Integrated Cryogenic Microwave Attenuators for Dense Transmission Lines
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Solution Overview
Problem
Conventional cryogenic devices with multiple transmission lines face challenges in reducing heat and thermal noise during quantum computing, as existing attenuators are impractical for high line densities due to large size, high crosstalk, and inadequate thermalization, limiting the number of qubits that can be operated efficiently.
Innovation Solution
A cryogenic device with multiple transmission lines fabricated on a high thermal conductivity substrate, featuring embedded microwave attenuators made from materials like Nichrome, Constantan, and Manganin, arranged with a separation gap to maintain crosstalk below -50 dB, allowing for increased line density and efficient operation across various temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If discrete attenuators are used for each transmission line, then attenuation performance is adequate, but device complexity and footprint become impractical for more than 50 lines
Solution Approach 1:
Multiple discrete attenuators are merged into a single integrated attenuator structure where multiple transmission lines share common attenuating elements. The patent shows multiple microstrip transmission lines fabricated on a substrate with shared resistive attenuator regions, allowing multiple lines to achieve attenuation without requiring individual discrete attenuator components for each line.
Solution Approach 2:
A single substrate structure performs multiple functions: it provides transmission pathways for multiple lines, integrates attenuation for all lines, provides thermalization, and maintains signal integrity. The substrate and embedded components serve as both structural support and functional elements for multiple transmission lines simultaneously.
2Productivity
If transmission lines are placed closer together to increase density, then line density increases, but crosstalk between lines increases
Solution Approach 1:
The substrate provides locally optimized characteristics including controlled impedance regions, separation gaps between transmission lines, and strategically placed ground planes. These local structural variations maintain signal integrity and minimize crosstalk even when lines are densely packed, allowing high line density without sacrificing signal quality.
3Ease of manufacture
If standard substrates are used, then manufacturing is simple, but thermalization of attenuators is inadequate leading to thermal noise
Solution Approach 1:
The patent employs a composite structure combining a substrate with embedded resistive materials and thermal pathways. The substrate integrates multiple material properties: electrical insulation, thermal conduction to heat sinks, and mechanical support. This composite approach enables effective thermalization of attenuators while maintaining manufacturing feasibility through standard semiconductor fabrication processes.
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 solution enables a significant increase in the number of qubits that can be operated while maintaining low crosstalk and a small footprint, facilitating efficient quantum computing by reducing thermal noise and heat extraction effectively.
Implementation Method 1
a substrate with a thermal conductivity above a defined threshold for reducing heat and thermal noise during quantum computing
Implementation Method 2
one or more microwave attenuators embedded on the plurality of transmission lines
Data Source
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AI summary
Techniques for implementing multiple microwave attenuators on a high thermal conductivity substrate for cryogenic applications to reduce heat and thermal noise during quantum computing are provided. In one embodiment, a device for using in cryogenic environment is provided that comprises a substrate having a thermal conductivity above a defined threshold, a plurality of transmission lines fabricated on the substrate and arranged with a separation gap between the plurality of transmission lines to maintain crosstalk below -50 decibels, and one or more microwave attenuators embedded on the plurality of transmission lines.