Electronics

Quantum Representation for Deterministic Push-Down Automata

Varun Puram, K. M. George, Johnson P. Thomas

Published Nov 18, 2024• 0 citations

Abstract

Abstract There are many papers presenting quantum computing models. The definitions parallel the classical definitions of finite state automata, push down automata, context-free grammars etc. Classical computing model definitions define languages precisely. We can state that a string belongs to a language or does not belong to it with no room for error. Quantum definitions do not possess this certainty. Sacrificing the certainty and adopting a quantum definition of a computing model does not appear to provide any concrete power to the model. Therefore, the path of this paper is to begin from the classical definition and end in a quantum circuit. In this paper we start from a Deterministic Push-Down Automaton (DPDA). We present circuit for state transition and stack operations. The circuits presented can be viewed as independent algorithms. As an example, the approach used to construct the circuit for state transition can be utilized to build the circuit for a function presented as a Boolean matrix.

DOI: 10.3390/electronics13224531

Related papers

Algorithm to build quantum circuit from classical description of DFSM

Varun Puram, Dingyi Kang, K. M. George +1 more

There are several papers that define quantum finite automaton analogous to classical finite automaton. Some papers describe the power of quantum automaton. In general, in quantum automata unitary matrices are associated to input symbols. Even though quantum circuits (or unitary matrices) are shown in specific cases, there is no general method given to construct a circuit or unitary matrix is found in the literature. This research focuses on construction of unitary matrices for each input symbol from the classical definition of a Deterministic Finite State Machine (DFSM). An algorithm is developed to associate a quantum circuit to an input symbol which considered as a mapping of classical DFSM states. IBM quantum composer is used to design circuits and build examples.

IEEE International Conference on Quantum Computing and Engineering (QCE)Sep 1, 20222 citations

Quantum Automata and Quantum Grammars

Cristopher Moore, James P. Crutchfield

To study quantum computation, it might be helpful to generalize structures from language and automata theory to the quantum case. To that end, we propose quantum versions of finite-state and push-down automata, and regular and context-free grammars. We find analogs of several classical theorems, including pumping lemmas, closure properties, rational and algebraic generating functions, and Greibach normal form. We also show that there are quantum context-free languages that are not context-free.

arXiv:quant-ph/9707031Jul 16, 19974 citations

Quantum automata and quantum computing

Marats Golovkins

Quantum finite automata were introduced by C.Moore and J.P.Crutchfield in [MC 97] and by A.Kondacs and J.Watrous in [KW 97]. This notion is not a generalization of the deterministic finite automata, but rather a generalization of deterministic reversible (permutation) automata. In [AF 98] A.Ambainis and R.Freivalds raised the question what kind of probabilistic automata can be viewed as a special case of quantum finite automata. To answer that question and study relationship between quantum finite automata and probabilistic finite automata, we introduce a notion of probabilistic reversible automata (PRA, or doubly stochastic automata). We give the necessary condition for a language to be recognized by PRA. We find that there is a strong relationship between different possible models of PRA and corresponding models of quantum finite automata. In these thesis we regard quantum automata, probabilistic reversible and deterministic reversible automata as reversible automata. At least two non-equivalent definitions of language recognition are used for one-way reversible finite automata in various papers. Both of these definitions have their own advantages and disadvantages, summarized in our classification of one-way reversible automata. Further, we introduce a notion of quantum finite multitape automata and prove that there is a language recognized by a quantum finite multitape automaton but not by deterministic finite multitape automata. Additionally we discover unexpected probabilistic automata recognizing complicated languages. Finally, we revise the concept of quantum pushdown automata (QPA), first introduced by C.Moore and J.P.Cruthchfield in [MC 97]. We give the definition of QPA in a non-equivalent way, including unitarity criteria, by using the definition of quantum finite automata of [KW 97]. It is established that the unitary criteria of QPA are not equivalent to the corresponding unitary criteria of quantum Turing machines [BV 97]. We show that QPA can recognize every regular language. We also present some simple non-context-free languages recognized by QPA (hence not recognizable by deterministic and nondeterministic pushdown automata).

Jan 1, 20020 citations

Expressive Power of Quantum Pushdown Automata with Classical Stack Operations under the Perfect-Soundness Condition

Masaki Nakanishi

One important question for quantum computing is whether a computational gap exists between models that are allowed to use quantum effects and models that are not. Several types of quantum computation models have been proposed, including quantum finite automata and quantum pushdown automata (with a quantum pushdown stack). It has been shown that some quantum computation models are more powerful than their classical counterparts and others are not since quantum computation models are required to obey such restrictions as reversible state transitions. In this paper, we investigate the power of quantum pushdown automata whose stacks are assumed to be implemented as classical devices, and show that they are strictly more powerful than their classical counterparts under the perfect-soundness condition, where perfect-soundness means that an automaton never accepts a word that is not in the language. That is, we show that our model can simulate any probabilistic pushdown automata and also show that there is a non-context-free language which quantum pushdown automata with classical stack operations can recognize with perfect soundness.

IEICE Transactions on Information and SystemsMar 1, 20067 citations

Regular quantum grammars and regular grammars

Wei Cheng, Jue Wang

To study quantum computation, Moore and Crutchfield (Theoret. Comput. Sci. vol. 237, pp. 275-306, 2000) proposed quantum versions of finite-state and push-down automata, as well as regular and context-free grammars. In this note, we show that the languages generated by regular quantum grammars are equivalent to the languages generated by regular grammars. Therefore, from the perspective of generating languages, regular quantum grammars are not more powerful than classical regular grammars. This implies that it may be necessary to look for more well-formed definitions of quantum grammars and maybe those of quantum automata.

International Conference on Communications, Circuits and SystemsJan 1, 20041 citation

Notes on Stack Machines and Quantum Stack Machines

Daowen Qiu

Multi-stack machines and Turing machines can simulate to each other. In this note, we give a succinct definition of multi-stack machines, and from this definition it is clearly seen that pushdown automata and deterministic finite automata are special cases of multi-stack machines. Also, with this mode of definition, pushdown automata and deterministic pushdown automata are equivalent and recognize all context-free languages. In addition, we are motivated to formulate concise definitions of quantum pushdown automata and quantum stack machines.

arXiv:2511.17264Nov 21, 20250 citations