通过纠缠交换实现N粒子任意态的概率传态

量子隐形传态的杰出安全特性使其在未来的通讯领域充满潜力.量子力学的不确定性原理和不可克隆定理禁止对量子态进行直接复制,因此,量子隐形传态将量子态划分为经典和量子两部分,信息分别经由经典和量子通道从发送者Alice传递给远方的接收者Bob,根据这两种信息,Bob实行相应操作就可以以一定的几率重建初始传送态.利用一般意义的隐形传态方案,提出一种简便的新方法实现了一个N粒子任意态的概率传态.方法采用N个非最大纠缠的三粒子GHZ态作为量子通道,避免了引入额外的辅助粒子.为了实现传态,Alice将所有粒子分成N份,对第i份的粒子对(i,x_i)实行Bell测量并将结果通过经典通道通知Bob,Bob对粒子(y_i,z_i)进行相应的操作就可以完成第i个粒子信息的传送.当完成N次相似的重复操作后,Bob就可以准确地重建初始传送态.文中以Bell态测量为基本手段,重复的操作同时也降低了实验难度,作为一个特例,文中给出了一个两粒子任意态的传态方案.

Probabilistic Teleportation of an Arbitrary N-qubit State via Entanglement Swapping

Recently, there is much interest in the study of quantum teleportation. Its marvelous security property makes it particularly attractive as potential means for future communication. Uncertain principal and no-cloning theories of quantum mechanics forbid exact copy of quantum states. To solve the problem, quantum teleportation devides message state into two parts: classical message and quantum message which are transmitted through relevant classical and quantum channels from a sender Alice to a distant receiver Bob, respectively. According to both message states,Bob can recover the original message state with certain possibility. Utilizing the general quantum teleportation protocol, in this scheme, a new method is presented by which multi-qubit quantum information can be teleported in a much easier way. It has been extended to teleportation of an arbitrary N-qubit state via entanglement swapping and probabilistic teleportation is investigated as well, which has a more general meaning. N non-maximally entangled triplet GHZ states (Greenberger-Horne-Zeilinger), taking the place of the previous EPR states (Einstein-podolsky-Rosen),serve as quantum channels, which avoids introducing extra auxiliary qubit. In order to complete the teleportation,Alice has to devide all qubits into N parts and make Bell-State measurement on qubit pair (i,x_i) and tell Bob the measurement result through classical channel, then Bob perform some simple local operations on qubits (y_i,z_i) to finish teleporting the i-th qubit. Conditioned on N-times similar repeat, Bob can faithfully reconstruct the initial state.Results show that, in this method, the identification difficulty of entangled states is considerably reduced, the new method is more feasible in technique. And the total possibility of successful teleportation is . As a special case, teleportation of an arbitrary two-qubit state is proposed.