Flux-Shuttle Josephson Current Source for Low-Dissipation DC Bias
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Solution Overview
Problem
Superconducting digital circuits using Josephson junctions face challenges with spurious magnetic fields and heat generation due to high power dissipation in bias resistor networks, which dominate the power budget and are inefficient compared to traditional resistance-based DC current sources.
Innovation Solution
A Josephson current source system employing a flux-shuttle loop with sequentially triggered Josephson junctions and a flux injector, utilizing inductively-coupled AC input signals to generate and control a DC output current through an output inductor, with selective activation and deactivation to manage current amplitude, reducing static power dissipation and heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a bias resistor network is used to provide DC bias current to Josephson junctions, then the DC bias current is provided, but spurious magnetic fields and heat are generated resulting in high power dissipation
Solution Approach 1:
The patent extracts the harmful bias resistor network from the system and replaces it with a flux-shuttle loop based current source. The bias function is separated from the dissipative resistor network and implemented using superconducting Josephson junctions that can provide DC bias current without the associated heat and magnetic field problems.
Solution Approach 2:
The patent changes the operating parameters by using AC drive signals at specific frequencies (e.g., 6.4 GHz) to control the flux-shuttle loop, enabling it to generate DC bias currents dynamically. This frequency-based control allows precise adjustment of bias current while maintaining low power dissipation and eliminating spurious magnetic fields.
2Productivity
If a bias resistor network is used to provide DC bias current, then the current is provided continuously, but static power consumption dominates the power budget regardless of device switching state
Solution Approach 1:
The patent implements periodic AC drive signals to the flux-shuttle loop that dynamically generate the required DC bias current only when needed for device operation. This periodic excitation replaces continuous DC power supply through resistors, eliminating static power consumption while maintaining necessary bias currents during active switching periods.
Solution Approach 2:
The flux-shuttle loop system generates its own DC bias current dynamically through AC-driven fluxon propagation, eliminating the need for external bias resistor networks. The system serves itself by converting AC drive energy into the required DC bias currents, achieving both low power consumption and high switching efficiency.
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 operates with reduced heat and power dissipation, maintaining a controlled DC output current amplitude efficiently, suitable for quantum and classical computing applications, and enhances power efficiency in high-performance computing environments.
Implementation Method 1
a flux-shuttle loop that includes a plurality of Josephson junctions spaced about the flux-shuttle loop and being configured, when activated, to sequentially trigger the plurality of Josephson junctions about the flux-shuttle loop, in response to an inductively-coupled AC input signal, to generate a DC output current provided through an output inductor
Implementation Method 2
in response to an inductively-coupled AC input signal
Implementation Method 3
a flux injector that is configured to selectively activate and deactivate the flux-shuttle loop to control an amplitude of 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) that is inductively coupled with an AC input signal. The flux-shuttle loop includes a plurality of Josephson junctions spaced about the flux-shuttle loop and being configured, when activated, to sequentially trigger the plurality of Josephson junctions about the flux-shuttle loop in response to the AC input signal to generate a DC output current provided through an output inductor. The system also includes a flux injector (18) that is configured to selectively activate and deactivate the flux-shuttle loop in response to an input signal to control an amplitude of the DC output current.