Abstract
Large-scale quantum computers with more than qubits will likely be built within the next decade. Trapped ions, semiconductor devices, and superconducting qubits among other physical implementations are still confined in the realm of medium-scale quantum integration ( qubits); however, they show promise toward large-scale quantum integration. Building large-scale quantum processing units will require truly scalable control and measurement classical coprocessors as well as suitable wiring methods. In this blue paper, we introduce a fully vertical interconnect that will make it possible to address superconducting qubits fabricated on a single silicon or sapphire chip: Pin-chip bonding. This method permits signal transmission from DC to GHz, both at room temperature and at cryogenic temperatures down to mK. At temperatures below K, the on-chip wiring contact resistance is close to zero and all signal lines are in the superconducting state. High-density wiring is achieved by means of a fully vertical interconnect that interfaces the qubit array with a network of rectangular coaxial ribbon cables. Pin-chip bonding is fully compatible with classical high-density test board applications as well as with other qubit implementations.