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IEEE Transactions on Applied Superconductivity

Noise Performance Comparison Between Current- and Voltage-Bias Readout Schemes for DC SQUID

Yongliang Wang, Guofeng Zhang, Shulin Zhang

Published Aug 24, 2021• 3 citations
Publisher

Abstract

There are two bias schemes, namely current-bias and voltage-bias, for the directly coupled readout circuit of direct current superconducting quantum interference device (dc SQUID). In order to find out the difference between two bias schemes, we present the theoretical analyses on their equivalent circuits, working point locations, and noise performances. The theoretical analysis and experimental validation prove that the voltage-bias scheme achieves a larger transfer coefficient and exhibits a better noise performance than the current-bias scheme in the reading of conventional dc SQUID.

DOI
10.1109/tasc.2021.3107326

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We propose a readout scheme for high-T c dc-SQUIDs (superconducting quantum interference devices) with alternating current bias and synchronized offset flux. By use of this scheme, low-frequency noise due to critical current fluctuations, which exist in grain boundary junctions, can be canceled. The readout electronics are simple and operation parameters requiring adjustment are minimized. The ac bias scheme has been applied to YBCO step-junction SQUIDs, where partial reduction of the equivalent flux noise below 100 Hz is observed.
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