Quantum Microwave Radiometry with a Superconducting Qubit
Zhixin Wang, Mingrui Xu, Xu Han, Wei Fu, Shruti Puri, S. M. Girvin, Hong X. Tang, Shyam Shankar, Michel Devoret
Abstract
The interaction of photons and coherent quantum systems can be employed to detect electromagnetic radiation with remarkable sensitivity. We introduce a quantum radiometer based on the photon-induced dephasing process of a superconducting qubit for sensing microwave radiation at the subunit photon level. Using this radiometer, we demonstrate the radiative cooling of a 1 K microwave resonator and measure its mode temperature with an uncertainty ∼0.01 K. We thus develop a precise tool for studying the thermodynamics of quantum microwave circuits, which provides new solutions for calibrating hybrid quantum systems and detecting candidate particles for dark matter.