Coupled Josephson Junctions for Cryogenic Memory Capacity
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Solution Overview
Problem
Current cryogenic memory designs, such as single flux quantum (SFQ) digital logic and hybrid superconducting CMOS, face limitations in capacity and power dissipation, with SFQ-based memories only demonstrating 4,096 bits and projecting to 85 Megawatts of power dissipation for a 1 Petabyte memory, necessitating the development of more efficient cryogenic memory solutions.
Innovation Solution
The development of cryogenic memory circuits based on small coupled arrays of Josephson junctions, where write and read operations can be performed using the same circuit, with low pulse energies (around 10−19 J) and fast access times (on the order of 10-100 ps), utilizing stochastic optimization procedures to optimize electrical parameters for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If single flux quantum (SFQ) digital logic is used for cryogenic memory, then logic performance is improved, but memory capacity is limited and power dissipation is high
Solution Approach 1:
The patent merges the logic and memory functions into a single unified circuit structure using coupled Josephson junctions. This integration eliminates the need for separate logic and memory components, allowing the system to achieve both high-performance logic operations and high-capacity memory storage within the same circuit architecture, thereby resolving the contradiction between logic performance and memory capacity.
Solution Approach 2:
The patent changes the fundamental operating parameters by using Josephson junctions with specific coupling configurations and pulse energy levels. By adjusting the coupling strength between junctions and optimizing the pulse energy to be below the switching threshold of adjacent junctions, the system achieves low power dissipation while maintaining high memory capacity through multiple stable states.
2Quantity of substance
If hybrid superconducting CMOS designs are used, then memory capacity is improved, but interface complexity and cost increase
Solution Approach 1:
The coupled Josephson junction circuit serves multiple functions simultaneously: it performs logic operations, stores memory data, and provides read/write capabilities through the same structure. This multi-functionality eliminates the need for complex hybrid interfaces between superconducting and CMOS components, as the single superconducting circuit handles all operations natively.
Solution Approach 2:
The patent combines logic and memory functions into a single unified circuit structure using coupled Josephson junctions. This integration eliminates the need for separate logic and memory components, allowing the system to achieve both high-performance logic operations and high-capacity memory storage within the same circuit architecture, thereby resolving the contradiction between logic performance and memory capacity.
3Reliability
If separate circuits are used for write and read operations, then operation reliability is improved, but area consumption increases and latency is higher
Solution Approach 1:
The coupled Josephson junction circuit serves multiple functions simultaneously: it performs logic operations, stores memory data, and provides read/write capabilities through the same structure. This multi-functionality eliminates the need for complex hybrid interfaces between superconducting and CMOS components, as the single superconducting circuit handles all operations natively.
4Reliability
If high pulse energy is used for memory operations, then switching reliability is improved, but energy consumption increases
Solution Approach 1:
The patent changes the fundamental operating parameters by using Josephson junctions with specific coupling configurations and pulse energy levels. By adjusting the coupling strength between junctions and optimizing the pulse energy to be below the switching threshold of adjacent junctions, the system achieves low power dissipation while maintaining high memory capacity through multiple stable states.
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
These memory circuits achieve efficient memory operations with minimal energy dissipation and fast access times, enabling the design of compact, energy-efficient cryogenic memory cells that can store data effectively in a cryogenic environment.
Implementation Method 1
Cryogenic memory cell circuits are disclosed based on a small coupled array of two or more Josephson junctions
Data Source
AI summary
Methods and apparatus are disclosed for operating a memory cell formed from the plurality of coupled Josephson junctions. The memory cell is configured such that applying an electrical signal to the junctions can cause at least one, but not all, of the junctions to change their respective phase states. Subsequent writes to the memory cell using substantially the same electrical pulse do not change the phase state of the plurality of junctions. The memory cell can be ready by providing another electrical pulse to one of the junctions and receiving an output electrical pulse generated in response by a different Josephson junction of the memory cell. A set of phase states are selected to represent the logic values that are stable across anticipated operating conditions for the memory cell. Methods of selecting electrical parameters and manufacturing memory cells are further disclosed.