Flip Chip Qubit Frequency Tuning via Interposer Conductive Surfaces

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Solution Overview

Problem

Fixed-frequency qubits in quantum processors face challenges such as frequency crowding, crosstalk, quantum decoherence, and imperfections in fabrication, leading to difficulties in controlling qubit resonance frequencies and enabling quantum gates without unwanted interactions.

Innovation Solution

A superconducting device and method for tuning qubit frequencies using a flip chip geometry, where a conductive surface on an interposer chip adjusts the resonance frequency of qubits based on measurements, such as Josephson junction resistance, to mitigate frequency collisions and allow for precise frequency tuning.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If fixed-frequency qubits are used in quantum processors, then fabrication is simplified, but frequency crowding and crosstalk occur leading to unwanted interactions between qubits

Engineering Contradiction:

Improvequbit fabrication simplicityVSAvoidfrequency crowding and crosstalk

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The patent implements frequency tuning structures that allow qubit resonance frequencies to be dynamically adjusted after fabrication. Conductive surfaces on an interposer chip can be modified to change the resonance frequency of individual qubits, transforming the static fixed-frequency design into a dynamic可调 system that avoids frequency collisions while maintaining fabrication simplicity

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the resonance frequency parameter of qubits by modifying the conductive surface properties on the interposer chip. By altering the geometry, position, or electrical properties of these conductive surfaces, the coupling capacitance between the interposer and qubit changes, thereby tuning the qubit frequency to avoid crowding and crosstalk

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If additional processing steps are applied to tune qubit frequency, then frequency control precision is improved, but the risk of junction damage increases

Engineering Contradiction:

Improvequbit frequency control precisionVSAvoidJosephson junction integrity

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent separates the frequency tuning function from the qubit fabrication process by implementing independent conductive surface structures on the interposer chip. This segmentation allows frequency adjustment to be achieved through external modifications rather than direct processing of the Josephson junction, thereby improving frequency control precision without compromising junction reliability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an interposer chip with conductive surfaces as an intermediary between the control system and the qubit. This intermediary structure enables indirect frequency tuning through capacitive coupling, avoiding direct contact with or processing of the fragile Josephson junction while achieving precise frequency control

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If qubit resonance frequencies are not tuned, then device complexity is reduced, but frequency collisions prevent effective quantum gate operation

Engineering Contradiction:

Improvefrequency tuning structure complexityVSAvoidquantum gate operation effectiveness

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent implements a universal frequency tuning mechanism using conductive surfaces on the interposer chip that can adjust the frequency of multiple qubits. This multi-functional approach allows a single type of structure to serve both as an electrical connection element and as a frequency tuning element, adding minimal complexity while enabling effective quantum gate operation by preventing frequency collisions

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 accurate control of qubit resonance frequencies, preventing frequency collisions and improving the performance of quantum gates by allowing for both increase and decrease in qubit frequency without additional processing steps on the qubit chip, thus reducing the risk of junction damage.

Implementation Method 1

the at least one dimension is determined based upon a capacitance change to achieve the frequency adjustment value

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS11195982B2Qubit frequency tuning structures and fabrication methods for flip chip quantum computing devices

Publication Date: 2021.12.07 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

In an embodiment, a method includes forming a first chip having a first substrate and one or more qubits disposed on the first substrate, each of the one or more qubits having an associated resonance frequency. In an embodiment, the method includes forming a second chip having a second substrate and at least one conductive surface disposed on the second substrate opposite the one or more qubits, the at least one conductive surface having at least one dimension configured to adjust the resonance frequency associated with at least one of the one or more qubits to a determined frequency adjustment value.