BioSFQ circuit family for neuromorphic computing: Bridging digital and analog domains of superconductor technologies

Abstract

Superconductor single flux quantum (SFQ) technology is attractive for neuromorphic computing due to low energy dissipation and high, potentially up to 100 GHz, clock rates. We have recently suggested a new family of bioSFQ circuits (V.K. Semenov et al., IEEE TAS, vol. 32, no. 4, 1400105, 2022) where information is stored as a value of current in a superconducting loop and transferred as a rate of SFQ pulses propagating between the loops. This approach, in the simplest case dealing with positive numbers, requires single-line transfer channels. In the more general case of bipolar numbers, it requires dual-rail transfer channels. To address this need, we have developed a new comparator with a dual-rail output. This comparator is an essential part of a bipolar multiplier that has been designed, fabricated, and tested. We discuss bioSFQ circuits for implementing an analog bipolar divide operation $Y/X$ and a square root operation $X^{1/2}$. We discuss strategic advantages of the suggested bioSFQ approach, e.g., an inherently asynchronous character of bioSFQ cells which do not require explicit clock signals. As a result, bioSFQ circuits are free of racing errors and tolerant to occasional collision of propagating SFQ pulses. This tolerance is due to stochastic nature of data signals generated by comparators operating within their gray zone. The circuits were fabricated in the eight-niobium-layer fabrication process SFQ5ee developed for superconductor electronics at MIT Lincoln Laboratory.

8 pages, 10 figures, 30 references. This paper was presented at Applied Superconductivity Conference, ASC 2022, October 23-28, 2022, Honolulu, Hawaii

References in corpus (3)

• Progress toward superconductor electronics fabrication process with planarized NbN and NbN/Nb layers
• A new family of bioSFQ logic/memory cells
• Self- and Mutual Inductance of NbN and Bilayer NbN/Nb Inductors in Planarized Fabrication Process With Nb Ground Planes

Cited by in corpus (4)

• Progress toward superconductor electronics fabrication process with planarized NbN and NbN/Nb layers
• Self- and Mutual Inductance of NbN and Bilayer NbN/Nb Inductors in Planarized Fabrication Process With Nb Ground Planes
• Contemporary implementations of spiking bio-inspired neural networks
• Digital-analog concept for superconducting perceptron-like neural networks