Quantum Microwave Radiometry with a Superconducting Qubit

TL;DR

This paper presents a superconducting qubit-based quantum radiometer capable of detecting microwave radiation at sub-photon levels, enabling precise thermometry and potential dark matter detection.

Contribution

Introduction of a novel quantum radiometer utilizing photon-induced dephasing in superconducting qubits for ultra-sensitive microwave detection.

Findings

Demonstrated radiative cooling of a 1-K microwave resonator.

Measured mode temperature with ~0.01 K uncertainty.

Developed a tool for quantum microwave thermodynamics and dark matter detection.

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 sub-unit-photon level. Using this radiometer, we demonstrated the radiative cooling of a 1-K microwave resonator and measured its mode temperature with an uncertainty ~0.01 K. We have thus developed 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.