Quantum sensors: when a quantum state becomes a measuring instrument

Quantum sensing is the area of quantum technology that can be applied most rapidly in industry. Quantum sensors are devices in which a well-controlled quantum system reacts extremely sensitively to environmental influences, allowing for very precise measurements of, for example, temperature or magnetic fields. Due to atomic-scale defects in silicon carbide (SiC), certain properties of electrons change easily. By exploiting this quantum mechanical phenomenon, we can detect even very weak signals that classical measuring instruments are no longer sensitive enough to detect. Quantum sensors are capable of measuring local information with extreme precision, making them suitable for the sensitive analysis of biological, medical, and chemical processes.

Two adjacent carbon and silicon atom vacancies in silicon carbide create spin-quantum bits that can operate even at room temperature, and the information stored in these quantum bits can be read out using infrared light.

The key is not the “surface” but the interface: how to turn a shallow quantum bit into a well-functioning sensor.

For quantum sensing, the quantum bit must be very close to the surface to “sense” external signals. However, the proximity of the surface often causes problems precisely where sensing would be most useful. The main idea of the Nature Materials study provides an answer to this problem: a simple yet engineering-effective surface chemistry solution can create a stable environment for SiC quantum bits located just a few nanometers deep. Ádám Gali’s idea was to coat the SiC surface with a hydrocarbon chain, thereby stabilizing the easily oxidizable surface that contains a lot of unwanted noise. This allows the quantum bits to detect external signals with high precision. The essence of the approach is that the surface is not a passive bystander, but has become a designable “interface” between the biological and chemical environments.

The publication was produced through international collaboration; while researchers at the HUN-REN Wigner Research Center for Physics provided the concept and guidance, researchers at the University of Science and Technology of China conducted the experiments and evaluated the results. This division of labor clearly demonstrates how a hypothesis in surface chemistry can, through international collaboration, be rapidly verified, measured, and transformed into results that are directly applicable in sensor technology.

The full Nature Materials article is available here: https://www.nature.com/articles/s41563-025-02382-9.