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 $\epsilon <7.32\times {10}^{-16}$ near 6.44 GHz ($26.6\mathrm{\mu }\mathrm{eV}$). 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.

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• Circuit quantum electrodynamics
• Non-gaussian quantum states
• Particle dark matter
• Quantum control
• Quantum measurements
• Quantum metrology
• Quantum optics
• Cavity resonators
• Dark matter detectors