Terahertz nano-imaging of heterogeneous dipole fields and charge scattering at a single nanojunction*

Decoherence in quantum states and the introduction of errors from cumulative gate operations are the main obstacles that need to be overcome to achieve full-scale quantum computing with superconducting qubits. To address such issues, it is thus imperative to identify and correlate electronic-photonic heterogeneity from interface and boundary imperfections in Josephson junctions, the key element in qubit devices. Here we discover and directly visualize interface nano-dipole near fields from terahertz (THz) light-junction coupling. Our results show a remarkable asymmetry in charge scattering across the junction that correlates with broken boundaries from the sequential lithographic steps in the Josephson junction fabrication. Near-field imaging of heterogeneous electrodynamics underpins distinguishing features that are absent in responses from topographic steps. The nano-THz probe of junction dipole fields at space-frequency limits represents a powerful and non-invasive tool to capture and leverage materials loss and decoherence in qubit devices.