A T-joint connector can be useful for connecting one or more flex circuit boards to quantum hardware including one or more qubits. The T-joint connector can include one or more flex circuit boards. Each of the one or more flex circuit boards can include one or more signal lines and one or more spring interconnects including a superconducting material. The one or more spring interconnects can be coupled to the one or more signal lines. The one or more spring interconnects can be configured to couple the one or more signal lines to one or more signal pads disposed on a mounting circuit board associated with the quantum hardware. The superconducting material can be superconducting at a temperature less than about 3 kelvin.