| Quantum information theory is a new discipline generated from quantum mechanics and information theory.This theory studies and analyzes quantum mechanics from the perspective of information theory,and reveals the physical essence of information conversely.Since quantum mechanics has many rules different from classical mechanics,many theories that can be verified and feasible in classical information theory would be forbidden under the corresponding framework of quantum information theory.Such theories are called “no-go”theory.such as,the famous quantum no-cloning theorem,quantum no-deleting theorem and so on.These theories play a vital role in the field of information security.This paper mainly discusses two important no-go theorems: quantum no-deleting theorem and quantum no-masking theorem.The structure of this dissertation is as follows:In Chapter 1,it introduces the basic knowledge background of quantum information theory involved in this dissertation.In Chapter 2,it exhibits the quantum information deletion of an arbitrary pair of non-orthogonal states via weak measurement.Similar to the quantum no-cloning theorem,arbitrary unknown quantum states cannot be deleted,but an arbitrary pair of nonorthogonal quantum states can be deleted probabilistically.Based on this,by performing weak measurement,the probability of deleting an arbitrary pair of non-orthogonal quantum states can be improved.Moreover,the deterministic quantum deleting process can be realized in special cases.In Chapter 3,it demonstrates that the quantum no-masking theorem is valid for3-qubit system.In addition,the deterministic masking and approximate masking of an arbitrary unknown qubit in multipartite qubit system are explored.Moreover,the functional relationship between the approximate masking effect and the entanglement measure of the quantum states employed is given.In Chapter 4,it shows the deterministic masking of arbitrary unknown quantum states in three and four-partite system based on quantum teleportation theory.This scheme clearly exhibits the process of masking and unmasking the information of unknown quantum states in multipartite systems after unitary evolution.These results provide a hand for the experimental implementation.In Chapter 5,it proves that it’s possible to mask all quantum states in a quantum system with higher dimension into the quantum correlation in a multi-partite quantum system composed of local systems with lower dimension.Compared with the existing masking schemes,this means that the same masking task can be completed with less resource.In chapter 6,the summary of the results in this dissertation and the researchable problems are given. |
