Superconducting qubits have emerged as powerful building blocks for a quantum computer. However, controlling superconducting qubits remains a challenge, particularly a fast, active and reliable reset of the qubit into the ground state. For this purpose, we have investigated, analyzed, and optimized the use of a quantum-circuit refrigerator (QCR), an electronic microcooler based on single-electron tunneling in a normal-metal–insulator–superconductor (NIS) junction. Within this project, we have optimized the device fabrication process and statistically analyzed the yield and reproducibility of devices. Furthermore, we have investigated device aging and decay over time, which leads to increased tunneling resistances. We have found that device storage in a vacuum at low temperatures can greatly extend the device lifetime. Our low-temperature electronic measurements have shown that our device parameters are suitable for implementation in qubit reset experiments.
