Vacuum-Bridged Josephson Junction Layout for Lower Interface Loss
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Solution Overview
Problem
Losses at interfaces between different materials in superconducting devices, particularly in Josephson junctions, lead to reduced performance and coherence time of qubits, such as transmon qubits.
Innovation Solution
The integration of bridge connections between the Josephson junction and external electrodes, formed using a method involving resist patterning and superconducting thin film deposition, ensures that the Josephson junction is not in direct contact with the external electrodes, thereby reducing parasitic effects and enhancing qubit performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the Josephson junction is directly connected to external electrodes, then the device complexity is reduced, but losses at material interfaces increase leading to poorer qubit performance
Solution Approach 1:
The patent introduces bridge connections as intermediary elements between the Josephson junction and external electrodes. These bridge connections are formed of superconducting material and physically separate the Josephson junction from direct contact with external electrodes, thereby mediating the electrical connection while minimizing parasitic losses at material interfaces. This resolves the contradiction by adding an intermediate structure that reduces energy losses without significantly increasing overall device complexity.
2Loss of energy
If the Josephson junction is spaced apart from external electrodes using bridge connections, then losses at material interfaces are reduced, but the device complexity increases
Solution Approach 1:
The bridge connections are implemented as thin superconducting film structures that span between the Josephson junction and external electrodes. These thin film bridges provide the necessary electrical connection while maintaining physical separation, minimizing interface losses without requiring complex three-dimensional structures. The use of thin films keeps the added complexity manageable while achieving the desired performance improvement.
3Duration of action of stationary object
If bridge connections are implemented to reduce parasitic effects, then coherence time is improved, but the manufacturing process complexity increases
Solution Approach 1:
The bridge connections are integrated into the existing superconducting circuit fabrication process by depositing superconducting material in the same lithography and deposition steps used for creating other superconducting elements. The bridge structures are formed simultaneously with other circuit components, merging the additional functionality into the existing manufacturing workflow rather than requiring separate fabrication processes. This approach improves coherence time while minimizing the increase in manufacturing complexity.
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 configuration minimizes parasitic effects, leading to improved coherence times and overall performance of superconducting qubits by reducing losses at material interfaces.
Implementation Method 1
depositing a superconducting thin film over the resist such that the thin film is in direct electrical contact with the contact pads
Implementation Method 2
Josephson junctions, for example those used in quantum processing units
Data Source
AI summary
The invention relates to the field of superconducting integrated circuits. The invention includes an integrated circuit device comprising a substrate, a Josephson junction on the substrate, external electrodes on the substrate and spaced apart from the Josephson junction, and bridge connections connecting the Josephson junction to the external electrodes. The invention also includes a method for manufacturing such an integrated circuit device.