On One-Dimensional Quantum Cellular Automata

Since Richard Feynman introduced the notion of quantum computation in 1982, various models of \quantum computers" have been proposed. These models include quantum Turing machines and quantum circuits. In this paper we deene another quantum computational model, one-dimensional quantum cellular automata, and demonstrate that any quantum Turing machine can be eeciently simulated by a one-dimensional quantum cellular automaton with constant slowdown. This can be accomplished by consideration of a restricted class of one-dimensional quantum cellular automata called one-dimensional partitioned quantum cellular automata. We also show that any one-dimensional partitioned quantum cellular automaton can be simulated by a quantum Turing machine with linear slowdown, but the problem of eeciently simulating an arbitrary one-dimensional quantum cellular automaton with a quantum Turing machine is left open. From this discussion, some interesting facts concerning these models are easily deduced.