Jodok Happacher will present a seminar entitled: Low Temperature Quantum Sensing with Single Nitrogen-Vacancy Centers in Diamond
Quantum sensing has emerged as a prominent field in quantum technology, with the Nitrogen-Vacancy (NV) center in diamond standing out as an exceptionally versatile platform. This atomic-scale defect combines remarkable optical and spin properties, enabling highly sensitive magnetic-field detection and nanoscale imaging. However, low-temperature operation introduces both fundamental and technical challenges. In this talk, I will present two approaches addressing these challenges.
We investigated how external fields influence the photophysical properties of individual Nitrogen-Vacancy centers by measuring their photoluminescence as a function of magnetic field across a wide temperature range. These measurements revealed strong dependencies on both magnetic field and strain, which lead to significant changes in optical spin contrast, a key factor for sensing performance. Combined with an extended theoretical model, the results offer new insight into the excited-state structure of the NV center and the role of phonon-induced orbital averaging at elevated temperatures. Our approach provides an alternative to conventional optical spectroscopy and can be applied to other optically active quantum systems. It further opens new opportunities for sensing modalities such as highly sensitive electric-field measurements at cryogenic temperatures.
In parallel, we developed a scanning NV magnetic imaging probe incorporating an integrated microwave (MW) near-field coupling device for optimized spin driving. The reproducible, lithography-free fabrication approach enables scalable probe production and demonstrates performance comparable to established microwave delivery methods without requiring an external MW delivery system This integrated approach is particularly well suited to low-temperature experiments, where it can reduce experimental complexity, technical barriers, and the thermal load associated with microwave delivery in NV magnetometry.
Together, these advances deepen the understanding of NV centers at low temperatures, support their continued development in quantum sensing and condensed-matter research, and reduce technical barriers to the broader adoption of NV magnetometry.