Alternating, private alternating, and quantum alternating realtime automata

We present new results on realtime alternating, private alternating, and quantum alternating automaton models. Firstly, we show that the emptiness problem for alternating one-counter automata on unary alphabets is undecidable. Then, we present two equivalent definitions of realtime private alternati...

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Main Authors: Gökalp Demirci, Mika Hirvensalo, Klaus Reinhardt, A. C. Cem Say, Abuzer Yakaryılmaz
Format: Article
Language:English
Published: Logical Methods in Computer Science e.V. 2019-08-01
Series:Logical Methods in Computer Science
Subjects:
Online Access:https://lmcs.episciences.org/4664/pdf
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author Gökalp Demirci
Mika Hirvensalo
Klaus Reinhardt
A. C. Cem Say
Abuzer Yakaryılmaz
author_facet Gökalp Demirci
Mika Hirvensalo
Klaus Reinhardt
A. C. Cem Say
Abuzer Yakaryılmaz
author_sort Gökalp Demirci
collection DOAJ
description We present new results on realtime alternating, private alternating, and quantum alternating automaton models. Firstly, we show that the emptiness problem for alternating one-counter automata on unary alphabets is undecidable. Then, we present two equivalent definitions of realtime private alternating finite automata (PAFAs). We show that the emptiness problem is undecidable for PAFAs. Furthermore, PAFAs can recognize some nonregular unary languages, including the unary squares language, which seems to be difficult even for some classical counter automata with two-way input. Regarding quantum finite automata (QFAs), we show that the emptiness problem is undecidable both for universal QFAs on general alphabets, and for alternating QFAs with two alternations on unary alphabets. On the other hand, the same problem is decidable for nondeterministic QFAs on general alphabets. We also show that the unary squares language is recognized by alternating QFAs with two alternations.
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spelling doaj.art-4b597330cf854fc4b935070b3d33658f2024-03-08T10:28:03ZengLogical Methods in Computer Science e.V.Logical Methods in Computer Science1860-59742019-08-01Volume 15, Issue 310.23638/LMCS-15(3:22)20194664Alternating, private alternating, and quantum alternating realtime automataGökalp DemirciMika HirvensaloKlaus ReinhardtA. C. Cem SayAbuzer YakaryılmazWe present new results on realtime alternating, private alternating, and quantum alternating automaton models. Firstly, we show that the emptiness problem for alternating one-counter automata on unary alphabets is undecidable. Then, we present two equivalent definitions of realtime private alternating finite automata (PAFAs). We show that the emptiness problem is undecidable for PAFAs. Furthermore, PAFAs can recognize some nonregular unary languages, including the unary squares language, which seems to be difficult even for some classical counter automata with two-way input. Regarding quantum finite automata (QFAs), we show that the emptiness problem is undecidable both for universal QFAs on general alphabets, and for alternating QFAs with two alternations on unary alphabets. On the other hand, the same problem is decidable for nondeterministic QFAs on general alphabets. We also show that the unary squares language is recognized by alternating QFAs with two alternations.https://lmcs.episciences.org/4664/pdfcomputer science - formal languages and automata theorycomputer science - computational complexitycomputer science - logic in computer sciencequantum physics
spellingShingle Gökalp Demirci
Mika Hirvensalo
Klaus Reinhardt
A. C. Cem Say
Abuzer Yakaryılmaz
Alternating, private alternating, and quantum alternating realtime automata
Logical Methods in Computer Science
computer science - formal languages and automata theory
computer science - computational complexity
computer science - logic in computer science
quantum physics
title Alternating, private alternating, and quantum alternating realtime automata
title_full Alternating, private alternating, and quantum alternating realtime automata
title_fullStr Alternating, private alternating, and quantum alternating realtime automata
title_full_unstemmed Alternating, private alternating, and quantum alternating realtime automata
title_short Alternating, private alternating, and quantum alternating realtime automata
title_sort alternating private alternating and quantum alternating realtime automata
topic computer science - formal languages and automata theory
computer science - computational complexity
computer science - logic in computer science
quantum physics
url https://lmcs.episciences.org/4664/pdf
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