Bright single-photon skyrmion sources in bullseye cavities.

Optical skyrmions, as structured light fields endowed with discrete topological numbers, open new opportunities for high-density encoding, robust information transport, and quantum light-matter interactions. However, most existing skyrmion generators rely on complex or bulky systems, hindering their application in scalable on-chip quantum technologies. Here, we propose a nanophotonic scheme based on semiconductor cavity quantum electrodynamics, whereby a circularly polarized quantum emitter is coupled to a concentric bullseye resonator. This configuration enables the efficient generation of single-photon Stokes vector skyrmions at subwavelength scales, as well as their high-order extensions. By exciting single-photon sources at different positions, the skyrmion number can be continuously switched between +2 and -2, while higher-order states are accessible by tuning the radius of cavity's center disc. This strategy couples the topological dimension of skyrmions with quantum states, laying the groundwork for quantum skyrmions in on-chip topological keying and quantum readout. Our work provides a practical device architecture for integrated nanophotonic quantum topological state platforms, offering a new paradigm for topologically protected quantum communications and on-chip quantum information processing.