Exploring coherent dynamics and field clocking of quantum-dot cellular automata circuits

硅技术和计算机设计工具的进步使拥有超过10亿个晶体管的芯片得以生产。然而，很明显，为了达到规模的终极极限，需要有根本不同的想法。由于工业界和政府的投资，可以在纳米和原子尺度上以令人难以置信的精度操纵物质的技术，使我们能够将分子和原子设备视为传统晶体管的潜在继任者。量子点细胞自动机(QCA)是一种基于双稳态分子和原子纳米结构动态阵列的场相互作用的计算范式，已被证明可以实现通用计算，并有助于显著降低功耗，这是扩展传统技术的主要挑战。最近令人兴奋的实验展示了一个在原子尺度上具有功能的QCA设备，提供了强有力的证据，证明QCA确实可以达到最终的尺度极限。 QCADesigner是用于QCA研究的最广泛使用的数值模拟工具，它使得对这一新兴技术的大量基础电路和系统级研究成为可能。使用该工具进行的分析和数值研究突出了QCA中相干动力学的关键问题及其对数值工具识别任意布局和输入矢量的正确系统基态的能力的影响。 这项基础性研究的目的是通过开发和集成相干动力学模型和模拟场控分子QCA阵列所需的工具，为QCA提供全新的理论和数值工具。这些工具将使对QCA电路和系统的行为进行广泛的全新研究成为可能，包括对相干动力学对时钟网络的影响、功率损耗、电路密度以及QCA作为可扩展量子计算技术的潜力的关键研究。这些研究将有助于改进对QCA商业潜力的评估，甚至在与其实施相关的所有技术挑战完全解决之前。

Advancements in silicon technology and the computer design tools have enabled the production of chips that have over a billion transistors. However, it has become clear that fundamentally different ideas are necessary in order to push the ultimate limits of scaling. As a result of the investment by both industry and governments, technology is available for manipulating matter at the nano and atomic scale with incredible precision allowing us to consider molecular and atomic devices as potential successors to the conventional transistor. Quantum-dot cellular automata (QCA), a computing paradigm based on the field interaction of dynamic arrays of bi-stable molecular and atomic nanostructures has been shown to implement general purpose computing, as well as contribute to significant reductions in power dissipation, a major challenge with scaling conventional technology. Exciting recent experiments demonstrated a functional QCA device at the atomic scale, providing strong evidence that QCA can indeed reach the ultimate limits of scaling. QCADesigner, the most widely used numerical simulation tool for QCA research has enabled a large number of fundamental circuit and system level studies of this emerging technology. Analytical and numerical research using this tool has highlighted the critical issue of coherent dynamics in QCA and its impact on the ability of the numerical tools to identify the correct system ground state for an arbitrary layout and input vector. The purpose of this fundamental research is to provide entirely new theoretical and numerical tools for QCA by developing and integrating a model for coherent dynamics and the necessary tools to simulate field clocked molecular QCA arrays. These tools will enable a broad range of fundamentally new research studies of the behaviour of QCA circuits and systems including critical studies of the effect of coherent dynamics on the clocking networks, power dissipation, circuit density, and the potential of QCA as a scalable quantum computing technology. These studies will facilitate an improved assessment of the commercial potential of QCA even before all the technical challenges associated with its implementation are fully solved.