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

A new A/D converter with quantum flux parametron

Nobutaka Shimizu, Y. Harada, Naoko Miyamoto, Eiichi Goto

Published Mar 1, 1989• 14 citations
Publisher

Abstract

A flash-type superconducting A/D (analog/digital) converter is proposed. The basis low-frequency operation of this converter, which compromises a quantum flux parametron (QFP) and an RF SQUID (superconducting quantum interference device), has been observed. The RF SQUID consists of a Josephson junction and a load inductor which is part of the QFP. It converts an analog signal to period digital signals of one quantum flux (2.07*10/sup -5/ W-b) per cycle. The QFP works as both an amplifier and a comparator of the periodic digital signals, by adding an exciting signal. This A/D converter is expected to achieve high-speed operation of 20 GHz. Several 4-bit A/D converter circuits were fabricated, using the conventional Nb-Pb alloy process, with a junction size of 5 mu m*5 mu m and supercurrent density of 200 A/cm/sup 2/. Basic operation at 100 KHz was confirmed experimentally.>

DOI
10.1109/20.92423

Related papers

High-speed experiments on a QFP-based comparator for ADCs with 18-GHz sample rate and 5-GHz input frequency

Y. Harada, J.B. Green

The authors report on the high-speed operation of a superconducting comparator circuit, based on coupling the quantum flux parametron (QFP) to an RF SQUID, which can be used to build a flash-type analog-to-digital converter (ADC). Simulations of this circuit show that it is expected to achieve operation with input signal bandwidths greater than 4 GHz and with a dynamic range equal to at least 4 b of resolution. A QFP-based comparator fabricated with a process using NbN/Pb-alloy Josephson junctions of 5 mu m by 5 mu m and a current density of 100 A/cm/sup 2/ has been examined to evaluate the properties of the QFP-ADC. Analog-to-digital conversion of the comparator has been observed with a QFP activation frequency up to 18.2 GHz. By employing a sampling method, input signals with frequencies up to 5.4 GHz have also been digitized.>

IEEE Transactions on Applied Superconductivity•Mar 1, 1992•10 citations

High Tc Superconducting Flash A/D Converter Using Planar Quasi-One Junction Superconducting Quantum Interference Devices (SQUIDs)

Toshimasa Umezawa, T. Fujita, Yasushi Higashino

We have designed and fabricated a planar HTS (DyBaCuO) superconducting quasi-one junction (QOS) Superconducting Quantum Interference Device (SQUID) for a flash A/D converter using step-edge Josephson junctions. The simulation suggests that the HTS QOS bandwidth is limited with 2.6 GHz by an external shunted capacitor. To fabricate a 1–2 µ m size SQUID inductance hole and step-edge junctions, a stepper photo-lithography process was employed. To make a sensitive comparator, a flux transformer was directly installed on the QOS, whose magnetic field gain of 833 was in agreement with the designed value of 828. The basic analog to digital conversion test of the QOS comparator was confirmed at a frequency of 10 kHz–1 MHz at 77 K. The dynamic range was estimated as 2Φ0.

Japanese Journal of Applied Physics•Aug 1, 1996•1 citation

Quantum Flux Parametron

The Quantum Flux Parametron (QFP) is a new cryogenic switching device based on the parametron principle and Josephson technology. Due to the magnetic flux quantization in superconducting devices, the switching mechanism of the QFP is quite different from that of semiconductors. This presentation describes the device characteristics. QFPs have been fabricated using the Nb/Pb-alloy Josephson junction process, and their basic operation is evaluated. Over 20dB current gain is attained. One-half frequency-divider operation up to 1.8GHz has been successfully observed.

WORLD SCIENTIFIC eBooks•Mar 1, 1991•9 citations

Quantum flux parametron

Y. Harada, Eiichi Goto Eiichi Goto, N. Miyamoto

The Quantum Flux Parametron (QFP) is a new cryogenic switching device based on the parametron principle and Josephson technology. Due to the magnetic flux quantization in superconducting devices, the switching mechanism of the QFP is quite different from that of semiconductors. This presentation describes the device characteristics. QFPs have been fabricated using the Nb/Pb-alloy Josephson junction process, and their basic operation is evaluated. Over 20dB current gain is attained. One-half frequency-divider operation up to 1.8GHz has been successfully observed.

