Quantum Precision as an Electrical Standard

Fijalkowski is a researcher at the Institute for Topological Insulators at JMU Würzburg and the Würzburg–Dresden Cluster of Excellence ctd.qmat — Complexity, Topology and Dynamics in Quantum Matter. He is working on a method for determining electrical resistance using a special effect from quantum physics: the quantum anomalous Hall effect.

The classical quantum Hall effect was discovered in 1980 by Würzburg Nobel laureate Klaus von Klitzing. This phenomenon occurs in a two-dimensional electron gas at very low temperatures and in strong magnetic fields. Under the right conditions, a very thin material can take on a specific electrical resistance that is independent of the shape and size of the material sample. Instead, it is determined by fundamental constants, including Planck’s constant and the elementary charge. This makes the quantum Hall effect particularly well suited as a stable, precise electrical standard.

Precision Without an External Magnetic Field

Previously, however, quantum Hall standards have generally required strong external magnetic fields. Working with two researchers from the Physikalisch-Technische Bundesanstalt (PTB), the National Metrology Institute of Germany, Fijalkowski has now shown that such a standard can also work without an applied magnetic field. This makes the method significantly simpler, opens up new possibilities for future measurement systems, and distinguishes the quantum anomalous Hall effect from the classical quantum Hall effect. Fijalkowski’s measurements were already highly precise, deviating from the internationally recognized reference value for electrical resistance by only a few parts per billion. This demonstrates that the quantum anomalous Hall effect is suitable in principle as the basis for a novel quantum resistance standard.

“Our goal is to trace electrical units directly back to unchanging properties of nature,” says Kajetan Fijalkowski. “A new quantum-based standard that does not require an external magnetic field plays an important role in this. We were able to demonstrate this new type of resistance standard, thereby contributing to the foundations of metrology.”

Implications for Volts, Ohms, and Amperes

The research is particularly important for electrical metrology — the science of measurement. In the long term, a reliable quantum-based resistance standard could help link different electrical units. For example, it could be combined with the Josephson effect, another important quantum standard that enables extremely precise measurements of electrical voltage but does not work with strong magnetic fields. In the future, this could lead to a comprehensive quantum-electrical measurement system in which voltage, resistance, and current are all traced back to common physical principles.

Such measurements would also be important for realizing the kilogram. Modern methods link mechanical and electrical quantities for this purpose. The more accurately these electrical quantities can be determined, the more precisely the kilogram can be reproduced in practice.

Fundamental Metrology Research with a Long-Term Perspective

Further development will be needed before the new standard can be used in everyday measuring instruments. At present, the experiments are conducted at extremely low temperatures and with very small electric currents. Industrial implementation would still be too expensive.

Even so, the research team’s work already shows how fundamental quantum phenomena can be used to develop future measurement standards. It therefore connects fundamental research into topological quantum materials with long-term prospects for applications in science, technology, and industry.

The research was carried out under the umbrella of EURAMET, the European Association of National Metrology Institutes, whose mission is to develop and maintain an internationally competitive metrology infrastructure for Europe. The work is supported by the European projects TOCHA and EURAMET QuAHMET. The findings were published in Nature Electronics in 2024. Fijalkowski received the 2026 Helmholtz Prize together with his two co-authors, Mattias Krustkopf and Dinesh Patel.

Helmholtz Prize for Exceptionally Accurate Measurement

The Helmholtz Prize is awarded every two years by the Helmholtz Association and the Helmholtz Fund. It honors outstanding scientific achievements in precision measurement and metrology, focusing on research that helps make measurements more accurate, reliable, and internationally comparable. The prize commemorates Hermann von Helmholtz, one of the most important German physicists of the nineteenth century. The award in the Fundamentals of Metrology category was presented to Kajetan Fijalkowski in Berlin on August 25, 2026.

ctd.qmat

The Cluster of Excellence ctd.qmat — Complexity, Topology and Dynamics in Quantum Matter — at Julius-Maximilians-Universität Würzburg and Technische Universität Dresden explores and develops novel quantum materials with tailored properties. Around 300 researchers from over 30 countries work at the interface of physics, chemistry, and materials science to lay the foundations for tomorrow’s technologies. In 2026, the cluster entered the second funding period of the German Excellence Strategy of the Federal and State Governments — with an expanded focus on the dynamics of quantum processes.

Contact

Dr. Kajetan M. Fijalkowski
Institut für Topologische Isolatoren
Julius-Maximilians-Universität Würzburg
Tel: +49 931 318 8900
Email: kajetan.fijalkowski@uni-wuerzburg.de