Source-linked AI summary
3D integrated superconducting qubits
D. Rosenberg, D. Kim, R. Das, D. Yost, S. Gustavsson, D. Hover, P. Krantz, A. Melville, L. Racz, G. O. Samach, S. J. Weber, F. Yan, J. Yoder, A. J. Kerman, W. D. Oliver
TL;DR
The paper addresses whether heterogeneous 3D integration can preserve superconducting-qubit coherence despite added processing and a nearby chip. It bonds a flux-qubit chip to a separate control/readout chip and finds high coherence alongside capacitive, inductive, and galvanic coupling, while identifying microwave-loss constraints in the bump interconnects.
Problem
Limited evidence exists on whether 3D integration and packaging are compatible with high-coherence superconducting qubits, despite their importance for larger-scale processors.
Method
The authors use an indium-bump flip-chip architecture with flux qubits on one chip and control/readout structures on a bonded interposer chip, testing qubit coherence and bump interconnects.
Results
Average T1 and T2,echo times were 20.9 µs and 24.6 µs, respectively, within the range of standard single-chip controls; extracted microwave bump resistances were 0.1 to 0.5 mΩ.
Takeaways & Limitations
Off-chip control and readout can maintain high qubit coherence, supporting heterogeneous 3D integration as a proof-of-principle route toward larger-scale quantum processors.
Takeaways & Limitations
In their present form, the bump interconnects are suitable for microwave power levels for qubit manipulation and measurement but not for high-Q resonators or transferring quantum information.
Abstract
from arXiv · showhide
As the field of superconducting quantum computing advances from the few-qubit stage to larger-scale processors, qubit addressability and extensibility will necessitate the use of 3D integration and packaging. While 3D integration is well-developed for commercial electronics, relatively little work has been performed to determine its compatibility with high-coherence solid-state qubits. Of particular concern, qubit coherence times can be suppressed by the requisite processing steps and close proximity of another chip. In this work, we use a flip-chip process to bond a chip with superconducting flux qubits to another chip containing structures for qubit readout and control. We demonstrate that high qubit coherence ($T_1$, $T_{2,\rm{echo}} > 20\,μ$s) is maintained in a flip-chip geometry in the presence of galvanic, capacitive, and inductive coupling between the chips.