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

Low-Jc Rapid Single Flux Quantum (RSFQ) Qubit Control Circuit

Thomas Ohki, Michael Wulf, M. J. Feldman

Published Jun 1, 2007• 8 citations
Publisher

Abstract

We designed a 30 A/cm2RSFQ-qubit control circuit and tested operation at 4 K. The integration of RSFQ technology and qubits monolithically requires great attention to thermal budgeting and electromagnetic compatibility. These issues are of primary concern when developing an RSFQ-qubit experiment. The interface of an SFQ circuit to a qubit requires tunable coupling since RSFQ inherently limits logical elements to single-flux storage. By measuring the quantum-tunneling rate of a phase qubit, we can determine the effect of changing the coupling strength between the classical and quantum systems. By looking at the same system, we can diagnose the impact, whether thermal or electromagnetic, of an active digital circuit. These tests would set an upper bound on the deleterious effects of monolithic integration.

DOI
10.1109/tasc.2007.898701

Related papers

Rapid single-flux quantum control of the energy potential in a double SQUID qubit circuit

Maria Gabriella Castellano, F. Chiarello, Roberto Leoni +6 more

We report on the development and test of an integrated system composed of a flux qubit and a rapid single-flux quantum (RSFQ) circuit that allows qubit manipulation. The goal is to demonstrate the feasibility of control electronics integrated on the same chip as the qubit, in view of the application in quantum computation with superconducting devices. RSFQ logic relies on the storage and transmission of magnetic flux quanta and can be profitably used with superconducting qubits because of the speed, scalability, compatibility with the qubit fabrication process and low temperature environment. While standard RSFQ circuitry is well assessed, the application to quantum computing requires a complete rescaling of parameter values, in order to preserve the qubit coherence and reduce the power dissipation. In the system presented in this paper, the qubit role is played by a superconducting loop interrupted by a small dc SQUID, usually called a double SQUID, which behaves as a tunable rf-SQUID. Its energy potential has the shape of a double well, with the barrier between the wells controlled by magnetic flux applied to the inner dc SQUID. Here for the first time we report measurements at a base temperature of 370 mK in which flux control pulses with desired characteristics were supplied by a RSFQ circuit fabricated using non-standard parameters in the same chip as the qubit.

Superconductor Science and Technology•May 3, 2007•16 citations

Low power single flux quantum qubit control circuit without high-frequency input

Bicong Weng, Wei Peng, Jie Ren

Abstract The use of high-frequency input signals from room-temperature microwave sources makes it difficult to scale up the number of quantum bits in universal quantum computers. To address this issue, superconducting single flux quantum (SFQ) integrated circuits are being explored as suitable candidates for qubit manipulation in universal quantum computers. This paper deals with a scalable SFQ qubit control circuit (SQCC) structure that requires only low-frequency input. The circuit mainly consists of a pulse generator and a counter, that output the SFQ pulse train with adjustable frequency and a controllable number of pulses, which is applicable to control single-qubit Clifford operations. The design of low-voltage rapid single flux quantum (LV-RSFQ) and energy-efficient rapid single flux quantum (ERSFQ) for the SQCC achieves low power consumption and provides a basis for scaling up SQCC to control more qubits. The proposed circuits are fabricated under the SIMIT-Nb03 process and successfully pass test verification. The achieved test results reveal that the adjustable output frequency ranges of the SQCC based on the LV-RSFQ and ERSFQ designs in order are [2.40, 8.11] GHz and [4.81, 5.14] GHz. In the operating frequency range, the circuit is able to generate the correct number of SFQ pulses under control. The controllable number range is from 1 to 128. When the circuits operate at 5 GHz, the total power consumptions of the above circuits in order are 23.88 μW and 6.2 μW. All input signals are low-frequency signals, which frees the control of large-scale qubits from limitations caused by high-frequency inputs produced by room-temperature microwave sources.

Superconductor Science and Technology•Jul 11, 2023•4 citations

Thermal design of superconducting digital circuits for millikelvin operation

Thomas Ohki, Jonathan L. Habif, M. J. Feldman +1 more

Niobium based rapid-single-flux-quantum (RSFQ) digital circuits generally operate at temperature 4 K. It is desirable to develop RSFQ circuits for operation at much lower temperatures, in particular to use as control and interface circuitry for superconducting qubits, and eventually for a full scale quantum computer. The total heat load is moderate - current designs generate 0.5 /spl mu/W per bias resistor, so simple RSFQ integrated circuits are easily compatible with commercial helium dilution refrigerators, and this power can readily be reduced by several orders of magnitude for complex future designs - but thermal conductivity will be a bottleneck. We present a simple model of heat flow through standard RSFQ structures. We find that circuits designed for 4 K operation can be used with little or no modification below one Kelvin. At lower temperatures however the heat generated on chip cannot be removed, and the temperature of a working circuit will rise. We suggest fabrication design rule changes to address this problem.

