Cascaded Josephson Isolators for Frequency-Multiplexed Microwave Signals

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Solution Overview

Problem

Existing microwave isolators in quantum computing are limited in their ability to isolate frequency-multiplexed microwave signals, as they typically operate within a narrow band of frequencies and cannot effectively handle signals outside their operational bandwidth, leading to incomplete isolation or propagation of signals with different frequencies.

Innovation Solution

A cascading multi-path interferometric Josephson isolator system is developed, utilizing nondegenerate three-wave-mixing Josephson devices with nonoverlapping bandwidths, where each device in the series isolates or propagates signals within its specific frequency range, allowing for broader bandwidth operation by series coupling Josephson devices with unique operating frequencies.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a single microwave isolator is used, then it can isolate signals within its operational bandwidth, but it cannot effectively handle signals outside its narrow frequency band

Engineering Contradiction:

Improvefrequency bandwidth coverageVSAvoidisolator system structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent divides the frequency isolation task into multiple segments by using several isolators, each tuned to a specific frequency band. Each isolator in the cascade handles a particular frequency range, and together they cover a broad spectrum. This segmentation allows the system to achieve wide bandwidth coverage without requiring each individual isolator to be complex or tunable across all frequencies.

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If multiple isolators with nonoverlapping bandwidths are cascaded, then broader bandwidth operation is achieved, but the device complexity increases

Engineering Contradiction:

Improvetotal isolation bandwidthVSAvoidcascading system configuration

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent combines multiple isolators with nonoverlapping bandwidths into a single cascaded system. Each isolator is designed with a specific frequency range, and when connected in cascade, they merge their isolation capabilities to provide comprehensive frequency-selective isolation. The merging of these specialized components creates a unified system that achieves broad bandwidth operation while maintaining the simplicity of individual isolator designs.

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If frequency-multiplexed microwave signals are processed, then quantum computing operations are enabled, but incomplete isolation or propagation of signals occurs with existing isolators

Engineering Contradiction:

Improvesignal isolation effectivenessVSAvoidfrequency multiplexed signal management

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies local quality by designing each isolator in the cascade to have specialized characteristics optimized for its specific frequency band. Each isolator is tuned to provide high isolation effectiveness for signals within its designated frequency range while allowing signals outside that range to pass through. This localized optimization ensures that frequency-multiplexed quantum computing signals are reliably isolated or propagated based on their specific frequencies, without requiring the entire system to be uniformly designed for all frequency ranges.

Inventive Principle:

Principle #3Local quality

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

The cascading system achieves comprehensive isolation or propagation of frequency-multiplexed microwave signals across a broader bandwidth than single isolators, ensuring efficient signal management in quantum computing applications by isolating signals within their respective frequency bands while allowing signals outside these bands to pass through without attenuation.

Implementation Method 1

A cascading multi-path interferometric Josephson isolator system is developed, utilizing nondegenerate three-wave-mixing Josephson devices

Methodology Applied

Scientific EffectJosephson effect: Josephson Effect

Implementation Method 2

nondegenerate three-wave-mixing Josephson devices with nonoverlapping bandwidths

Methodology Applied

Scientific EffectThree-wave mixing:

Data Source

PatentUS20190171974A1Isolation of frequency multiplexed microwave signals using cascading multi-path interferometric josephson isolators with nonoverlapping bandwidths

Publication Date: 2019.06.06 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

A cascading microwave isolator (cascade) includes a set of Josephson devices, each Josephson device in the set having a corresponding operating bandwidth of microwave frequencies. Different operating bandwidths have different corresponding center frequencies. A series coupling is formed between first Josephson device from the set and an nth Josephson device from the set. The series coupling causes the first Josephson device to isolate a signal at a first frequency from a frequency multiplexed microwave signal (multiplexed signal) in a first signal flow direction through the series coupling and the nth Josephson device to isolate a signal at an nth frequency from the multiplexed signal in the first signal flow direction through the series.