S. E. Thompson EEL Quantum cellular Automata Quantum Cellular Automata (QCA) refers to any one of several models of quantum computation, which have been devised in analogy to conventional models of cellular automata introduced by von Neumann. It may also refer to quantum dot cellular automata, which is a proposed physical implementation of "classical" cellular automata by exploiting quantum mechanical phenomena.

S. E. Thompson EEL Quantum cellular Automata 4 quantum SED dot 2 electrons added to system System will minimize electro-static energy 0 1

S. E. Thompson EEL Quantum cellular Automata :Example Input 1 Propagate a 1

S. E. Thompson EEL Quantum cellular Automata: Logic Based on neighbor interaction –Vs movement of charge Key advantages –Very low power Key disadvantage –No gain. –Input not isolated from output

S. E. Thompson EEL Quantum cellular Automata : Logic Gate example Input A 0 Propagate a 0 Input C Input B Voting gate

S. E. Thompson EEL 6935 An Inverter 6

S. E. Thompson EEL History Proposed in 1993 by Lent et. al. Based on ground state computation System moves to lowest electro-static energy state State of lowest energy uniquely defined Key issue is energy level between states and kT physical implementation of QCA produced –Tunnnel junctions and Al islands –Experiment at 10mK

S. E. Thompson EEL

Ferroelectric RAM 9 DRAM