Repurposing Josephson Junctions At The Cell Boundaries For Fan-out (UCSB)


A technical paper titled “Low-Cost Superconducting Fan-Out with Repurposed Josephson Junctions” was published by researchers at UC Santa Barbara.  The paper received an award at the Applied Superconductivity Conference in Oct 2022 and was highlighted in this UCSB news article.

“Superconductor electronics (SCE) promise computer systems with orders of magnitude higher speeds and lower energy consumption than their complementary metal-oxide semiconductor (CMOS) counterpart. At the same time, the scalability and resource utilization of superconducting systems are major concerns. Some of these concerns come from device-level challenges and the gap between SCE and CMOS technology nodes, and others come from the way Josephson Junctions (JJs) are used. Towards this end, we notice that a considerable fraction of hardware resources are not involved in logic operations, but rather are used for fan-out and buffering purposes. In this paper, we ask if there is a way to reduce these overheads; propose the repurposing of JJs at the cell boundaries for fan-out; and establish a set of rules to discretize critical currents in a way that is conducive to this reassignment. Finally, we demonstrate the accomplished gains through detailed analog simulations and modeling analyses. Our experiments indicate that the introduced method leads to a 48% savings in the JJ count in a tree with a fan-out of 1024, as well as an average of 43% of the JJ count for signal splitting and 32% for clock fan-out in ISCAS’85 benchmarks.”

Find the technical paper here. Published 2022.

Volk, Jennifer, et al. “Low-Cost Superconducting Fan-Out with Repurposed Josephson Junctions.” arXiv preprint arXiv:2206.07817 (2022).

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