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

Japanese Journal of Applied Physics

A Vortex Transitional NDRO Josephson Memory Cell

Shuichi Tahara, Y. Wada

Published Sep 1, 1987• 17 citations
Publisher

Abstract

A new vortex transitional NDRO memory cell has been proposed for use as a high-speed cache memory. The memory cell consists of two superconducting loops with one Josephson junction and a two-junction interferometer gate. The superconducting loop stores single-flux quantum. The interferometer gate operates as a sense gate. The memory cell employs a vortex transition in the superconducting loop for the writing and reading of data. The sense gate current margin increases to ±38% since the coupling magnetic flux is amplified by the vortex transition for nominally designed cell parameters. The memory cell operates with a ±33% address signal current margin. This paper describes the memory cell design and the dynamic behavior of computer simulations.

DOI
10.1143/jjap.26.1463

Related papers

Experimental vortex transitional nondestructive read-out Josephson memory cell

Shuichi Tahara, Ichiro Ishida, Yumi Ajisawa +1 more

A proposal vortex transitional nondestructive read-out Josephson memory cell is successfully fabricated and tested. The memory cell consists of two superconducting loops in which a single flux quantum is stored and a two-junction interferometer gate as a sense gate. The memory cell employs vortex transitions in the superconducting loops for writing and reading data. The vortex transitional memory operation of the cell contributes to improving its sense discrimination and operating margin. The memory cell is activated by two control signals without timing control signals. Memory cell chips have been fabricated using a niobium planarization process. A±21% address signal current margin and a ±33% sense gate current margin have been obtained experimentally. Successful memory operations of a cell driven by two-junction interferometer gates has been demonstrated. The single flux quantum operations of this memory cell makes it an attractive basic element for a high-speed cache memory.

Journal of Applied Physics•Jan 15, 1989•42 citations

A capacitively coupled SFQ Josephson memory cell

Hideo Suzuki, S. Hasuo

The design and experimental results for a novel type of Josephson memory cell are presented. The cell has a simpler construction than the conventional Henkels-type, using a one-junction SQUID (superconducting quantum interference device) capacitively coupled to a single junction. Binary data are stored as single flux quanta and are destructively read out by sensing a pulse caused by a vortex-mode transition. Computer simulations suggest that the read operation could be performed with a bias margin for the sense junction of +or-28% and that the rise time of the sense current in a 16-bit memory cell would be as fast as 30 ps, despite having to sense a vortex-mode transition. Results are presented for a memory cell fabricated with Nb-AlO/sub x/-Nb junctions.>

IEEE Transactions on Electron Devices•Jul 1, 1988•10 citations

High density NDRO SFQ Joshepson interferometer momory cell

H. Beha

A new Single Flux-Quantum (SFQ) Nondestructive Read-Out (NDRO) random-access asymmetric 2-Josephson-junction interferometer memory cell with only one control line has been investigated and designed. The binary information is stored in the cell nonvolatilely without a bias current. For random access, this is the first known interferometer memory cell without a diagonal line. Therefore, this NDRO SFQ memory cell leads intrinsically to smaller cell area and simpler decoder schemes. A cell design of only 52 lithographic squares is given to demonstrate the potential for high-density memory chips. Wide nominal read and write operating margins are obtained. The NDRO interferometer memory cell proposed is promising for use in a high-performance Josephson computer.

IEEE Transactions on Magnetics•Nov 1, 1981•2 citations

Two-Josephson-junction interferometer memory cell for n.d.r.o.

H. Beha

A single-flux-quantum random-access memory cell for nondestructive read-out and write has been designed and successfully simulated. The binary information is stored in an interferometer with two unequal Josephson junctions. No bias current is needed to store the information. Reasonable operation margins are obtained.

Electronics Letters•Sep 29, 1977•11 citations

Memories with Josephson Junctions

Peter Wolf

The talk is based on an overview which was published recently (1). For this reason, only an abstract is given here, which includes Later results not contained in the aforementioned overview. The presently-known Josephson memory cells store information as persistent currents in superconducting loops, or what is equivalent as a magnetic flux in the area of the ring. This method of storage is nonvolatile and has no power consumption in the storing state. In a superconducting ring system, the magnetic flux is quantized, and cells have been built which operate either with only one flux quantum, or with many of them. For the Latter cells with many flux quanta (ring cells), quite a number of designs exist. They have one or two Josephson junctions in the ring, which allow writing. An external junction which is controlled by the ring current serves for non-destructive reading of the information. The smallest cell realized had an area of 900 ?m2 with a 2 ?m minimum line width. Switching speed was ? 80 ps. Cells which store information as a single-flux quantum (single flux-quantum cells = SFQ cells) in the ring, usually contain two Josephson junctions used for reading and writing. Read-out in most of these cells is destructive, but methods of reading non-destructively have also been proposed. The smallest device made had an area of ? 150 ?m2 with a minimum line width of 2 ?m. The read signal had a rise time ? 100 ps.

