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

## TL;DR

This paper demonstrates that QCA wires and inverters can reliably transmit information via excited states, even with non-nearest neighbor interactions, while complex gates require ground states for correct operation.

## Contribution

It shows that QCA wires and inverters can operate reliably in excited states, expanding the understanding of non-adiabatic effects in quantum dot cellular automata circuits.

## Key findings

- Wires and inverters transmit information correctly via excited states.
- Non-nearest neighbor interactions do not affect this reliability.
- Complex gates require ground states for correct operation.

## 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.