SOFSEM '00 Proceedings of the 27th Conference on Current Trends in Theory and Practice of Informatics
Journal of the ACM (JACM)
Measurement-based and universal blind quantum computation
SFM'10 Proceedings of the Formal methods for quantitative aspects of programming languages, and 10th international conference on School on formal methods for the design of computer, communication and software systems
ICALP'12 Proceedings of the 39th international colloquium conference on Automata, Languages, and Programming - Volume Part II
Information and Computation
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Linear quantum cellular automata were introduced recently as one of the models of quantum computing. A basic postulate of quantum mechanics imposes a strong constraint on any quantum machine: it has to be unitary, that is its time evolution operator has to be a unitary transformation. In this paper we give an efficient algorithm to decide if a linear quantum cellular automaton is unitary. The complexity of the algorithm is O(n(4r-3)/(r+1))=O(n/sup 4/) if the automaton has a continuous neighborhood of size r.