Olaya David, Biesecker John, Castellanos-Beltran Manuel, Sirois Adam, Howe Logan, Dresselhaus Paul, Benz Samuel, Hopkins Peter
Department of Physics at the University of Colorado, Boulder, CO; RF Technology Division of the National Institute of Standards and Technology, Boulder, CO, USA.
RF Technology Division of the National Institute of Standards and Technology, Boulder, CO, USA.
IEEE Trans Appl Supercond. 2022 Aug;33(5). doi: 10.1109/tasc.2023.3249141.
We demonstrate Josephson arbitrary waveform synthesizers (JAWS) with increased operating temperature range for temperatures below 4 K. These JAWS synthesizers were fabricated with externally-shunted Nb/-Si/Nb junctions whose critical current exhibits improved temperature stability compared to the self-shunted Nb/NbSi/Nb junctions typically used. Vertical stud resistors made of 230 nm of PdAu were developed to provide the milliohm shunt resistance required for junction overdamping while maintaining a small footprint suitable for high-density series arrays embedded in a coplanar waveguide. We evaluated the performance of these resistors from 3.8 K down to 20 mK. We designed, fabricated and tested a JAWS circuit with 4650 externally shunted Nb/-Si/Nb JJs with a critical current density () of 0.12 and critical current () of 3 mA. This circuit was designed to be mounted to the 3 K stage of a dilution refrigerator and used to control and calibrate a qubit mounted at the 10 mK stage. To increase the circuit density of the JAWS circuits we made arrays of two-junction vertical stacks. Current-voltage () curves of this JAWS circuit with stacked junctions under microwave excitation show Shapiro steps with quantum-locking ranges similar to those of JAWS circuits used for qubit control.
我们展示了适用于4K以下温度的、工作温度范围有所提高的约瑟夫森任意波形合成器（JAWS）。这些JAWS合成器是用外部分流的Nb/-Si/Nb结制造的，与通常使用的自分流Nb/NbSi/Nb结相比，其临界电流表现出更好的温度稳定性。开发了由230nm的PdAu制成的垂直柱形电阻器，以提供结过阻尼所需的毫欧级分流电阻，同时保持适合嵌入共面波导中的高密度串联阵列的小尺寸。我们评估了这些电阻器在3.8K至20mK温度范围内的性能。我们设计、制造并测试了一个具有4650个外部分流Nb/-Si/Nb结的JAWS电路，其临界电流密度（）为0.12 ，临界电流（）为3mA。该电路设计用于安装在稀释制冷机的3K级，并用于控制和校准安装在10mK级的量子比特。为了提高JAWS电路的电路密度，我们制作了双结垂直堆叠阵列。该具有堆叠结的JAWS电路在微波激励下的电流-电压（）曲线显示出与用于量子比特控制的JAWS电路类似的量子锁定范围的夏皮罗台阶。
