Resonator Coupling Bus With Tunable Inductive Qubit Control

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Solution Overview

Problem

Existing superconducting quantum computing systems face challenges in scaling up the number of qubits without introducing additional noise and unwanted exchange interactions, particularly in achieving high ON/OFF ratios and controlling long-range qubit-qubit couplings to ensure high-fidelity gate operations.

Innovation Solution

Implementing a coupling bus with a series of transmission line resonators and tunable inductive couplers to control qubit interactions, allowing for dynamic adjustment of exchange coupling and suppression of low-frequency modes, using flux-tunable inductive couplers and fixed coupling devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the number of qubits is increased to scale up quantum processing power, then quantum computing capability is improved, but noise and unwanted exchange interactions between qubits increase

Engineering Contradiction:

Improvequantum computing capabilityVSAvoidnoise and unwanted exchange interactions

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The coupling bus is divided into multiple transmission line resonators that are coupled in series, creating segmented sections between qubits. This segmentation allows for better control of interactions and suppression of unwanted coupling effects, enabling scaling while maintaining low noise levels.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Transmission line resonators are introduced as intermediary elements between qubits to mediate their interactions. These resonators act as controlled coupling channels that enable desired qubit-qubit interactions while suppressing direct unwanted exchange interactions and noise transmission.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Area of stationary object

If long-range interactions between qubits are implemented to increase integration density, then device compactness is improved, but control precision of exchange coupling decreases

Engineering Contradiction:

Improvequantum chip areaVSAvoidexchange coupling control precision

Core Design Contradiction:

Area of stationary objectVSManufacturing precision

Solution Approach 1:

Tunable inductive couplers are incorporated into the coupling bus to dynamically adjust the coupling strength between qubits. This dynamic control mechanism allows precise regulation of exchange coupling interactions even over long ranges, maintaining control precision while enabling compact high-density layouts.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The coupling characteristics of the transmission line resonators are modified by changing parameters such as inductance and capacitance through tunable inductive couplers. This allows dynamic adjustment of coupling strength to achieve precise control over exchange interactions regardless of qubit separation distance.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If direct qubit-qubit coupling is used to simplify the system, then device complexity is reduced, but the ability to suppress unwanted interactions and achieve high ON/OFF ratios deteriorates

Engineering Contradiction:

Improvecoupling system complexityVSAvoidgate operation fidelity

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

Transmission line resonators serve as intermediary coupling elements between qubits, replacing direct qubit-qubit coupling. This intermediary structure provides controlled interaction pathways that enable high ON/OFF ratios and suppress unwanted exchange interactions, improving gate fidelity despite increased structural complexity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

Instead of directly coupling qubits, the system inverts the approach by coupling qubits to transmission line resonators, which then mediate the interaction. This inverted coupling architecture enables precise control and suppression of unwanted interactions that cannot be achieved with direct coupling.

Inventive Principle:

Principle #13The other way round (Inversion)

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

Enables long-range, highly tunable control of qubit interactions, suppressing unwanted low-frequency modes and improving ON/OFF ratios for high-fidelity two-qubit gate operations, thereby enhancing the performance of superconducting quantum computers.

Implementation Method 1

at least one tunable inductive coupler to control a coupling between a first transmission line resonator and a second transmission line resonator

Methodology Applied

Scientific EffectInductance: Inductor

Implementation Method 2

The coupling bus comprises a plurality of transmission line resonators which are coupled in series

Methodology Applied

Scientific EffectResonance: Resonance

Implementation Method 3

superconducting quantum bits (qubits) are electronic circuits which are implemented using components such as superconducting tunnel junctions (e.g., Josephson junctions)

Methodology Applied

Scientific EffectJosephson effect: Josephson Effect

Implementation Method 4

superconducting quantum computing systems... constructed using quantum circuit components such as, e.g., superconducting quantum bits and other types of superconducting quantum devices

Methodology Applied

Scientific EffectSuperconductivity: Superconductivity

Data Source

PatentUS12587192B2Mediating coupling of quantum bits using chains of resonators and tunable inductive couplers

Publication Date: 2026.03.24 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

Techniques are provided for mediating interactions (e.g., long range interactions) between quantum bits to facilitate quantum computing operations such as two-qubit gate operations. A device comprises a first quantum bit, a second quantum bit, and a coupling bus connecting the first quantum bit and the second quantum bit. The coupling bus comprises a plurality of transmission line resonators which are coupled in series, and at least one tunable inductive coupler to control a coupling between a first transmission line resonator and a second transmission line resonator of the plurality of transmission line resonators.