Porous Cryogenic Microstrip Dielectrics for Lower TLS Loss

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Solution Overview

Problem

Multilevel wiring (MLW) environments in quantum computing systems are inherently lossy, leading to two-level system (TLS) saturation that hinders qubit calibration and affects signal fidelity.

Innovation Solution

Implement a dielectric structure with a void percentage of at least 50% by creating air gaps or voids in the dielectric material, supported by ground planes, to reduce dielectric losses and modify resonator layouts to change segment capacitance and inductance values.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a multilevel wiring (MLW) environment is used to route dense layouts, then wiring density and electromagnetic environment are improved, but dielectric losses increase causing TLS saturation

Engineering Contradiction:

Improvewiring densityVSAvoiddielectric losses

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The patent introduces a porous dielectric structure with air gaps (voids) created by depositing dielectric material over a patterned substrate and selectively removing portions. This porous structure reduces dielectric losses by minimizing TLS saturation while maintaining the MLW environment's wiring density and electromagnetic benefits. The air gaps act as low-loss regions that prevent energy loss in the dense wiring layout.

Inventive Principle:

Principle #31Porous materials

2Strength

If dielectric material is used to support signal lines in MLW, then structural support is provided, but TLS saturation occurs reducing signal fidelity

Engineering Contradiction:

Improvestructural supportVSAvoidsignal fidelity

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent applies local quality by creating regions of different dielectric properties within the MLW structure. Solid dielectric regions provide structural support where needed, while air gap regions reduce TLS saturation and improve signal fidelity. This spatial variation in dielectric quality allows simultaneous optimization of mechanical support and electrical performance in different locations of the same structure.

Inventive Principle:

Principle #3Local quality

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 improves resonator performance by decreasing dielectric losses, offsetting resonance modes, and enhancing the quality factor, thereby improving signal fidelity and qubit calibration.

Implementation Method 1

The MLW environment is inherently lossy. Recent hardware experiments have highlighted the problem of two-level system (TLS) saturation in such structures

Methodology Applied

Scientific EffectDielectric loss reduction: Dielectric

Implementation Method 2

modifying the original distributed resonator layout by changing at least one of the materials to change at least one of the segment shunt capacitance values or at least one of the segment inductance values

Methodology Applied

Scientific EffectCapacitance modification: Capacitance

Data Source

PatentUS20250309515A1Loss reduction and impedance engineering for cryogenic applications

Publication Date: 2025.10.02 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

An apparatus (e.g., microstrip or stripline) includes a signal line and a lower ground plane that is beneath, and spaced from, the signal line. A dielectric structure supports the signal line and is located at least partially between the lower ground plane and the signal line. The dielectric structure includes a dielectric material defining a plurality of voids and having a void percentage of at least 50%.