Reactive near-field subwavelength microwave imaging with a non-invasive Rydberg probe

TL;DR

This paper introduces a non-invasive, subwavelength microwave imaging technique using Rydberg atoms, achieving high resolution and minimal disturbance, suitable for applications like chip diagnostics and biomedical imaging.

Contribution

It demonstrates for the first time reactive near-field subwavelength microwave imaging with a Rydberg atom-based probe that is compact, non-invasive, and highly accurate.

Findings

Achieved imaging resolution of λ/56.

Measured field distributions closely match simulations.

Confirmed the probe's non-invasive and isotropic properties.

Abstract

Non-invasive microwave field imaging--accurately mapping field distributions without perturbing them--is essential in areas such as aerospace engineering, biomedical imaging and integrated-circuit diagnostics. Conventional metal probes, however, inevitably perturb reactive near fields: they act as strong scatterers that drive induced currents and secondary radiation, remap evanescent components and thereby degrade both accuracy and spatial resolution, particularly in the reactive near-field regime that is most relevant to these applications. Here we demonstrate, to our knowledge for the first time, reactive near-field subwavelength imaging of microwave fields using the quantum non-demolition properties of Rydberg atoms, realized with a compact, non-invasive single-ended fibre-integrated Rydberg probe engineered to minimize field disturbance. The probe achieves an imaging resolution of {\unboldmath$\lambda/56$}, and the measured field distributions agree with full-wave simulations with structural similarity approaching unity, confirming both its subwavelength spatial resolution and its genuinely non-invasive character compared with conventional metal-based probes. Because the atomic sensor is intrinsically isotropic, the same device can faithfully image multi-dimensional field structures without orientation-dependent calibration. Our results therefore establish a general, non-invasive route to high-accuracy, subwavelength reactive near-field microwave imaging, with particular promise for applications such as chip-defect detection and integrated-circuit diagnostics, where even small perturbations by the probe can mask the underlying physics of interest.