Local Vacuum Cavity for Low-Noise Superconducting Quantum Circuits
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Solution Overview
Problem
Quantum computing devices face issues with dissipation and frequency noise due to lossy dielectrics and surface adsorbates, which limit their performance and coherence.
Innovation Solution
Creating a local vacuum environment around quantum circuit elements using a sealed cavity with a cap layer bonded to the substrate, maintaining pressures below 10^-6 Torr, and using getter layers to adsorb contaminants and reduce frequency noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If quantum devices operate in atmospheric environment, then device complexity is low, but dissipation and frequency noise increase due to lossy dielectrics and surface adsorbates
Solution Approach 1:
The device is segmented into two environments: the quantum circuit elements operate in a vacuum-sealed cavity to minimize dissipation and frequency noise, while the bonding cap layer and substrate interface are engineered to maintain hermetic sealing. This segmentation allows the quantum components to benefit from vacuum isolation without requiring the entire system to be in vacuum, thus improving coherence while managing complexity through localized environmental control.
Solution Approach 2:
The patent applies the inert environment principle by creating a vacuum atmosphere within the sealed cavity surrounding the quantum circuit elements. This vacuum environment eliminates atmospheric gases and moisture that would otherwise form lossy dielectric layers and adsorbates on surfaces, thereby reducing dissipation and frequency noise. The vacuum acts as an inert environment that prevents harmful interactions between the quantum devices and atmospheric contaminants.
2Reliability
If vacuum pressure is reduced to below 10^-6 Torr, then frequency noise decreases, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by performing ion milling and surface preparation of the bonding cap layer and substrate before vacuum bonding. These preparatory steps are conducted in atmospheric conditions to remove contaminants and create optimal bonding surfaces, then the components are transferred to vacuum for hermetic sealing. This preliminary preparation eliminates the need to perform complex surface treatments inside the vacuum chamber, thereby achieving high vacuum quality without proportionally increasing manufacturing complexity.
Solution Approach 2:
The bonding cap layer acts as an intermediary element that enables hermetic sealing between the vacuum environment and the external atmosphere. The cap layer is engineered with specific materials and surface properties to achieve strong bonding to the substrate while maintaining vacuum integrity. This intermediary component simplifies the manufacturing process by providing a dedicated sealing interface that can be bonded under controlled conditions, then sealed to maintain vacuum without requiring complex in-situ bonding procedures.
3Reliability
If getter layers are added to the cap layer, then adsorbate removal improves, but device structure becomes more complex
Solution Approach 1:
The bonding cap layer is designed with multi-functionality, serving both as a hermetic seal to maintain vacuum and as a getter layer to actively remove adsorbates. By integrating gettering functionality into the cap layer itself rather than adding separate getter components, the design achieves enhanced vacuum maintenance and adsorbate removal without proportionally increasing structural complexity. The cap layer materials are selected to provide both sealing and gettering properties simultaneously.
Solution Approach 2:
The patent merges the functions of the cap layer and getter materials into a single integrated component. Instead of having separate cap and getter elements, the cap layer is constructed with materials that combine hermetic sealing capabilities with strong adsorbate gettering properties. This merging of functions reduces the number of discrete components and simplifies the overall device structure while maintaining effective vacuum maintenance and frequency noise reduction.
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 approach reduces dissipation and frequency noise by minimizing weakly bound molecules and adsorbates, improving the quality factor and stability of quantum circuit elements.
Implementation Method 1
bonding a cap layer to the substrate to form a sealed cavity between the cap layer and the substrate, in which the sealed cavity comprises a vacuum
Implementation Method 2
a surface of the cap layer that faces the sealed cavity comprises a getter layer
Data Source
AI summary
A device includes: a substrate including a superconductor quantum device, the superconductor quantum device including a superconductor material that exhibits superconducting properties at or below a corresponding critical temperature; a cap layer bonded to the substrate; and a sealed cavity between the cap layer and the substrate.