Single-ion microwave near-field quantum sensor

TL;DR

This paper presents a model and experimental validation of 2D microwave near-fields at centimeter wavelengths localized to microns, using a single 9Be+ ion as a quantum sensor for applications in quantum tech and integrated circuits.

Contribution

It introduces an effective five-parameter model for near-field characterization and demonstrates its application with high-resolution measurements using a single ion.

Findings

Agreement between measurements and simulations at sub-micron and degree levels

Effective description of near-fields with five key parameters

Potential applications in quantum information and integrated microwave devices

Abstract

We develop an intuitive model of 2D microwave near-fields in the unusual regime of centimeter waves localized to tens of microns. Close to an intensity minimum, a simple effective description emerges with five parameters which characterize the strength and spatial orientation of the zero and first order terms of the near-field, as well as the field polarization. Such a field configuration is realized in a microfabricated planar structure with an integrated microwave conductor operating near 1 GHz. We use a single 9Be+ ion as a high-resolution quantum sensor to measure the field distribution through energy shifts in its hyperfine structure. We find agreement with simulations at the sub-micron and few-degree level. Our findings give a clear and general picture of the basic properties of oscillatory 2D near-fields with applications in quantum information processing, neutral atom trapping and manipulation, chip-scale atomic clocks, and integrated microwave circuits.