No abstract

A two-level quantum system can absorb or emit not more than one photon at a time. Using this fundamental property, we demonstrate how a superconducting quantum system strongly coupled to a transmission line can be used as a sensor of the photon flux. We propose four methods and analyse them for the absolute calibration of power by measuring spectra of scattered radiation from the twolevel system. Our results suggest that the absolute power calibration is independent of dephasing as long as its non-radiative relaxation is negligible. Our approach can be used for practical applications for example in calibration of transmission lines within dilution refrigerators. arXiv:1905.05104v1 [quant-ph]

The microwave properties of nano-scale structures are important in a wide variety of applications in quantum technology. Here we describe a low-power cryogenic near-field scanning microwave microscope (NSMM) which maintains nano-scale dielectric contrast down to the single microwave photon regime, up to 10 9 times lower power than in typical NSMMs. We discuss the remaining challenges towards developing nano-scale NSMM for quantum coherent interaction with two-level systems as an enabling tool for the development of quantum technologies in the microwave regime.