Theoretical Study On Quantum Key Distribution And Quantum Secret Sharing

Quantum communication is an important part of quantum information and hasprogressed very fast in the last two decades or so. Quantum information provides a newway for secure communication. One such technology is the quantum key distributionand another is the quantum secret sharing.My study involves two areas in quantum communication, i.e., quantum key distri-bution(QKD) and quantum secret sharing(QSS).In the field of quantum key distribution, we have developed two theoreticalschemes. Firstly, we proposed a six-state quantum key distribution scheme withmeasuring-basis encryption technique. In this scheme, Alice and Bob use a con-trol key to synchronize the use of their measuring-basis so that they always use thesame measuring-basis. This scheme retains the advantage of higher security and at thesame time has a higher efficiency. Secondly, we proposed a scheme by using twelvenonorthogonal states in a 4-state system and the measuring-basis encryption technique.In this scheme, two bits of classical information can be encoded on one 4-state particleand the transmitted particles can be fully used just because two parties of the commu-nication needn't publicly announce their measuring bases. Moreover, this scheme ismore sensitive to the eavesdropping and thus has higher security.In the field of quantum secret sharing, we also have developed two theoreticalschemes. Firstly, we designed a high-dimension multiparty quantum secret sharingscheme by using EPR pairs and local unitary operators. This scheme has the advan-tage of not only having higher capacity, but also saving storage space. Secondly, weproposed a scheme for multiparty quantum secret sharing of classical and quantummessages by using entanglement swapping. This scheme can distribute not only theclassical information but also the quantum information between N agents.