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

Study of the Flux-to-Voltage Characteristics of DC SQUID With a Small Screening Parameter and a Large Stewart-McCumber Parameter

Bao Wu, Hai Wang, Zhidan Zhang, Meiling Wang, Xiangyan Kong

Published Aug 12, 2021• 3 citations
Publisher

Abstract

It is known that SQUID has three important parameters, namely, Stewart-McCumber parameterβC, Screening parameterβLand thermal noise parameterΓ. They play a very important role in SQUID performance, especiallyβC. Recently, researchers extended the SQUID operating area toβc > 1 due to a large noise parameterΓin experiments. WhenβC> 1, SQUID exhibits a large flux-voltage transfer coefficient∂V/∂Φ, which is beneficial in reducing the noise contribution of the readout circuitδΦe. From the simulation results, we found that whenβC>1, SQUID produces a larger∂V/∂Φ thanβC∂V/∂Φ increases with the decrease ofβL. In order to further verify our findings, we selected two groups of SQUIDs for experiments (βCβC> 1), by changing the value of the shunt resistance on the Josephson junction to adjust the value of changingβC, and then we observe the value of∂V/∂Φ. Finally, we find that whenβL∂V/∂Φ of SQUID increases whileβCincreasing. A large∂V/∂Φ will help us to obtain an optimal SQUID measure system.

DOI
10.1109/tasc.2021.3103726

Related papers

Dependence of SQUID Intrinsic Flux Noise on Stewart–McCumber Parameter $\beta_{c}$ of Josephson Junction

Hai Wang, Yongliang Wang, Xiangyan Kong +3 more

It is known that three superconducting quantum interference device (SQUID) parameters, namely, the intrinsic flux noise δΦs, the flux-to-voltage transfer coefficient ∂V/∂Φ, and the dynamic resistance Rd, increase with increasing the Stewart- McCumber parameter βcof Josephson junction. It is very difficult to obtain the low values of δΦsfor a strongly damped SQUID due to its small ∂V/∂Φ. In this paper, we employ a two-stage scheme (TSS) to measure δΦsdirectly. Here, we use single chip readout electronics and a weakly damped SQUID with a βcof flux noise of the readout-SQUID system is about 4.8 μΦ0/√Hz 1.2, both acting as a readout-SQUID system (a preamplifier). The with a corner frequency of about 10 Hz. The front-end SQUID is coupled to the readout SQUID via the input coil with a mutual inductance of Mi. In our experiment, the flux gain for a readout SQUID, i.e., GΦ= Mi× (∂I/∂Φ)front-endis adjusted to be 20. Using the TSS, we measured δΦswith different βcchanging from 0.3 to 13.5 and found δΦsincreasing from 1.0 to 5.0 μΦ0/√Hz. We also discussed the relations between Ls, βc, and δΦsquantitatively. Finally, we proposed designing a suitable βcto match the preamplifier in a direct readout scheme to simplify a SQUID measurement system.

IEEE Transactions on Applied Superconductivity•May 12, 2016•4 citations

Experimental Study of Noise Characteristics of Large-β dc SQUID with Resistively Shunted Inductance

Satoshi Kohjiro, Keiji Enpuku, Keiji Yoshida +1 more

Noise characteristics of dc SQUIDs in large β regimes have been studied experimentally in the case when a SQUID inductance is resistively shunted. Here, β=2L I 0/Φ0 is the modulation parameter, L is the SQUID inductance, I 0 is the critical current of the Josephson junction and Φ0 is the flux quantum. It is shown experimentally that the performance of the SQUID does not degrade significantly even for large β values; for example, the minimum energy resolution of the SQUID is as small as ε=25h and the flux region where ε<50h is as wide as 0.1Φ0, even for the case β=12, where h is the Planck constant. The experimental results agree quantitatively with the theoretical ones.

Japanese Journal of Applied Physics•Oct 1, 1988•8 citations

Conversion Efficiency of a Large-β DC-SQUID with a Resistively Shunted Inductance

Satoshi Kohjiro, Keiji Enpuku, Keiji Yoshida +1 more

The conversion efficiency between a signal magnetic flux and the output power of a large-β dc SQUID, i.e., a SQUID with a modulation parameter β larger than unity, have been studied theoretically. In our investigation the inductance of the SQUID was shunted by using a damping resistor. The dependence of the output power on such SQUID parameters as β, the McCumber parameter βc and the damping parameter γ=R s /R d (R s and R d are the shunt and the damping resistances, respectively) was investigated in detail. It has been shown that an order-of-magnitude increase in the output power can be realized with a large-β SQUID without a degradation of noise characteristics, compared with the case of β=1. It has also been shown that the values of βc=0.4 and γ=1 are optimum with regard to a large output power and a low-noise operation of the SQUID.

