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arXiv · 1404.0534

A near-field scanning microwave microscope based on a superconducting resonator for low power measurements

S. E. de Graaf·A. V. Danilov·A. Adamyan·S. E. Kubatkin
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Abstract

We report on the design and performance of a cryogenic (300 mK) near-field scanning microwave microscope. It uses a microwave resonator as the near-field sensor, operating at a frequency of 6 GHz and microwave probing amplitudes down to 100 uV, approaching low enough photon population (N~1000) of the resonator such that coherent quantum manipulation becomes feasible. The resonator is made out of a miniaturized distributed fractal superconducting circuit that is integrated with the probing tip, micromachined to be compact enough such that it can be mounted directly on a quartz tuning-fork, and used for parallel operation as an atomic force microscope (AFM). The resonator is magnetically coupled to a transmission line for readout, and to achieve enhanced sensitivity we employ a Pound-Drever-Hall measurement scheme to lock to the resonance frequency. We achieve a well localized near-field around the tip such that the microwave resolution is comparable to the AFM resolution, and a capacitive sensitivity down to 6.4x10^-20 F/rtHz, limited by mechanical noise. We believe that the results presented here are a significant step towards probing quantum systems at the nanoscale using near-field scanning microwave microscopy.

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S. E. de Graaf, A. V. Danilov, A. Adamyan, S. E. Kubatkin. 2014-04-02. A near-field scanning microwave microscope based on a superconducting resonator for low power measurements. https://doi.org/10.1063/1.4792381

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