Demonstration of a six-dot quantum cellular automata system

We report an experimental demonstration of a logic cell for quantum-dot cellular automata ~QCA!. This nanostructure-based computational paradigm allows logic function implementation without the use of transistors. The four-dot QCA cell is defined by a pair of series-connected double dots, and the coupling between the input and the output double dots is provided by lithographically defined capacitors. We demonstrate that, at low temperature, an electron switch in the input double dot induces an opposite electron switch in the output double dot, resulting in a polarization change of the QCA cell. Switching is verified from the electrometer signals, which are coupled to the output double dot. We perform theoretical simulations of the device characteristics and find excellent agreement with theory. © 1998 American Institute of Physics. @S0003-6951~98!01417-X#