Abstract
Near field Scanning Microwave Microscopy (NSMM) is a scanning probe technique that non-invasively can obtain material properties on the nano-scale at microwave frequencies. While focus has been on developing room-temperature systems it was recently shown that this technique can potentially reach the quantum regime, opening up for applications in materials science and device characterization in solid state quantum information processing. In this paper we theoretically investigate this new regime of NSMM. Specifically we show that interaction between a resonant NSMM probe and certain types of two-level systems become possible when the NSMM probe operates in the (sub-) single photon regime, and we expect a high signal-to-noise ratio if operated under the right conditions. This would allow to detect single atomic material defects with energy splittings in the GHz range with nano-scale resolution, provided that individual defects in the material under study are well enough separated. We estimate that this condition is fulfilled for materials with loss tangents below tan δ ∼ 10−3 which holds for materials used in today’s quantum circuits and devices where typically tan δ < 10−5. We also propose several extensions to a resonant NSMM that could improve sensitivity and functionality also for microscopes operating in a high power regime.
Highlights
Quartz tuning-fork Near field Scanning Microwave Microscopy (NSMM) sensor Sample systems since it operates in the same microwave domain
A NSMM based on a high-Q cavity could be used to gain important information about defects that can lead to improved materials and increased coherence times of solid state quantum devices
We discuss the prospects of developing NSMM systems with the requirements for two-level fluctuators (TLFs) detection based on recent developments[14] and we propose several modifications of a NSMM setup that could benefit NSMM operation in the high power limit
Summary
Systems since it operates in the same microwave domain. The class of resonant NSMMs (where the microwave probe is a resonance cavity) have an enhanced sensitivity (the smallest frequency shift that can be detected, determined by, for example, frequency noise of the cavity) compared to non-resonant NSMMs. Note that if the TLF dipole is oriented in the plane of the sample (η = 0), it will instead couple to the radial component of the electric field from the tip and the observed feature will have a dipole-like appearance rather than radial symmetry, which is the case considered throughout this manuscript. This anisotropy could be used to determine the angle of the TLF dipole and its orientation with respect to the dielectric lattice. As the tip is scanned across the surface we change r, but h is assumed to remain constant
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