Quantum-dot Cellular Automata
(QCA) Quantum logic circuits created by orientating pairs of quantum cells so that their relative positions determine their affect on each other. This is functionally analogous but structurally different from how individual gates in integrated circuits are combined to create logical and memory circuitry.
The advantages of quantum-dot cellular automata over conventional circuitry are extremely small size/high density, low power requirements, and potentially high processing speeds. Disadvantages (in 2000) are difficulty of fabrication and low yield.