Superconducting Gate Memory Circuit Using SFQ Loop-State Storage
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Solution Overview
Problem
Current digital logic technologies, such as CMOS, face limitations in terms of speed, power dissipation, computational density, and interconnect bandwidth, prompting the need for alternative solutions like superconducting Josephson junction-based circuits for higher performance.
Innovation Solution
A superconducting gate memory circuit utilizing a Josephson D-gate and storage loop, which sets and reads digital states based on the presence or absence of single flux quantum pulses, enabling efficient data storage and retrieval through a bi-stable loop current amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If CMOS technology is used for digital logic, then manufacturing maturity and ease of manufacture are maintained, but speed, power dissipation, computational density, and interconnect bandwidth are limited
Solution Approach 1:
The patent replaces CMOS electronic switching mechanisms with superconducting Josephson junctions that utilize quantum mechanical tunneling effects. This substitution enables significantly higher operating speeds (20 Gb/s and greater) while reducing power dissipation to around 4 nW per gate, addressing the speed and power limitations of conventional CMOS technology.
Solution Approach 2:
The invention changes the fundamental operating parameters by transitioning from room-temperature CMOS operation to cryogenic superconducting operation at around 4° Kelvin. This parameter change enables the use of Josephson junctions that provide both high-speed operation and low power consumption, while the bi-stable loop architecture maintains data integrity through quantum state stability.
2Use of energy by moving object
If superconducting Josephson junction circuits are used, then speed and power dissipation are improved, but operating temperature requirements become more stringent
Solution Approach 1:
The patent exploits the superconducting phase transition of materials at cryogenic temperatures to achieve zero electrical resistance and enable lossless current flow through Josephson junctions. By operating at around 4° Kelvin, the system achieves extremely low power dissipation (around 4 nW per gate) while maintaining stable quantum states for data storage and processing.
3Reliability
If a bi-stable loop is used to store digital states, then data storage capability is achieved, but device complexity increases
Solution Approach 1:
The patent divides the memory cell into distinct functional segments: a bi-stable loop for data storage, Josephson junctions for state switching, and separate read/write pathways. This segmentation allows each component to be optimized independently while maintaining overall system reliability through modular architecture.
Solution Approach 2:
The bi-stable loop structure serves multiple functions simultaneously: it stores digital data states, provides regenerative feedback for state maintenance, and enables both read and write operations through controlled Josephson junction triggering. This multi-functionality reduces the need for separate dedicated circuits for each operation.
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 provides a high-performance digital memory system capable of storing and reading data efficiently, leveraging the principles of reciprocal quantum logic to achieve improved speed and power efficiency in quantum and classical digital circuits.
Implementation Method 1
superconducting Josephson junctions
Implementation Method 2
superconducting gate memory circuit
Data Source
Figure 1~8
Figure 2
Figure 3
AI summary
One embodiment includes a superconducting gate memory circuit. The circuit comprises a gate circuit configured to set a digital state as one of a first data state and a second data state in response to a presence of or absence of a write data single flux quantum, SFQ, pulse provided on a data write input. The circuit further comprises a storage loop coupled to the gate circuit and configured to conduct a loop current having an amplitude that is set based on the digital state.