Progressive digitalization and global interconnectedness are based on microelectronics. For decades, its development followed Moore’s law, which predicted continuous miniaturization and increasing performance of electronic components. Today, however, device structures have reached the nanometre scale, where quantum-mechanical effects increasingly limit classical scaling concepts.

Quantum information processing addresses precisely these effects. Its aim is to deliberately exploit quantum-mechanical properties to achieve significant speed-ups for specific classes of problems, such as factorization, unstructured database search, or quantum-chemical simulations. Among the platforms currently under intensive investigation are superconducting circuits, trapped ions, solid-state defects, and photonic systems. The latter are particularly attractive because they are compatible with room-temperature photonics and use single photons as information carriers.

Single-photon sources are key building blocks of photonic quantum technologies. They are essential not only for quantum computing, but also for quantum cryptography and other quantum information applications. Semiconductor quantum dots are considered among the most powerful sources, as they emit photons with high purity and indistinguishability, albeit typically requiring operation at temperatures around 4 kelvin. Single-atom emitters, by contrast, rely on complex trapping schemes and often exhibit a low integrated photon yield.

Against this background, simple solid-state quantum emitters have increasingly moved into the focus of research. The subproject NOA (C2) investigates such systems using optical near-field methods on the nanoscale. The aim is to spatially resolve and characterize the emission properties of individual quantum emitters and to analyse light–matter interactions beyond the diffraction limit. In this way, the project contributes to a deeper physical understanding and lays the groundwork for the targeted development of quantum emitters for future photonic quantum technologies.

Project C2 is a subproject of the Collaborative Research Centre 1375/2 NOA and is funded by the Deutsche Forschungsgemeinschaft under project number 398816777.