Sacrificial Shorting Straps for Superconducting Qubit Protection

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Solution Overview

Problem

Three-dimensional superconducting qubits suffer from electrostatic discharge due to the antenna effect of their large paddles, and existing solutions, such as manually cutting shorting straps, are not scalable and introduce particulates and lossy features into the qubit system.

Innovation Solution

The use of sacrificial shorting straps made of conductive materials like niobium, which can be selectively etched using vapor or wet etchants after device mounting, to protect the tunnel junction from electrostatic discharge by providing a path for electrostatic energy to bypass the delicate junction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If manually cutting shorting straps is used to protect tunnel junction from electrostatic discharge, then the tunnel junction is protected, but particulates and lossy features are introduced into the qubit system

Engineering Contradiction:

Improvetunnel junction protectionVSAvoidparticulates and lossy features

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The sacrificial shorting strap is formed before the tunnel junction to provide pre-protection against electrostatic discharge. The strap is prepared in advance as a protective measure that will be removed later through selective etching, preventing the need for manual cutting that introduces particulates.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The sacrificial shorting strap is selectively removed after serving its protective function. The etching process extracts only the sacrificial strap material while leaving the tunnel junction and other qubit components intact, eliminating the source of electrostatic discharge protection once the junction is formed.

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If sacrificial shorting strap is used to protect tunnel junction, then electrostatic discharge is prevented, but extraneous capacitance is introduced

Engineering Contradiction:

Improveelectrostatic discharge protectionVSAvoidextraneous capacitance

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The sacrificial shorting strap is designed to be temporary and is completely removed after serving its protective purpose during fabrication. By discarding the strap after etching, the extraneous capacitance it introduces is eliminated, leaving no residual effect on the qubit system.

Inventive Principle:

Principle #34Discarding and recovering

3Productivity

If scalable fabrication method is implemented, then manufacturing efficiency is improved, but manual cutting operations are eliminated

Engineering Contradiction:

Improvemanufacturing scalabilityVSAvoidmanual cutting operation

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The manual mechanical cutting operation is replaced with a chemical etching process. The sacrificial shorting strap is removed using vapor or liquid etchants that selectively dissolve the strap material, enabling automated, scalable fabrication without manual intervention and eliminating the limitations of manual cutting.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 method effectively eliminates extraneous capacitance and lossy features, preventing damage to the qubit system by removing the sacrificial shorting strap without leaving residues, thus enhancing the coherence times of qubits.

Implementation Method 1

protect the tunnel junction from electrostatic discharge by providing a path for electrostatic energy to bypass the delicate junction

Methodology Applied

Scientific EffectElectrostatic discharge: Electrostatic Discharge

Implementation Method 2

etching away the sacrificial shorting strap in the vacuum chamber

Methodology Applied

Scientific EffectChemical etching:

Data Source

PatentUS10256106B2Sacrificial shorting straps for superconducting qubits

Publication Date: 2019.04.09 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

A technique relates to protecting a tunnel junction. A first electrode paddle and a second electrode paddle are on a substrate. The first and second electrode paddles oppose one another. A sacrificial shorting strap is formed on the substrate. The sacrificial shorting strap connects the first electrode paddle and the second electrode paddle; The tunnel junction is formed connecting the first electrode paddle and the second electrode paddle, after forming the sacrificial shorting strap. The substrate is mounted on a portion of a quantum cavity. The portion of the quantum cavity is placed in a vacuum chamber. The sacrificial shorting strap is etched away in the vacuum chamber while the substrate is mounted to the portion of the quantum cavity, such that the sacrificial shorting strap no longer connects the first and second electrode paddles. The tunnel junction has been protected from electrostatic discharge by the sacrificial shorting strap.