标题： 磁场依赖的约瑟夫森行波参量放大器及其在高场设置中的集成 显示英文标题

标题： Magnetic-field dependence of a Josephson traveling-wave parametric amplifier and integration into a high-field setup

摘要： 我们研究了磁场对光子晶体约瑟夫森行波参量放大器（TWPA）的影响。 我们表明，观察到的TWPA光子带隙和等离子体频率的变化可以通过考虑由于弗劳恩霍夫效应导致的约瑟夫森结（JJs）临界电流的抑制以及超导能隙的关闭来建模。 考虑JJ的几何结构对于理解场依赖性至关重要。 在一个平面方向上，可以使用高达60 mT的磁场将TWPA带隙移动2 GHz，而不会损失增益或带宽，这表明没有SQUID的TWPAs可以进行磁场调谐。 在另一个平面方向上，磁场垂直于约瑟夫森结的较大边，因此弗劳恩霍夫效应的周期较小。 JJs的这个较大边被调制以产生带隙。 磁场与较大的结相互作用更强，因此随着磁场的增加，TWPA带隙会关闭并重新打开，导致TWPA在2 mT时就严重受损。 在垂直于平面的磁场下，发现稍高的工作极限为5 mT，此时TWPA的响应具有滞后性。 这些测量结果揭示了在需要样品处高磁场的实验中使用TWPAs所需的磁屏蔽要求；我们表明，通过磁屏蔽，可以在对样品施加超过2 T的情况下操作TWPA。 显示英文摘要

摘要： We investigate the effect of magnetic field on a photonic-crystal Josephson traveling-wave parametric amplifier (TWPA). We show that the observed change in photonic bandgap and plasma frequency of the TWPA can be modeled by considering the suppression of the critical current in the Josephson junctions (JJs) of the TWPA due to the Fraunhofer effect and closing of the superconducting gap. Accounting for the JJ geometry is crucial for understanding the field dependence. In one in-plane direction, the TWPA bandgap can be shifted by 2 GHz using up to 60 mT of field, without losing gain or bandwidth, showing that TWPAs without SQUIDs can be field tunable. In the other in-plane direction, the magnetic field is perpendicular to the larger side of the Josephson junctions, so the Fraunhofer effect has a smaller period. This larger side of the JJs is modulated to create the bandgap. The field interacts more strongly with the larger junctions, and as a result, the TWPA bandgap closes and reopens as the field increases, causing the TWPA to become severely compromised already at 2 mT. A slightly higher operating limit of 5 mT is found in out-of-plane field, for which the TWPA's response is hysteretic. These measurements reveal the requirements for magnetic shielding needed to use TWPAs in experiments where high fields at the sample are required; we show that with magnetic shields we can operate the TWPA while applying over 2 T to the sample.