Near-Field Scanning Microwave Microscopy in the Single Photon Regime

S Geaney,T Lindström,R Shaikhaidarov,A V Danilov,T Hönigl-Decrinis,D Cox,S E Kubatkin,S E De Graaf

doi:10.1038/s41598-019-48780-3

Abstract

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 109 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.

Highlights

Near-field scanning microwave microscopy (NSMM) combines microwave characterisation with either STM8 or AFM9,10 using either a broadband[11] or resonant[12] probe
The critical photon number for saturation in the dispersive regime is given by ηc =2/4g2, where g is the coupling strength[31], which implies that the average number of photons in the resonator 〈n〉 ≪ ηc, must be close to one i.e. the near-field scanning microwave microscope (NSMM) should operate in the near single photon regime. (iii) The resonator loss rate Qi−1 should be smaller than the coupling strength g, requiring a high-Q resonator. (iv) Nanometer scale distance control between the tip and the sample surface is needed for a well defined coupling between the probe and a two-level systems (TLS), prompting the integration with AFM in a system that is well isolated from vibrations
One of the requirements for coherent NSMM is to operate at low power to reach the single photon regime[18]

Summary

Introduction

Near-field scanning microwave microscopy (NSMM) combines microwave characterisation with either STM8 or AFM9,10 using either a broadband[11] or resonant[12] probe. We show that our NSMM is capable of obtaining nano-scale dielectric information in this regime of ultra-low power This is an important step towards developing the future tool kit for characterisation of solid state quantum circuits and truly non-invasive nanoscale microwave interrogation of quantum materials and devices. This technique is compatible with a cryogenic environment due to its low dissipation electrical readout[32].

Methods

Results

Conclusion