Implementing a Quantum CNOT and Quantum Memory Using a Quantum-Dot Cellular Automata Array

In this work, we develop a method to use Quantum- Dot Cellular Automata (QCA) for universal quantum computing. This method is based conceptually on refocusing in NMR systems. We show how an array of QCA cells can be used for isolated single qubit, as well as multi-qubit operations, such as the CNOT, by dividing the cells into active and passive sets such that the active cells undergo the transform while passive cells hold their quantum states. The same technique is used for developing a multi-qubit quantum memory. The effect of imperfect control parameters is discussed and the total time for a typical quantum operation is given. Using this approach, different quantum gates are implemented using pulse sequences applied to the QCA cells via control fields and potentials, while the layout remains the same.