Quantum Microwave Radiometry with a Superconducting Qubit

The interaction of photons and coherent quantum systems can be employed to detect electromagnetic radiation with remarkable sensitivity. We introduce a radiometer based on the photon-induced dephasing process superconducting qubit for sensing microwave at subunit photon level. Using this radiometer, we demonstrate radiative cooling 1 K resonator measure its mode temperature an uncertainty $\ensuremath{\sim}0.01\text{ }\text{ }\mathrm{K}$. thus develop precise tool studying thermodynamics circuits, which provides new solutions calibrating hybrid detecting candidate particles dark matter.