Josephson Flux-Shuttle Current Source for Low-Dissipation Biasing
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Solution Overview
Problem
Superconducting digital circuits using Josephson junctions face challenges with high power dissipation due to static power consumption in bias resistor networks, leading to spurious magnetic fields and heat, which are not efficiently managed in existing systems.
Innovation Solution
A Josephson current source system with a flux-shuttle loop and a flux injector system that uses an AC clock signal to sequentially trigger Josephson junctions, generating a DC output current through an output inductor, and automatically deactivates/reactivates based on feedback current thresholds, reducing static power dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bias resistor network is used to provide DC bias current to Josephson junctions, then the junctions can be biased properly, but spurious magnetic fields and heat are generated due to high power dissipation
Solution Approach 1:
The patent extracts and removes the bias resistor network from the system entirely, replacing it with a flux-shuttle loop that generates bias current through electromagnetic induction. This eliminates the source of spurious magnetic fields and heat generation while maintaining proper Josephson junction biasing.
Solution Approach 2:
The patent substitutes the resistive electrical system with a magnetic field-based electromagnetic induction system. The flux-shuttle loop uses time-varying magnetic flux to induce bias current in the Josephson junctions, replacing the traditional resistive biasing mechanism with an electromagnetic field-based approach that avoids continuous power dissipation.
2Reliability
If a bias resistor network is used to provide DC bias current, then the junctions can operate, but static power consumption dominates the power budget whether or not the active device is switching
Solution Approach 1:
The patent employs periodic action by using a time-varying magnetic flux applied to the flux-shuttle loop at a frequency matching the Josephson junction operating frequency. This periodic flux variation induces the necessary bias current only when needed for switching operations, eliminating continuous static power consumption while maintaining junction operation during active periods.
Solution Approach 2:
The flux-shuttle loop system is self-regulating, where the magnetic flux automatically induces the appropriate bias current in the Josephson junctions during switching operations. The system serves itself by using electromagnetic induction to generate exactly the current needed for proper junction operation without requiring continuous external power supply through resistors.
3Power
If an AC clock signal is used to sequentially trigger Josephson junctions in a flux-shuttle loop, then a DC output current can be generated, but the system requires automatic deactivation capability to minimize power consumption
Solution Approach 1:
The patent implements feedback by monitoring the state of the flux-shuttle loop and automatically deactivating the AC clock signal when the loop reaches a predetermined state or completes its function. This feedback mechanism ensures the system generates the required DC output current only when necessary, automatically shutting down to minimize power consumption during idle periods.
Solution Approach 2:
The system dynamically adjusts its operation by transitioning between active and deactivated states based on real-time conditions. The AC clock signal is applied only when needed to generate DC output current, and the system automatically transitions to a low-power deactivated state when the current generation is complete, optimizing power consumption dynamically.
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 system achieves efficient and autonomous power management, minimizing heat generation and static power consumption, thereby improving the performance and efficiency of superconducting circuits in quantum and classical digital applications.
Implementation Method 1
The flux-shuttle loop is configured, when activated, to sequentially trigger the at least one Josephson junction in each of the plurality of stages about the flux-shuttle loop based onto an inductively-coupled alternating current (AC) clock signal to generate a direct current (DC) output current
Implementation Method 2
a set of transformers configured to couple the AC clock signal to the flux-shuttle loop, such that the AC clock signal provides a bias current in the flux-shuttle loop
Implementation Method 3
a flux injector system that is configured to activate the flux-shuttle loop based on an injection current. The injection current is inductively induced from a DC injection signal
Implementation Method 4
The flux injector system is further configured to automatically deactivate the flux-shuttle loop based on an amplitude of a feedback current increasing to a predetermined deactivation threshold. The feedback current is inductively induced from the DC output current
Data Source
Figure 1~3
Figure 2
Figure 4~5
AI summary
One embodiment describes a Josephson current source system (14). The system includes a flux-shuttle loop (16) comprising a plurality of stages arranged in a series loop. Each of the plurality of stages includes at least one Josephson junction. The flux-shuttle loop (16) can be configured, when activated, to sequentially trigger the at least one Josephson junction in each of the plurality of stages about the flux-shuttle loop in response to an inductively-coupled AC clock signal (CLK) to generate a DC output current (IOUT) provided through an output inductor. The system also includes a flux injector system (18) that is configured to activate the flux-shuttle loop (16). The flux injector system is further configured to automatically deactivate the flux-shuttle loop in response to an amplitude of the DC output current increasing to a predetermined deactivation threshold.