Influence of scaling up technologies on transmon coherence

The fabrication of superconducting qubits with long coherence times is an important milestone on the way towards useful quantum applications. Although significant improvements in coherence time have been achieved on single qubit devices, maintaining high coherence times while scaling up the number of qubits maintains challenging. Our single qubit devices achieve T1 times of above 800 µs. In this work, we investigate how scaling-up technologies, such as airbridges and 3D integration, impact the coherence times of our circuits. This analysis is essential to differentiate losses due to the increased design complexity from those caused by additional fabrication processes.