the magnetic field. A laser excites the atoms in the vapor, and their interaction with the field is read out via the transmitted light.

“This technology achieves a sensitivity that, until now, was only possible with superconducting magnetometers (SQUIDs) – but without their complex cryogenic requirements,” explains Ronny Stolz. He and his team developed the optical quantum magnetometer so that it can determine individual vector components of the Earth’s magnetic field – a key prerequisite for geophysical applications.

New Possibilities for ­Science and Technology

The magnetometer was developed as part of the OPTEM project, which explores optical methods for raw material exploration. In the future, the sensors are intended to replace the established superconducting systems previously used for geophysical measurements. Since they do not require cryogenic cooling, the new magnetometers are more energy-efficient.

But the range of applications goes far beyond geophysics. The sensors’ high sensitivity also makes them interesting for medical uses. “In the long term, they could be used to detect biomagnetic signals from the heart and nervous system – enabling new approaches to noninvasive diagnostics,” says Stolz. The magnetometers could also be used in industry – for example, in non-destructive materials testing. And in archaeology, they could help detect buried structures without the need for excavation.

From Raw Material ­Exploration to Medicine

The next step is to miniaturize the system. “Our goal is to integrate the magnetometer into compact, portable devices,” explains Thomas Schönau. “We see great potential for mobile and cost-effective sensors.” The team has already filed a patent application for the method.

Leibniz IPHT researches a wide range of optical techniques to measure physical quantities with the highest precision – from molecular structures to electromagnetic fields. The new magnetometers also follow this principle: they use light to detect even the finest magnetic signals without contact. “With this, we are expanding the scope of optical measurement technology and unlocking new applications,” ­emphasizes Ronny Stolz.

Original publication: https://doi.org/10.1103/PhysRevApplied.23.024006