Quantum Processor Filter with Frequency-Selective Surface

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Solution Overview

Problem

Existing filter arrangements for quantum processors face challenges in achieving high attenuation at frequencies above the operating band while maintaining good in-band performance, particularly due to interference from radiation in the superconducting gap frequency range.

Innovation Solution

A filter arrangement using a waveguiding structure with a frequency-selective surface (FSS) that is electromagnetically reflective for low-frequency bands and transparent for high-frequency bands, guiding electromagnetic waves away from the main path, combined with absorber and shielding arrangements to enhance attenuation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If electromagnetic absorbent material is used to fill transmission lines for high-frequency filtering, then attenuation at high frequencies is improved, but in-band matching and attenuation performance deteriorate

Engineering Contradiction:
Improvehigh-frequency radiation attenuationVSAvoidin-band matching and loss performance
Core Design Contradiction:
Object-affected harmful factorsVSReliability

Solution Approach 1:

The filter is divided into distinct functional sections: a first section with electromagnetic absorbent material for high-frequency attenuation, and a second section with resonant structures for stopband filtering. This segmentation allows each section to optimize its specific function without compromising the other, resolving the contradiction between high-frequency attenuation and in-band performance.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The filter combines two different filtering mechanisms (electromagnetic absorbent material and resonant structures) into a composite filter arrangement. This composite approach leverages the strengths of both methods: the absorbent material provides broadband high-frequency attenuation while the resonant structures provide selective stopband filtering, achieving both high-frequency protection and good in-band performance.

Inventive Principle:
Principle #40Composite materials

2Reliability

If microwave lowpass filters based on resonant structures are used, then in-band matching and loss performance are improved, but attenuation at high frequencies far from in-band frequencies deteriorates

Engineering Contradiction:
Improvein-band matching and loss performanceVSAvoidattenuation at 100 GHz relative to 1-10 GHz
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The filter is divided into distinct functional sections: a first section with electromagnetic absorbent material for high-frequency attenuation, and a second section with resonant structures for stopband filtering. This segmentation allows each section to optimize its specific function without compromising the other, resolving the contradiction between high-frequency attenuation and in-band performance.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The filter combines two different filtering mechanisms (electromagnetic absorbent material and resonant structures) into a composite filter arrangement. This composite approach leverages the strengths of both methods: the absorbent material provides broadband high-frequency attenuation while the resonant structures provide selective stopband filtering, achieving both high-frequency protection and good in-band performance.

Inventive Principle:
Principle #40Composite materials

3Object-affected harmful factors

If electromagnetic absorbent material is used for high-frequency filtering, then high-frequency attenuation is improved, but device complexity and manufacturing difficulty increase

Engineering Contradiction:
Improvehigh-frequency radiation attenuationVSAvoidfilter construction complexity
Core Design Contradiction:
Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The filter is divided into distinct functional sections: a first section with electromagnetic absorbent material for high-frequency attenuation, and a second section with resonant structures for stopband filtering. This segmentation allows each section to optimize its specific function without compromising the other, resolving the contradiction between high-frequency attenuation and in-band performance.

Inventive Principle:
Principle #1Segmentation

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 filter arrangement provides improved attenuation of high-frequency radiation, maintaining high isolation and good in-band performance by redirecting high-frequency waves away from the main path, thus protecting quantum processors from harmful interference.

Implementation Method 1

The FSS is arranged to be electromagnetically reflective for a low-frequency band and arranged to be electromagnetically transparent in a direction away from the main waveguiding path at a high-frequency band

Methodology Applied
Scientific EffectElectromagnetic reflection: Reflection

Implementation Method 2

The waveguiding structure comprises a frequency-selective surface (FSS) arranged along at least a part of the main waveguiding path

Methodology Applied
Scientific EffectFrequency-selective surface filtering: Filter (optical)

Implementation Method 3

arranged to be electromagnetically transparent in a direction away from the main waveguiding path at a high-frequency band... these high-frequency waves may be terminated in various ways

Methodology Applied
Scientific EffectElectromagnetic absorption: Absorption (EM radiation)

Data Source

PatentEP4500631B1A filter arrangement for quantum processors
Publication Date: 2026.01.14 SWEDEN QUANTUM AB
  • EP4500631B1 patent drawingFigure 1A~1B
  • EP4500631B1 patent drawingFigure 2A~3B
  • EP4500631B1 patent drawingFigure 4A~4B

AI summary

A filter arrangement (100) for a quantum processor. The filter arrangement comprises a waveguiding structure (110) arranged to guide electromagnetic waves along a main waveguiding path (111) between a first port (112) and a second port (113). The waveguiding structure (110) comprises a frequency-selective surface, FSS, (120) arranged along at least a part of the main waveguiding path (111). The FSS is arranged to be electromagnetically reflective for a low-frequency band and arranged to be electromagnetically transparent in a direction away from the main waveguiding path (111) at a high-frequency band.