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 Applied Superconductivity

Effect of thermal noise on the bit error rate of SFQ devices

J.H. Kang, John X. Przybysz, A. Hodge Worsham, D.L. Miller

Published Jun 1, 1999• 2 citations
Publisher

Abstract

To measure the effect of thermal noise on switching a Josephson junction to the voltage state a simple SFQ circuit constructed with resistively shunted Nb/AlO/sub x//Nb junctions was used. Based on a good agreement between the measured data and the thermal activation theory, the effect of thermal noise on the bit error rate of SFQ devices was studied, The effective thermal noise temperature of 10 K used to fit the data was higher than the bath temperature of 4.2 K. Careful circuit design to get large critical margins is necessary to achieve high operating temperature of SFQ logic devices.

DOI
10.1109/77.783987

Related papers

Thermal noise in digital Josephson devices

J.D. Feder, M. Klein, C.J. Anderson

A method of accurately estimating the I/sub 0/ (critical current) of a Josephson junction (JJ) with thermal noise was developed by measuring the effective thermal noise temperature of a JJ. The effective thermal noise temperature of various JJ devices was measured and calculated. The JJ devices evaluated included inductively and resistively coupled logic devices and JJ devices in the presence of various noise sources. The noise sources included room-temperature resistors, switched JJ devices, and JJ devices in the linear I-V region beyond the gap. The R/sub NN/ compensator is shown to result in a noise temperature of about 6 K at an interferometer. The addition of a shunt junction lessens the noise penalty introduced by the compensator. A switched isolation interferometer in a two-input AND gate contributes negligible noise at the injection device. It is also shown that bandwidth connections to room-temperature equipment result in very large excess noise and require special input and output circuits on the chip.>

IEEE Transactions on Applied Superconductivity•Mar 1, 1993•4 citations

Measurement and data-assisted simulation of bit error rate in RQL circuits

Quentin Herr, Alex Braun, Andrew Brownfield +4 more

Abstract A circuit-simulation-based method is used to determine the thermally-induced bit error rate of superconducting Single Flux Quantum logic circuits. Simulations are used to evaluate the multidimensional Gaussian integral across noise current sources attached to the active devices. The method is data-assisted and has predictive power. Measurement determines the value of a single parameter, effective noise bandwidth, for each error mechanism. The errors in the distributed networks of comparator-free Reciprocal Quantum Logic nucleate across multiple Josephson junctions, so the effective critical current is about three times that of the individual devices. The effective noise bandwidth is only 6%–23% of the junction plasma frequency at a modest clock rate of 3.4 GHz, which is 1% of the plasma frequency. This analysis shows the ways measured bit error rate comes out so much lower than simplistic estimates based on isolated devices.

arXiv:2104.07092•Superconductor Science and Technology•Jan 12, 2022•6 citations

Thermal noise induced switching of Josephson logic devices

M. Klein, A. Mukherjee

Thermal noise induced switching of Josephson logic devices is studied, both theoretically and experimentally. The results are critical for the design of the operating bias points for these devices. An analysis of the relevant energy contours shows that a three-junction superconducting quantum interference device has the same noise switching rate as a point junction with the same maximum critical current. Experimental results, for the dependence of the thermal noise induced switching rate on the gate current bias ratio, are in very good agreement with the theory.

Applied Physics Letters•Apr 15, 1982•37 citations

Noise analysis for intrinsic and external shunted Josephson junctions

Thomas Ortlepp, Hermann F. Uhlmann

In the design of electronic applications (for example, rapid single flux quantum (RSFQ) circuits), the properties of Josephson junctions (JJs) provided by technology are the major requirement. The characteristic voltage IcRn an dt he dynamic parameter βc are non-negligibly important, bu tt he external shunted junctions are only completely described by including the parasitic inductance between the junction area and the shunt resistor. The first publications of the RSFQ circuit technique were closely followed by many studies on the dynamic influence of this inductance. It has been pointed out that no practical value of this parameter has to be taken into account in the circuit design and optimization process. The operation of RSFQ logic circuits made of high-temperature superconductors (HTS) are strongly influenced by thermal noise. Our paper contains the determination of the digital bit-error rate for all different types of JJs by using a Fokker–Planck equation for describing the influence of thermal fluctuations. Ou ra nalysis shows that the parasitic inductance cannot be neglected in terms of noise. The intrinsic shunted junctions like high current density-, SINIS- and all kinds of HTS-JJs provide the best noise immunity for a fixed temperature.

Superconductor Science and Technology•Feb 19, 2004•19 citations

A general approach for determining the switching probability in rapid single flux quantum logic circuits

Thomas Ortlepp, Hannes Toepfer, Hermann F. Uhlmann

A major restriction in the development of a working Rapid Single Flux Quantum (RSFQ) logic circuit with high-Tc superconductors is given by the influence of thermal noise. This gives reason to ask for a general determination of the digital bit error rate. As other approaches, our method of calculating the switching probability is based on the Fokker-Planck equation. In the past few years the bit error rates for a single Josephson junction, SQUIDs and the comparator were calculated by using this theory. We demonstrate numerical solution of the multidimensional Fokker-Planck equation to calculate bit error rates due to thermal noise for a Toggle Flip Flop circuit. In the present work, we combine thermal noise analysis with the effects of process variations in order to derive rules for designing high-Tc RSFQ logic circuits.

