Qubit Coupler Readout Circuit for High-Density Quantum Integration

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Solution Overview

Problem

Existing electronic circuits with multiple nonlinear elements face challenges in achieving high-density qubit integration due to the need for large surface area and separate readout resonators, which hinder efficient space utilization and qubit coherence.

Innovation Solution

The integration of a first coupler with coupled resonators and a Purcell filter allows for qubit state readout through the coupler, eliminating the need for a separate readout resonator, thereby enabling high-density qubit placement and improved space conservation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If separate readout resonators are used for each qubit, then qubit state readout can be achieved, but the surface area increases and qubit integration density decreases

Engineering Contradiction:
Improvequbit state readoutVSAvoidsurface area
Core Design Contradiction:
Measurement precisionVSArea of stationary object

Solution Approach 1:

The patent merges the readout resonator with the coupler structure, creating a shared resonant element that serves both as the coupling mechanism between qubits and as the readout resonator. This integration eliminates the need for separate readout resonators, thereby reducing the total surface area while maintaining qubit state readout capability through the shared resonant frequency of the coupler

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The coupler is designed to perform multiple functions: it acts as both the coupling element that enables quantum gate operations between qubits and as the readout resonator that facilitates qubit state measurement. This multi-functionality reduces the overall component count and surface area required for qubit operations

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

2Measurement precision

If large surface area is allocated for readout resonators, then qubit state readout is enabled, but qubit integration density is reduced

Engineering Contradiction:
Improvequbit state readoutVSAvoidqubit integration density
Core Design Contradiction:
Measurement precisionVSQuantity of substance

Solution Approach 1:

By combining the readout resonator functionality into the coupler structure, the patent enables multiple qubits to share a single readout resonator resource. This merging approach increases the number of qubits that can be integrated per unit area, as each qubit does not require its own dedicated readout resonator, thereby improving qubit integration density

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The patent transitions from a one-to-one mapping between qubits and readout resonators to a many-to-one configuration where multiple qubits share a single readout resonator. This dimensional change in the system architecture allows for higher qubit integration density by reducing the per-qubit resource allocation in the spatial domain

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

3Measurement precision

If separate readout resonators are used for each qubit, then individual qubit readout is possible, but space utilization efficiency decreases

Engineering Contradiction:
Improvequbit state readoutVSAvoidspace utilization efficiency
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent merges the readout resonator function into the coupler structure, creating a more compact and efficient device layout. This integration reduces the total device footprint and improves space utilization efficiency by eliminating redundant components and optimizing the spatial arrangement of qubit elements

Inventive Principle:
Principle #5Merging (Combining)

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 configuration achieves high-speed readout with low error probability and good qubit coherence time, facilitating compact and efficient qubit circuits with enhanced gate fidelity.

Implementation Method 1

a first Josephson junction 51J and a first capacitor 51C, a second Josephson junction 52J and a second capacitor 52C, a first coupler Josephson junction 11K

Methodology Applied
Scientific EffectJosephson effect: Josephson Effect

Data Source

PatentEP4303779B1Electronic circuit and calculating device
Publication Date: 2026.03.25 KK TOSHIBA
  • EP4303779B1 patent drawingFigure 1
  • EP4303779B1 patent drawingFigure 2~3
  • EP4303779B1 patent drawingFigure 4

AI summary

According to one embodiment, an electronic circuit includes a first qubit, a second qubit, a first coupler, a first readout conductive member, and a first filter. The first coupler includes a first resonator and a second resonator. The first resonator is couplable with the first qubit. The second resonator is couplable with the second qubit. The first filter includes a first filter portion, a first other-filter portion, and a first readout portion. The first filter portion is couplable with the first resonator. The first other-filter portion is couplable with the second resonator. The first readout portion is couplable with the first readout conductive member.