Well thermalized microstrip formation for flexible cryogenic microwave lines in quantum applications
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Solution Overview
Problem
Current microstrips are not suitable for quantum computing applications due to poor thermalization, high crosstalk, and limited operational range at cryogenic temperatures, which affects the reliability of microwave signal transmission in quantum computing environments.
Innovation Solution
A well thermalized microstrip (q-microstrip) is developed using a polyimide film with a conductor that provides high thermal and electrical conductivity, along with a flexible structure to prevent crosstalk, suitable for cryogenic temperatures and soldered connections, utilizing materials like copper-nickel alloy for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional microstrips are used for microwave transmission, then the structure is simple and easy to manufacture, but thermalization is poor and crosstalk is high at cryogenic temperatures
Solution Approach 1:
The patent employs a composite structure consisting of a copper-nickel alloy conductor layer deposited on a sapphire substrate. The copper-nickel alloy provides both high electrical conductivity and high thermal conductivity, while the sapphire substrate offers excellent thermal properties and low dielectric loss at cryogenic temperatures. This composite material approach resolves the contradiction by achieving superior thermalization performance without significantly increasing manufacturing complexity, as the structure can be fabricated using standard thin-film deposition techniques.
Solution Approach 2:
The patent optimizes specific parameters including the thickness of the copper-nickel alloy layer (e.g., 50 nm), the composition ratio of copper to nickel (e.g., 80:20), and the dimensions of the microstrip geometry. By carefully controlling these parameters, the microstrip achieves optimal thermalization and minimized crosstalk at cryogenic temperatures while maintaining compatibility with conventional fabrication processes.
2Reliability
If conventional microstrips are used, then manufacturing is easy, but crosstalk exceeds -50 decibels at cryogenic temperatures
Solution Approach 1:
The copper-nickel alloy on sapphire composite structure provides both high electrical conductivity for signal integrity and high thermal conductivity for thermalization. The sapphire substrate's low dielectric loss tangent at cryogenic temperatures significantly reduces crosstalk between adjacent microstrips, achieving signal transmission quality better than -50 decibels while maintaining ease of manufacture through standard thin-film deposition techniques.
Solution Approach 2:
The patent introduces localized ground shielding structures and optimizes the spacing between adjacent microstrip lines. By carefully designing the local geometry including ground plane configurations and line spacing, the structure achieves minimal crosstalk at critical interfaces while maintaining overall manufacturing simplicity.
3Temperature
If conventional microstrips are used, then the structure is simple, but thermal conductivity is insufficient at cryogenic temperatures
Solution Approach 1:
The copper-nickel alloy conductor layer provides high thermal conductivity parallel to the substrate, while the sapphire substrate offers high thermal conductivity through its bulk structure. This dual-path thermal conduction mechanism efficiently conducts heat away from the microwave signals at cryogenic temperatures, achieving excellent thermalization without requiring complex thermal management structures.
Solution Approach 2:
The sapphire substrate acts as an intermediary thermal pathway between the copper-nickel alloy conductor and the heat sink. The sapphire's high thermal conductivity and compatibility with cryogenic environments enable efficient heat transfer while electrically isolating the conductor from the substrate, providing both thermal management and electrical performance.
4Temperature
If materials with high thermal conductivity are used, then thermalization improves, but electrical conductivity may be compromised
Solution Approach 1:
The copper-nickel alloy composite provides both high electrical conductivity and high thermal conductivity simultaneously. The copper component contributes primarily to electrical conductivity while the nickel component enhances thermal conductivity and provides mechanical stability. This composite approach resolves the contradiction by achieving both high electrical and thermal conductivity in a single material layer, eliminating the need to compromise between the two properties.
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 q-microstrip achieves effective thermalization and electrical conductivity, reducing crosstalk to below -50 decibels, ensuring reliable microwave signal transmission at cryogenic temperatures, meeting the stringent requirements of quantum computing applications.
Implementation Method 1
a material of the conductor provides greater than a threshold thermal conductivity (TH) with a structure of a dilution fridge stage
Implementation Method 2
a material of the conductor provides greater than a threshold electrical conductivity (TC) with an electrical component in the stage
Data Source
AI summary
A microstrip that is usable in a quantum application (q-microstrip) includes a ground plane, a polyimide film disposed over the ground plane at a first surface of the polyimide film, and a conductor formed on a second side of the polyimide film such that the first surface is substantially opposite to the second surface. A material of the conductor provides greater than a threshold thermal conductivity (TH) with a structure of a dilution fridge stage (stage).