Japanese Journal of Applied Physics•Feb 1, 1988•6 citations

Study on Noise Matching Between SQUID Sensor and Its Readout Electronics

Hai Wang, Hua Chen, Xiangyan Kong +3 more

Noise matching between superconducting quantum interference device (SQUID) sensor and readout electronics has always been an important problem. Conventionally, in order to avoid the hysteresis, SQUIDs should be operated in the range of βccis the Stewart-McCumber parameter. Recently, Liu et al. extended the SQUID operating area to βc > 1 due to a large noise parameter Γ*. When βc> 1, SQUID exhibits a large ∂V/∂Φ, which is beneficial in reducing the noise contribution of the readout electronics, δΦe. In this work, we compare the SQUID system noise δΦsmeasured with four different readout electronics. Here, the four readout electronics employed are as follows: 1) the flux modulation scheme (FMS); 2) the direct readout scheme (DRS), which uses six parallel connected bipolar transistor as its preamplifier (DRS-PCBT); 3) the DRS, which uses a single preamplifier AD797 (DRS-AD797); and 4) the two-stage scheme. The preamplifier voltage noise of DRS-PCBT and DRS-AD797 are about 0.4 nV/√Hz and 0.9 nV/√Hz, respectively. For a two-stage scheme, the equivalent flux noise reaches about 0.25 μΦ0/√Hz, the measured SQUID intrinsic noise, δΦi, will dominate δΦs. In other readout schemes, however, δΦsdepends on the value of βc. Finally, we found that FMS is suitable to match SQUIDs with βccc> 3.

IEEE Transactions on Applied Superconductivity•Nov 30, 2016•4 citations

Noise characteristics of a dc SQUID with a resistively shunted inductance

Keiji Enpuku, T. Muta, Keiji Yoshida +1 more

Noise characteristics of a dc SQUID with an inductance shunted by a damping resistance are studied numerically. It is shown that the damping resistance improves considerably the resolution of the SQUID in the case of large β, where β=2LI0/Φ0, I0 is a critical current, L is a loop inductance and Φ0 is the flux quantum. The energy resolutions for β=4 and β=10 are only about 2 and 4 times larger than that for β=1, respectively. Furthermore, the ranges of both the bias current and the external flux, where good resolution is obtained, become very wide compared with the conventional SQUID. Therefore, the SQUID with the damping resistance can be used for large β (or L) without the significant degradation of the resolution, and will much improve the coupling properties between the SQUID and the input circuitry. The numerical simulation results are also compared with analytical ones, and a reasonable agreement is obtained.

Journal of Applied Physics•Sep 1, 1985•43 citations

An insight into voltage-biased superconducting quantum interference devices

Chao Liu, Yi Zhang, Michael Mück +5 more

We experimentally studied two important parameters of helium-cooled superconducting quantum interference devices (SQUIDs) in the voltage bias mode: the dynamic resistance Rd and the flux-to-current transfer coefficient ∂i/∂Φ, with different junction shunt resistors RJ. We investigated a voltage-biased SQUID using the direct readout current-to-voltage converter scheme involving an operational amplifier. At higher RJ, the flux-to-voltage conversion coefficient ∂V/∂Φ becomes sufficiently large to effectively suppress the room-temperature amplifier's noise without any need for additional feedback circuits. The McCumber parameter limits the rise of ∂V/∂Φ. We discuss the performance of voltage-biased SQUIDs at different effective McCumber parameters.