Technical digest - International Electron Devices Meeting/Technical digest•Jan 1, 1987•10 citations

Design and Demonstration of a 5-Bit Flash-Type SFQ A/D Converter Integrated With Error Correction and Interleaving Circuits

Hideo Suzuki, M. Oikawa, K. Nishii +4 more

We have designed a fully integrated 5-bit flash-type single-flux quantum (SFQ) analog-to-digital converter (ADC), in which an error correction and a bit-interleaving circuit are integrated with complementary quasi-one-junction SQUID (CQOS) comparators, and we verified its operation in experiments. Two types of look-back error correction circuits with different clock schemes were designed for the integrated ADCs to avoid the gray zone in comparators and to convert gray code to binary code. The interleaving circuit was also used in the ADC to add one extra bit. A binary 5-bit A/D converter was integrated into an IC chip. Then, input waveforms at low frequencies were successfully retrieved from the binary data of the A/D converter without any errors. We also confirmed that the A/D converter operated properly by conducting tests in our cryocooling system using a 4K-GM cryocooler after the chip was flip-chip bonded onto a multi-chip-module (MCM) carrier. We also used the beat frequency method to test and confirm that the CQOS comparator operated effectively at high frequency, i.e., 3 bits at 15 GHz in the binary code operation and 4 bits at 15 GHz in the gray code operation. Furthermore, operations at sampling frequencies of up to 32 and 50 GHz with a low-frequency analog input signal were experimentally confirmed for a 4-bit comparator circuit with a critical current density Jcof 2.5 kA/cm2and 10 kA/cm2, respectively.

IEEE Transactions on Applied Superconductivity•Dec 22, 2010•15 citations

A comparison of two types of single flux quantum comparators for a flash ADC with 10 GHz input bandwidth

Paul D. Bradley, Sergey V. Rylov

We compare the SQUID wheel/Quantum Flux Parametron (QFP) comparator to a new Rapid Single Flux Quantum (RSFQ) compatible design. Both have been simulated to demonstrate /spl sim/0.5 ps threshold accuracy which would permit the construction of a flash analog-to-digital converter with six effective bits of resolution at 10 GHz input bandwidth, over three times better than the best performance demonstrated with any technology, At lower input frequencies, both designs have demonstrated that a 10-bit flash ADC is possible. Although simulations of the QFP-based design are more accurate at high signal slew rates due to its symmetry, the RSFQ-based design has a better signal-to-noise ratio and a faster and more flexible clocking scheme which ultimately prove to be more important.

