对已有的Z变换时域有限差分法(Z-transformation Finite Difference Time Domain,Z-FDTD)在电磁波与非均匀磁化等离子体中的传输特性分析的计算误差问题进行了研究,并探讨了一种修正计算误差的Z变换时域有限差分方法(Modified Z-transfo...对已有的Z变换时域有限差分法(Z-transformation Finite Difference Time Domain,Z-FDTD)在电磁波与非均匀磁化等离子体中的传输特性分析的计算误差问题进行了研究,并探讨了一种修正计算误差的Z变换时域有限差分方法(Modified Z-transform Finite Difference Time Domain,MZ-FDTD),以提升Z-FDTD方法对非均匀磁化等离子体的适用性。对MZ-FDTD和Z-FDTD之间的计算误差问题,通过严格的公式推导求得该误差的计算公式,并引入误差分析因子,对比分析了该误差受空间步长和非均匀磁化等离子体的物理特性的影响特征,在充分的误差分析与网格参数对比后,以电磁波在非均匀磁化等离子体中的传输特性为分析目标,举例说明了MZ-FDTD的优越性。研究结果表明,相比于经典Z-FDTD,通过MZ-FDTD方法计算得到的数值结果具有更高的计算准确度,较低的运行时间和较少的运行内存占用。此外,对电磁波在非均匀等离子体中传输特性分析的举例说明也证明了相比于Z-FDTD,优化的Z-FDTD方法无论是在较低频段还是较高频段都保持较好的稳定性。在今后的工作中,使用MZ-FDTD方法研究非均匀磁化等离子体问题将会获得更好的计算结果,这项工作中的误差分析方法也将对某些计算电磁学在等离子体中的应用与优化工作起到一定的帮助作用。展开更多
An analysis of a 3 dB lumped-element directional coupler （LEDC） based on arbitrary terminal impedance is described numerically. To solve the conflicted requirement for broad bandwidth and small size in LEDC, a new s...An analysis of a 3 dB lumped-element directional coupler （LEDC） based on arbitrary terminal impedance is described numerically. To solve the conflicted requirement for broad bandwidth and small size in LEDC, a new structure of coupler is introduced, which can significantly improve bandwidth and whose size is only 3 cm×4 cm on the conditions of the frequency domain of 410 MHz to 490 MHz. The measure results are in good agreement with simulations despite the unexpected resistor loss.展开更多
Josephson parametric amplifiers (JPAs) with nearly quantum-limited noise performance have become indispensable devices for the measurements of superconducting quantum information. We have developed an all-Nb lumped-el...Josephson parametric amplifiers (JPAs) with nearly quantum-limited noise performance have become indispensable devices for the measurements of superconducting quantum information. We have developed an all-Nb lumped-element flux-driven JPA operating in the three-wave mixing mode. Our Nb-based JPA comprises Nb/Al-AlOx/Nb Josephson junctions, a parallel-plate capacitor with SiO2 dielectric sandwiched between two Nb layers, a bottom coplanar waveguides layer, and a top Nb wiring layer. We experimentally demonstrate a 20 dB gain over a 190 MHz bandwidth, a mean 1 dB compression of -123 dBm, and near quantum-limited noise performance. This fabrication process can be further used to design impedance transformed parametric amplifiers for multiple-qubit readout.展开更多
文摘对已有的Z变换时域有限差分法(Z-transformation Finite Difference Time Domain,Z-FDTD)在电磁波与非均匀磁化等离子体中的传输特性分析的计算误差问题进行了研究,并探讨了一种修正计算误差的Z变换时域有限差分方法(Modified Z-transform Finite Difference Time Domain,MZ-FDTD),以提升Z-FDTD方法对非均匀磁化等离子体的适用性。对MZ-FDTD和Z-FDTD之间的计算误差问题,通过严格的公式推导求得该误差的计算公式,并引入误差分析因子,对比分析了该误差受空间步长和非均匀磁化等离子体的物理特性的影响特征,在充分的误差分析与网格参数对比后,以电磁波在非均匀磁化等离子体中的传输特性为分析目标,举例说明了MZ-FDTD的优越性。研究结果表明,相比于经典Z-FDTD,通过MZ-FDTD方法计算得到的数值结果具有更高的计算准确度,较低的运行时间和较少的运行内存占用。此外,对电磁波在非均匀等离子体中传输特性分析的举例说明也证明了相比于Z-FDTD,优化的Z-FDTD方法无论是在较低频段还是较高频段都保持较好的稳定性。在今后的工作中,使用MZ-FDTD方法研究非均匀磁化等离子体问题将会获得更好的计算结果,这项工作中的误差分析方法也将对某些计算电磁学在等离子体中的应用与优化工作起到一定的帮助作用。
文摘An analysis of a 3 dB lumped-element directional coupler （LEDC） based on arbitrary terminal impedance is described numerically. To solve the conflicted requirement for broad bandwidth and small size in LEDC, a new structure of coupler is introduced, which can significantly improve bandwidth and whose size is only 3 cm×4 cm on the conditions of the frequency domain of 410 MHz to 490 MHz. The measure results are in good agreement with simulations despite the unexpected resistor loss.
基金Project supported by the National Natural Science Foundation of China(Grant No.92065116)Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA18000000)the Key-Area Research and Development Program of Guangdong Province,China(Grant No.2020B0303030002).
文摘Josephson parametric amplifiers (JPAs) with nearly quantum-limited noise performance have become indispensable devices for the measurements of superconducting quantum information. We have developed an all-Nb lumped-element flux-driven JPA operating in the three-wave mixing mode. Our Nb-based JPA comprises Nb/Al-AlOx/Nb Josephson junctions, a parallel-plate capacitor with SiO2 dielectric sandwiched between two Nb layers, a bottom coplanar waveguides layer, and a top Nb wiring layer. We experimentally demonstrate a 20 dB gain over a 190 MHz bandwidth, a mean 1 dB compression of -123 dBm, and near quantum-limited noise performance. This fabrication process can be further used to design impedance transformed parametric amplifiers for multiple-qubit readout.
