UPLOAD-ANYON: Progress Towards an Optimised Twisted Anyon Cavity with High-Sensitivity AM-Noise Detection for an Ultralight Axion Dark Matter Search

We propose a superconducting single-mode microwave haloscope based on helical cavity resonators for the detection of ultralight dark matter axions over the mass range $10^{-18}$ to $10^{-13}\,\mathrm{eV}$. Building on the single-mode helical-cavity concept introduced by Bourhill et al. [Phys. Rev. D 108, 052014 (2023); arXiv:2208.01640], we use an inverse-design framework to develop practical resonator geometries compatible with superconducting niobium fabrication. The optimisation employs a figure of merit derived to minimise the measurement time required to achieve a fixed experimental sensitivity. Relative to the heuristic M\"obius-geometry benchmark, the best subtractively manufacturable bulk-niobium design achieves a figure of merit more than three orders of magnitude larger. An experimentally informed microwave interferometric readout model, incorporating measured electronics noise and active suppression of pump amplitude noise, is used to project the sensitivity of the proposed experiment. For an acquisition time of three months, the haloscope is projected to reach $g_{a\gamma\gamma}<10^{-11}\,\mathrm{GeV}^{-1}$ across more than four orders of magnitude in axion mass. The projected sensitivity extends approximately one order of magnitude below the current exclusion limits set by CAST, providing a practical pathway towards a high-sensitivity direct search for ultralight dark matter axions.