Reversible Fluxon Logic Gates With Ballistic Asynchronous Operation

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Solution Overview

Problem

Reversible superconducting logic gates face limitations in energy efficiency and practicality due to reliance on conventional Josephson Transmission Lines, which restrict the implementation of reversible and asynchronous operations in ballistic and non-ballistic gates.

Innovation Solution

The development of a reversible superconducting circuit using Long Josephson Junctions and shunt capacitors, allowing fluxons to travel ballistically without external power, enabling efficient storage and transmission of fluxons with preserved polarity, and the implementation of novel shift registers that operate asynchronously without the need for external power.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If conventional Josephson Transmission Lines are used, then device complexity is reduced, but energy efficiency and reversibility are limited

Engineering Contradiction:

Improveenergy efficiencyVSAvoiddevice complexity

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The circuit is divided into distinct functional modules: Long Josephson Junctions for ballistic fluxon transmission, shunt capacitors for timing control, and storage circuits for bit retention. Each segment performs a specific function that contributes to overall energy efficiency while maintaining manageable complexity through modular design.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the fundamental operating parameters by using Long Josephson Junctions instead of conventional short junctions, enabling ballistic transport of fluxons without external power. The system operates in an asynchronous regime where timing is determined by fluxon arrival rather than clock signals, fundamentally changing the energy consumption profile.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If external power is supplied for fluxon transmission, then transmission reliability is improved, but energy consumption increases

Engineering Contradiction:

Improvetransmission reliabilityVSAvoidexternal power consumption

Core Design Contradiction:

ReliabilityVSUse of energy by stationary object

Solution Approach 1:

The Long Josephson Junctions are designed to transmit fluxons ballistically using only the kinetic energy of the incoming fluxons themselves. The junctions' inductive properties and the fluxon's magnetic energy are sufficient to drive transmission through the junction array without external power sources, achieving self-powered operation while maintaining reliable transmission.

Inventive Principle:

Principle #25Self-service

3Productivity

If asynchronous operation is implemented, then productivity is improved, but device complexity increases

Engineering Contradiction:

Improveoperational speedVSAvoidcontrol circuit complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The system uses periodic fluxon generation from storage circuits to create a rhythmic flow of data through the logic gates. Each storage circuit releases fluxons at regular intervals determined by the fluxon circulation time, creating an asynchronous but predictable operation pattern that simplifies control compared to fully event-driven systems.

Inventive Principle:

Principle #19Periodic action

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 solution achieves high energy efficiency and practicality in reversible logic operations, allowing for the creation of efficient shift registers and multi-bit serial-in-serial-out shift registers with improved output-to-input velocity ratios, enabling effective bit storage and processing without external power consumption.

Implementation Method 1

Reversible Fluxon Logic gates use Long Josephson Junctions (LJJs) combined with other elements to create new logic gates

Methodology Applied

Scientific EffectJosephson effect: Josephson Effect

Implementation Method 2

an interface cell, coupled to the first and second Josephson transmission lines, including a first shunt capacitor, coupled to the first Josephson transmission line, a second shunt capacitor, coupled to the second Josephson transmission line

Methodology Applied

Scientific EffectResonance: Resonance

Implementation Method 3

RFL uses the polarity of a flux soliton or fluxon to encode the bit state

Methodology Applied

Scientific EffectSoliton: Soliton

Data Source

PatentUS11791525B1Asynchronous reversible flux soliton logic gates

Publication Date: 2023.10.17 GOVERNMENT OF THE UNITED STATES AS REPRESENTED BY THE DIRECTOR NAT SECURITY AGENCY

AI summary

A reversible superconducting circuit includes two Josephson transmission lines. Inductors connect Josephson Junctions in the array. Each transmission line passes a fluxon along the Junctions. The circuit includes an interface with first and second shunt capacitors coupled to the first and second transmission lines, and a third shunt capacitor, forming a connecting circuit with the first and second shunt capacitors. The shunt capacitors include Josephson junctions in parallel. The connecting circuit receives an input fluxon and transmits an output fluxon. The circuit also includes a Josephson Junction and inductor in parallel with the third shunt capacitor, forming a storage circuit. The storage circuit stores a SFQ. The output fluxon has polarity based on the SFQ stored when the first fluxon is received. The input fluxon causes the polarity of the stored SFQ to be the same as the polarity of the input fluxon, immediately after the input fluxon is received.