A lower bound for the nondeterministic space complexity of context-free recognition
Information Processing Letters
SIAM Journal on Computing
Word Problems Solvable in Logspace
Journal of the ACM (JACM)
Information Processing Letters
Space-bounded Quantum complexity
Journal of Computer and System Sciences
Quantum automata and quantum grammars
Theoretical Computer Science
Analogies and differences between quantum and stochastic automata
Theoretical Computer Science
Characterizations of 1-Way Quantum Finite Automata
SIAM Journal on Computing
Two-way finite automata with quantum and classical states
Theoretical Computer Science - Natural computing
Some Observations on 2-way Probabilistic Finite Automata
Proceedings of the 12th Conference on Foundations of Software Technology and Theoretical Computer Science
Quantum Reversibility and a New Model of Quantum Automaton
FCT '01 Proceedings of the 13th International Symposium on Fundamentals of Computation Theory
On the power of quantum finite state automata
FOCS '97 Proceedings of the 38th Annual Symposium on Foundations of Computer Science
1-way quantum finite automata: strengths, weaknesses and generalizations
FOCS '98 Proceedings of the 39th Annual Symposium on Foundations of Computer Science
Optimal Lower Bounds for Quantum Automata and Random Access Codes
FOCS '99 Proceedings of the 40th Annual Symposium on Foundations of Computer Science
Closure Properties of Stochastic Languages
Closure Properties of Stochastic Languages
Introduction to probabilistic automata (Computer science and applied mathematics)
Introduction to probabilistic automata (Computer science and applied mathematics)
Real-Time Computation by n-Dimensional Iterative Arrays of Finite-State Machines
IEEE Transactions on Computers
Determining the equivalence for one-way quantum finite automata
Theoretical Computer Science
Various Aspects of Finite Quantum Automata
DLT '08 Proceedings of the 12th international conference on Developments in Language Theory
Languages Recognized with Unbounded Error by Quantum Finite Automata
CSR '09 Proceedings of the Fourth International Computer Science Symposium in Russia on Computer Science - Theory and Applications
Quantum computing: 1-way quantum automata
DLT'03 Proceedings of the 7th international conference on Developments in language theory
Unbounded-error quantum computation with small space bounds
Information and Computation
Quantum computation with write-only memory
Natural Computing: an international journal
State succinctness of two-way finite automata with quantum and classical states
Theoretical Computer Science
Proving the Power of Postselection
Fundamenta Informaticae - MFCS & CSL 2010 Satellite Workshops: Selected Papers
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The nondeterministic quantum finite automaton (NQFA) is the only known case wherea one-way quantum finite automaton (QFA) model has been shown to be strictly superiorin terms of language recognition power to its probabilistic counterpart. We give acharacterization of the class of languages recognized by NQFAs, demonstrating that itis equal to the class of exclusive stochastic languages. We also characterize the class oflanguages that are recognized necessarily by two-sided error by QFAs. It is shown thatthese classes remain the same when the QFAs used in their definitions are replaced byseveral different model variants that have appeared in the literature. We prove severalclosure properties of the related classes. The ramifications of these results about classicaland quantum sublogarithmic space complexity classes are examined.