The objective of the QUADRANT project is the development of a technology for the implementation of logic circuits based on a Quantum Cellular Automata (QCA) architecture. A co-ordinated theoretical and experimental effort will be undertaken for the design and fabrication of QCA cells characterised by two possible polarisation states. Coupling between such cells and propagation of the polarisation along chains of cells will also be investigated, with the aim of demonstrating their functionality as building blocks for logic circuits.
The cellular automata concept is very promising for possible circuit applications of quantum devices, because it overcomes some of their intrinsic problems, such as the very limited available fan-out and the inability of efficiently driving interconnect lines. Other problems do, however, exist, such as that of achieving a bistable behaviour with a number of electrons per cell larger than two or of reliably interfacing the cellular automata system with the outer world and, in particular, with traditional electronics without perturbing its operation. We plan to address these issues through the development of improved cell designs and the realisation of probes capable of detecting the polarisation state of a cell without significantly affecting it.
The relative advantages of different semiconductor material systems will be explored, pushing the total dimensions of each cell down to a few tens of nanometers in order to raise the operating temperature and decrease the sensitivity to external interferences, issues of paramount importance for any future industrial application. Thus, during the first phase of the project, one of the main objectives will consist in the development of an improved technology for the fabrication of quantum dots with the smallest possible number of electrons. It will therefore be possible to investigate experimentally the operation of the cell topologies that up to now have been discussed in the literature only from a theoretical point of view. As a consequence of the strong interaction between theoretical and experimental groups, it will be possible to tune models so that they will be able to quantitatively and reliably predict the behaviour of a single cell and of arrays of cells. Such models will be implemented into simulation packages that will allow the design of optimised devices. Close co-ordination and exchange of information with the group at Notre Dame University that first proposed the cellular automata concept will further increase the effectiveness of the project.
Funding SchemeCSC - Cost-sharing contracts
L8S 4M1 Hamilton
CB2 1TN Cambridge
IN 46556 Notre Dame