Flip-Chip Crossover for Spurious Microwave Mode Removal
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Solution Overview
Problem
Conventional methods for removing spurious microwave modes in coplanar waveguides, such as wire-bond straps and microfabricated shorting straps, are either impractical for complex designs due to space constraints and dielectric loss issues, especially in superconducting circuits where they can degrade the quality factor and qubit performance.
Innovation Solution
A coplanar waveguide device with an add-on chip having a metalized pattern-trenched surface is used to remove spurious microwave modes by providing continuous metallization between ground planes, effectively acting as a short at microwave frequencies without the need for dielectrics, thus isolating qubits and maintaining resonator quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If wire-bond straps are used to connect ground planes, then spurious microwave modes are removed, but device complexity increases and space constraints are violated
Solution Approach 1:
The patent extracts the ground plane connection function from the main chip structure and implements it on a separate flip-chip. This removes the spurious modes caused by on-chip ground plane discontinuities while avoiding the complexity of implementing complex strap structures directly on the main chip.
Solution Approach 2:
The patent introduces a flip-chip as an intermediary component that provides the ground plane connection function. This mediator chip contains the complex strap structures, isolating them from the main qubit circuit chip and reducing overall device complexity.
2Object-affected harmful factors
If microfabricated shorting straps are used to connect ground planes, then spurious microwave modes are removed, but dielectric loss increases and quality factor decreases
Solution Approach 1:
The patent changes the material parameter by using superconducting materials for the flip-chip metallization instead of conventional dielectric-supported straps. This eliminates dielectric loss while maintaining the shorting function, thereby preserving the high quality factor of the resonators.
Solution Approach 2:
The patent employs a composite structure combining superconducting metal layers with a thin superconducting dielectric spacer. This composite approach provides both the mechanical support and electrical isolation functions while minimizing dielectric losses through the use of superconducting materials.
3Object-affected harmful factors
If through-vias are used to connect ground planes, then spurious microwave modes are removed, but manufacturing complexity and processing time increase
Solution Approach 1:
The patent segments the device into two separate chips: the main qubit circuit chip and the flip-chip containing the ground plane connection structures. This segmentation avoids the need for complex through-via processing in the substrate, as the connections are established through the flip-chip assembly process instead.
4Object-affected harmful factors
If embedded stripline designs are used, then spurious microwave modes are removed, but device performance degrades due to multi-layer processing
Solution Approach 1:
The patent transitions from a planar embedded stripline design to a three-dimensional flip-chip architecture. The ground plane connections are established in the vertical dimension through the flip-chip assembly, avoiding the need for complex multi-layer embedded processing that degrades device performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively isolates qubits from neighboring resonant systems, enhancing coherence time and allowing for precise control of qubit operations by eliminating spurious modes without degrading the quality factor of the resonators, making it suitable for complex quantum computing applications.
Implementation Method 1
an add-on chip having a metalized pattern-trenched surface, and disposed over the substrate
Implementation Method 2
the large ground planes help confine the electromagnetic mode in a relevant region of interest
Implementation Method 3
The resonator is addressed via capacitive coupling to the ports via CPW microwave feedlines
Data Source
AI summary
A coplanar waveguide device includes a coplanar waveguide structure disposed on a substrate, at least one qubit coupled to the coplanar waveguide structure and an add-on chip having a metallized trench, and disposed over the substrate.