Presentation Information
[ED7-03]Design of a Traveling-Wave Parametric Amplifier with a π-Josephson Junction
*Shuyuan Cui1, Daiki Fukuyo1, Hiroshi Shimada1, Yoshinao Mizugaki1 (1. The University of Electro-Communications (Japan))
Keywords:
Josephson Traveling-Wave Parametric Amplifier,π-Josephson Junction,Superconducting Quantum Interference Device
[Purpose]
A Josephson traveling-wave parametric amplifier (JTWPA) is indispensable for the high-fidelity readout of superconducting qubits, owing to their broadband gain and near-quantum-limited noise performance. However, conventional designs (0-JTWPA) require a significant external flux bias to tune nonlinearity and achieve phase matching, which complicates cryogenic hardware, introduces sensitivity to flux noise, and limits scalability in large arrays. The purpose of this study is to develop a π-junction-based JTWPA (π-JTWPA) that intrinsically shifts the operating point, thereby reducing the required flux bias while preserving broadband amplification. This approach aims to simplify flux-bias distribution, enhance stability against flux noise, and provide a pathway toward scalable, multiplexed quantum readout architectures.
[Method]
We propose a π-junction JTWPA (π-JTWPA) that exploits the intrinsic π-phase shift of π-Josephson junctions. A 1,500-cell circuit with π-junction rf-SQUID unit cells and shunt capacitors was modeled using the JoSIM simulator to evaluate gain characteristics.
[Results]
Time-domain simulations show that with a small flux-bias current of 1 µA (0.04 Φ0), a pump of −64 dBm at 12.4 GHz and a signal of −113 dBm provide ≧12 dB gain over 2.1–10 GHz with a peak gain of 31 dB. In contrast, a conventional 0-JTWPA with identical parameters requires 13.3 μA (0.54 Φ0) flux bias for similar performance.
[Consideration]
The π-junction approach reduces flux-bias current by 0.50 Φ0, simplifying flux distribution in large arrays and simplifying integration in multiplexed readout systems. Future work will focus on designing and validating a flux-bias-free π-JTWPA.
A Josephson traveling-wave parametric amplifier (JTWPA) is indispensable for the high-fidelity readout of superconducting qubits, owing to their broadband gain and near-quantum-limited noise performance. However, conventional designs (0-JTWPA) require a significant external flux bias to tune nonlinearity and achieve phase matching, which complicates cryogenic hardware, introduces sensitivity to flux noise, and limits scalability in large arrays. The purpose of this study is to develop a π-junction-based JTWPA (π-JTWPA) that intrinsically shifts the operating point, thereby reducing the required flux bias while preserving broadband amplification. This approach aims to simplify flux-bias distribution, enhance stability against flux noise, and provide a pathway toward scalable, multiplexed quantum readout architectures.
[Method]
We propose a π-junction JTWPA (π-JTWPA) that exploits the intrinsic π-phase shift of π-Josephson junctions. A 1,500-cell circuit with π-junction rf-SQUID unit cells and shunt capacitors was modeled using the JoSIM simulator to evaluate gain characteristics.
[Results]
Time-domain simulations show that with a small flux-bias current of 1 µA (0.04 Φ0), a pump of −64 dBm at 12.4 GHz and a signal of −113 dBm provide ≧12 dB gain over 2.1–10 GHz with a peak gain of 31 dB. In contrast, a conventional 0-JTWPA with identical parameters requires 13.3 μA (0.54 Φ0) flux bias for similar performance.
[Consideration]
The π-junction approach reduces flux-bias current by 0.50 Φ0, simplifying flux distribution in large arrays and simplifying integration in multiplexed readout systems. Future work will focus on designing and validating a flux-bias-free π-JTWPA.