Quantum Microwave Radiometry with a Superconducting Qubit

  1. Zhixin Wang,
  2. Mingrui Xu,
  3. Xu Han,
  4. Wei Fu,
  5. Shruti Puri,
  6. S. M. Girvin,
  7. Hong X. Tang,
  8. S. Shankar,
  9. and M. H. Devoret
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.
arxiv pdf

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