Fabrication of the Impedance-Matched Josephson Parametric Amplifier and the Study of the Gain Profile

Abstract

We designed and fabricated an impedance matched Josephson junction parametric amplifier (JPA) working in the flux-pump mode for the broadband amplification of microwave signals. We developed a very simple fabrication method suitable for a small lab. We studied the phase response, as well as the gain, as a function of frequency and pump power at various pump frequencies. The phase response can be explained with the behavior of the non-linear Duffing oscillator. The observed decrease of the resonance frequency as the pump power increases, as well as the emergency of an unstable bifurcation zone, are the characteristic non-linear behavior of the Duffing oscillator. The gain profile in the stable zone can be explained with a model adapted from the theoretical model for the two-dimensional gain profile of an impedance-matched current-pumped JPA. With an appropriate environmental impedance, the theoretical model captures the features and morphology of the gain profile, such as the emergence of a gain hot zone with two branches around the resonance frequency of the JPA. Based on the gain profile, we propose that the best working zone is the merging point of the two branches of the gain hot zone before the emergence of the bifurcation zone, which gives a large bandwidth and a good gain. Over 17dB gain with a bandwidth larger than 300MHz was observed. The impedance matched JPA is used in our experiments for improving the fast readout fidelity of the transmon qubits.

A Sub-GHz Impedance-Engineered Parametric Amplifier for the Readout of Sensors and Quantum Dots

“…In contrast with the TWPA, our JPA is relatively simple to fabricate: the estimated JJ count is 1-2 orders of magnitude lower. We demonstrate that a lower quality factor of the JPA resonator [19], [20] and an external impedance transformer [21]- [23] help us achieve five times and 50 times larger bandwidth, respectively, than our previous JPA at 600 MHz [10]. We measure a −3 dB bandwidth of 10 MHz at 20 dB gain, which also improves upon the recent achievement of a 6-MHz JPA bandwidth for the readout of a silicon quantum dot at 622 MHz [7].…”

Compact superconducting microwave resonators based on Al-AlOx-Al capacitor

“…The method facilitates fast and affordable fabrication recipes and reduces the complexity of the total fabrication. Our results show the possible applications of such PPC capacitors in compact resonators for qubit readout, impedance matched [23] or travelling-wave [24] JPAs, compact Purcell filters [25], kinetic inductance detectors [26] and superconducting metamaterials. This technology paves the way for the miniaturization of essential on-chip components.…”

Recent progress of superconducting electronics in China

“…2015年, 加州大学伯克利分校和麻省理工学院联 合开发了基于约瑟夫森结的行波参量放大器 [201] , 纠缠态 [200] . 2016年起, 清华大学使用参量放大器 实现超导量子比特单发测量, 并应用于各种超导量 子信息实验中 [202] . 已报道的文献中, 物理所、中科 大、浙江大学联合团队实现了阻抗变化的参量放大 器, 放大器带宽约300-400 MHz [203,204] .…”