RQL A-And-Not-B Gate Using Josephson Junction Pulse Blocking
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Solution Overview
Problem
CMOS technology-based digital circuits face limitations in device size and power consumption, especially at high clock speeds, due to static power dissipation and current leakage even when inactive, leading to inefficiencies in high-performance systems like data center servers.
Innovation Solution
The development of a superconducting logic-based A-and-not-B gate circuit using Josephson junctions and inductors, which operates with single flux quantum pulses and alternating current power, eliminating static power dissipation and ground return current, and enabling efficient data encoding with reciprocal quantum logic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CMOS technology is used for digital circuits, then device integration is achieved, but static power dissipation and current leakage occur even when circuits are inactive
Solution Approach 1:
The patent replaces CMOS-based digital logic circuits with superconducting logic circuits that use Josephson junctions. This substitution eliminates static power dissipation by using quantum tunneling effects in superconducting materials, where current flows without resistance when below critical temperature, thereby resolving the contradiction between device integration and static power loss.
Solution Approach 2:
The invention changes the operating parameters by using alternating current (AC) power supply instead of direct current (DC) voltage, and operates the Josephson junctions at temperatures below their critical temperature. This parameter change enables zero static power dissipation while maintaining logical functionality, addressing the energy loss issue in integrated circuits.
2Duration of action of stationary object
If DC voltage is used to power CMOS circuits, then continuous operation is enabled, but current leakage occurs even when circuits are inactive
Solution Approach 1:
The patent employs alternating current (AC) power supply with periodic oscillation instead of continuous DC voltage. The Josephson junctions are driven by AC signals at frequencies and amplitudes that enable logical operations during active phases while allowing complete relaxation during inactive phases, eliminating current leakage while maintaining continuous operational capability.
Solution Approach 2:
The invention changes the power supply parameter from DC voltage to AC voltage, and operates the superconducting circuits at temperatures below the critical temperature of the superconducting materials. This parameter change enables the circuits to achieve zero resistance state during operation, eliminating current leakage while maintaining continuous operation through periodic AC driving.
3Loss of energy
If superconducting logic devices are used, then static power dissipation is eliminated, but device complexity increases
Solution Approach 1:
The patent implements a nested structure where multiple Josephson junctions are stacked vertically to form compact logic gates. The first and second Josephson junctions are coupled in series between the AC power supply and ground, with intermediate nodes connecting to inductors and other junctions. This nesting approach reduces the horizontal footprint while maintaining the zero static power dissipation advantage.
Solution Approach 2:
The invention transitions from planar two-dimensional circuit layout to three-dimensional vertical stacking of Josephson junctions. By coupling junctions in series vertically and using vertical interconnections, the design achieves compact area efficiency while eliminating static power dissipation, resolving the contradiction between energy efficiency and device complexity.
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
This solution results in low-power operation with zero static power dissipation and area-efficient design, reducing power wastage and improving performance in digital circuits by using AC power and eliminating current leakage.
Implementation Method 1
a first Josephson junction, JJ, coupled to the output terminal and coupled to receive the first set of SFQ pulses; a second JJ coupled to the first JJ and coupled to the output terminal resulting in a stacked arrangement of the first JJ and the second JJ
Data Source
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AI summary
Superconducting circuits-based devices and methods, including reciprocal quantum logic, RQL, based devices and methods are provided. A circuit for an A-and-not-B gate including an output terminal (no), a first input terminal (ai) for receiving a first set of single flux quantum, SFQ, pulses, and a second input terminal (bi) for receiving a second set of SFQ pulses is provided. The circuit further includes a first Josephson junction (104), JJ, coupled to receive the first set of SFQ pulses. The circuit further includes a second JJ (114), where the second JJ when positively biased is configured to negatively bias the first JJ such that the circuit is configured to not pass the first set of SFQ pulses to the output terminal only when the second set of SFQ pulses have arrived at the second input terminal prior to an arrival of the first set of SFQ pulses at the first input terminal.