Related papers: Flip-chip integrated superconducting qubits using electroplated bump bonds

Flip-chip integrated superconducting qubits using electroplated bump bonds

URL: http://arxiv.org/abs/2608.07306v1
Date: Fri, 07 Aug 2026 15:01:24 GMT
Title: Flip-chip integrated superconducting qubits using electroplated bump bonds
Abstract summary: We develop a three-dimensional transmon architecture using electroplated indium.<n>We evaluate electroplated indium interconnects for superconducting quantum circuits.
Score: 1.5030949006750438
License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
Abstract: Flip-chip integration offers a promising route toward scalable superconducting quantum processors and hybrid semiconductor-superconductor quantum devices. We develop a three-dimensional transmon architecture using electroplated indium in which the qubit electric field is shared nearly equally between two bump-bonded substrates while maintaining low participation at the indium-bump interface. The resulting geometry is well suited for future hybrid qubits, enabling the integration of distinct material platforms while minimizing sensitivity to bump-interface loss. Using this platform, we evaluate electroplated indium interconnects for superconducting quantum circuits. Flip-chip transmons incorporating electroplated indium bumps exhibit qubit quality factors around $10^6$. In addition, a systematic study of coplanar-waveguide resonators is used to identify losses associated with the electroplating process. In particular, we find that surface losses associated with the gold-layer, used to enable good electric contact with the indium, is likely the primary contributor to the qubit decay rate. These results demonstrate the compatibility of electroplated indium technology with high-coherence superconducting circuits and establish a promising platform for three-dimensional hybrid quantum integration.

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