An easily-prepared impedance matched Josephson parametric amplifier

An impedance matched parametric amplifier(IMPA)with Josephson junctions is fabricated and characterized.A hybrid structure containing coplanar and strip structures is implemented to realize an impedance taper line and a plate capacitor in an LC nonlinear resonator based on Josephson junctions.The upper plate of the capacitor is isolated with SiNx without grounding as well as the strips.Such easily-prepared designs greatly reduce the requirements for lithography alignment and precision,which makes the fabrication process more reliable.The experimental results show that in such IMPA a gain higher than 25 dB with a bandwidth of about 100 MHz can be obtained.This broadband amplifier operates close to the quantum limit.By adjusting the working point,a higher bandwidth of about 400 MHz can be obtained with a gain of about 17 dB.

基于FPGA的微波相干源线性检测和特性表征

微波光子的检测和表征对于量子信息具有重要意义。通常使用Hanbury Brown-Twiss(HBT)干涉仪对光子源性质进行检测和表征,然而,由于微波光子信噪比较低,在对其进行检测和表征过程中常常需要多次计算才能移除噪声影响。本工作基于现场可编程门阵列(FPGA),提出一种快速、可扩展的测量方案用于分析微波光子源性质,可更快速地实现该计算过程。利用该方案对频率为3 MHz的相干源进行了模拟测量,分析了二阶相关函数所具有的特性,发现测量结果与理论具有良好的一致性。该系统的实现对未来进行单光子源检测具有重要意义。