IEEE Transactions on Applied Superconductivity•Jun 1, 2003•8 citations

Unleashing the Power of T1-cells in SFQ Arithmetic Circuits

Rassul Bairamkulov, Mingfei Yu, Giovanni De Micheli

Rapid single-flux quantum (RSFQ) is one of the most advanced cryogenic superconductive electronics technologies. With orders of magnitude smaller power dissipation, RSFQ is an attractive technology for cloud computing, aerospace electronics, and high-speed interfacing with quantum computing systems. Technological challenges however greatly complicate the realization of VLSI-complexity RSFQ systems. For example, gate-level pipelining in SFQ systems incurs a significant area overhead due to the need for path balancing. This issue is particularly detrimental to SFQ systems due to the limited layout density of RSFQ systems.

ACM/IEEE Design Automation Conference (DAC)•Jun 23, 2024•1 citation

Recent Progress in Rapid-Single-Flux-Quantum Circuits

Akira Fujimaki, Takahiro Yamada, Masamitsu Tanaka +4 more

We describe recent topics of rapid-single-flux-quantum (RSFQ) circuits. Much higher integration and higher-speed operation are required for commercializing the RSFQ circuits in any application. To satisfy this requirement, we measure several kinds of time fluctuations that possibly limit the integration level and operating speed, and introduce the flexible passive transmission line technology including a multicasting transmitter. In addition, we describe our ongoing applications. A multiple-detectors-system is expected to open a new application field of an RSFQ-based analog-to-digital converter and a digital signal processor. As for a microprocessor application, increased number of arithmetic logic units may be effective for enhancing the computing performances.

Advances in science and technology•Oct 1, 2006•0 citations

Implementation of superconductive passive phase shifters in high-speed integrated RSFQ digital circuits

Boyko Dimov, D Balashov, M. Khabipov +5 more

The reduction of the critical current density in rapid single-flux quantum (RSFQ) circuits enables new application fields, like quantum computing and photonic detector readout. The low current density fabrication process creates new design challenges, such as lower stability against thermal fluctuations, violation of the lumped elements condition for microstrip inductances and increased sensitivity to the technological spread. To overcome these issues, we suggest a passive phase shifter as a promising alternative technique for superconductive phase dropping in the RSFQ electronics. Here, we study experimentally their applicability in high-speed RSFQ digital circuits. Conclusions are drawn about the impact of the passive phase shifters on the complexity, the speed and the bit error rate of the investigated RSFQ circuits. We demonstrate the successful operation of different circuits with implemented passive phase shifters at low and high speeds.

