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

Two-Stage SQUID Amplifier With Bias Current Re-Use

M. Kiviranta, Leif Grönberg

Published Dec 16, 2024• 2 citations
Publisher

Abstract

Biasing arrangements in multi-channel multi-stage SQUID amplifier systems, such as Transition Edge Sensor matrices for astronomical observation (Barrett et al., 2023) or quantum science (Hummatov et al., 2023), typically require a large number of wires. This is due to the need for two or more cascaded SQUID stages to obtain sufficiently large power gain over a sufficient bandwidth, and due to moderate obtainable multiplexing factors, which forces implementation of many parallel readout chains to serve all the sensor pixels. We suggest an arrangement where one bias line and one flux setpoint line are shared by two cascaded SQUID stages on a single chip, halving the number of lines two cascaded stages would ordinarily require. The stages are connected in series, sharing a single supplycurrent, dual to ordinary integrated transistor circuits in which many transistor stages are connected in parallel and share a single supplyvoltage. We show experimental results atT= 4.2 K for a proof-of-concept amplifier chip, fabricated in the VTT Micronova foundry, using SWAPS Josephson junctions (Grönberg et al., 2017) atJC= 20 μA/(μm)2critical current density. The device shows larger than 3 kΩ transresistance, when operating fromLIN= 29 nH input inductance toRD< 150 Ω output dynamic resistance.

DOI
10.1109/tasc.2024.3514594

Related papers

Two-stage SQUID amplifier with bias current re-use

M. Kiviranta

We have designed and fabricated an integrated two-stage SQUID amplifier, requiring only one bias line and one flux setpoint line. From the biasing viewpoint the two stages are connected in series while from the signal propagation viewpoint the stages are cascaded. A proof-of principle demonstration at T = 4.2 K is presented.

arXiv:2012.15362•Dec 30, 2020•0 citations

Components for Multiplexed DC-SQUID Readouts of Transition Edge Sensor Arrays

M. Kiviranta, Leif Grönberg

A SQUID tandem is a two-stage amplifier consisting of the front end SQUID atTT∼ 4 K. We give an overview of the dc SQUID design for the tandem used in the recent 37-pixel frequency domain multiplexed (FDM) readout demonstration of X-ray calorimeters. The SQUID devices were fabricated with pillar-type Josephson junctions at the nominalJC= 500 A/cm2critical current density. We further discuss possible improvements to the FDM tandem configuration, including (i) the class-B operation for better power efficiency, (ii) the input power combiner as an improvement over the simple T-junction summing, with the promise for larger multiplexing factors, and (iii) the new booster SQUID device. The new improved booster is a 8-parallel 66-series SQUID array fabricated with SWAPS Josephson junctions at the nominal JC= 1.5 kA/cm2 critical current density, and it shows dV/dΦ > 30 mV/Φ0gain in the symmetric-slope operation, as well as ΦN≈ 0.05 μΦ0/ Hz1/2flux noise.

IEEE Transactions on Applied Superconductivity•Apr 17, 2023•4 citations

Low-noise ultra-high-speed dc SQUID readout electronics

D. Drung, Colmar Hinnrichs, H.-J. Barthelmess

User-friendly ultra-high-speed readout electronics for dc superconducting quantum interference devices (SQUIDs) are presented. To maximize the system bandwidth, the SQUID is directly read out without flux modulation. A composite preamplifier is used consisting of a slow dc amplifier in parallel with a fast ac amplifier. In this way, excellent dc precision and a high amplifier bandwidth of 50 MHz are achieved, simultaneously. A virtual 50 Ω amplifier input resistance with negligible excess noise is realized by active shunting, i.e., by applying feedback from preamplifier output to input via a high resistance. The white voltage and current noise levels are 0.33 nV Hz −1 and 2.6 pA Hz −1/2 , respectively. The electronics is fully computer controlled via a microcontroller integrated into the flux-locked loop (FLL) board. Easy-to-use software makes the various electronic settings accessible. A wide bias voltage range of 1.3 mV enables the readout of series SQUID arrays. Furthermore, additional current sources allow the operation of two-stage SQUIDs or transition edge sensors. The electronics was tested using various SQUIDs with input inductances between 30 nH and 1.5 µH. Typically, the maximum FLL bandwidth was 20 MHz, which is close to the theoretical limit given by transmission line delay within the FLL. Slew rates of up to 4.6 Φ 0 µs −1 were achieved with series SQUID arrays. Current noise levels as low as 0.47 pA Hz −1/2 and coupled energy sensitivities between 90 h and 500 h were measured at 4.2 K, where h is the Planck constant. The noise did not degrade when the system bandwidth was increased to the maximum value of about 20 MHz. With a two-stage set-up, intrinsic white energy sensitivities of 30 h and 2.3 h were measured at 4.2 and 0.3 K, respectively.

