SIAM Journal on Computing
Quantum circuits with mixed states
STOC '98 Proceedings of the thirtieth annual ACM symposium on Theory of computing
Undecidability on quantum finite automata
STOC '99 Proceedings of the thirty-first annual ACM symposium on Theory of computing
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
Quantum computation and quantum information
Quantum computation and quantum information
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
Probabilistic Two-Way Machines
Proceedings on Mathematical Foundations of Computer Science
Lower Space Bounds for Randomized Computation
ICALP '94 Proceedings of the 21st International Colloquium on Automata, Languages and Programming
On the power of quantum finite state automata
FOCS '97 Proceedings of the 38th 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
Space-bounded quantum computation
Space-bounded quantum computation
On the complexity of simulating space-bounded quantum computations
Computational Complexity
Decidable and Undecidable Problems about Quantum Automata
SIAM Journal on Computing
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
Exponential Separation of Quantum and Classical Online Space Complexity
Theory of Computing Systems - Special Issue: Symposium on Parallelism in Algorithms and Architectures 2006; Guest Editors: Robert Kleinberg and Christian Scheideler
Quantum computing: 1-way quantum automata
DLT'03 Proceedings of the 7th international conference on Developments in language theory
Languages recognized by nondeterministic quantum finite automata
Quantum Information & Computation
UC'11 Proceedings of the 10th international conference on Unconventional computation
Characterizations of one-way general quantum finite automata
Theoretical Computer Science
Superiority of exact quantum automata for promise problems
Information Processing Letters
Quantum computation with write-only memory
Natural Computing: an international journal
On the complexity of minimizing probabilistic and quantum automata
Information and Computation
Computation with multiple CTCs of fixed length and width
Natural Computing: an international journal
Inverting well conditioned matrices in quantum logspace
Proceedings of the forty-fifth annual ACM symposium on Theory of computing
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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We prove the following facts about the language recognition power of quantum Turing machines (QTMs) in the unbounded error setting: QTMs are strictly more powerful than probabilistic Turing machines for any common space bound s satisfying s(n)=o(loglogn). For ''one-way'' Turing machines, where the input tape head is not allowed to move left, the above result holds for s(n)=o(logn). We also give a characterization for the class of languages recognized with unbounded error by real-time quantum finite automata (QFAs) with restricted measurements. It turns out that these automata are equal in power to their probabilistic counterparts, and this fact does not change when the QFA model is augmented to allow general measurements and mixed states. Unlike the case with classical finite automata, when the QFA tape head is allowed to remain stationary in some steps, more languages become recognizable. We define and use a QTM model that generalizes the other variants introduced earlier in the study of quantum space complexity.