| As an important branch of quantum communication,quantum key distribution has been widely studied in recent decades.It is based on the laws of quantum mechanics to achieve unconditional secure key distribution between sender and receiver.However,in actual experimental conditions,the photon source and measurement device are not perfect,resulting in some security holes in the protocol.In 2012,the mesurement-device-independent quantum key distribution protocol can successfully resist all attacks on measuring devices.Combined with the decoy state method,the protocol can ensure its security even with practical imperfect photon sources and photon detectors.However,this protocol has a disadvantage that the key generation rate is relatively low.In order to improve the key rate,high-dimensional coding or hyperentanglement can be used.At present,these two schemes have been widely used in various quantum communication protocols.The first work of this paper is to propose a high-dimensional measurement-device-independent quantum key distribution protocol that can be implemented under existing conditions.In this protocol,the key generation rate is improved by using a single photon encoded in two degrees of freedom of polarization and momentum,and a hyper-entangled Bell state measurement scheme which is feasible under current experimental conditions is adopted,which greatly improves the feasibility of this protocol.In addition,as a basic resource of quantum communication and quantum computing,entanglement has always been the focus of people’s research.In particular,with the development of various high-dimensional quantum communication protocols,the generation of high-dimensional entanglement has become the prerequisite to implement these protocols.From the degree of freedom of entanglement,high-dimensional entanglement can be divided into single degree of freedom entanglement and hyperentanglement in multiple degrees of freedom at the same time.The second work of this paper is to propose two kinds of preparation schemes of hyperentanglement in three degrees of freedom,including hyperentanglement in polarization,discrete frequency and time-bin degrees of freedom,hyperentanglement in polarization,space and time-bin degrees of freedom.These two schemes generate two kinds of hyperentanglement in three degrees of freedom through the spontaneous parametric down-conversion process in nonlinear crystal and some other linear optical devices,which will have important applications in future high-dimensional protocols. |
