Our laboratory is located in the Department of Physics of the University of Basel in Switzerland. Our research is centered around the emerging field of "Quantum sensing", where the use of individual, well-controlled quantum systems as high-performance sensing devices is being explored. We concentrate on implementing various types of such sensors and on applying them to outstanding scientific tasks in mesoscopic physics, nano-science and technology. At the moment, our quantum system of choice for these purposes is the Nitrogen-Vacancy (NV) color center in diamond, whose exceptional quantum-coherent properties allow for high-performance sensing applications (such as single-electron spin detection) even at room temperature.
We present high-resolution optically detected magnetic resonance (ODMR) spectroscopy on single nitrogen-vacancy (NV) center spins in diamond at and around zero magnetic field. The experimentally observed transitions depend sensitively on the interplay between the microwave (MW) probing field and the local intrinsic effective field comprising strain and electric fields, which act on the NV spin.
In our work we present a new approach combining top-down fabrication with bottom-up overgrowth to create diamond diamond nanopyramids, which form a very promising system for applications in nanoscale quantum sensing, with tip radii on the order of 10 nm and high collection efficiencies from color centers incorporated close to the pyramid apex.
The NV center in diamond offers a powerful platform for quantum information science and quantum metrology. But parasitic local intrinsic fields limit the effectiveness of sensing techniques operating at low external fields. Based on a theoretical model we characterize these intrinsic effective fields at the level of single NV centers using high-resolution spectroscopy in the absence of external fields. This allows us to extend the capabilities of NV-based sensing applications to low-field operation and strengthen the existing toolkit of quantum sensing techniques.
Out-of-plane-oriented NV centers in (111) diamond scanning probes bring significant benefits to magnetometry, ranging from improved magnetic field reconstruction capabilities to higher sensitivities. We fabricate and characterize (111) scanning probes and demonstrate their polarization independent fluorescence. Furthermore, we perform nanoscale NV magnetomety and show that the measured magnetic stray field is antisymmetric and not distorted as with (100) scanning probes.