Superconducting Pulse Conserving Logic and Josephson-SRAM

Abstract

Superconducting digital Pulse-Conserving Logic (PCL) and Josephson SRAM (JSRAM) memory together enable scalable circuits with energy efficiency 100x beyond leading-node CMOS. Circuit designs support high throughput and low latency when implemented in an advanced fabrication stack with high-critical-current-density Josephson junctions of 1000$\mu$A/$\mu$m${}^2$. Pulse-conserving logic produces one single-flux-quantum output for each input, and includes a three-input, three-output gate producing logical or3, majority3 and and3. Gate macros using dual-rail data encoding eliminate inversion latency and produce efficient implementations of all standard logic functions. A full adder using 70 Josephson junctions has a carry-out latency of 5ps corresponding to an effective 12 levels of logic at 30 GHz. JSRAM (Josephson SRAM) memory uses single-flux-quantum signals throughout an active array to achieve throughput at the same clock rate as the logic. The unit cell has eight Josephson junctions, signal propagation latency of 1ps, and a footprint of 2$\mu$m${}^2$. Projected density of JSRAM is 4 MB/cm${}^2$, and computational density of pulse-conserving logic is on par with leading node CMOS accounting for power densities and clock rates.

6 pages, 2 figures

References in corpus (2)

• Very Large Scale Integration of Josephson-Junction-Based Superconductor Random Access Memories
• ERSFQ 8-bit Parallel Arithmetic Logic Unit