Research On Quantum Control Algorithm And Simulation Based On Quantum Walk

With the advent of the information age,many breakthroughs have been made in the research of quantum informatics.As two important research directions of quantum informatics,quantum cryptography and quantum computing have also brought new opportunities for the development of science and technology.Compared with classical cryptography,quantum cryptography has higher security and accuracy;and compared with classical algorithms,quantum algorithms also have a huge improvement in computing speed,in which the speedup can reach exponential levels.However,in an open system,factors such as noise and decoherence will easily affect quantum cryptography and quantum computing,resulting in a decrease in the accuracy and rate of information acquisition,which cannot meet the expected requirements of the algorithm.The research of this paper aims to solve this problem.There are three innovations in this paper.First,we proposed a quantum private query protocol that can resist collective-dephasing noise,proved its security;second we improved a quantum walk algorithm with iterative automatic control;in the last,we proposed a multi-particle quantum walk search algorithm with feedback control.Firstly,we studied the quantum private query protocol under collective-dephasing noise.The logical Bell state is constructed by 4-qubit decoherence-free state,which is applied to the quantum private query.The logical Bell state is used as measurement base to measure the logical qubit.Make the protocol itself resistant to the influence of noise during the protocol process.The impact of database security,user security and the third-party attacks on the protocol is analyzed,and the security of both communication parties is guaranteed on the premise of ensuring the normal operation of the protocol function.Secondly,we studied the quantum walk algorithm with iterative automatic control.On the basis of the original SKW algorithm,a controllable quantum walk search algorithm under the condition of unknown target state number is constructed,which improves the search accuracy and solves the problem of target detection in the previous algorithm.It solves the problem that the number of target detections in the previous algorithm is single,the number of Oracle calls is large,and the accuracy rate is low.Finally,we studied the feedback control search algorithm of quantum walk on multi-particle rings based on permutation group.This algorithm can control the direction of quantum walk on the ring by controlling the coin operator.Thus,the feedback control can be formed.Thereby the the time consumption of the walk algorithm can be reducd and the controllability and accuracy of the algorithm can be improved.