Isochronous Data Link Across a Superconducting Nb Flex Cable with 5 femtojoules per Bit

TL;DR

This paper demonstrates a superconducting isochronous data link for board-to-board communication with high efficiency, achieving 5 femtojoules per bit at 4.2 K, enabling scalable high-performance superconducting digital systems.

Contribution

It introduces a novel superconducting isochronous data link for board-to-board communication, utilizing over-sampling and configurable delay for synchronization.

Findings

Successful demonstration of on-chip and multi-chip module data links

Achieved correct operation with a 3 dB clock margin at 3.6 GHz

Power consumption of 5 fJ/bit at 4.2 K

Abstract

Interconnect properties position superconducting digital circuits to build large, high performance, power efficient digital systems. We report a board-to-board communication data link, which is a critical technological component that has not yet been addressed. Synchronous communication on chip and between chips mounted on a common board is enabled by the superconducting resonant clock/power network for RQL circuits. The data link is extended to board-to-board communication using isochronous communication, where there is a common frequency between boards but the relative phase is unknown. Our link uses over-sampling and configurable delay at the receiver to synchronize to the local clock phase. A single-bit isochronous data link has been demonstrated on-chip through a transmission line, and on a multi-chip module (MCM) through a superconducting tape between driver and receiver with variable phase offset. Measured results demonstrated correct functionality with a clock margin of 3 dB at 3.6 GHz, and with 5 fJ/bit at 4.2 K.