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.
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.
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.
Lucas' paper entitled "Probing magnetism in 2D materials at the nanoscale with single spin microscopy" was published in Science. We demonstrate quantitative, nanoscale imaging of magnetisation, localised defects and magnetic domains in Cri3, a ferromagnetic 2D van der Waals crystals. We determine the magnetisation of a monolayer and establish that the inscrutable even-odd effect is intimately connected to the material structure.
We are delighted to announce that Märta Tschudin was awarded an QCQT Excellence Fellowship. The fellowship is aimed at outstanding PhD students from in- and outside Switzerland within the research area of quantum computing, quantum measurements, spintronics and quantum magnonics, quantum sensing, quantum optics and cold atoms, quantum transport and nanoelectronics, topological properties of condensed matter systems, and quantum communication.
Shortcuts to adiabaticity are a recently developed protocols to speed up adiabatic state transfer. We exploit these techniques to prepare well-defined single spin dressed states, which exhibit efficient coherence protection. Besides a detailed study of the transfer process, we show direct coherent manipulation in the dressed state manifold. Thereby, our results offer attrative avenues for applications in quantum information processing and quantum sensing.
Magnetoelectric antiferromagnets play an important role as a platform for spintronic applications including all electrical reading and writing of magnetic memories. In this paper we investigate the formation of domains in thin-film Cr2O3 using a combination of NV magnetometry and zero offset Hall magnetometry (ZOHM). We develop a model of the domain formation and extract important parameters, including the intergranular exchange coupling and critical temperature distribution.
Magnetic imaging using color centers in diamond through both scanning and wide-field methods offers a combination of unique capabilities for studying superconductivity, for example, enabling accurate vector magnetometry at high temperature or high pressure, with spatial resolution down to the nanometer scale. The paper briefly reviews various experimental modalities in this rapidly developing nascent field and provides an outlook towards possible future directions.