Tuning a minimal Kitaev chain qubit device without transport

Quantum-dot–superconductor arrays realizing short Kitaev chains provide a versatile platform to explore topological superconductivity and Majorana zero modes. However, conventional tuning approaches rely on normal leads that continuously inject quasiparticles, making them incompatible with coherent qubit operation and impractical for longer chains. Here, we demonstrate a method to tune two coupled two-site Kitaev chains in a qubit geometry using only a superconducting lead connected to a resonator, without requiring any normal transport. This approach enables tune-up of Majorana qubits using a single superconducting lead and can be extended to arbitrarily long Kitaev chains.