Quantum cellular automata based on mixed-valence molecules: Some theoretical hints for cell design^†

The purpose of this short review article is to discuss at a simple qualitative level some key requirements the mixed-valence (MV) molecules should meet to be potentially applicable as cells of quantum cellular automata (QCA), and also how different interactions affect their fulfillment. We focus on two requirements, which are closely related to encoding and propagating of binary information within the electronic circuits and power dissipation caused by the logical opera-tions. The physical features behind these requirements are the following: the ability of MV molecules to be efficiently switched between two logical binary states which assumes high polar-izability manifesting itself in a strong non-linear cell-cell response and a low heat release caused by molecular rearrangements accompanying logical operations. We discuss the role of such electronic interactions as intramolecular electron transfer, intramolecular interelectronic Coulomb repulsion and the interaction of the excess electrons of a molecular cell with the electric field produced by the neighboring polarized cell. The pivotal role of the interaction of the excess electrons with the molecular vibrations (pseudo Jahn-Teller vibronic coupling) is discussed as well. Finally, the optimal conditions expressed as a parametric regime ensuring simultaneous fulfillment of the aforenamed requirements are discussed.