# 3D integrated superconducting qubits

## TL;DR

This paper demonstrates that superconducting flux qubits can be integrated in a 3D flip-chip architecture without significant loss of coherence, supporting scalable quantum computing.

## Contribution

It shows that high coherence times are maintained in 3D flip-chip integration of superconducting qubits, addressing a key challenge for scalable quantum processors.

## Key findings

- Qubit coherence times exceed 20 microseconds in flip-chip configuration
- High coherence is preserved despite galvanic, capacitive, and inductive coupling
- 3D integration is compatible with high-coherence superconducting qubits

## Abstract

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 ($T_1$, $T_{2,\rm{echo}} > 20\,\mu$s) is maintained in a flip-chip geometry in the presence of galvanic, capacitive, and inductive coupling between the chips.