Abstract
Two dimensional electron gases based on SrTiO₃ are an intriguing platform for exploring mesoscopic superconductivity combined with spin-orbit coupling, offering electrostatic tunability from insulator to metal to superconductor within a single material. So far, however, quantum effects in SrTiO₃ nanostructures have been complicated by disorder. Here we introduce a facile approach to achieving high mobility and patterning gate-tunable structures in SrTiO₃, and use it to demonstrate ballistic constrictions with clean normal state conductance quantization. Conductance plateaus show two-fold degeneracy that persists to magnetic fields of at least 5 T - far beyond what one would expect from the g-factor extracted at high fields - a potential signature of electron pairing extending outside the superconducting regime.