A production line device prepares a superconducting circuit layer on a substrate. The device prepares an under bump metallization (UBM) layer on an upper surface of the superconducting circuit layer. A superconducting connection is formed between the UBM layer and the superconducting circuit layer. The production device prepares a welding spot on an upper surface of the UBM layer to obtain a qubit assembly configured for a flip-chip superconducting quantum chip. A superconducting electrical connection is formed between the welding spot and the UBM layer.