Realization of a 2-V Programmable Josephson Junction Array Using Balanced Segmentation Scheme

This article proposes a balanced segmentation scheme to improve the microwave transmission and develops a 2-V programmable Josephson junction array using double-stacked superconductor-normal-metal-superconductor Josephson junctions. The junction numbers of the sub-Josephson arrays are divided into a ternary sequence. The least significant bit is one stack or two junctions. In order to characterize the chip with many subarrays, an automatic measurement system with self-made multichannel current sources was established. It can analyze the critical current, the margin of the voltage steps, and the number of junctions in each subarray. The measurement found that the mentioned junction arrays can work at several microwave frequency ranges with an operating margin higher than 1.5 mA. Moreover, the circuit can produce intrinsically stable dc voltages from –2 to +2 V and generate stepwise-approximated ac voltages.