Abstract
Quantum-dot cellular automata (QCA) is a low-power, non-von-Neumann, general-purpose paradigm for classical computing using transistor-free logic. Here, classical bits are encoded on the charge configuration of individual computing primitives known as “cells.” A cell is a system of quantum dots with a few mobile charges. Device switching occurs through quantum mechanical inter-dot charge tunneling, and devices are interconnected via the electrostatic field. QCA devices are implemented using arrays of QCA cells. A molecular implementation of QCA may support THz-scale clocking or better at room temperature. Molecular QCA may be clocked using an applied electric field, known as a clocking field. A time-varying clocking field may be established using an array of conductors. The clocking field determines the flow of data and calculations. Various arrangements of clocking conductors are laid out, and the resulting electric field is simulated. It is shown that that control of molecular QCA can enable feedback loops, memories, planar circuit crossings, and versatile circuit grids that support feedback and memory, as well as data flow in any of the ordinal grid directions. Logic, interconnect and memory now become indistinguishable, and the von Neumann bottleneck is avoided.
Highlights
Low-power computation is a crucial need for our modern society in the information age, and this need is only growing in importance
In order to highlight different topologies for the clocking field, we focus on qualitative features of the fields, such as the timing and direction of information flow as driven by active domains
It is worth noting that the desirable length scale of molecular quantum-dot cellular automata (QCA) cells is much shorter than the length scale of the clocking wires: cells were simulated having a length scale of a = 1 nm, where a is the center-to-center distance drs between the corner dots r and s
Summary
Low-power computation is a crucial need for our modern society in the information age, and this need is only growing in importance. Information and computing technologies consume a significant and growing percentage of the global electrical power [2]. A departure from transistor-based computing, quantum-dot cellular automata (QCA) is a non-von-Neumann paradigm for general-purpose, classical computing, which was designed to leverage quantum phenomena, overcome the challenges posed by the physical limits of scaling in complementary metal-oxide semiconductor (CMOS) devices, and allow energy-efficient digital devices [3,4]. Clocking is important in QCA because it provides power gain to strengthen weak signals, enables latching, and allows adiabatic device operation [9,10,11]. As will be simulated and demonstrated here, a rich set of topologies may be designed for molecular QCA clocking systems, providing a wide array of information processing capabilities in molecular QCA
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