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Two quantum finite automata are equivalent if for any input string x the two automata accept x with equal probability. In this paper, we focus on determining the equivalence for 1-way quantum finite automata with control language (CL-1QFAs) defined by Bertoni et al and measure-many 1-way quantum finite automata (MM-1QFAs) introduced by Kondacs and Watrous.(More)
Two-way quantum automata with quantum and classical states (2QCFA) were introduced by Ambainis and Watrous in 2002. In this paper we study state succinctness of 2QCFA. For any m ∈ Z and any < 1/2, we show that: 1. there is a promise problem A(m) which can be solved by a 2QCFA with one-sided error in a polynomial expected running time with a constant number(More)
Multi-letter quantum finite automata (QFAs) can be thought of quantum variants of the one-way multi-head finite automata (Hromkovič, Acta Informatica 19:377–384, 1983). It has been shown that this new one-way QFAs (multi-letter QFAs) can accept with no error some regular languages, for example (a + b)*b, that are not acceptable by QFAs of Moore and(More)
Generally, unitary transformations limit the computational power of quantum finite automata (QFA). In this paper we study a generalized model named one-way general quantum finite automata (1gQFA), in which each symbol in the input alphabet induces a trace-preserving quantum operation, instead of a unitary transformation. Two different kinds of 1gQFA will be(More)
Boyer, Kenigsberg, and Mor [Phys.Rev.Lett.99, 140501(2007)] proposed a novel idea of semi-quantum key distribution where a key can be securely distributed between Alice who can perform any quantum operation and Bob who is classical. Extending the idea of “semiquantum” to other tasks of quantum information processing is of interest and worth considering. In(More)
We introduce 2-way finite automata with quantum and classical states (2qcfa’s). This is a variant on the 2-way quantum finite automata (2qfa) model which may be simpler to implement than unrestricted 2qfa’s; the internal state of a 2qcfa may include a quantum part that may be in a (mixed) quantum state, but the tape head position is required to be(More)
Quantum automata, as theoretical models of quantum computers, include quantum finite automata (QFA), quantum sequential machines (QSM), quantum pushdown automata (QPDA), quantum Turing machines (QTM), quantum cellular automata (QCA), and the others, for example, automata theory based on quantum logic (orthomodular lattice-valued automata). In this paper, we(More)