A decision procedure for well-formed linear quantum cellular automata
Proceedings of the workshop on Randomized algorithms and computation
A Decision Procedure for Unitary Linear Quantum Cellular Automata
SIAM Journal on Computing
On one-dimensional quantum cellular automata
FOCS '95 Proceedings of the 36th Annual Symposium on Foundations of Computer Science
One-Dimensional Quantum Cellular Automata over Finite, Unbounded Configurations
Language and Automata Theory and Applications
Algebraic characterizations of unitary linear quantum cellular automata
MFCS'06 Proceedings of the 31st international conference on Mathematical Foundations of Computer Science
One-Dimensional Quantum Cellular Automata over Finite, Unbounded Configurations
Language and Automata Theory and Applications
Unitarity plus causality implies localizability
Journal of Computer and System Sciences
Partitioned quantum cellular automata are intrinsically universal
Natural Computing: an international journal
A simple n-dimensional intrinsically universal quantum cellular automaton
LATA'10 Proceedings of the 4th international conference on Language and Automata Theory and Applications
LATA'12 Proceedings of the 6th international conference on Language and Automata Theory and Applications
ICALP'12 Proceedings of the 39th international colloquium conference on Automata, Languages, and Programming - Volume Part II
Intrinsically universal n-dimensional quantum cellular automata
Journal of Computer and System Sciences
Information and Computation
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One-dimensional quantum cellular automata (QCA) consist in a line of identical, finite dimensional quantum systems. These evolve in discrete time steps according to a causal, shift-invariant unitary evolution. By causal we mean that no instantaneous long-range communication can occur. In order to define these over a Hilbert space we must restrict to a base of finite, yet unbounded configurations. We show that QCA always admit a two-layered block representation, and hence the inverse QCA is again a QCA. This is a striking result since the property does not hold for classical one-dimensional cellular automata as defined over such finite configurations. As an example we discuss a bijective cellular automata which becomes non-causal as a QCA, in a rare case of reversible computation which does not admit a straightforward quantization. We argue that a whole class of bijective cellular automata should no longer be considered to be reversible in a physical sense. Note that the same two-layered block representation result applies also over infinite configurations, as was previously shown for one-dimensional systems in the more elaborate formalism of operators algebras [13]. Here the proof is simpler and self-contained, moreover we discuss a counterexample QCA in higher dimensions.