标题： 皮秒约瑟夫森采样器：建模与测量 显示英文标题

标题： Picosecond Josephson Samplers: Modeling and Measurements

摘要： 超导约瑟夫森结(JJ)电路产生的信号的测量需要位于生成电路附近且具有超高速特性的元件。 我们报告了对基于JJ的采样器最优设计准则的详细研究，该准则在最高采样带宽（最短10%--90%上升时间）与最小采样波形失真之间取得平衡。 我们探讨了使用单个欠阻尼JJ作为逻辑采样元件（比较器）实现的采样器性能受所采用的信号-比较器耦合方案类型（欧姆、电感或电容）的影响。 在这些仿真中，我们通过比较器阈值检测模拟整个波形重建采样过程，同时扫描波形被采样的时间位置。 我们提取采样波形的上升时间（或FWHM）作为比较器的Stewart-McCumber参数的函数，以及作为被测器件与比较器之间耦合强度的函数。 根据我们的仿真结果，我们设计、制造并表征了一个低温冷却（3.6 K工作温度）的JJ采样器，该采样器利用了NIST最先进的Nb/非晶硅/Nb结。 我们通过在采样器运行期间实施与仿真中相同的二进制搜索比较器阈值检测技术，分别对与比较器和采样触发发生器在同一芯片上的阶跃信号和脉冲发生器进行采样。 通过此技术，系统是全数字和自动化的，制造设备的操作直接反映仿真结果。 我们的采样器技术显示10%--90%上升时间为3.3 ps，并能够测量2.5 ps FWHM的瞬态脉冲宽度。 对采样波形的线性系统分析表明3 dB带宽为225 GHz，但我们证明了对高于此频率的信号的有效测量——高达600 GHz。 显示英文摘要

摘要： Measurement of signals generated by superconducting Josephson junction (JJ) circuits require ultra-fast components located in close proximity to the generating circuitry. We report a detailed study of optimal design criteria for a JJ-based sampler which balances the highest sampler bandwidth (shortest 10\%--90\% rise time) with minimal sampled waveform distortion. We explore the impacts on performance of a sampler, realized using a single underdamped JJ as the logical sampling element (the comparator), due to the type of signal-comparator coupling scheme that is utilized (galvanic, inductive, or capacitive). In these simulations we emulate the entire waveform reconstruction sampling process, via comparator threshold detection, while sweeping the time location at which the waveform is being sampled. We extract the sampled waveform rise time (or FWHM) as a function of the comparator's Stewart-McCumber parameter and as a function of the coupling strength between the device under test and comparator. Based on our simulation results we design, fabricate, and characterize a cryocooled (3.6 K operating temperature) JJ sampler utilizing the NIST state-of-the-art Nb/amorphous-Si/Nb junctions. We separately sample a step signal and impulse generator co-located on-chip with the comparator and sampling strobe generator by implementing the same binary search comparator threshold detection technique during sampler operation as is used in simulation. With this technique the system is fully-digital and automated and operation of the fabricated device directly mirrors simulation. Our sampler technology shows a 10\%--90\% rise time of 3.3 ps and the capability to measure transient pulse widths of 2.5 ps FWHM. A linear systems analysis of sampled waveforms indicate a 3 dB bandwidth of 225 GHz, but we demonstrate effective measurement of signals well above this -- as high as 600 GHz.