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Chinese Physics B

Design and characterization of an SQUID microwave amplifier with impedance transformers

Junhao Hou, Liliang Ying, Wei 炜 Peng 彭, Wentao Wu, Zhirong Lin

Published Oct 28, 2025• 0 citations
Publisher

Abstract

Abstract High-performance cryogenic amplifiers are essential components for quantum information technology and astronomical observation. In this work, we report the design and characterization of a microwave amplifier based on a superconducting quantum interference device (SQUID). The design incorporates input and output impedance transformers to center the operating frequency at approximately 5.5 GHz for specific applications. Preliminary characterization at a bath temperature of 4.2 K demonstrates a peak gain of 10.79 dB at 5.39 GHz and a saturation power of approximately −115 dBm.

DOI
10.1088/1674-1056/ae1819

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Abstract High-performance cryogenic amplifiers are essential components for quantum information technology and astronomical observation. In this work, we report the design and characterization of a microwave amplifier based on a superconducting quantum interference device (SQUID). The design incorporates input and output impedance transformers to center the operating frequency at approximately 5.5 GHz for specific applications. Preliminary characterization at a bath temperature of 4.2 K demonstrates a peak gain of 10.79 dB at 5.39 GHz and a saturation power of approximately −115 dBm.
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Due to their superior noise performance, superconducting quantum interference devices (SQUIDs) are an attractive alternative to high electron mobility transistors for constructing ultra-low-noise microwave amplifiers for cryogenic use. We describe the use of a lumped element SQUID inductively coupled to a quarter wave resonator. The resonator acts as an impedance transformer and also makes it possible to accurately measure the input impedance and intrinsic microwave characteristics of the SQUID. We present a model for input impedance and gain, compare it to the measured scattering parameters, and describe how to use the model for the systematic design of low-noise microwave amplifiers with a wide range of performance characteristics.
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