Mode-Selective Qubit Couplers for Frequency Collision Reduction

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Solution Overview

Problem

Existing quantum computing systems face challenges with frequency collisions among superconducting qubits due to imperfections in nanofabrication, leading to difficulties in maintaining distinct transition frequencies, which affect performance and require reduced lattice connectivity to mitigate these collisions.

Innovation Solution

Implementing a quantum computing lattice using two-junction transmon qubits coupled by mode-selective couplers, which facilitate selective cross-resonance entanglement with three distinct sets of qubits, reducing the likelihood of frequency collisions without decreasing lattice connectivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If nanofabrication is used to manufacture superconducting qubits, then qubit production is enabled, but frequency collisions occur due to manufacturing imperfections

Engineering Contradiction:
Improvequbit productionVSAvoidfrequency distinction
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The patent introduces mode-selective couplers that can dynamically change the coupling parameters between qubits. By adjusting the coupling strength and selectivity parameters, the system can accommodate frequency variations from nanofabrication imperfections while maintaining reliable quantum operations. The couplers enable parameter tuning to avoid frequency collisions without requiring perfect manufacturing precision.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If lattice connectivity is reduced to mitigate frequency collisions, then frequency collision probability decreases, but quantum computing performance deteriorates

Engineering Contradiction:
Improvefrequency collision reductionVSAvoidquantum computing performance
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

The patent introduces mode-selective couplers as intermediary devices between qubits in the quantum computing lattice. These couplers mediate the interactions between qubits, providing frequency selectivity that prevents direct frequency collisions while maintaining the full lattice connectivity. The couplers act as frequency-filtering intermediaries that enable reliable quantum operations without requiring reduced connectivity.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Reliability

If mode-selective couplers are implemented, then frequency collision probability reduces, but device complexity increases

Engineering Contradiction:
Improvefrequency collision reductionVSAvoidcoupling mechanism complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The mode-selective couplers are designed to perform multiple functions: they provide frequency selectivity to prevent collisions, enable controlled coupling between qubits, and maintain lattice connectivity. This multi-functionality reduces the need for additional specialized components, thereby limiting the increase in overall device complexity while achieving frequency collision reduction.

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

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

Reduces the probability and prevalence of frequency collisions by ensuring sufficient differences in structural characteristics of qubits, enabling selective entanglement even with degenerate targets, thus improving the performance of quantum computing systems.

Implementation Method 1

the first mode-selective coupler capacitively couples the middle capacitor pad of the control qubit to the middle capacitor pad of the first target qubit

Methodology Applied
Scientific EffectCapacitive coupling: Capacitance

Implementation Method 2

facilitate selective cross-resonance entanglement between the control qubit and the first target qubit

Methodology Applied
Scientific EffectCross-resonance entanglement: Resonance

Data Source

PatentEP4162410B1Mode-selective couplers for frequency collision reduction
Publication Date: 2026.03.04 INTERNATIONAL BUSINESS MACHINE CORPORATION
  • EP4162410B1 patent drawingFigure 1
  • EP4162410B1 patent drawingFigure 2
  • EP4162410B1 patent drawingFigure 3

AI summary

Systems and techniques that facilitate mode-selective couplers for frequency collision reduction are provided. In various embodiments, a device can comprise a control qubit. In various aspects, the device can comprise a first target qubit coupled to the control qubit by a first mode-selective coupler. In various instances, the first mode-selective coupler can facilitate A-mode coupling between the control qubit and the first target qubit. In various embodiments, the device can comprise a second target qubit coupled to the control qubit by a second mode-selective coupler. In various aspects, the second mode selective coupler can facilitate B-mode coupling between the control qubit and the second target qubit.