7 research outputs found

    Two Topics Ahead Membrane Computing

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    Two topics from the area of probability theory and randomness challenging membrane computing together with open problems and research proposals are discussed

    A Randomized Algorithm for 3-SAT

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    In this work we propose and analyze a simple randomized algorithm to find a satisfiable assignment for a Boolean formula in conjunctive normal form (CNF) having at most 3 literals in every clause. Given a k-CNF formula phi on n variables, and alpha in{0,1}^n that satisfies phi, a clause of phi is critical if exactly one literal of that clause is satisfied under assignment alpha. Paturi et. al. (Chicago Journal of Theoretical Computer Science 1999) proposed a simple randomized algorithm (PPZ) for k-SAT for which success probability increases with the number of critical clauses (with respect to a fixed satisfiable solution of the input formula). Here, we first describe another simple randomized algorithm DEL which performs better if the number of critical clauses are less (with respect to a fixed satisfiable solution of the input formula). Subsequently, we combine these two simple algorithms such that the success probability of the combined algorithm is maximum of the success probabilities of PPZ and DEL on every input instance. We show that when the average number of clauses per variable that appear as unique true literal in one or more critical clauses in phi is between 1 and 1.9317, combined algorithm performs better than the PPZ algorithm

    Solving the 3-SAT problem using quantum algorithms

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    La computació quàntica és una àrea de les ciències de la computació que aplica els principis de la mecànica quàntica per crear un paradigma de computació diferent del que estem acostumats. Aquest projecte explora com solucionar 3-SAT utilitzant algorismes quàntics per trobar una assignació que ens satisfaci una fórmula donada. El primer enfocament del problema consisteix a utilitzar l'algorisme de Grover amb una fórmula per trobar les seves possibles solucions. L'algorisme de Grover, ens permet aconseguir un speedup quadràtic respecte a un algorisme de força bruta que busca en l'espai de totes les possibles assignacions d'una fórmula. A més, s'utilitza l'algorisme Quantum counting per determinar el nombre de solucions que té la nostra fórmula i així poder maximitzar la probabilitat d'èxit en l'algorisme de Grover mitjançant la repetició del seu operador. Els ordinadors clàssics poden solucionar el problema d'una forma més eficient que a força bruta, i per això es compara l'algorisme quàntic anterior amb un dels millors algoritmes clàssics per 3-SAT com és l'algorisme de Schöning. Finalment, l'algorisme de Grover és generalitzat i utilitzat juntament amb l'algorisme de Schöning par aconseguir un speedup quadràtic d'aquest últim. Els diferents algoritmes han estat implementats amb Qiskit, un programari desenvolupat per IBM que ens permet treballar amb ordinadors quàntics fent ús del llenguatge de programació Python.Quantum computing is an area of computer science that applies quantum mechanics principles to create a different computational paradigm than the one we are used to. This project explores how to solve 3-SAT using quantum algorithms to find a satisfying assignment of a given formula. The first approach to the problem consists of using Grover's algorithm with a given formula to find its possible solutions. Grover's algorithm allows us to achieve a quadratic speedup over a brute-force search algorithm that searches in the space of all the possible assignments of the formula. In addition, the Quantum counting algorithm is used to determine how many solutions there are beforehand and thus maximize the probability of success in Grover's by repeating the Grover operator. Classical computers can solve the problem more efficiently than just using brute-force search. Therefore, the previous quantum algorithm is compared with Schöning's, one of the best classical algorithms for 3-SAT. Finally, Grover's algorithm is generalized and used with Schöning's to obtain a quadratic speedup of the latter. The different algorithms have been implemented using Qiskit, an open-source software development kit (SDK) developed by IBM to work with quantum computers using the Python Programming Language

    Quantum algorithms for quantum many-body systems and small quantum computers

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    Randomized algorithms for 3-SAT

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