Quantum Mechanical Simulation of QCA with a Reduced Hamiltonian Model

Molecular quantum-dot cellular automata (QCA) is an emerging computing paradigm which utilizes electrostatic coupling between electronic configurations in neighboring molecules to perform information processing. A simulation tool for this technology, QCADesigner, exists and allows designers to quickly layout and simulate QCA circuits constructed with up to thousands of QCA cells. However, in general, large quantum mechanical systems are not suitable for efficient simulation on a classical computer, and as a result, QCADesigner uses the Hartree-Fock approximation to reduce the computational complexity of the simulation. Under certain circumstances, this approximation can lead to the incorrect ground state and hence, produce logically incorrect results at the outputs. In this work, we provide examples of problem circuits and propose a method to identify areas that must be simulated using the full Hamiltonian.