Quantum Computing Algorithms and Computational Complexity

<p>This Special Issue is mainly concerned with quantum algorithms their mathematics from behind and the complexity issues arising from them. It comprises seven papers: Two of them are focused on improving the performance by means of quantum algorithms over the best instances of classical ones: A Fast Quantum Image Component Labeling Algorithm [1] by Yan Li Dapeng Hao Yang Xu and Kinkeung Lai. Quantum Algorithms for Some Strings Problems Based on Quantum String Comparator [2] by Kamil Khadiev Artem Ilikaev and Jevgenijs Vihrovs. Another four papers deal with enhanced quantum algorithms: Progress towards Analytically Optimal Angles in Quantum Approximate Optimisation: [3] by Daniil Rabinovich Richik Sengupta Ernesto Campos Vishwanathan Akshay and Jacob Biamonte. Quantum Weighted Fractional Fourier Transform [4] by Tieyu Zhao Tianyu Yang and Yingying Chi. On the Amplitude Amplification of Quantum States Corresponding to the Solutions of the Partition Problem [5] by Mauro Mezzini Jose J. Paulet Fernando Cuartero Hernan I. Cruz and Fernando L. Pelayo. On the Complexity of Finding the Maximum Entropy Compatible Quantum State [6] by Serena Di Giorgio and Paulo Mateus. Last but not least one paper researched a classical operational research problem by means of quantum annealing: GPS: A New TSP Formulation for Its Generalizations Type QUBO [7] by Saul Gonzalez-Bermejo Guillermo Alonso-Linaje and Parfait Atchade-Adelomou. As Guest Editors of this Special Issue we would like to thank the authors and reviewers who made this possible by promoting spreading research on and supporting quantum computing.</p>