Superconductor Science and Technology•Feb 27, 2006•72 citations

Development of low-noise two-stage dc-SQUID for TES detector readout

Nan Li, Mengjie Song, Sixiao Hu +9 more

Abstract Direct-current superconducting quantum interference devices (dc-SQUIDs) are one of the most sensitive magnetic detectors. These sensors are extensively used in the readout of superconducting transition edge sensors (TESs), which are used for the detection of weak signals. A cosmic microwave background (CMB) polarization telescope operating in 22–48 GHz is currently under developing. The TESs calorimeter of the telescope will be readout by a time-division multiplexer SQUID readout system. We develop a two-stage dc-SQUID amplifier circuit, comprising an input-stage SQUID with 4 SQUID cells and a series SQUID array with 100 SQUID cells. This configuration has been shown to achieve extremely high signal gain while effectively controlling system noise. We assess the system noise at 300 mK in an adiabatic demagnetization refrigerator. The measured magnetic flux noise of the two-stage SQUID circuit system is approximately 0.3 μ Φ 0 / Hz at 10 kHz. The current noise equivalent to the input coil of input SQUID is about 2.4 pA / Hz . This result meets the low-noise readout requirements of the CMB TES and other applications with TES detectors.

Superconductor Science and Technology•Apr 1, 2026•0 citations

Instabilities in SQUID Series Arrays due to the Internal and External Parasitics

Daniil Vili, M. Kiviranta

SQUID Series Arrays (SSAs) are widely used amplification devices for cryogenic readout chains such as Transition Edge Sensor (TES) matrices for space observation (Barrett et al., 2023) or quantum science (Hummatov et al., 2023). Either wiring-related external or on-chip internal parasitics often cause SSAs to show instabilities, which may limit the obtainable gain from a SSA design or may constrain the cryogenic setup that can be made stable for measurements. We shall show a rough model of typical parasitics in a setup and estimate the associated stability criteria. Modelling is backed up with experimental data from SSAs fabricated at VTT (M. Kiviranta et al., 2021) and operated at T = 4.2 K. In experiments the SSA has been augmented with a set of controlled external parasitic elements and the instability threshold observed. Results show correlation between simulations and experimental data, suggesting the SSAs to be prone to instabilities caused by internal and external parasitics.

IEEE Transactions on Applied Superconductivity•May 20, 2026•0 citations

A low-noise, two-stage DC SQUID amplifier with high bandwidth and dynamic range

R. Cantor, L. P. Lee, Andrei N. Matlashov +1 more

We describe a low-noise, two-stage dc Superconducting QUantum Interference Device (SQUID) amplifier that is designed for applications requiring high bandwidth and dynamic range. The output signal of a low-noise SQUID in the input stage coherently modulates a series array of identical SQUIDs in the output stage via a common modulation line. The input stage is designed so its output signal does not produce multiple modulation periods in the output stage. The output stage is designed to have sufficient gain so the output noise is dominated by the amplified noise of the input SQUID and exceeds the noise of a preamplifier in the room temperature readout electronics. The SQUID amplifier may therefore be operated without flux modulation or any impedance matching network, resulting in a large dynamic range and high bandwidth.

