Highly stable aluminum air-bridges with stiffeners

Air-bridges play a crucial role in the performance of microwave circuits integrated with superconducting quantum bits, and their mechanical stability is important for reliable operation. This study is devoted to the technological issues that lead to air-bridge instability. We propose an optimized bridge geometry designed to improve the mechanical properties. Through systematic testing, we established that bridges incorporating this novel geometry achieved complete stability for lengths up to 170μm in our technological processes. The findings provide insight into the problem and a practical solution for technologists facing the challenges of the air-bridge stability. The implementation of our technology has the potential to improve significantly the mechanical robustness of air-bridges in multi-qubit circuits for quantum computations.