Qubit Readout Resonator Frequency Placement for Crosstalk Control

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Solution Overview

Problem

Crosstalk between coupling elements in superconducting circuits of quantum computers leads to unwanted interference and performance degradation, particularly as the number of components increases, making it difficult to control and scale quantum computing operations.

Innovation Solution

The placement of qubit readout resonators is optimized by using distinct resonance frequencies and qubit frequencies for nearest neighbor qubits, with readout resonators grouped into separate frequency bands and coupled to dedicated transmission lines, ensuring minimal interference and efficient readout.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If coupling elements are placed in close proximity to enable quantum operations, then quantum computing operations can be performed, but crosstalk between coupling elements occurs causing unwanted interference and performance degradation

Engineering Contradiction:
Improvequantum computing operationsVSAvoidcrosstalk interference
Core Design Contradiction:
ProductivityVSObject-affected harmful factors

Solution Approach 1:

The system segments the frequency spectrum into distinct bands, assigning different frequency ranges to different coupling elements and their associated qubits. This frequency segmentation allows multiple coupling elements to operate simultaneously without interfering with each other, resolving the crosstalk problem while maintaining close physical proximity for quantum operations.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The invention changes the frequency parameter of each coupling element and its associated qubit to distinct values. By tuning the operating frequencies of coupling elements and qubits to different values, the system enables simultaneous operation of multiple coupling elements without mutual interference, thus eliminating crosstalk while maintaining high productivity.

Inventive Principle:
Principle #35Parameter changes

2Quantity of substance

If the number of components is scaled to larger chips, then large-scale quantum computing is enabled, but crosstalk becomes harder to control

Engineering Contradiction:
Improvenumber of componentsVSAvoidcrosstalk control difficulty
Core Design Contradiction:
Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The frequency spectrum is segmented into multiple bands, with each coupling element assigned a unique frequency or frequency range. This segmentation strategy allows the system to scale to larger chips with more components without increasing crosstalk control difficulty, as each element operates in its own designated frequency segment.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

As the number of components increases, the system changes the frequency parameters of coupling elements and qubits to maintain distinct separation. This parameter adjustment approach enables scalable quantum computing by systematically assigning different frequencies to additional components, keeping crosstalk under control regardless of system size.

Inventive Principle:
Principle #35Parameter changes

3Device complexity

If coupling elements operate at the same frequency, then system simplicity is maintained, but unwanted interference and performance degradation occur

Engineering Contradiction:
Improvesystem configurationVSAvoidcircuit performance
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The invention changes the frequency parameter of coupling elements from identical to distinct values. By operating each coupling element at a different frequency, the system eliminates unwanted interference and performance degradation while maintaining relatively simple device architecture, thus improving reliability without significantly increasing complexity.

Inventive Principle:
Principle #35Parameter changes

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 reduces crosstalk, allows for reliable qubit state detection, and maintains optimal qubit-resonator detuning, enhancing the performance and scalability of quantum processors.

Implementation Method 1

each qubit of the plurality of qubits arranged to electromagnetically couple to a readout resonator of the plurality of readout resonators

Methodology Applied
Scientific EffectElectromagnetic coupling: Electromagnetic Induction

Implementation Method 2

each readout resonator of the first readout resonator group arranged to electromagnetically couple to a respective qubit

Methodology Applied
Scientific EffectResonance: Resonance

Implementation Method 3

a first readout transmission line arranged to electromagnetically couple to a first readout resonator group of at least two readout resonators

Methodology Applied
Scientific EffectElectromagnetic coupling: Electromagnetic Induction

Implementation Method 4

the magnetic field from one coupling element can couple to another coupling element, qubit, or resonator. This can cause changes in the magnetic flux and current distribution in the affected component

Methodology Applied
Scientific EffectMagnetic field coupling: Electromagnetic Induction

Implementation Method 5

Coupling elements may also couple through capacitive coupling, which occurs when the electric field from one coupling element affects the electric potential of other components

Methodology Applied
Scientific EffectCapacitive coupling: Capacitance

Data Source

PatentEP4575922A1Frequency placement of qubit readout resonators
Publication Date: 2025.06.25 IQM FINLAND OY
  • EP4575922A1 patent drawingFigure 1A~1B
  • EP4575922A1 patent drawingFigure 2
  • EP4575922A1 patent drawingFigure 3

AI summary

A device includes: a plurality of qubits arranged in a two-dimensional topology and a plurality of readout resonators. Each readout resonator of a first readout resonator group is arranged to electromagnetically couple to a respective qubit of a first qubit group. Each readout resonator of a second readout resonator group is arranged to electromagnetically couple to a respective qubit of a second qubit group. Resonance frequencies of the readout resonators of the first readout resonator group comprise resonance frequencies from a first resonance frequency band and resonance frequencies of the readout resonators of the second readout resonator group comprise resonance frequencies from a second resonance frequency band, and resonance frequencies of the readout resonators of the first readout resonator group and resonance frequencies of the readout resonators of the second readout resonator group are permuted at least for the nearest neighbors.