European Solid-State Circuits Conference (ESSCIRC)•Sep 1, 1978•0 citations

An Improved Josephson Interferometer Memory Cell for Nondestructive Read-Out

Masafumi Yamamoto, Akira Ishida

An improved single flux-quantum Josephson interferometer memory cell which brought stable nondestructive read-out (NDRO) operation was proposed. The cell was constructed with an end-fed asymmetric two-junction interferometer, in which the bit operating current level could be set far above the critical point for stable NDRO operation. Damping condition for proper memory operation was studied by computer simulation. The NDRO operation was experimentally obtained for the McCumber damping parameter βc of 300–400.

International Conference on Solid State Devices and Materials (SSDM)•Aug 26, 1980•3 citations
A new vortex transitional NDRO memory cell has been proposed for use as a high-speed cache memory. The memory cell consists of two superconducting loops with one Josephson junction and a two-junction interferometer gate. The superconducting loop stores single-flux quantum. The interferometer gate operates as a sense gate. The memory cell employs a vortex transition in the superconducting loop for the writing and reading of data. The sense gate current margin increases to ±38% since the coupling magnetic flux is amplified by the vortex transition for nominally designed cell parameters. The memory cell operates with a ±33% address signal current margin. This paper describes the memory cell design and the dynamic behavior of computer simulations.
A proposal vortex transitional nondestructive read-out Josephson memory cell is successfully fabricated and tested. The memory cell consists of two superconducting loops in which a single flux quantum is stored and a two-junction interferometer gate as a sense gate. The memory cell employs vortex transitions in the superconducting loops for writing and reading data. The vortex transitional memory operation of the cell contributes to improving its sense discrimination and operating margin. The memory cell is activated by two control signals without timing control signals. Memory cell chips have been fabricated using a niobium planarization process. A±21% address signal current margin and a ±33% sense gate current margin have been obtained experimentally. Successful memory operations of a cell driven by two-junction interferometer gates has been demonstrated. The single flux quantum operations of this memory cell makes it an attractive basic element for a high-speed cache memory.
The design and experimental results for a novel type of Josephson memory cell are presented. The cell has a simpler construction than the conventional Henkels-type, using a one-junction SQUID (superconducting quantum interference device) capacitively coupled to a single junction. Binary data are stored as single flux quanta and are destructively read out by sensing a pulse caused by a vortex-mode transition. Computer simulations suggest that the read operation could be performed with a bias margin for the sense junction of +or-28% and that the rise time of the sense current in a 16-bit memory cell would be as fast as 30 ps, despite having to sense a vortex-mode transition. Results are presented for a memory cell fabricated with Nb-AlO/sub x/-Nb junctions.>
A new Single Flux-Quantum (SFQ) Nondestructive Read-Out (NDRO) random-access asymmetric 2-Josephson-junction interferometer memory cell with only one control line has been investigated and designed. The binary information is stored in the cell nonvolatilely without a bias current. For random access, this is the first known interferometer memory cell without a diagonal line. Therefore, this NDRO SFQ memory cell leads intrinsically to smaller cell area and simpler decoder schemes. A cell design of only 52 lithographic squares is given to demonstrate the potential for high-density memory chips. Wide nominal read and write operating margins are obtained. The NDRO interferometer memory cell proposed is promising for use in a high-performance Josephson computer.
The talk is based on an overview which was published recently (1). For this reason, only an abstract is given here, which includes Later results not contained in the aforementioned overview. The presently-known Josephson memory cells store information as persistent currents in superconducting loops, or what is equivalent as a magnetic flux in the area of the ring. This method of storage is nonvolatile and has no power consumption in the storing state. In a superconducting ring system, the magnetic flux is quantized, and cells have been built which operate either with only one flux quantum, or with many of them. For the Latter cells with many flux quanta (ring cells), quite a number of designs exist. They have one or two Josephson junctions in the ring, which allow writing. An external junction which is controlled by the ring current serves for non-destructive reading of the information. The smallest cell realized had an area of 900 ?m2 with a 2 ?m minimum line width. Switching speed was ? 80 ps. Cells which store information as a single-flux quantum (single flux-quantum cells = SFQ cells) in the ring, usually contain two Josephson junctions used for reading and writing. Read-out in most of these cells is destructive, but methods of reading non-destructively have also been proposed. The smallest device made had an area of ? 150 ?m2 with a minimum line width of 2 ?m. The read signal had a rise time ? 100 ps.
An improved single flux-quantum Josephson interferometer memory cell which brought stable nondestructive read-out (NDRO) operation was proposed. The cell was constructed with an end-fed asymmetric two-junction interferometer, in which the bit operating current level could be set far above the critical point for stable NDRO operation. Damping condition for proper memory operation was studied by computer simulation. The NDRO operation was experimentally obtained for the McCumber damping parameter βc of 300–400.