Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

IEEE Transactions on Magnetics

Variable threshold logic with superconducting quantum interferometers

Norio Fujimaki, Hiromasa Hoko, H. Shibayama, S. Hasuo, Toyoshi Yamaoka

Published May 1, 1983• 3 citations
Publisher

Abstract

This paper proposes a two-junction interferometer called Variable Threshold Logic. It has both magnetically-coupled control-lines and current-injection terminals. The threshold curve of this gate can be shifted by the applied currents. This property enables its use for both OR and AND function with the same structure by only changing the wiring. Operating margins of ±12 % for OR and ± 29 % for AND are obtained with the optimized device parameters. Any logic circuit can be obtained by Josephson master-slice LSI of this gate with a dual-rail logic system.

DOI
10.1109/tmag.1983.1062279

Related papers

Josephson logic circuits based on nonlinear current injection in interferometer devices

Tushar R. Gheewala

Nonlinear current-injection switching of Josephson interferometer devices is achieved by current injection into an asymmetric feedpoint. This method of switching interferometers has two important features: higher gain than in previous approaches and a novel nonlinear threshold curve which is of practical interest. A new family of high-performance logic gates based on nonlinear current injection is described. Logic circuits have been experimentally tested and preliminary results are presented.

Applied Physics Letters•Oct 15, 1978•30 citations

Josephson compensating junction logic

C.J. Anderson

A Josephson superconducting quantum interference device (SQUID) digital logic family was developed that uses the R/sub nn/ region of a Josephson junction (JJ) to compensate for variations in where R/sub nn/ is the effective resistance of a JJ in the linear I-V region beyond the gap. The basic compensating junction logic (CJL) circuit is two 2-input-OR 1-2-1 interferometer isolators that, when switched, inject current into a 2-input-AND 1-2-1 interferometer. The R/sub nn/ region of several JJs is used in series with a resistor to set the current from the power supply to the 2-input-OR interferometers. The 2-input-AND interferometer is implemented with both current injection and magnetic coupling. The latch circuit uses both current injection and magnetic coupling design techniques to increase the range of I/sub O/, inductance, and resistance variation over which the latch will function correctly. Experimental measurements of CJL circuits are described.>

IEEE Transactions on Applied Superconductivity•Mar 1, 1993•0 citations

A 4-bit×4-bit multiplier and 3-bit counter in Josephson threshold logic

Y. Hatano, Y. Harada, Kei Yamashita +2 more

A fast Josephson circuit using a threshold logic is developed for application to a multiplier and a binary counter. The former is a typical combinational circuit and the latter is a typical sequential circuit. The junction and barrier materials used were Nb-AlO/SUB X/-Nb. An optimized asymmetric two-junction interferometer maximized the operating margin of the threshold gate. A speed-up junction was introduced to decrease the switching delay without sacrificing the operating margin. A dumping resistor, which was inserted parallel to the input signal line of the threshold gate between its two terminals, decreased the reflection of the input signal caused by the gate inductance, thereby ensuring the margin and speed. To demonstrate the high-speed possibility of the Josephson threshold logic, a high-speed experiment for the circuits was performed. The multiplier demonstrated 210-ps operation.

IEEE Journal of Solid-State Circuits•Aug 1, 1987•14 citations

Superconductive logic circuits constructed by the use of two thresholds of SQUID

Masahiro Kawai, Yoichiro Sato, Hiroto Kagotani +1 more

This paper proposes a method for constructing superconductive logic circuits by actively using two thresholds in a superconducting quantum interference device (SQUID). First, it is demonstrated that the input–output characteristics of a SQUID with multiple inputs can be represented as a two-threshold logic function. Next, a SQUID structure is shown in which all of the input currents have the same significance and the threshold current can be varied without varying the characteristics of the Josephson junction. Each input is weighted by adjusting the internal impedance rather than the input current, and the SQUID thresholds are varied using the value of the steady current applied to an additional input. Finally, it is explained that when logic functions of two to four variables are realized using such SQUIDs, the number of logic functions that can be realized with a single SQUID is much greater than when an existing method is used, and the operating regions are reduced only slightly. © 2005 Wiley Periodicals, Inc. Syst Comp Jpn, 36(2): 42–50, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.20136

Systems and Computers in Japan•Jan 1, 2005•0 citations

Current-injection Josephson latch employing a single-flux quantum. I

J. Sone, Toshishige Yamada

A new current-injection Josephson latch employing a single-flux quantum is proposed. It has a master-slave circuit configuration and operates under ac power supply. In the circuit, data are stored as a circulating current in a superconducting loop consisting of a single junction and inductances. A two-junction interferometer gate directly coupled to the loop reads out the stored data. Dual-rail signals are generated from the read-out data by Josephson junctions and resister-coupled Josephson logic gates. The isolation between a master circuit and a slave circuit is realized using high-impedance states in the Josephson junctions. The circuit design and computer-simulation results on the circuit operation are described in this paper.

