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Two-way Quantum One-counter Automata

Tomohiro Yamasaki·Hirotada Kobayashi·Hiroshi Imai
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Abstract

After the first treatments of quantum finite state automata by Moore and Crutchfield and by Kondacs and Watrous, a number of papers study the power of quantum finite state automata and their variants. This paper introduces a model of two-way quantum one-counter automata (2Q1CAs), combining the model of two-way quantum finite state automata (2QFAs) by Kondacs and Watrous and the model of one-way quantum one-counter automata (1Q1CAs) by Kravtsev. We give the definition of 2Q1CAs with well-formedness conditions. It is proved that 2Q1CAs are at least as powerful as classical two-way deterministic one-counter automata (2D1CAs), that is, every language L recognizable by 2D1CAs is recognized by 2Q1CAs with no error. It is also shown that several non-context-free languages including {a^n b^{n^2}} and {a^n b^{2^n}} are recognizable by 2Q1CAs with bounded error.

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Tomohiro Yamasaki, Hirotada Kobayashi, Hiroshi Imai. 2001-10-02. Two-way Quantum One-counter Automata. https://arxiv.org/abs/cs/0110005

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