07-06-2009, 01:21 AM
The latest idea for the search for a viable successor to silicon computer technology is known as molecular computers, or moletronics, in which single molecules serve as switches, 'quantum wires' a few atoms thick serve as wiring, and the hardware is synthesized chemically from the bottom up. An 'assembler', which is little more than a submicroscopic robotic arm can be built and be controlled. It Can be used to secure and position compounds in order to direct the precise location at which chemical reactions occur. This general approach allows the construction of large, atomically precise objects by initiating a sequence of controlled chemical reactions. Moletronics is expected to touch almost every aspect of our lives, right down to the water we drink and the air we breathe. Experimental work has already resulted in the production of molecular tweezers, a carbon nanotube transistor, and logic gates. Theoretical work is progressing as well. Moletronic circuit--QCA basics The interaction between cells is Coulombic, and provides the necessary computing power. No current flows between cells and no power or information is delivered to individual internal cells. Local interconnections between cells are provided by the physics of cell-cell interaction. The links below describes the QCA cell and the process of building up useful computational elements from it. The discussion is mostly qualitative and based on the intuitively clear behavior of electrons in the cell. Fundamental Aspects of QCA A QCA cell consists of 4 quantum dots positioned at the vertices of a square and contains 2 extra electrons. The configuration of these electrons is used to encode binary information. The 2 electrons sitting on diagonal sites of the square from left to right and right to left are used to represent the binary '1' and '0' states respectively. For an isolated cell these 2 states will have the same energy. However for an array of cells, the state of each cell is determined by its interaction with neighboring cells through the Coulomb interaction.
