Qubit Substrate Spacer Structure to Limit Electromagnetic Coupling

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Solution Overview

Problem

Existing qubit devices face challenges in preventing or reducing the penetration of electromagnetic waves between qubit substrates, which can lead to deterioration of quantum characteristics such as a decrease in coherence time.

Innovation Solution

A qubit device design that includes a first and second qubit substrate with a connection substrate faced by a spacer portion, where the spacer is in contact with the peripheral portion of the qubit substrate and lower than the surface, forming a recess to inhibit electromagnetic wave propagation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of moving object

If qubit substrates are disposed close to each other for miniaturization, then device integration density is improved, but electromagnetic wave penetration between substrates increases causing quantum characteristic deterioration

Engineering Contradiction:
Improvedevice integration densityVSAvoidelectromagnetic wave penetration
Core Design Contradiction:
Area of moving objectVSObject-affected harmful factors

Solution Approach 1:

A connection substrate is introduced as an intermediary component between the first and second qubit substrates. This connection substrate includes a spacer portion that physically separates the qubit substrates while enabling electrical connection through conductive portions, thereby reducing direct electromagnetic wave penetration while maintaining functional integration.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent introduces a vertical dimension by stacking qubit substrates with a connection substrate in between, rather than placing them side-by-side. This three-dimensional arrangement allows for better electromagnetic isolation while maintaining compact form factor, as the spacer portion creates vertical separation distance.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Reliability

If spacer portion height is increased to improve electromagnetic wave shielding, then quantum characteristic stability is improved, but device height increases

Engineering Contradiction:
Improvequantum characteristic stabilityVSAvoiddevice height
Core Design Contradiction:
ReliabilityVSLength of stationary object

Solution Approach 1:

The patent optimizes the spacer portion height to a specific parameter range (10-100 μm) that provides sufficient electromagnetic wave shielding while limiting excessive height increase. This parameter optimization balances quantum characteristic stability with compact device dimensions.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The connection substrate is formed as a composite structure with insulating base material and integrated conductive portions. This composite design provides electromagnetic isolation through the insulating material while maintaining electrical connectivity through the conductive portions, achieving shielding without excessive height.

Inventive Principle:
Principle #40Composite materials

3Adaptability or versatility

If connection substrate is added to connect qubit substrates, then qubit connectivity is improved, but device complexity increases

Engineering Contradiction:
Improvequbit connectivityVSAvoidstructure complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The connection substrate merges multiple functions into a single component: it provides mechanical support through the base material, electromagnetic isolation through the insulating property, and electrical connection through the conductive portions. This merging reduces the need for separate components and simplifies the overall device structure.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The connection substrate serves multiple purposes simultaneously: it acts as a mechanical support structure, an electromagnetic shield, and an electrical interconnection medium. This multi-functionality reduces the number of separate components needed, thereby reducing overall device complexity despite adding connectivity capabilities.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Data Source

PatentEP4712751A1Qubit device and method of manufacturing qubit device
Publication Date: 2026.03.18 FUJITSU LTD
  • EP4712751A1 patent drawingFigure 1A~1C
  • EP4712751A1 patent drawingFigure 2
  • EP4712751A1 patent drawingFigure 3A~3C

AI summary

A qubit device (100) includes a first qubit substrate (10a) having a first qubit (30a) formed on a first surface (12a), a second qubit substrate (10b) having a second qubit (30b) formed on a second surface (12b), a connection substrate (40) disposed to face the first surface and the second surface, and a spacer portion (50) provided to be located at least between the connection substrate and the first qubit substrate, wherein the first surface and the second surface are located in a same plane, and the spacer portion is provided to be in contact with a third surface (15a) that is provided in a peripheral portion of the first qubit substrate and is lower than the first surface.