Tunable Inductive Resonator Coupling for Low-Crosstalk Qubits

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional qubit-to-qubit interactions in quantum computing are limited by crosstalk and unwanted interactions with spectator qubits, which hinder the attainable length and effectiveness of these interactions.

Innovation Solution

Utilizing pairs of resonators with tunable inductive coupling, specifically through iteratively tuning the flux of a dc-SQUID and rf-SQUID loops to achieve a non-hysteretic regime, allowing for long-range interactions between qubits while suppressing crosstalk and spectator errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If conventional qubit-to-qubit interaction techniques are used, then qubit interactions can be achieved, but crosstalk and unwanted interactions with spectator qubits occur, limiting the attainable length of interactions

Engineering Contradiction:

Improveattainable length of qubit-to-qubit interactionsVSAvoidcrosstalk and unwanted interactions with spectator qubits

Core Design Contradiction:

Length of moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent introduces resonators as intermediary elements between qubits to mediate interactions. The resonators couple to both qubits and enable long-range interactions while suppressing direct harmful couplings. The resonator system acts as a mediator that selectively enables desired qubit interactions while blocking unwanted crosstalk paths.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs tunable inductive coupling through flux-controlled SQUID loops that can dynamically adjust coupling parameters. By changing the flux through the SQUID loops, the inductance values are modified, enabling the system to transition between different interaction states (on/off) and optimize coupling strengths to achieve long-range interactions while minimizing crosstalk.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If conventional interaction techniques are used, then qubit coupling can be achieved, but the on/off ratio is limited and hysteretic behavior occurs

Engineering Contradiction:

Improveon/off ratio of qubit interactionVSAvoidhysteretic regime in flux tuning

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent uses flux-controlled SQUID loops to dynamically adjust inductance parameters, enabling precise control over coupling strength. By changing the flux parameter through the SQUID loops, the system achieves high on/off ratios and can operate in a non-hysteretic regime, improving reliability and stability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements dynamic flux tuning through feedback control mechanisms that adjust the SQUID loop flux in real-time. This dynamic control allows the system to transition smoothly between interaction states and maintain stable operation by avoiding hysteretic behavior, thereby improving the on/off ratio and operational reliability.

Inventive Principle:

Principle #15Dynamics

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 enables long-range qubit interactions with high on/off ratios, suppresses crosstalk, and facilitates the creation of a scalable quantum computer by enhancing qubit connectivity and reducing spectator errors.

Implementation Method 1

pairs of resonators with tunable inductive coupling

Methodology Applied

Scientific EffectInductive coupling: Electromagnetic Induction

Implementation Method 2

the corresponding resonators couple and hybridize with each other

Methodology Applied

Scientific EffectResonance: Resonance

Implementation Method 3

iteratively tuning a flux of a de-SQUID loop and tuning a flux of an rf-SQUID loop to half of a magnetic flux quantum

Methodology Applied

Scientific EffectFlux tuning: Magnetic Field

Implementation Method 4

dc-SQUID loop and the rf-SQUID loop being coupled to the two qubit devices

Methodology Applied

Scientific EffectJosephson effect: Josephson Effect

Data Source

PatentUS20250306136A1Qubit-to-qubit interactions mediated by pairs of resonators with tunable inductive coupling

Publication Date: 2025.10.02 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

A qubit interaction circuit includes a first qubit device, a second qubit device, a first resonator, a second resonator, a first capacitor coupling the first qubit device to the first resonator and a second capacitor coupling the second qubit device to the second resonator. An rf-SQUID circuit includes an rf-SQUID loop, an rf-SQUID controller, and a dc-SQUID loop. The rf-SQUID controller is configured to influence a first flux of the rf-SQUID loop and the dc-SQUID loop, the rf-SQUID circuit coupling the first resonator with the second resonator. A dc-SQUID controller is configured to influence a second flux of the rf-SQUID loop and the dc-SQUID loop.