Applied Physics Letters•Nov 26, 2012•20 citations
It is known that SQUID has three important parameters, namely, Stewart-McCumber parameterβC, Screening parameterβLand thermal noise parameterΓ. They play a very important role in SQUID performance, especiallyβC. Recently, researchers extended the SQUID operating area toβc > 1 due to a large noise parameterΓin experiments. WhenβC> 1, SQUID exhibits a large flux-voltage transfer coefficient∂V/∂Φ, which is beneficial in reducing the noise contribution of the readout circuitδΦe. From the simulation results, we found that whenβC>1, SQUID produces a larger∂V/∂Φ thanβC∂V/∂Φ increases with the decrease ofβL. In order to further verify our findings, we selected two groups of SQUIDs for experiments (βCβC> 1), by changing the value of the shunt resistance on the Josephson junction to adjust the value of changingβC, and then we observe the value of∂V/∂Φ. Finally, we find that whenβL∂V/∂Φ of SQUID increases whileβCincreasing. A large∂V/∂Φ will help us to obtain an optimal SQUID measure system.
Dependence of SQUID Intrinsic Flux Noise on Stewart–McCumber Parameter βc\beta_{c}βc​ of Josephson Junction
It is known that three superconducting quantum interference device (SQUID) parameters, namely, the intrinsic flux noise δΦs, the flux-to-voltage transfer coefficient ∂V/∂Φ, and the dynamic resistance Rd, increase with increasing the Stewart- McCumber parameter βcof Josephson junction. It is very difficult to obtain the low values of δΦsfor a strongly damped SQUID due to its small ∂V/∂Φ. In this paper, we employ a two-stage scheme (TSS) to measure δΦsdirectly. Here, we use single chip readout electronics and a weakly damped SQUID with a βcof flux noise of the readout-SQUID system is about 4.8 μΦ0/√Hz 1.2, both acting as a readout-SQUID system (a preamplifier). The with a corner frequency of about 10 Hz. The front-end SQUID is coupled to the readout SQUID via the input coil with a mutual inductance of Mi. In our experiment, the flux gain for a readout SQUID, i.e., GΦ= Mi× (∂I/∂Φ)front-endis adjusted to be 20. Using the TSS, we measured δΦswith different βcchanging from 0.3 to 13.5 and found δΦsincreasing from 1.0 to 5.0 μΦ0/√Hz. We also discussed the relations between Ls, βc, and δΦsquantitatively. Finally, we proposed designing a suitable βcto match the preamplifier in a direct readout scheme to simplify a SQUID measurement system.
Noise characteristics of dc SQUIDs in large β regimes have been studied experimentally in the case when a SQUID inductance is resistively shunted. Here, β=2L I 0/Φ0 is the modulation parameter, L is the SQUID inductance, I 0 is the critical current of the Josephson junction and Φ0 is the flux quantum. It is shown experimentally that the performance of the SQUID does not degrade significantly even for large β values; for example, the minimum energy resolution of the SQUID is as small as ε=25h and the flux region where ε<50h is as wide as 0.1Φ0, even for the case β=12, where h is the Planck constant. The experimental results agree quantitatively with the theoretical ones.
The conversion efficiency between a signal magnetic flux and the output power of a large-β dc SQUID, i.e., a SQUID with a modulation parameter β larger than unity, have been studied theoretically. In our investigation the inductance of the SQUID was shunted by using a damping resistor. The dependence of the output power on such SQUID parameters as β, the McCumber parameter βc and the damping parameter γ=R s /R d (R s and R d are the shunt and the damping resistances, respectively) was investigated in detail. It has been shown that an order-of-magnitude increase in the output power can be realized with a large-β SQUID without a degradation of noise characteristics, compared with the case of β=1. It has also been shown that the values of βc=0.4 and γ=1 are optimum with regard to a large output power and a low-noise operation of the SQUID.
Noise matching between superconducting quantum interference device (SQUID) sensor and readout electronics has always been an important problem. Conventionally, in order to avoid the hysteresis, SQUIDs should be operated in the range of βccis the Stewart-McCumber parameter. Recently, Liu et al. extended the SQUID operating area to βc > 1 due to a large noise parameter Γ*. When βc> 1, SQUID exhibits a large ∂V/∂Φ, which is beneficial in reducing the noise contribution of the readout electronics, δΦe. In this work, we compare the SQUID system noise δΦsmeasured with four different readout electronics. Here, the four readout electronics employed are as follows: 1) the flux modulation scheme (FMS); 2) the direct readout scheme (DRS), which uses six parallel connected bipolar transistor as its preamplifier (DRS-PCBT); 3) the DRS, which uses a single preamplifier AD797 (DRS-AD797); and 4) the two-stage scheme. The preamplifier voltage noise of DRS-PCBT and DRS-AD797 are about 0.4 nV/√Hz and 0.9 nV/√Hz, respectively. For a two-stage scheme, the equivalent flux noise reaches about 0.25 μΦ0/√Hz, the measured SQUID intrinsic noise, δΦi, will dominate δΦs. In other readout schemes, however, δΦsdepends on the value of βc. Finally, we found that FMS is suitable to match SQUIDs with βccc> 3.
Noise characteristics of a dc SQUID with an inductance shunted by a damping resistance are studied numerically. It is shown that the damping resistance improves considerably the resolution of the SQUID in the case of large β, where β=2LI0/Φ0, I0 is a critical current, L is a loop inductance and Φ0 is the flux quantum. The energy resolutions for β=4 and β=10 are only about 2 and 4 times larger than that for β=1, respectively. Furthermore, the ranges of both the bias current and the external flux, where good resolution is obtained, become very wide compared with the conventional SQUID. Therefore, the SQUID with the damping resistance can be used for large β (or L) without the significant degradation of the resolution, and will much improve the coupling properties between the SQUID and the input circuitry. The numerical simulation results are also compared with analytical ones, and a reasonable agreement is obtained.
We experimentally studied two important parameters of helium-cooled superconducting quantum interference devices (SQUIDs) in the voltage bias mode: the dynamic resistance Rd and the flux-to-current transfer coefficient ∂i/∂Φ, with different junction shunt resistors RJ. We investigated a voltage-biased SQUID using the direct readout current-to-voltage converter scheme involving an operational amplifier. At higher RJ, the flux-to-voltage conversion coefficient ∂V/∂Φ becomes sufficiently large to effectively suppress the room-temperature amplifier's noise without any need for additional feedback circuits. The McCumber parameter limits the rise of ∂V/∂Φ. We discuss the performance of voltage-biased SQUIDs at different effective McCumber parameters.