Fraunhofer IAF is developing quantum magnetometers based on diamond. These nano-diamond structures either have nitrogen-vacancy centers (NV centers) or are doped with alkali atoms whose optical properties depend on the magnetic field. Both methods make it possible to detect magnetic fields with a spatial resolution of a few nanometers down to individual electron and nuclear spins. Due to the physical material properties, this works at room temperature, which is ideal for industrial applications.
Fraunhofer IAF develops diamond based quantum magnetometers. These nano-diamond structures have either nitrogen vacancy centers (NV centers) or are doped with alkali atoms whose optical properties react correspondent to magnetic field changes. Both methods allow to detect magnetic fields with a spatial resolution of a few nanometers down to single electron or even nuclear spins. This works at room temperature due to the physical material properties, what makes the technology ideal for industrial applications.
Magnetometers are currently only suitable for industrial use to a limited extent, as their operation is complex and sometimes only possible with extreme cooling. In addition, their spatial resolution or sensitivity is too low for many applications.
For this reason, Fraunhofer researchers from six institutes have joined forces in the 'Quantum Magnetometry' (QMag) project to develop sensors that can be used to image tiny magnetic fields with unprecedented spatial resolution and sensitivity at room temperature. The aim of the Fraunhofer lighthouse project is to transfer quantum magnetometry from the university research environment to specific industrial applications: By 2024, the project partners will realize quantum magnetometers for industrial use in nanoelectronics, chemical analysis and materials testing.
QMag is funded in equal parts by the Fraunhofer-Gesellschaft and the state of Baden-Württemberg with a total of 10 million euros. The Freiburg Fraunhofer Institutes for Applied Solid State Physics IAF, for Physical Measurement Techniques IPM and for Mechanics of Materials IWM form the core team of the research consortium. Three other Fraunhofer Institutes are contributing their scientific and technological expertise: the Fraunhofer Institute for Microengineering and Microsystems IMM, the Fraunhofer Institute for Integrated Systems and Device Technology IISB and the Fraunhofer Centre for Applied Photonics CAP in Glasgow.
Major advances in material development
The QMag project is testing two systems that are based on the same physical measurement principles and methods, but are used for different applications: On the one hand, the researchers are developing an imaging scanning probe magnetometer based on NV centers in diamond for the most precise measurements of nanoelectronic circuits. On the other hand, they are realizing measurement systems based on highly sensitive optically pumped magnetometers (OPMs) for applications in materials testing and process analytics.
"With regard to the scanning probe magnetometers, we were able to make great progress in the development and optimization of diamond sensor tips in the first half of the project," says Dr Ralf Ostendorf, project coordinator at QMag. This concerns both the growth of high-quality diamond and the targeted generation and placement of NV centers in the diamond tips. In addition, the researchers have developed microlenses and synthesized magnetic nanoparticles that are inserted into the diamond tips in order to further optimize them in terms of accuracy and efficiency.
Measuring the smallest magnetic fields with diamond and laser
The second research project presented by Fraunhofer IAF in the field of quantum magnetometry is aimed at applications in medical diagnostics: in the project 'NV-doped CVD diamond for ultra-sensitive laser threshold magnetometry' (DiLaMag), a team is researching the development of an extremely sensitive sensor that can measure the weak magnetic fields of heart and brain activity in the human body, for example. This could enable diseases to be detected earlier.
"Our aim is to develop an extremely sensitive magnetic field sensor that works at room temperature as well as in existing background fields and is therefore practical for clinical implementation," explains Dr. Jan Jeske, project manager at DiLaMag.
At this year's Laser World of Photonics trade fair, there was an exhibition area dedicated to quantum technologies for the first time. In the World of Quantum (Hall A4) - named after the trade fair - the participating Fraunhofer Institutes IAF, IPM and IWM presented their QMag project. The joint exhibit demonstrated material testing with OPMs. In addition, Fraunhofer IAF presented its research work in the field of diamond growth and NV-doped diamond and demonstrated the basic principle of measurement with NV diamonds.
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Quantum magnetometry
The development of quantum magnetometry was accelerated in part because today's magnetometers have too low a spatial resolution or sensitivity for many future applications. The aim of the Fraunhofer QMag consortium is therefore to further develop magnetometers and test them for applications. Two different magnetometer principles based on quantum technology concepts are being used:
Firstly, nitrogen-vacancy centers in diamond will be used to act as the smallest sensing magnets in an imaging scanning probe magnetometer. This turns a single atomic system into a highly sensitive sensor that can be operated at room temperature. On the other hand, an alternative measuring method is used that utilizes the magnetic field dependence of the optical properties of alkali atoms (optically pumped alkali magnetometer, OPM).
Based on prototypes of such magnetometers, cost-effective, complete measuring systems are to be developed for specific applications. The two measurement methods are complementary in terms of maximum spatial resolution and extreme sensitivity, so that different new applications can be developed as a result. Such novel quantum magnetometers could be used, for example, to test and optimize micro- and nanoelectronic components in a non-destructive manner. Even individual bits in storage media could be visualized. In addition, process nuclear magnetic resonance for chemical process analysis and stray magnetic field measurement for contact-free material testing are to be tested and established.
Fraunhofer lighthouse project QMag
The Fraunhofer-Gesellschaft is facing up to current challenges for German industry and is setting strategic priorities with lighthouse projects in order to generate concrete solutions for the benefit of the location. The lighthouse projects therefore aim to quickly turn original scientific ideas into marketable products. The participating Fraunhofer Institutes pool their expertise and involve industry partners in the projects at an early stage.
The Fraunhofer Institutes IAF, IPM and IWM are involved in the lead project QMag. The aim of this project is to develop two complementary quantum magnetometers to measure the smallest magnetic fields with high resolution and high sensitivity at room temperature, as described in the article. The budget for the 5-year lead project - which runs until March 2024 - is €10 million. This sum is financed in equal parts by the FhG and the state of Baden-Württemberg.
