Non-Uniform Magnetic Shielding for Superconducting Qubits
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Solution Overview
Problem
Conventional magnetic shielding systems are ineffective in redirecting flux lines in both radial and axial directions, leading to inadequate protection of superconducting computing systems from external magnetic fields, which can interfere with quantum information processing.
Innovation Solution
A magnetic shielding system with shields and shield caps that have varying thickness and magnetic permeability along their axial and lateral directions, respectively, to create a low-reluctance path and effectively redirect flux lines away from the superconducting processor, using materials like mu-metal, permalloy, and ferrite, and an inner shielding layer with low permeability and high coercivity to minimize residual magnetization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional magnetic shielding systems are used, then the structure is simple and easy to manufacture, but the shielding effectiveness is insufficient and cannot redirect flux lines in both radial and axial directions
Solution Approach 1:
The shield cap is designed with non-uniform thickness, where the thickness varies in the radial direction. The thickness is greater at the perimeter and smaller at the center, creating different local shielding properties to effectively redirect both radial and axial flux lines away from the superconducting processor
Solution Approach 2:
The shield cap features an asymmetric geometry with a flange that extends beyond the shield body perimeter. This asymmetric design creates a larger surface area at the perimeter to intercept flux lines coming from lateral directions, improving overall shielding effectiveness
2Reliability
If uniform shields and shield caps are used, then the manufacturing is easier, but the flux lines cannot be effectively redirected in both radial and axial directions
Solution Approach 1:
The shield cap thickness parameter is deliberately varied in the radial direction, transitioning from a constant thickness in conventional designs to a gradient thickness profile. This parameter change optimizes the magnetic permeability distribution to redirect flux lines more effectively while maintaining manufacturability
3Reliability
If shield caps without flanges are used, then the structure is simpler, but the perimeter flux lines cannot be effectively blocked
Solution Approach 1:
The shield cap design extends into a new dimensional space by adding a flange that protrudes from the main shield body. This flange creates an additional shielding surface at the perimeter that intercepts flux lines in the lateral direction, providing protection that a simple capped design cannot achieve
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 system achieves a uniform low-magnetic field environment, reducing interference and enhancing the coherence and readout fidelity of superconducting qubits by effectively redirecting transverse and longitudinal fields, thereby improving the operational stability of superconducting computing systems.
Implementation Method 1
creating a low reluctance path around a region where a superconducting processor is positioned
Implementation Method 2
a magnetic permeability that varies along at least a portion of an axial direction
Implementation Method 3
a superconducting material may generally only act as a superconductor if it is cooled below a critical temperature that is characteristic of the specific material in question
Implementation Method 4
shield cap geometry does not contribute significantly to shielding longitudinal fields in comparison to other considerations such as shield geometry and spacing between shield layers
Data Source
AI summary
A magnetic shielding system that includes a shield that is non-uniform in the axial direction and a shield cap that is non-uniform in the radial direction. Each shield in the system may have a magnetic permeability, thickness, and/or radius that varies in the axial direction to create low-reluctance paths that redirect flux away from a sample towards the ends of the shield. Each shield cap in the system may have a magnetic permeability and/or thickness that varies in the radial direction to create low-reluctance paths that redirect flux away from the sample towards shield walls. An inner shielding layer formed from a material of low permeability and moderate-to-high coercivity may be implemented as the innermost layer of a magnetic shielding system.