IEEE Transactions on Applied Superconductivity•Jun 1, 1997•11 citations
Biasing arrangements in multi-channel multi-stage SQUID amplifier systems, such as Transition Edge Sensor matrices for astronomical observation (Barrett et al., 2023) or quantum science (Hummatov et al., 2023), typically require a large number of wires. This is due to the need for two or more cascaded SQUID stages to obtain sufficiently large power gain over a sufficient bandwidth, and due to moderate obtainable multiplexing factors, which forces implementation of many parallel readout chains to serve all the sensor pixels. We suggest an arrangement where one bias line and one flux setpoint line are shared by two cascaded SQUID stages on a single chip, halving the number of lines two cascaded stages would ordinarily require. The stages are connected in series, sharing a single supplycurrent, dual to ordinary integrated transistor circuits in which many transistor stages are connected in parallel and share a single supplyvoltage. We show experimental results atT= 4.2 K for a proof-of-concept amplifier chip, fabricated in the VTT Micronova foundry, using SWAPS Josephson junctions (Grönberg et al., 2017) atJC= 20 μA/(μm)2critical current density. The device shows larger than 3 kΩ transresistance, when operating fromLIN= 29 nH input inductance toRD< 150 Ω output dynamic resistance.
A SQUID tandem is a two-stage amplifier consisting of the front end SQUID atTT∼ 4 K. We give an overview of the dc SQUID design for the tandem used in the recent 37-pixel frequency domain multiplexed (FDM) readout demonstration of X-ray calorimeters. The SQUID devices were fabricated with pillar-type Josephson junctions at the nominalJC= 500 A/cm2critical current density. We further discuss possible improvements to the FDM tandem configuration, including (i) the class-B operation for better power efficiency, (ii) the input power combiner as an improvement over the simple T-junction summing, with the promise for larger multiplexing factors, and (iii) the new booster SQUID device. The new improved booster is a 8-parallel 66-series SQUID array fabricated with SWAPS Josephson junctions at the nominal JC= 1.5 kA/cm2 critical current density, and it shows dV/dΦ > 30 mV/Φ0gain in the symmetric-slope operation, as well as ΦN≈ 0.05 μΦ0/ Hz1/2flux noise.
User-friendly ultra-high-speed readout electronics for dc superconducting quantum interference devices (SQUIDs) are presented. To maximize the system bandwidth, the SQUID is directly read out without flux modulation. A composite preamplifier is used consisting of a slow dc amplifier in parallel with a fast ac amplifier. In this way, excellent dc precision and a high amplifier bandwidth of 50 MHz are achieved, simultaneously. A virtual 50 Ω amplifier input resistance with negligible excess noise is realized by active shunting, i.e., by applying feedback from preamplifier output to input via a high resistance. The white voltage and current noise levels are 0.33 nV Hz −1 and 2.6 pA Hz −1/2 , respectively. The electronics is fully computer controlled via a microcontroller integrated into the flux-locked loop (FLL) board. Easy-to-use software makes the various electronic settings accessible. A wide bias voltage range of 1.3 mV enables the readout of series SQUID arrays. Furthermore, additional current sources allow the operation of two-stage SQUIDs or transition edge sensors. The electronics was tested using various SQUIDs with input inductances between 30 nH and 1.5 µH. Typically, the maximum FLL bandwidth was 20 MHz, which is close to the theoretical limit given by transmission line delay within the FLL. Slew rates of up to 4.6 Φ 0 µs −1 were achieved with series SQUID arrays. Current noise levels as low as 0.47 pA Hz −1/2 and coupled energy sensitivities between 90 h and 500 h were measured at 4.2 K, where h is the Planck constant. The noise did not degrade when the system bandwidth was increased to the maximum value of about 20 MHz. With a two-stage set-up, intrinsic white energy sensitivities of 30 h and 2.3 h were measured at 4.2 and 0.3 K, respectively.
Abstract Direct-current superconducting quantum interference devices (dc-SQUIDs) are one of the most sensitive magnetic detectors. These sensors are extensively used in the readout of superconducting transition edge sensors (TESs), which are used for the detection of weak signals. A cosmic microwave background (CMB) polarization telescope operating in 22–48 GHz is currently under developing. The TESs calorimeter of the telescope will be readout by a time-division multiplexer SQUID readout system. We develop a two-stage dc-SQUID amplifier circuit, comprising an input-stage SQUID with 4 SQUID cells and a series SQUID array with 100 SQUID cells. This configuration has been shown to achieve extremely high signal gain while effectively controlling system noise. We assess the system noise at 300 mK in an adiabatic demagnetization refrigerator. The measured magnetic flux noise of the two-stage SQUID circuit system is approximately 0.3 μ Φ 0 / Hz at 10 kHz. The current noise equivalent to the input coil of input SQUID is about 2.4 pA / Hz . This result meets the low-noise readout requirements of the CMB TES and other applications with TES detectors.
SQUID Series Arrays (SSAs) are widely used amplification devices for cryogenic readout chains such as Transition Edge Sensor (TES) matrices for space observation (Barrett et al., 2023) or quantum science (Hummatov et al., 2023). Either wiring-related external or on-chip internal parasitics often cause SSAs to show instabilities, which may limit the obtainable gain from a SSA design or may constrain the cryogenic setup that can be made stable for measurements. We shall show a rough model of typical parasitics in a setup and estimate the associated stability criteria. Modelling is backed up with experimental data from SSAs fabricated at VTT (M. Kiviranta et al., 2021) and operated at T = 4.2 K. In experiments the SSA has been augmented with a set of controlled external parasitic elements and the instability threshold observed. Results show correlation between simulations and experimental data, suggesting the SSAs to be prone to instabilities caused by internal and external parasitics.
We describe a low-noise, two-stage dc Superconducting QUantum Interference Device (SQUID) amplifier that is designed for applications requiring high bandwidth and dynamic range. The output signal of a low-noise SQUID in the input stage coherently modulates a series array of identical SQUIDs in the output stage via a common modulation line. The input stage is designed so its output signal does not produce multiple modulation periods in the output stage. The output stage is designed to have sufficient gain so the output noise is dominated by the amplified noise of the input SQUID and exceeds the noise of a preamplifier in the room temperature readout electronics. The SQUID amplifier may therefore be operated without flux modulation or any impedance matching network, resulting in a large dynamic range and high bandwidth.