Electromagnetic induction imaging with atomic magnetometers: unlocking the low-conductivity regime

Electromagnetic induction imaging with atomic magnetometers has disclosed unprecedented domains for imaging, from security screening to material characterization. However, applications to low-conductivity specimens -- most notably for biomedical imaging -- require sensitivity, stability, and tunability only speculated thus far. Here, we demonstrate contactless and non-invasive imaging down to 50 S/m using a 50 fT/Hz$^{-1/2}$ $^{87}$Rb radio-frequency atomic magnetometer operating in an unshielded environment and near room temperature. Two-dimensional images of test objects are obtained with a near-resonant imaging approach, which reduces the phase noise by a factor 172, with projected sensitivity of 1 S/m. Our results, an improvement of more than three orders of magnitude on previous imaging demonstrations, push electromagnetic imaging with atomic magnetometers to regions of interest for semiconductors, insulators, and biological tissues.