Search for Dark Photon Dark Matter with a Mass around 36.1 μeV Using a Frequency-tunable Cavity Controlled through a Coupled Superconducting Qubit

We report the results of a search for dark photon dark matter using a cavity that employs a transmon qubit as a frequency tuner. The tuning mechanism utilizes the energy level shift arising from the mode mixing between the qubit and the cavity mode. This method is advantageous in the absence of thermal noise and electromagnetic leakage. We searched for a dark matter signal in the mass range 36.079 \, μeV - 36.176 \, μeV and found no significant evidence. As a result, we set the exclusion limit on the kinetic mixing parameter down to approximately 10⁻¹², surpassing the existing bound set by cosmology.