Quantum-dot cellular automata

Abstract

Quantum-dot Cellular Automata (QCA) is a promising architecture which employs quantum dots for digital computation. It is a revolutionary approach which addresses the issues of device density and power dissipation. With a dot size of 20 nm an entire full adder would occupy only one square micron, and the power delay product is as low as a few kT. A basic QCA cell consists of four quantum dots coupled capacitively and by tunnel barriers. The cell is biased to contain two excess electrons within the four dots, which are forced to opposite "corners" of the four-dot system by Coulomb repulsion. These two possible polarization states of the cell represent logic "0" and "1". Properly arranged, arrays of these basic cells can implement Boolean logic functions. We present experimental results from functional QCA devices built of nanoscale metal dots defined by tunnel barriers.