Light Dark Matter Detection with Sub-eV Transition-Edge Sensors

We present a comprehensive analysis of high-resolution transition-edge sensors (TESs) as a quantum sensing platform for detecting dark matter (DM). Operating near the thermodynamic noise limit with sub-eV energy resolution, TESs offer a powerful approach for probing light DM in the sub-GeV mass range. Optical TESs, realized on superconducting films with critical temperatures below 150 mK, achieve energy thresholds below 100 meV and enable precise calorimetric detection of individual energy depositions. We model TES response by incorporating fundamental noise sources and applying optimal filtering techniques, and evaluate their sensitivity across a range of DM interaction channels, accounting for in-medium effects in the target material. We show that even ng-month-scale exposures can reach previously unexplored DM-electron scattering cross sections below $10^{-27}$ cm$^2$ for sub-MeV masses, and can probe the MeV-scale mass range for DM-nucleon couplings. Combining high energy resolution, photon-number sensitivity, and scalability, optical TESs provide a compelling quantum sensing platform for rare-event searches at the intersection of particle physics and quantum metrology.