High-Density Qubit Wiring: Pin-Chip Bonding for Fully Vertical Interconnects

Abstract

Large-scale quantum computers with more than 10 5 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 (∼ 100 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 ∼ 10 5 superconducting qubits fabricated on a single silicon or sapphire chip: Pin-chip bonding. This method permits signal transmission from DC to ∼ 10 GHz, both at room temperature and at cryogenic temperatures down to ∼ 10 mK. At temperatures below ∼ 1 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.

The Quantum Socket and DemuXYZ-Based Gates with Superconducting Qubits

“…An alternative approach allowing for galvanic (superconducting) couplings similar to the quantum socket would rely on terminating the ribbon cables into micromachined rigid pins. Instead of using springs to provide a suitable force at the pinpad connection, the pins would pierce into an array of indium bumps fabricated on the qubit chip [34]. Both approaches can be miniaturized such that each signal line has a similar footprint of a physical qubit (i.e., approximately 100 µm) all the way from the qubit chip to room temperature.…”

Toward Realization of Scalable Packaging and Wiring for Large-Scale Superconducting Quantum Computers

“…However, stacking two chips does not guarantee the scalability of the wiring, as the wiring is in the end made through the edges of the routing chip. To implement a fully scalable three-dimensional package, we need either a multi-layer stack of the routing chip [39] or to connect coaxial cables from the vertical direction [30], [40]. Spring probes are one of the possible methods of connecting the coaxial cables to the qubit chip directly [41], [42].…”

Solid-state qubits integrated with superconducting through-silicon vias

“…air bridges and standard flipchip bonding) or by a single layer of vertical I/O (i.e. pin-chips, pogo pins, and similar technologies) [6,[10][11][12][13][14][15][16]. However, larger and more complex quantum system architectures may need to utilize multiple levels of qubits and complex signal routing, which necessitates the development of multi-layer control and routing capabilities.…”