IEEE Transactions on Applied Superconductivity•Mar 1, 2001•9 citations

Measurement of the error rate of single flux quantum circuits with high temperature superconductors

Ben J. Ruck, Yonuk Chong, Regina Dittmann +6 more

The determination of bit error rates in single flux quantum logic circuits operating at temperatures well above the temperature of liquid helium is essential since the question of stability against thermal noise arises. We determined experimentally the static and for the first time the dynamic error rate at temperatures of about 40 K with the help of simple test circuits. The static error rate has been investigated using two different circuits with bicrystal junctions in either single-layer or multilayer configuration. In both cases the internal state of a storage loop was observed by a dc-SQUID. A ring oscillator based on a Josephson transmission line allowed us to measure the dynamic error rate of a Josephson comparator at high frequencies. This circuit has been fabricated using junctions by focused-electron-beam irradiation. It is specially suited for the detection of seldom occurring switching errors.

IEEE Transactions on Applied Superconductivity•Jun 1, 1999•15 citations
To measure the effect of thermal noise on switching a Josephson junction to the voltage state a simple SFQ circuit constructed with resistively shunted Nb/AlO/sub x//Nb junctions was used. Based on a good agreement between the measured data and the thermal activation theory, the effect of thermal noise on the bit error rate of SFQ devices was studied, The effective thermal noise temperature of 10 K used to fit the data was higher than the bath temperature of 4.2 K. Careful circuit design to get large critical margins is necessary to achieve high operating temperature of SFQ logic devices.
A method of accurately estimating the I/sub 0/ (critical current) of a Josephson junction (JJ) with thermal noise was developed by measuring the effective thermal noise temperature of a JJ. The effective thermal noise temperature of various JJ devices was measured and calculated. The JJ devices evaluated included inductively and resistively coupled logic devices and JJ devices in the presence of various noise sources. The noise sources included room-temperature resistors, switched JJ devices, and JJ devices in the linear I-V region beyond the gap. The R/sub NN/ compensator is shown to result in a noise temperature of about 6 K at an interferometer. The addition of a shunt junction lessens the noise penalty introduced by the compensator. A switched isolation interferometer in a two-input AND gate contributes negligible noise at the injection device. It is also shown that bandwidth connections to room-temperature equipment result in very large excess noise and require special input and output circuits on the chip.>
Abstract A circuit-simulation-based method is used to determine the thermally-induced bit error rate of superconducting Single Flux Quantum logic circuits. Simulations are used to evaluate the multidimensional Gaussian integral across noise current sources attached to the active devices. The method is data-assisted and has predictive power. Measurement determines the value of a single parameter, effective noise bandwidth, for each error mechanism. The errors in the distributed networks of comparator-free Reciprocal Quantum Logic nucleate across multiple Josephson junctions, so the effective critical current is about three times that of the individual devices. The effective noise bandwidth is only 6%–23% of the junction plasma frequency at a modest clock rate of 3.4 GHz, which is 1% of the plasma frequency. This analysis shows the ways measured bit error rate comes out so much lower than simplistic estimates based on isolated devices.
Thermal noise induced switching of Josephson logic devices is studied, both theoretically and experimentally. The results are critical for the design of the operating bias points for these devices. An analysis of the relevant energy contours shows that a three-junction superconducting quantum interference device has the same noise switching rate as a point junction with the same maximum critical current. Experimental results, for the dependence of the thermal noise induced switching rate on the gate current bias ratio, are in very good agreement with the theory.
In the design of electronic applications (for example, rapid single flux quantum (RSFQ) circuits), the properties of Josephson junctions (JJs) provided by technology are the major requirement. The characteristic voltage IcRn an dt he dynamic parameter βc are non-negligibly important, bu tt he external shunted junctions are only completely described by including the parasitic inductance between the junction area and the shunt resistor. The first publications of the RSFQ circuit technique were closely followed by many studies on the dynamic influence of this inductance. It has been pointed out that no practical value of this parameter has to be taken into account in the circuit design and optimization process. The operation of RSFQ logic circuits made of high-temperature superconductors (HTS) are strongly influenced by thermal noise. Our paper contains the determination of the digital bit-error rate for all different types of JJs by using a Fokker–Planck equation for describing the influence of thermal fluctuations. Ou ra nalysis shows that the parasitic inductance cannot be neglected in terms of noise. The intrinsic shunted junctions like high current density-, SINIS- and all kinds of HTS-JJs provide the best noise immunity for a fixed temperature.
A major restriction in the development of a working Rapid Single Flux Quantum (RSFQ) logic circuit with high-Tc superconductors is given by the influence of thermal noise. This gives reason to ask for a general determination of the digital bit error rate. As other approaches, our method of calculating the switching probability is based on the Fokker-Planck equation. In the past few years the bit error rates for a single Josephson junction, SQUIDs and the comparator were calculated by using this theory. We demonstrate numerical solution of the multidimensional Fokker-Planck equation to calculate bit error rates due to thermal noise for a Toggle Flip Flop circuit. In the present work, we combine thermal noise analysis with the effects of process variations in order to derive rules for designing high-Tc RSFQ logic circuits.
The determination of bit error rates in single flux quantum logic circuits operating at temperatures well above the temperature of liquid helium is essential since the question of stability against thermal noise arises. We determined experimentally the static and for the first time the dynamic error rate at temperatures of about 40 K with the help of simple test circuits. The static error rate has been investigated using two different circuits with bicrystal junctions in either single-layer or multilayer configuration. In both cases the internal state of a storage loop was observed by a dc-SQUID. A ring oscillator based on a Josephson transmission line allowed us to measure the dynamic error rate of a Josephson comparator at high frequencies. This circuit has been fabricated using junctions by focused-electron-beam irradiation. It is specially suited for the detection of seldom occurring switching errors.