Adiabatic quantum-flux-parametron cell library adopting minimalist design

Abstract

We herein build an adiabatic quantum-flux-parametron (AQFP) cell library adopting minimalist design and a symmetric layout. In the proposed minimalist design, every logic cell is designed by arraying four types of building block cells: buffer, NOT, constant, and branch cells. Therefore, minimalist design enables us to effectively build and customize an AQFP cell library. The symmetric layout reduces unwanted parasitic magnetic coupling and ensures a large mutual inductance in an output transformer, which enables very long wiring between logic cells. We design and fabricate several logic circuits using the minimal AQFP cell library so as to test logic cells in the library. Moreover, we experimentally investigate the maximum wiring length between logic cells. Finally, we present an experimental demonstration of an 8-bit carry look-ahead adder designed using the minimal AQFP cell library and demonstrate that the proposed cell library is sufficiently robust to realize large-scale digital circuits.

Recent Progress on Reversible Quantum-Flux-Parametron for Superconductor Reversible Computing

“…Recently, much effort has been spent on the development of energy-efficient AQFP microprocessors [20]- [22] and AQFP interfaces for superconductor detectors [23] through building the circuit design environment for AQFP logic [22], [24]- [26].…”

Inductance and Current Distribution Extraction in Nb Multilayer Circuits with Superconductive and Resistive Components

“…The same pattern is reflected in the rows of matrix A. In order to support extraction of circuit models with resistance and coupling such as Adiabatic Quantum Flux Parametron (AQFP) cells [16], we have now improved InductEx to use the double precision real Lapack function dgelsd to solve the purely real matrices. For the example problem in Fig.…”

“…AQFP cell layouts need to be carefully designed to suppress unwanted magnetic coupling between the ac clock line and the output inductance. Therefore, in previous works, we adopted superconductor magnetic shields [12] or symmetric layout [16]. In this study, we use AQFP gates with symmetric layout.…”

“…This should be placed so that it feeds all bias currents. The circuit can then be modeled as single impedance in parallel to the exci- 16 Modulus of current density in the main ground plane (M7) of (a) an AND gate in the ADP2 cell library using the standard device structure [21] when the cell is biased with 2.5 mV, and (b) the same AND gate with the same bias, but with the ground contact stacks placed around the dc bias pillars as proposed in [19]. tation port.…”

“…AQFP gates have up to now been demonstrated in the STP2 process. An AQFP cell library was built using minimalist design [16], where logic cells are designed by simply arraying several types of building blocks. Using the cell library, AQFP logic circuits with up to approximately 1,000 Josephson junctions have been successfully demonstrated.…”