Journal of Applied Physics•May 1, 1986•2 citations

Josephson dual rail two-bit adder circuit utilizing magnetically coupled OR-AND gates

Hirotaka Yamada, Yoshichika Ichimiya, Akira Ishida

A novel Josephson logic gate called the asymmetrical interferometer device (AID) is presented. It is composed of a pair of asymmetrical interferometers whose outputs are injected into a single junction. The interferometers are individually operated as two input OR and the single junction is worked as AND.(A + B) (C + D)operation is accomplished by only one AID gate. They have a serial fan-in capability due to their magnetic coupling scheme. The gate size is reduced by half, compared with the previous current injection logic (CIL) gate. With these AID gates, a high-speed two-bit dual rail adder circuit is configured, which provides the logic circuits performing with both true and complement inputs and without any timing circuits. The AID gate fabricated by standard 5-µm Pb-alloy technology showed a wide margin over ±20 percent that was in good agreement with statically designed characteristics. Experimental adder operation was also successfully performed.

IEEE Transactions on Electron Devices•Mar 1, 1984•5 citations
This paper proposes a two-junction interferometer called Variable Threshold Logic. It has both magnetically-coupled control-lines and current-injection terminals. The threshold curve of this gate can be shifted by the applied currents. This property enables its use for both OR and AND function with the same structure by only changing the wiring. Operating margins of ±12 % for OR and ± 29 % for AND are obtained with the optimized device parameters. Any logic circuit can be obtained by Josephson master-slice LSI of this gate with a dual-rail logic system.
A Josephson superconducting quantum interference device (SQUID) digital logic family was developed that uses the R/sub nn/ region of a Josephson junction (JJ) to compensate for variations in where R/sub nn/ is the effective resistance of a JJ in the linear I-V region beyond the gap. The basic compensating junction logic (CJL) circuit is two 2-input-OR 1-2-1 interferometer isolators that, when switched, inject current into a 2-input-AND 1-2-1 interferometer. The R/sub nn/ region of several JJs is used in series with a resistor to set the current from the power supply to the 2-input-OR interferometers. The 2-input-AND interferometer is implemented with both current injection and magnetic coupling. The latch circuit uses both current injection and magnetic coupling design techniques to increase the range of I/sub O/, inductance, and resistance variation over which the latch will function correctly. Experimental measurements of CJL circuits are described.>
A fast Josephson circuit using a threshold logic is developed for application to a multiplier and a binary counter. The former is a typical combinational circuit and the latter is a typical sequential circuit. The junction and barrier materials used were Nb-AlO/SUB X/-Nb. An optimized asymmetric two-junction interferometer maximized the operating margin of the threshold gate. A speed-up junction was introduced to decrease the switching delay without sacrificing the operating margin. A dumping resistor, which was inserted parallel to the input signal line of the threshold gate between its two terminals, decreased the reflection of the input signal caused by the gate inductance, thereby ensuring the margin and speed. To demonstrate the high-speed possibility of the Josephson threshold logic, a high-speed experiment for the circuits was performed. The multiplier demonstrated 210-ps operation.
This paper proposes a method for constructing superconductive logic circuits by actively using two thresholds in a superconducting quantum interference device (SQUID). First, it is demonstrated that the input–output characteristics of a SQUID with multiple inputs can be represented as a two-threshold logic function. Next, a SQUID structure is shown in which all of the input currents have the same significance and the threshold current can be varied without varying the characteristics of the Josephson junction. Each input is weighted by adjusting the internal impedance rather than the input current, and the SQUID thresholds are varied using the value of the steady current applied to an additional input. Finally, it is explained that when logic functions of two to four variables are realized using such SQUIDs, the number of logic functions that can be realized with a single SQUID is much greater than when an existing method is used, and the operating regions are reduced only slightly. © 2005 Wiley Periodicals, Inc. Syst Comp Jpn, 36(2): 42–50, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.20136
A new current-injection Josephson latch employing a single-flux quantum is proposed. It has a master-slave circuit configuration and operates under ac power supply. In the circuit, data are stored as a circulating current in a superconducting loop consisting of a single junction and inductances. A two-junction interferometer gate directly coupled to the loop reads out the stored data. Dual-rail signals are generated from the read-out data by Josephson junctions and resister-coupled Josephson logic gates. The isolation between a master circuit and a slave circuit is realized using high-impedance states in the Josephson junctions. The circuit design and computer-simulation results on the circuit operation are described in this paper.
A novel Josephson logic gate called the asymmetrical interferometer device (AID) is presented. It is composed of a pair of asymmetrical interferometers whose outputs are injected into a single junction. The interferometers are individually operated as two input OR and the single junction is worked as AND.(A + B) (C + D)operation is accomplished by only one AID gate. They have a serial fan-in capability due to their magnetic coupling scheme. The gate size is reduced by half, compared with the previous current injection logic (CIL) gate. With these AID gates, a high-speed two-bit dual rail adder circuit is configured, which provides the logic circuits performing with both true and complement inputs and without any timing circuits. The AID gate fabricated by standard 5-µm Pb-alloy technology showed a wide margin over ±20 percent that was in good agreement with statically designed characteristics. Experimental adder operation was also successfully performed.