Reliable Information Transmission along QCA Wires in the Presence of Non-Adiabatic Transitions

Abstract

Quantum dot cellular automata (QCA) computing schemes use arrays of quantum dots as computational devices. Typically, these operate ideally by maintaining arrays in their ground state to ensure correct computational output. For large QCA circuits, thermal fluctuations make this impossible, so adiabatic clocking has been proposed as a means of dividing large circuit computations into subcircuit computations that are more reliable. In this report, it is shown that wires and inverters can transmit information correctly via their excited states just as well as their ground states. A characteristic example of a 4 cell wire is simulated, and a theoretical derivation of this result is given. When, non-nearest neighbor interactions are included in the Hamiltonian, this result still holds true. On the other hand, QCA majority gates and more complex circuits give incorrect results when operated in excited states. These results suggest that gates of reliable QCA circuits should be contained in smaller clocking zones, while wires relaying information can be contained in larger clocking zones.