Capacitively-Shunted Flux Qubit Coupler Spectator Effect Suppression

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Solution Overview

Problem

Existing quantum computing technologies face challenges in suppressing spectator effects, which are caused by stray coupling between qubits and non-adjacent couplers, leading to quantum errors and decreased accuracy.

Innovation Solution

The use of capacitively-shunted flux qubit (CSFQ) couplers in a tunable-coupler qubit (TCQ) configuration, where the middle pad of the TCQ is coupled to a first CSFQ coupler and the outer pads are coupled to a second CSFQ coupler, effectively suppresses coupling across the TCQ between the couplers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional qubit coupling methods are used, then qubit interaction is achieved, but spectator effects and stray coupling between non-adjacent qubits occur

Engineering Contradiction:

Improvequantum operation accuracyVSAvoidspectator effects

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces CSFQ couplers as intermediary components between qubits and TCQs. These couplers act as mediators that enable controlled interaction while blocking unwanted direct coupling pathways, thereby suppressing spectator effects between non-adjacent qubits through the intermediary coupling mechanism

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent utilizes flux tuning to dynamically change the coupling parameters between qubits and couplers. By adjusting the flux through the SQUID loop in the CSFQ coupler, the coupling strength can be modulated to achieve desired interaction while minimizing stray coupling, thus changing system parameters to suppress harmful effects

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If TCQ is coupled to multiple couplers, then quantum information storage and interaction are enabled, but coupling across the TCQ between couplers occurs

Engineering Contradiction:

Improvequbit coupling configurationVSAvoidcoupling across TCQ

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The CSFQ couplers serve as intermediary elements that couple to different pads of the TCQ. This intermediary coupling structure enables the TCQ to interact with multiple qubits while the coupler design inherently suppresses direct coupling across the TCQ, preventing harmful interactions between non-adjacent couplers

Inventive Principle:

Principle #24Intermediary (Mediator)

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 reduces next-nearest neighbor coupling to less than 35 kHz, significantly suppressing spectator effects and improving the accuracy of quantum operations by minimizing quantum errors.

Implementation Method 1

capacitively-shunted flux qubit (CSFQ) couplers

Methodology Applied

Scientific EffectCapacitive shunting: Capacitance

Implementation Method 2

comprising a capacitor and a superconducting quantum interference device (SQUID) loop with a flux tunable to a first flux value that corresponds to a first quantum state of the SQUID

Methodology Applied

Scientific EffectMagnetic flux: Magnetic Field

Data Source

PatentUS20250131307A1Suppression of spectator effects with capacitively-shunted flux qubit coupler

Publication Date: 2025.04.24 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

Devices and/or computer-implemented methods facilitating suppression of spectator effects between qubits are provided. In an embodiment, a device can comprise a tunable-coupler qubit (TCQ), wherein a middle pad of the TCQ is coupled to a first capacitively-shunted flux qubit (CSFQ) coupler and wherein outer pads of the TCQ are coupled to a second CSFQ coupler; a first superconducting qubit coupled to the first CSFQ coupler; and a second superconducting qubit coupled to the second CSFQ coupler.