Hybrid superconductor–semiconductor (S–Sm) junctions are emerging as key enablers of next-generation quantum computing, combining electrostatic tunability with the coherence and energy efficiency of superconducting electronics. This talk presents cryogenic quantum circuits based on voltage-addressable S–Sm devices integrated with niobium (Nb) superconducting platforms. Using split-gate-induced electrostatic fields, we demonstrate nanoscale control of carrier transport, enabling switching and logic functionalities essential for scalable architectures. We report on the fabrication and experimental realisation of large-scale, gate-tunable electronic switches. Microwave spectroscopy and transport measurements highlight their switching performance and coherence characteristics.