Superconducting Qubit Readout Circuit With Embedded Ground Bridge
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Solution Overview
Problem
Existing qubit chip devices using superconducting qubits face issues such as slot modes and crosstalk due to asymmetric coplanar waveguides, which affect performance and are difficult to manufacture without damaging the qubits.
Innovation Solution
A qubit chip device with a conductive bridge embedded in the substrate connecting ground plate portions across the signal line, made of the same superconducting material, which suppresses crosstalk and slot modes, and allows for precise adjustment of resonance frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If asymmetric coplanar waveguides are used in superconducting qubit devices, then the device structure is simpler and easier to manufacture, but slot modes and crosstalk occur which degrade performance
Solution Approach 1:
The patent extracts and removes the problematic slot mode from the coplanar waveguide structure by introducing a ground plate that cancels the slot mode field distribution, thereby eliminating crosstalk while maintaining the simple CPW geometry
Solution Approach 2:
The patent introduces a ground plate as an intermediary element between the signal line and the substrate. This ground plate acts as a mediator that suppresses slot modes and prevents crosstalk, allowing the simple CPW structure to function reliably
2Ease of manufacture
If conventional manufacturing methods are used for qubit chips, then standard fabrication processes can be applied, but the qubits are damaged during manufacturing
Solution Approach 1:
The patent performs preliminary actions by forming the ground plate and adjusting its position before final qubit assembly. This allows optimization of the ground plate configuration to prevent slot modes from developing, thereby protecting qubit integrity during subsequent manufacturing steps
3Reliability
If ground plate patterns are optimized to suppress slot modes, then crosstalk is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent changes key parameters of the ground plate including its width, position, and distance from the signal line to optimize slot mode suppression. By adjusting these parameters, the design achieves effective crosstalk reduction while maintaining manufacturability with standard precision tolerances
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
The conductive bridge structure enhances qubit performance by reducing interference and enabling easier manufacturing without damaging the qubits, allowing for high freedom in design and adjustment of thickness and width.
Implementation Method 1
a conductive bridge embedded in the substrate and connecting two portions of the ground plate in a direction crossing the signal line
Implementation Method 2
the signal line, the ground plate and the conductive bridge each comprise a same superconductive material
Data Source
Figure 1~2
Figure 3A~3B
Figure 4A~4B
AI summary
A qubit chip device (100) includes: a substrate (110); a superconducting qubit (140) on the substrate; and a readout circuit (180) on the substrate and electrically connected to the superconducting qubit, the readout circuit including: a signal line (SL) on a surface of the substrate; a ground plate (GP) on the surface of the substrate, the ground plate including a pattern forming a coplanar waveguide along the signal line and offset from the signal line; and a conductive bridge embedded in the substrate and connecting two portions of the ground plate in a direction crossing the signal line.