Robust consistent single quantum dot strong coupling in plasmonic nanocavities

Strong coupling between a single quantum emitter and an optical cavity (at rate Ω) accesses fundamental quantum optics and provides an essential building block for photonic quantum technologies. However, the minimum mode volume of conventional dielectric cavities restricts their operation to cryogenic temperature for strong coupling. Here we harness surface self-assembly to make deterministic strong coupling at room temperature using CdSe/CdS quantum dots (QDs) in nanoparticle-on-mirror (NPoM) plasmonic nanocavities. We achieve a fabrication yield of ~70% for single QD strong coupling by optimizing their size and nano-assembly. A clear and reliable Rabi splitting is observed both in the scattering of each nanocavity and their photoluminescence, which are however not equal. Integrating these quantum elements with electrical pumping allows demonstration of strong coupling in their electroluminescence. This advance provides a straightforward way to achieve practical quantum devices at room temperature, and opens up exploration of their nonlinear, electrical, and quantum correlation properties.