A controlled quantum teleportation scheme of an N-particle unknown state via three-particle W1 states

In this paper a controlled quantum teleportation scheme of an N-particle unknown state is proposed when N groups of three-particle W1 states are utilized as quantum channels. The quantum information of N-particle unknown state is transmitted from the sender to the recipient under the control of all supervisors. It can be realized with a certain probability. After the sender makes Bell-state measurements and the supervisors perform the computational basis measurements, the recipient will introduce auxiliary particles and carry out unitary transformations depending on classical information from the sender and the supervisors. Finally, the computational basis measurement will be performed by the recipient to confirm whether the teleportation succeeds or not. The successful completion of the scheme relies on all supervisors＇ cooperation. In addition, the fidelity and security of the scheme are discussed.     

一种三粒子一般态的远程控制传送方案

基于七粒子纠缠态信道,提出一种三粒子一般态的远程控制传送方案.发送者进行投影测量后,发布测量结果.在控制者的控制下,接受者根据发送者的测量结果对所在处的粒子进行适当的幺正操作从而重构原始态.此方案可用来实现控制量子通信.     

一种三粒子一般态的远程控制传送方案

基于七粒子纠缠态信道,提出一种三粒子一般态的远程控制传送方案.发送者进行投影测量后,发布测量结果.在控制者的控制下,接受者根据发送者的测量结果对所在处的粒子进行适当的幺正操作从而重构原始态.此方案可用来实现控制量子通信.     

Construction and application of multi-partner communication network

In this paper, we present a multi-partner communication network protocol. The supervisor prepares numerous Einstein-Podolsky-Rosen （EPR） pairs and auxiliary qubits. He then performs a controlled-NOT（CNOT） gate operation on one qubit of each EPR pair and an auxiliary, which induces the entanglement between the EPR pair and the auxiliary. The supervisor keeps one qubit sequence in his laboratory and sends the others to the outside world. After security approval, the network can be constructed successfully, which can be applied to quantum secret sharing and quantum secure direct communication.     

高压下Pca21相TiO_2直接相变的第一性原理研究

利用第一性原理的GGA+U方法对TiO_2的金红石相(P42/mnm)、铌铁矿相(Pbcn)和Pca21相(Pca21)进行了计算。首先,优化了这几个相的晶体结构及相关参数,分析了焓曲线图,发现在减压至8.4 GPa时,Pca21相直接相变为铌铁矿相。其次,通过拟合分析了三阶Birch-Murnaghan状态方程得到Pca21相的体弹模量B0与类萤石结构实验值(202 GPa)非常符合。最后,通过讨论Pca21相的相变压强和体弹模量,进一步证明Pca21相结构更符合类萤石实验结果。     

4d过渡金属掺杂石墨烯体系对NO_2分子的吸附

基于第一性原理的密度泛函理论对NO_2分子吸附在4d过渡金属掺杂的石墨烯体系进行了研究。发现Cd原子价电子构型为4d~(10)5s~2,形成饱和结构,不容易掺入石墨烯体系。调查了三种NO_2分子的吸附情况,分别是N原子、一个O原子、两个O原子靠近石墨烯体系吸附点。通过能量优化获得最稳定的吸附构型。通过吸附能、电荷转移等数据研究了各吸附构型对NO_2的吸附情况。纯的石墨烯体系对NO_2分子的吸附较弱,吸附能小于0.2 e V,而4d掺杂可以明显提高吸附体系的吸附性能,多数吸附能超过了2 e V。其中掺Nb原子对NO_2吸附效果最好,且吸附构型较稳定,吸附能为3.686 e V。此外,通过比较吸附前后带隙的变化,可发现掺Zr原子,石墨烯体系由半导体转变为金属,而掺Nb原子,石墨烯体系由金属转变为半导体。     

高压下铌铁矿相TiO2直接相变的第一性原理研究

利用第一性原理的GGA+U方法对TiO2的金红石相、铌铁矿相、萤石相、黄铁矿相和四方P42/nmc相进行了计算。首先，优化了这几个相的晶体结构及相关参数，分析了焓曲线图，发现了在50.1GPa压强下，铌铁矿相突然直接转变成一个新的四方P42/nmc相。其次，通过GGA+U和HSE06两种方法计算讨论了四方P42/nmc相的能带结构，并拟合分析了三阶B-M状态方程和XRD图谱。最后，通过分析相变压强范围、体弹模量和XRD图谱，本文认为四方P42/nmc相与立方萤石相是共存的，能很好符合2004年立方TiO2的实验结果。     

Unknown State Transmission Using GHZ States via Collective Noise Channel

Two protocols for transmitting an unknown single-photon state and an unknown non-maximally entangled EPR state are presented by using the quantum channel of three-phonton GHZ （Greenberger-Horne-Zeilinger） state, which can be realized with unitary success probability when collective noise is taken into account. The protocols can also be generalized to transmit multi-photon state or to realize quantum communication in collective noise channel.     

A new representation and probabilistic teleportation of an arbitrary and unknown N-particle state

A new representation of an arbitrary and unknown N-particle state is presented at first. As an application, a scheme for teleporting an arbitrary and unknown N-particle state is proposed when N pairs of two-particle non- maximally entangled states are utilized as quantum channels. After Alice （sender） makes Bell-state measurement on her particles, Bob （recipient） introduces an auxiliary particle and carries out appropriate unitary transformation on his particle and the auxiliary particle depending on classical information from Alice. Then, von Neumann measurement that confirms whether the teleportation succeeds or not is performed by Bob on the auxiliary particle. In order to complete the teleportation, another N-1 times operations need to be performed which are similar to the above ones. It can be successfully realized with a certain probability which is determined by the product of the smaller coefficients of non-maximally entangled pairs. All possible unitary transformations are given in detail.     

一种两粒子任意态的概率传送方案

提出一种采用两组一般三粒子W态作为信道的传送两粒子任意态的方案.在此方案中,在发送者作Bell基测量后,接受者需要采用幺正变换和冯·诺依曼测量来实现传送方案.接受者可以选择在不同的粒子上恢复未知态,选择适当的幺正变换可使传态成功概率相等.