Superconductor Science and Technology•Feb 25, 2008•10 citations
We designed a 30 A/cm2RSFQ-qubit control circuit and tested operation at 4 K. The integration of RSFQ technology and qubits monolithically requires great attention to thermal budgeting and electromagnetic compatibility. These issues are of primary concern when developing an RSFQ-qubit experiment. The interface of an SFQ circuit to a qubit requires tunable coupling since RSFQ inherently limits logical elements to single-flux storage. By measuring the quantum-tunneling rate of a phase qubit, we can determine the effect of changing the coupling strength between the classical and quantum systems. By looking at the same system, we can diagnose the impact, whether thermal or electromagnetic, of an active digital circuit. These tests would set an upper bound on the deleterious effects of monolithic integration.
We report on the development and test of an integrated system composed of a flux qubit and a rapid single-flux quantum (RSFQ) circuit that allows qubit manipulation. The goal is to demonstrate the feasibility of control electronics integrated on the same chip as the qubit, in view of the application in quantum computation with superconducting devices. RSFQ logic relies on the storage and transmission of magnetic flux quanta and can be profitably used with superconducting qubits because of the speed, scalability, compatibility with the qubit fabrication process and low temperature environment. While standard RSFQ circuitry is well assessed, the application to quantum computing requires a complete rescaling of parameter values, in order to preserve the qubit coherence and reduce the power dissipation. In the system presented in this paper, the qubit role is played by a superconducting loop interrupted by a small dc SQUID, usually called a double SQUID, which behaves as a tunable rf-SQUID. Its energy potential has the shape of a double well, with the barrier between the wells controlled by magnetic flux applied to the inner dc SQUID. Here for the first time we report measurements at a base temperature of 370 mK in which flux control pulses with desired characteristics were supplied by a RSFQ circuit fabricated using non-standard parameters in the same chip as the qubit.
Abstract The use of high-frequency input signals from room-temperature microwave sources makes it difficult to scale up the number of quantum bits in universal quantum computers. To address this issue, superconducting single flux quantum (SFQ) integrated circuits are being explored as suitable candidates for qubit manipulation in universal quantum computers. This paper deals with a scalable SFQ qubit control circuit (SQCC) structure that requires only low-frequency input. The circuit mainly consists of a pulse generator and a counter, that output the SFQ pulse train with adjustable frequency and a controllable number of pulses, which is applicable to control single-qubit Clifford operations. The design of low-voltage rapid single flux quantum (LV-RSFQ) and energy-efficient rapid single flux quantum (ERSFQ) for the SQCC achieves low power consumption and provides a basis for scaling up SQCC to control more qubits. The proposed circuits are fabricated under the SIMIT-Nb03 process and successfully pass test verification. The achieved test results reveal that the adjustable output frequency ranges of the SQCC based on the LV-RSFQ and ERSFQ designs in order are [2.40, 8.11] GHz and [4.81, 5.14] GHz. In the operating frequency range, the circuit is able to generate the correct number of SFQ pulses under control. The controllable number range is from 1 to 128. When the circuits operate at 5 GHz, the total power consumptions of the above circuits in order are 23.88 μW and 6.2 μW. All input signals are low-frequency signals, which frees the control of large-scale qubits from limitations caused by high-frequency inputs produced by room-temperature microwave sources.
Niobium based rapid-single-flux-quantum (RSFQ) digital circuits generally operate at temperature 4 K. It is desirable to develop RSFQ circuits for operation at much lower temperatures, in particular to use as control and interface circuitry for superconducting qubits, and eventually for a full scale quantum computer. The total heat load is moderate - current designs generate 0.5 /spl mu/W per bias resistor, so simple RSFQ integrated circuits are easily compatible with commercial helium dilution refrigerators, and this power can readily be reduced by several orders of magnitude for complex future designs - but thermal conductivity will be a bottleneck. We present a simple model of heat flow through standard RSFQ structures. We find that circuits designed for 4 K operation can be used with little or no modification below one Kelvin. At lower temperatures however the heat generated on chip cannot be removed, and the temperature of a working circuit will rise. We suggest fabrication design rule changes to address this problem.
Rapid single-flux quantum (RSFQ) is one of the most advanced cryogenic superconductive electronics technologies. With orders of magnitude smaller power dissipation, RSFQ is an attractive technology for cloud computing, aerospace electronics, and high-speed interfacing with quantum computing systems. Technological challenges however greatly complicate the realization of VLSI-complexity RSFQ systems. For example, gate-level pipelining in SFQ systems incurs a significant area overhead due to the need for path balancing. This issue is particularly detrimental to SFQ systems due to the limited layout density of RSFQ systems.
We describe recent topics of rapid-single-flux-quantum (RSFQ) circuits. Much higher integration and higher-speed operation are required for commercializing the RSFQ circuits in any application. To satisfy this requirement, we measure several kinds of time fluctuations that possibly limit the integration level and operating speed, and introduce the flexible passive transmission line technology including a multicasting transmitter. In addition, we describe our ongoing applications. A multiple-detectors-system is expected to open a new application field of an RSFQ-based analog-to-digital converter and a digital signal processor. As for a microprocessor application, increased number of arithmetic logic units may be effective for enhancing the computing performances.
The reduction of the critical current density in rapid single-flux quantum (RSFQ) circuits enables new application fields, like quantum computing and photonic detector readout. The low current density fabrication process creates new design challenges, such as lower stability against thermal fluctuations, violation of the lumped elements condition for microstrip inductances and increased sensitivity to the technological spread. To overcome these issues, we suggest a passive phase shifter as a promising alternative technique for superconductive phase dropping in the RSFQ electronics. Here, we study experimentally their applicability in high-speed RSFQ digital circuits. Conclusions are drawn about the impact of the passive phase shifters on the complexity, the speed and the bit error rate of the investigated RSFQ circuits. We demonstrate the successful operation of different circuits with implemented passive phase shifters at low and high speeds.