基于rf-SQUID的行波参量放大器：在超过一个倍频程带宽内具有-84 dBm输入饱和功率
An rf-SQUID-based traveling-wave parametric amplifier with -84 dBm input saturation power across more than one octave bandwidth
AI总结：
本文实现了一种基于rf-SQUID的行波参量放大器，在3.5-8.5 GHz带宽内获得20 dB增益和-84 dBm饱和功率，比先前工作高十倍，并测得额外噪声为0.8-1.5光子。
摘要：
行波参量放大器（TWPAs）已成为量子电路读出和暗物质搜寻的重要工具。我们报道了一种基于rf-SQUID的约瑟夫森行波参量放大器的实现，其平均饱和功率为-84 dBm，同时在3.5至8.5 GHz频率范围内提供20 dB的平均功率增益。这一宽带宽是通过降低信号频带内色散的曲率并抑制有害的混频过程实现的。我们的器件包含2393个rf-SQUID，具有与先前工作相当数量的非线性元件，但饱和功率却高出十倍，这表明使用rf-SQUID可以在器件长度和饱和功率之间实现更有利的权衡。利用宽带表征技术，我们测得该TWPA在量子极限以上的额外噪声为0.8至1.5个光子。此外，我们验证了信噪比改善作为调谐TWPA以最小化总系统噪声的实际度量，并证明其最优值并不与最高增益重合。
英文摘要：
Traveling-wave parametric amplifiers (TWPAs) have become an essential tool for the readout of quantum circuits and the search for dark matter. We report on the implementation of an rf-SQUID-based Josephson TWPA with an average saturation power of -84 dBm, while providing an average power gain of 20 dB from 3.5 to 8.5 GHz. This wide bandwidth is enabled by reducing the curvature of the dispersion in the signal band while suppressing detrimental mixing processes. With 2393 rf-SQUIDs our device has a comparable number of nonlinear elements, but achieves ten times higher saturation power than previous works, showing that using rf-SQUIDs results in a more favorable trade-off between device length and saturation power. Harnessing wideband characterization techniques we determine the TWPA's excess noise above the quantum limit to be 0.8 to 1.5 photons. In addition, we validate signal-to-noise ratio improvement as a practical measure for tuning the TWPA to minimize the total system noise, and demonstrate that its optimum does not coincide with the highest gain.
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