Vertical Silicon Josephson Junction Qubit Device
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Solution Overview
Problem
Existing superconducting quantum computing technologies face challenges in fabricating high-quality Josephson Junction (JJ) qubit devices with efficient superconducting properties, particularly in maintaining a contiguous crystalline structure and minimizing defects.
Innovation Solution
A vertical JJ qubit device is fabricated using crystalline silicon material with an epitaxial silicon substrate, a lower superconducting electrode made of doped epitaxial silicon, and an upper superconducting electrode made of a metallic superconductor. The process involves doping the substrate with boron or gallium, growing epitaxial silicon as a junction layer, and depositing the metallic superconductor, all while maintaining a contiguous crystalline structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fabrication methods are used for Josephson Junction qubit devices, then the device can be manufactured with existing processes, but the superconducting properties are degraded and defects increase due to disruption of the crystalline structure
Solution Approach 1:
The patent transitions from conventional planar Josephson Junction fabrication to a vertical configuration. The epitaxial silicon substrate is grown vertically over the doped superconducting region, creating a vertical stack where the junction layer is positioned above the doped region. This vertical arrangement preserves the crystalline structure continuity while enabling Josephson Junction functionality, thereby improving superconducting properties without sacrificing manufacturability through standard epitaxial growth processes.
Solution Approach 2:
The invention combines doped epitaxial silicon (forming the superconducting region) with undoped or differently doped epitaxial silicon (forming the junction layer) in a vertical stack. The dopant concentration varies through the depth of the structure, creating a composite material system where the superconducting region has high dopant concentration and the junction layer has lower dopant concentration. This composite structure enables both superconductivity and Josephson Junction functionality while maintaining crystalline continuity.
2Manufacturing precision
If the crystalline structure is disrupted during fabrication, then conventional processing steps can be applied, but the quality of the Josephson Junction and superconducting properties deteriorate
Solution Approach 1:
The superconducting region is formed by ion implantation or in-situ doping during the epitaxial growth process, before the junction layer is grown. This preliminary doping action creates the superconducting region with the desired dopant concentration while the crystalline structure remains intact. The subsequent junction layer growth occurs on this pre-formed superconducting region, ensuring crystalline continuity throughout the structure without requiring disruptive post-growth processing.
3Stability of the object's composition
If standard Josephson Junction fabrication is used, then the device structure is simpler, but the superconducting region cannot maintain a contiguous crystalline structure with the substrate
Solution Approach 1:
The patent implements a vertical Josephson Junction structure where the junction layer is positioned vertically above the doped superconducting region rather than laterally adjacent to it. This vertical stacking enables the epitaxial silicon substrate to grow continuously over the doped region, maintaining a contiguous crystalline structure through the entire depth of the device. The vertical configuration preserves crystalline stability while achieving Josephson Junction functionality through the vertical stack architecture.
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 results in a JJ qubit device with improved superconducting properties and minimized defects, enhancing the performance and reliability of superconducting quantum computing devices.
Implementation Method 1
a lower superconducting electrode that is a superconducting region of the epitaxial silicon
Implementation Method 2
The superconducting region is boron or gallium doped epitaxial silicon
Implementation Method 3
A Josephson Junction utilizes the Josephson effect, which is a phenomenon that occurs when two superconductors are placed in proximity, with some barrier or restriction between them
Implementation Method 4
The process grows epitaxial silicon over the substrate and the doped superconducting region as a junction layer of the superconducting device
Data Source
AI summary
A vertical Josephson Junction (JJ) qubit device that is fabricated from crystalline silicon material is provided. The JJ device has a substrate of epitaxial silicon, a lower superconducting electrode that is a superconducting region of the epitaxial silicon and an upper superconducting electrode of a metallic superconductor. The JJ device also has a junction layer. A section of the junction layer between the lower and upper superconducting electrodes forms a junction of the JJ device. Resonator and/or capacitor wiring of the JJ device is also fabricated using the metallic superconductor. The superconducting region is epitaxial silicon that is doped or implanted with boron or gallium. The substrate, the junction layer, and the implanted epitaxial silicon share a contiguous crystalline structure.