21Nanomagnet Logic: A Magnetic Implementation of Quantum-dot Cellular Automata

Michael T. Niemier, György Csaba, and Wolfgang Porod

University of Notre Dame, USA

21.1 Introduction

The system-level, information processing architectures to be discussed here are potential targets for devices that can be organized in the automata-like architecture proposed in [1] – which suggested using the position of electrons on quantum dots to represent binary state and process information.

Initially, experimentalists targeted metal-dot implementations of the Quantum-dot Cellular Automata (or QCA) device architecture (see device, wire, and gate schematic in Figure 21.1a, Figure 21.1b, and Figure 21.1c respectively), and individual devices [2], gates [3], latches [4], power gain [5], and fanout [6] were soon demonstrated. However, metal-dot QCA devices require cryogenic operating temperatures that severely limit the potential for deployed hardware – and hence application spaces. In an effort to raise operating temperatures, some research groups pursued/continue to pursue QCA devices that take the form of a synthesized chemical molecule [7]. (Scaling device size downward can increase the energy separation between states [8], and hence operating temperature.) Experimentally, a self-assembled monolayer of mixed-valence compounds appears to switch between states that could be mapped to logic 1s and 0s [9]. However, both practical devices, and a mechanism for the deterministic placement of ∼1 × 1 ...

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