Not yet reviewed by Pith; the record is open.

We have proposed a new approach to search for axion dark matter with an optical ring cavity [Phys. Rev. Lett. 121, 161301 (2018)]. The coupling of photons to axions or axion-like particles makes a modulated difference in the phase velocity between left- and right-handed photons. Our method is to measure this phase velocity difference with a ring cavity, by measuring the resonant frequency difference between two circular polarizations. Our estimation shows that the sensitivity to axion-photon coupling constant $g_{a \gamma}$ for axion mass $m \lesssim 10^{-10}$ eV can be improved by several orders of magnitude compared with the current best limits. In this paper, we present the principles of the Dark matter Axion search with riNg Cavity Experiment (DANCE) and the status of the prototype experiment, DANCE Act-1.