High-speed metallic quantum-dot cellular automata

The computation approach known as quantum-dot cellular automata (QCA) is based on encoding binary information in the charge configuration of quantum-dot cells. This paradigm provides a possible route to transistor-less electronics at the nano-scale. QCA devices using single-electron switching in metal-dot cells have been fabricated. Here we examine the limits of switching speed and temperature in QCA circuits. We calculate the dynamic behavior of a semi-infinite shift register. We employ the orthodox theory of Coulomb blockade and a master-equation approach for the dynamics. A complete phase diagram of the operational space of the circuit as a function of clock speed and temperature is constructed. The crucial role of power gain as a function of temperature is evident.