Pan Zheng, Yanyan Cai, Bin Xu, Shengcheng Wen, Libo Zhang, Zhongchu Ni, Jiasheng Mai, Yanjie Zeng, Lin Lin, Ling Hu, Xiaowei Deng, Song Liu, Jing Shu, Yuan Xu, Dapeng Yu
Quantum metrology has recently emerged as a powerful approach for dark matter (DM) searches, particularly using nonclassical bosonic states in microwave cavities that are sensitive to weak signals. Nonclassical cat states-macroscopic superpositions of coherent states featuring sub-Planck interference structures-offer promising advantages for high-precision measurements. However, their practical utility in DM search remains unexplored. Here, we report the first experimental application of four-component cat states within a high-quality superconducting microwave cavity to search for dark photons, a potential DM candidate. We demonstrate an 8.1-fold enhancement in the signal photon rate and constrain the dark photon kinetic mixing angle to an unprecedented ε<7.32×10^{-16} near 6.44 GHz (26.6 μeV). By employing a parametric sideband drive to actively tune the cavity frequency, we achieve dark photon searches and background subtraction across multiple frequency bins, yielding a sensitivity at the 10^{-16} level within a 100 kHz bandwidth. Our cat-assisted DM search and frequency-scanning techniques demonstrate substantial improvements over previous results, promising potential implications in quantum-enhanced searches for new physics.