IEEE Transactions on Applied Superconductivity•Jun 1, 1997•16 citations
A flash-type superconducting A/D (analog/digital) converter is proposed. The basis low-frequency operation of this converter, which compromises a quantum flux parametron (QFP) and an RF SQUID (superconducting quantum interference device), has been observed. The RF SQUID consists of a Josephson junction and a load inductor which is part of the QFP. It converts an analog signal to period digital signals of one quantum flux (2.0710/sup -5/ W-b) per cycle. The QFP works as both an amplifier and a comparator of the periodic digital signals, by adding an exciting signal. This A/D converter is expected to achieve high-speed operation of 20 GHz. Several 4-bit A/D converter circuits were fabricated, using the conventional Nb-Pb alloy process, with a junction size of 5 mu m5 mu m and supercurrent density of 200 A/cm/sup 2/. Basic operation at 100 KHz was confirmed experimentally.>
The authors report on the high-speed operation of a superconducting comparator circuit, based on coupling the quantum flux parametron (QFP) to an RF SQUID, which can be used to build a flash-type analog-to-digital converter (ADC). Simulations of this circuit show that it is expected to achieve operation with input signal bandwidths greater than 4 GHz and with a dynamic range equal to at least 4 b of resolution. A QFP-based comparator fabricated with a process using NbN/Pb-alloy Josephson junctions of 5 mu m by 5 mu m and a current density of 100 A/cm/sup 2/ has been examined to evaluate the properties of the QFP-ADC. Analog-to-digital conversion of the comparator has been observed with a QFP activation frequency up to 18.2 GHz. By employing a sampling method, input signals with frequencies up to 5.4 GHz have also been digitized.>
We have designed and fabricated a planar HTS (DyBaCuO) superconducting quasi-one junction (QOS) Superconducting Quantum Interference Device (SQUID) for a flash A/D converter using step-edge Josephson junctions. The simulation suggests that the HTS QOS bandwidth is limited with 2.6 GHz by an external shunted capacitor. To fabricate a 1–2 µ m size SQUID inductance hole and step-edge junctions, a stepper photo-lithography process was employed. To make a sensitive comparator, a flux transformer was directly installed on the QOS, whose magnetic field gain of 833 was in agreement with the designed value of 828. The basic analog to digital conversion test of the QOS comparator was confirmed at a frequency of 10 kHz–1 MHz at 77 K. The dynamic range was estimated as 2Φ0.
The Quantum Flux Parametron (QFP) is a new cryogenic switching device based on the parametron principle and Josephson technology. Due to the magnetic flux quantization in superconducting devices, the switching mechanism of the QFP is quite different from that of semiconductors. This presentation describes the device characteristics. QFPs have been fabricated using the Nb/Pb-alloy Josephson junction process, and their basic operation is evaluated. Over 20dB current gain is attained. One-half frequency-divider operation up to 1.8GHz has been successfully observed.
The Quantum Flux Parametron (QFP) is a new cryogenic switching device based on the parametron principle and Josephson technology. Due to the magnetic flux quantization in superconducting devices, the switching mechanism of the QFP is quite different from that of semiconductors. This presentation describes the device characteristics. QFPs have been fabricated using the Nb/Pb-alloy Josephson junction process, and their basic operation is evaluated. Over 20dB current gain is attained. One-half frequency-divider operation up to 1.8GHz has been successfully observed.
We have designed a fully integrated 5-bit flash-type single-flux quantum (SFQ) analog-to-digital converter (ADC), in which an error correction and a bit-interleaving circuit are integrated with complementary quasi-one-junction SQUID (CQOS) comparators, and we verified its operation in experiments. Two types of look-back error correction circuits with different clock schemes were designed for the integrated ADCs to avoid the gray zone in comparators and to convert gray code to binary code. The interleaving circuit was also used in the ADC to add one extra bit. A binary 5-bit A/D converter was integrated into an IC chip. Then, input waveforms at low frequencies were successfully retrieved from the binary data of the A/D converter without any errors. We also confirmed that the A/D converter operated properly by conducting tests in our cryocooling system using a 4K-GM cryocooler after the chip was flip-chip bonded onto a multi-chip-module (MCM) carrier. We also used the beat frequency method to test and confirm that the CQOS comparator operated effectively at high frequency, i.e., 3 bits at 15 GHz in the binary code operation and 4 bits at 15 GHz in the gray code operation. Furthermore, operations at sampling frequencies of up to 32 and 50 GHz with a low-frequency analog input signal were experimentally confirmed for a 4-bit comparator circuit with a critical current density Jcof 2.5 kA/cm2and 10 kA/cm2, respectively.
We compare the SQUID wheel/Quantum Flux Parametron (QFP) comparator to a new Rapid Single Flux Quantum (RSFQ) compatible design. Both have been simulated to demonstrate /spl sim/0.5 ps threshold accuracy which would permit the construction of a flash analog-to-digital converter with six effective bits of resolution at 10 GHz input bandwidth, over three times better than the best performance demonstrated with any technology, At lower input frequencies, both designs have demonstrated that a 10-bit flash ADC is possible. Although simulations of the QFP-based design are more accurate at high signal slew rates due to its symmetry, the RSFQ-based design has a better signal-to-noise ratio and a faster and more flexible clocking scheme which ultimately prove to be more important.