Implementation of energy efficient single flux quantum digital circuits with sub-aJ/bit operation

Abstract

We report the first experimental demonstration of recently proposed energy-efficient single flux quantum logic, eSFQ. This logic can represent the next generation of RSFQ logic eliminating dominant static power dissipation associated with a dc bias current distribution and providing over two orders of magnitude efficiency improvement over conventional RSFQ logic. We further demonstrate that the introduction of passive phase shifters allows the reduction of dynamic power dissipation by about 20%, reaching ~0.8 aJ per bit operation. Two types of demonstration eSFQ circuits, shift registers and demultiplexers (deserializers), were implemented using the standard HYPRES 4.5 kA/cm 2 fabrication process. In this paper, we present eSFQ circuit design and demonstrate the viability and performance metrics of eSFQ circuits through simulations and experimental testing.

Cryogenic Computing Complexity Program: Phase 1 Introduction

“…First, new families of single flux quantum (SFQ) logic have been developed over the past several years that have no static power dissipation [7]- [10]. Previously, almost 98% of the power for digital SFQ circuits was static dissipation in the biasing resistors [8].…”

Magnetic field calculations in the vicinity of superconductive circuit structures

“…We use an eSFQ shift register cell as described in [20] with a shielded bias line and a sky plane shield over the cell. We also analyse two artificial variations: one without the sky plane and another without superconductive shielding around the bias line (see Fig.…”

“…Field is calculated between the first and second wiring layers in the plane of the Josephson junctions. (a) An eSFQ shift register cell[20] with sky plane shield (layer M3 in the Hypres 4.5 kA.cm -2 process) and shielded dc bias line at the top, (b) the same eSFQ cell without a sky plane and (c) the same eSFQ cell with no sky plane and no shielding around the dc bias line. Three-dimensional renderings were done with InductEx, and all layer heights are multiplied by 5 for clarity.The bias connection to each cell is severed so that only the effects of the current in the main dc bias line are examined.…”

A random-access-memory cell based on quantum flux parametron with three control lines

“…Energy-efficient superconducting circuits based on rapid single flux quantum (RSFQ) circuits [1] have been proposed recently, which include eSFQ [2], ERSFQ [3], RQL [4], and LV-RSFQ [5]. We have been developing adiabatic quantum flux parametron (AQFP) circuits based on QFP circuits [6], which are extremely energy efficient superconducting circuits [7][8][9][10].…”