Quantum emitters in diamond
Optically active nitrogen vacancy centers (NV centers) in diamond have been established in recent years as well-controllable artificial atoms in solids. They are particularly suitable for measuring quantum effects, thus allowing high-precision measurements. Therefore, in addition to quantum metrology with NV centers, we are also interested in better understanding the nitrogen defect in diamond solids.
Investigation of charge effects and paramagnetic samples:
In this project, we investigate the charge conversion of the negatively charged NV center to the neutrally charged NV center in a single nanodiamond. In particular, we are interested in the influences of this ionization on the measurement procedure of T1 relaxometry. For this purpose, we apply common pulse sequences and study the fluorescence of the two NV charge states independently in separate detectors. We will use the improvements in the pulse sequences obtained from our results to characterize paramagnetic samples in the vicinity of the nanodiamond. See for details: arXiv:2301.01063
Quantum distance measurements:
Rabi oscillations in NV centers in diamonds can be used for distance measurements between an antenna and a NV center. For this purpose, we fabricate silver structures on the tip of an optical fiber in an additive process (metallic direct laser writing), which are used as an antenna for microwave excitations in the NV center. The distance between the antenna structure and NV center in a diamond can then be determined by its Rabi frequency, which we measure optically through the optical fiber. Currently, we are working on quantifying the sensitivity and improving it with experimental methods such as "Spin-to-Charge Conversion" and "Double Quantum Spin Magnetometry". https://doi.org/10.3390/mi10120827 / https://doi.org/10.1063/5.0100330
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.(DOI 10.1088/1367-2630/ac6bb8)
