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The author presents a review of numerical methods for modelling the electronic properties of quantum nanostructure devices. The appropriate boundary conditions for solving the Poisson and Schrodinger equations in modeling the self-consistent screening potential and electron states are emphasised. Besides providing a framework for understanding the physics of nanoscale structures, realistic computer modeling constitutes a valuable tool for designing quantum devices that the author argues enables the development of a nanoelectronic technology along with the associated advances in fabrication technologies. Nanoelectronic devices make use of the quantized energy levels of confined electrons to control the flow of charge. The potential energy environment that gives rise to such levels is, however, a strongly sensitive function of the geometry and layer properties of the device structure. The relevant device variables must therefore be rather precisely specified, and the most cost-efficient means of developing realistic designs is to use modeling tools that are based on fundamental physical laws.

Two methods of using switches to implement reversible computations are discussed. The first method has an energy dissipation which is proportional to the square of the error in the voltage, while the second method has an energy dissipation which can in principle be reduced indefinitely by slowing the speed of computation. The first method is basically an extension to 'pass logic' which has been previously used with both nMOS (hot clock nMOS) and CMOS transmission gates to achieve low energy dissipation. The second method is a novel thermodynamically reversible logic system based on CCD-like operations which switches charge packets in a reversible fashion to achieve low energy dissipation.

A lateral-resonant-tunneling quantum-dot cell is described which is configurable to span the complete range of three-input functions. The cell area could be of the order of 0.1 mu m². This cell could enable large, edge-fed, cellular cascade arrays. These arrays could perform general logic functions.

The authors formulate a new paradigm for computing with cellular automata (CAS) composed of arrays of quantum devices-quantum cellular automata. Computing in such a paradigm is edge driven. Input, output, and power are delivered at the edge of the CA array only; no direct flow of information or energy to internal cells is required. Computing in this paradigm is also computing with the ground state. The architecture is so designed that the ground-state configuration of the array, subject to boundary conditions determined by the input, yields the computational result. The authors propose a specific realization of these ideas using two-electron cells composed of quantum dots. The charge density in the cell is very highly polarized (aligned) along one of the two cell axes, suggestive of a two-state CA. The polarization of one cell induces a polarization in a neighboring cell through the Coulomb interaction in a very non-linear fashion. Quantum cellular automata can perform useful computing. The authors show that AND gates, OR gates, and inverters can be constructed and interconnected.