Simple and Re-useable Flip-Chip Method for Hybrid Quantum Sytems*

The flexibility and scalability of solid-state qubit systems can be greatly improved with the use of flip-chip geometries, as these provide a third dimension for interconnects and allow coupling of systems on different substrates [1,2]. Indium bump-bonded flip-chips can be prohibitively costly for a university lab, and do not offer a means to re-use the substrates. Here, we describe a simple, low cost, non-galvanic approach to flip-chip bonding, demonstrated using superconducting qubits coupled to other quantum systems, including acoustic and electromagnetic resonators. We achieve less than two microns of placement error, and provide a cryogenically-compatible bonded structure that can be disassembled using acetone. We have tested the approach using inductively coupled coplanar waveguide resonators, and we have designed a multi-qubit experiment with direct inductive coupling between qubits on separate substrates.

[1] Rosenberg, D. et al. npj Quantum Information 3, 42 (2017).
[2] Satzinger, K. J. et al. arXiv:1804.07308