We investigated the hardware implementation of an area-efficient superconducting lookup table (LUT) based on a single flux quantum (SFQ) logic by using a newly proposed small memory cell. The memory cell is composed of a nondestructive read-out (NDRO) flip-flop with input circuits that convert the input dc current to an SFQ pulse signal. The datum can be written to the selected memory cell in the 2-D memory cell array by applying both x- and y-directional dc control currents. The data stored in the memory cell array can be reset simultaneously by applying a dc current to a common reset line. By employing the new memory cell, wiring for reconfiguring the data and resetting the memory cell array can be drastically simplified compared to that of the conventional SFQ LUT. We implemented and tested the memory cell and confirmed the correct operation with wide dc bias and input-current margins. We designed the 16-b LUT using the designed memory cells. The circuit area and the number of Josephson junctions of the 16-b LUT is reduced by approximately 24 and 41%, respectively, compared to those of the LUT based on the conventional architecture. We experimentally obtained the correct operation and reconfiguration of the 4-b LUT that uses the new memory cells with a normalized bias margin of –22 to +7%.

中文翻译：

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由外部直流控制电流重构的二维存储单元阵列组成的紧凑型超导查找表

我们通过使用新提出的小型存储单元研究了基于单通量量子 (SFQ) 逻辑的面积高效超导查找表 (LUT) 的硬件实现。存储单元由无损读出 (NDRO) 触发器和输入电路组成，可将输入直流电流转换为 SFQ 脉冲信号。通过同时施加 x 和 y 方向的直流控制电流，可以将数据写入二维存储单元阵列中的选定存储单元。通过向公共复位线施加直流电流，可以同时复位存储在存储单元阵列中的数据。通过采用新的存储单元，与传统的 SFQ LUT 相比，可以大大简化用于重新配置数据和重置存储单元阵列的布线。我们实施并测试了存储单元，并确认了具有宽直流偏置和输入电流裕度的正确操作。我们使用设计的存储单元设计了 16-b LUT。与基于传统架构的 LUT 相比，16-b LUT 的电路面积和约瑟夫森结的数量分别减少了约 24% 和 41%。我们通过实验获得了 4-b LUT 的正确操作和重新配置，该 LUT 使用具有 –22 至 +7% 归一化偏置裕度的新存储单元。