1Henan Key Laboratory of Quantum Information and Cryptography, Zhengzhou 450001 2Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026
Abstract：When applying Grover's algorithm to an unordered database, the probability of obtaining correct results usually decreases as the quantity of target increases. A four-phase improvement of Grover's algorithm is proposed to fix the deficiency, and the unitary and the phase-matching condition are also proposed. With this improved scheme, when the proportion of target is over 1/3, the probability of obtaining correct results is greater than 97.82% with only one iteration using two phases. When the computational complexity is $O(\sqrt{M/N})$, the algorithm can succeed with a probability no less than 99.63%.
2017, Vol. 34 
