Quantum emitter in diamond
Optically active nitrogen-vacancy centers (NV centers) in diamonds have established themselves in recent years as easily controllable, artificial atoms in solids. They are particularly suitable for measuring quantum effects and thus allow high-precision measurements. In addition to quantum metrology with NV centers, we are therefore also interested in gaining a better understanding of the nitrogen vacancy in diamond solids.
Investigation of magnetic properties of spin-crossover complexes
In this project we investigate the temperature-dependent magnetic properties of spin-crossover complexes (SCO). NV centers are used as quantum sensors to measure the fluctuating magnetic fields. For this purpose, the SCO complexes are applied to a diamond surface and structural changes in the material are detected using various relaxometry techniques.
Improving the accuracy of magnetometry with NV centers through analytical formulas and fitting models
In this project, we want to improve the experimental accuracy of magnetic field measurements with NV centers using analytical formulas. We derive an exact formula to calculate the resonance frequencies from a known magnetic field and vice versa.
Development of a fiber-based endoscopic NV-based sensor for magnetic field measurement
In this project, we have developed a sensor with which we can measure high-resolution, vectorial magnetic fields. For this purpose, an NV-doped nanodiamond is located directly on the tip of the sensor head. Next to the diamond is a laser-written antenna structure to excite the NV center during the measurements. To produce the antenna structure, we use additive manufacturing techniques such as direct laser writing of polymer structures and silver coatings.
Deterministic positioning of NV centers in waveguide structures
In this project, we want to position NV centers deterministically in a waveguide structure using optical tweezers. For this purpose, optical tweezers are to be integrated into the direct laser writing system in order to place the nanodiamonds during the manufacturing process of the waveguide structures.
Collective effects
Swarm behavior, as we know it from birds and fish, for example, also shows up in the quantum world. The goal of our research is to understand this cooperative behavior of quantum ensembles and to make it useful for future applications.
In nanodiamonds with a high number of NV centers, quantum emitters are confined in a volume smaller than their emission wavelength. In this case, the system can be described as a coherent quantum ensemble and accelerated collective spontaneous photoemission of a macroscopic dipole occurs, which is also called superradiance. In this process, the fluorescence lifetime and the underlying photon statistics are reduced.
Our research in this direction aims to characterize this collective behavior at different system sizes and to investigate the scalability of such collective quantum effects. For this purpose, we use different agglomerates of nanodiamonds and detect the photoemission from NV ensembles of different sizes. The quantum optical observables here are the fluorescence lifetime and the second-order photon correlation function.
Our results so far show enhanced spontaneous photoemission and the expected change in photon statistics. Here, our quantitative analysis shows that collective effects increase with system size overall, but this collective behavior is observed only in smaller domains.
