Detection of Single Electron Charges in Nanoscale Dipoles and Anyon-Type Quantum Dots

In topological quantum computation, quantum information is encoded in a deco-herence free and fault-tolerant manner using exotic Majorana fermion quasiparticles. Recent advancements have revealed solid-state quantum dots hosting non-Abelian anyons, where a single electron contributes to the formation of a Majorana-bound vortex. This property makes them highly attractive for charge sensing applications. To evaluate charge sensing fidelity before detecting unit charges in candidate quantum dots, we fabricated and tested various nano-scale dipole structures consisting of two sub-20nm metal dots separated by a tunnel barrier. We experimentally demonstrate robust detection of single-electron switching within the various dipole structures using both single-electron transistors (SETs) and radio-frequency gate reflectometry. Single-electron switching detection within a dipole structure of this length scale has not been reported before. Additionally, we present a composite simulation frame-work combining COMSOL Multiphysics and SPICE to calculate the induced charge in the SET due to electron switching in the dipole, achieving excellent agreement with experimental results. Furthermore, we fabricated site-controlled non-Abelian anyon-type InP quantum dots and attempted spatial sensing of unit charges by positioning SETs in close proximity to the dots. However, our experimental observations are primarily attributed to substrate effects under light illumination. These findings highlight the necessity of carefully accounting for substrate effects in quantum dot experiments to ensure accurate and measurable outcomes.