Research On Quantum Repeater Scheme Based On Generalized Quantum Parity Code

Quantum information is an interdisciplinary subject based on quantum mechanics and classical information.Similar to classical information,the distribution of quantum information over long distance will be significantly affected by photon loss.Straightforward amplification as in classical telecommunications is not an option in quantum communication because of the no-cloning theorem.This problem could be overcome by implementing quantum repeater scheme.At present,a cutting-edge scheme for realizing quantum repeaters is based on the use of quantum teleportation,in combination with linear optical Bell measurement to perform necessary operations.Compared with the traditional quantum repeater scheme,it has the potential of higher transmission rate.So it gains more and more attention all around the world.In this thesis,the quantum repeater scheme based on quantum teleportation and the structural characteristics of quantum parity code(QPC)are analyzed and innovated as follows:First of all,we analyzes the basic principles of the quantum repeater scheme based on quantum teleportation and proves All kinds of Calderbank-Shor-Steane(CSS)codes can be transmitted through quantum teleportation.Secondly,considering that in practical applications,the measurement efficiency of Bell states on linear optical is only 1/2,resulting in a large number of CSS codes that cannot be correctly distinguished after the measurement.Therefore,this thesis analyzes the Bell measurement strategy necessary to perform quantum teleportation,and derives the conditions that must be met for CSS codes that can effectively transmit between repeaters information under this constraint.Thirdly,in this thesis,the efficiency measured by Bell states on the logical level is close to 1 as the code length increases.The relationship between the performance of the QPC code and its parameters is analyzed,and the parameter required to construct a high-performance QPC code is proposed.Finally,based on the previous work of this thesis,drawing on the essential structural characteristics of QPC codes,a new construction method of QPC codes is given.We call this new QPC code generalized QPC code.Traditional QPC can be classified as a special case of generalized QPC code.Compared with traditional QPC codes through numerical calculation and simulation analysis,compared with traditional QPC codes,the generalized QPC codes we provide are more flexible and have better performance,which can greatly improve the successful transmission probability of logical quantum states in photon attenuation channels.For example,the successful transmission probability of generalized QPC code with a code rate of 1/20 can be increased by up to 14% compared with the QPC code.In addition,by analyzing the optimal block mode of generalized QPC codes,this thesis presents a method for constructing high-performance generalized QPC codes under a given noise model.