Linear Flux-Shuttle Current Source Without Resistive Bias Networks
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Solution Overview
Problem
Superconducting circuits using Josephson junctions face issues with spurious magnetic fields and heat due to high power dissipation in bias resistor networks, which dominate the power budget and can lead to dithering effects in flux pumps, affecting current compliance and circuit performance.
Innovation Solution
A linear flux pump current source system utilizing a series arrangement of Josephson transmission line stages with clock inputs and output inductors, where Josephson junctions trigger in sequence to generate a direct current output in response to input pulses and clock signals, eliminating the need for bias resistor networks and mitigating dithering.
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, 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 flux pump circuit entirely. Instead of using resistors to provide DC bias current, the invention uses a superconducting current source that generates bias current without dissipative elements, thereby eliminating the source of spurious magnetic fields and heat while maintaining reliable bias current provision to Josephson junctions
Solution Approach 2:
The patent substitutes the resistive (dissipative) biasing mechanism with a superconducting-based biasing mechanism. The superconducting current source uses Josephson junctions and inductors to generate DC bias current through flux pumping, replacing the traditional resistive bias network and eliminating Joule heating and associated magnetic fields
2Ease of operation
If a bias resistor network is used to provide DC bias current, then biasing is simple, but the power budget is dominated by static power consumption
Solution Approach 1:
The patent removes the bias resistor network that caused high static power consumption. The superconducting current source provides bias current dynamically generated from clock signals, eliminating the need for continuously powered resistive bias networks and dramatically reducing static power consumption in the flux pump circuit
Solution Approach 2:
The patent uses periodic clock signals to drive the superconducting current source, which then generates continuous DC bias current. This periodic triggering mechanism replaces continuous resistive biasing, maintaining ease of operation through simple clock signal input while eliminating dominant static power consumption
3Reliability
If traditional flux-shuttle loop arrangements are used, then DC bias can be provided, but dithering effects occur that affect current compliance
Solution Approach 1:
The patent extracts the flux pump from the traditional loop configuration and implements it as a linear superconducting current source. This structural change eliminates the feedback path that causes dithering effects in loop-based flux pumps, providing stable DC bias current with improved current compliance without oscillatory behavior
Solution Approach 2:
The patent inverts the traditional approach by using Josephson junctions to actively generate bias current through flux pumping rather than passively providing bias through resistors in a loop. This active generation method provides stable, compliant current without the dithering effects inherent in passive loop-based systems
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 reduces power dissipation, enhances current compliance, simplifies biasing, and prevents flux trapping, offering improved performance and scalability in superconducting circuits by generating a stable DC output current without the drawbacks of traditional flux-shuttle loop arrangements.
Implementation Method 1
Each of the JTL stages includes at least one Josephson junction, an output inductor, and a clock input. The linear flux-shuttle can be configured to generate a direct current (DC) output current via the output inductor associated with each of the JTL stages in response to the at least one Josephson junction triggering in a sequence
Data Source
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AI summary
One example describes a superconducting current source system (100) comprising a linear flux-shuttle (106). The linear flux-shuttle includes an input (IN) and a plurality of Josephson transmission line (JTL) stages (108). Each of the JTL stages includes at least one Josephson junction, an output inductor, and a clock input. The linear flux-shuttle (106) can be configured to generate a direct current (DC) output current (Iout) via the output inductor associated with each of the JTL stages in response to the at least one Josephson junction triggering in a sequence in each of the JTL stages along the linear flux-shuttle in response to receiving an input pulse at the input (IN) and in response to a clock signal provided to the clock input (CLK) in each of the JTL stages.