基于交叉相位调制制备四光子偏振纠缠态及其在隐形传态上的运用

利用克尔介质、偏振分束器、半波片和对强相干探测场的零拍探测,呈现了一个关于制备四光子偏振Diche态、GHZ态和W态的方案,当前量子光学实验技术条件均能有效满足该方案的要求.强的探测模相继和多个信号模光子相互作用,每次对于探测模而言,都会产生一个相位旋转.接下来,对探测模利用零拍探测,信号模可以投影得到想要的光子偏振纠缠态.此外,为了展现所制备的纠缠态作为重要的量子信息资源的价值,基于交叉相位调制进一步提出了一个隐形传送三光子偏振纠缠态的实验方案.     

The decoherence of quantum entanglement and teleportation in Bell-diagonal states

We study the dynamics of entanglement and teleportation in Bell-diagonal states. Using the concepts of concurrence and fidelity, the analytical expressions of the entanglement, the output entanglement and the average fidelity with decoherence are obtained for this model. We discover a class of initial states in which the output entanglement and the average fidelity are destroyed by decoherence. The quality of teleportation depends on the system parameters and time.     

Faithful Controlled Teleportation of an Arbitrary Unknown Two-Atom State via Special W-States and QED Cavity

A scheme is proposed for the controlled teleportation of an arbitrary two-atom state via special W-type entangled states and QED cavity. The scheme does not involve the direct joint Bell-state-measurement （BSM）. We show that the quantum information is split into two parts~ thus the original atomic state cannot be perfectly restored by the receiver without the other agent＇s collaboration and classical communication. In addition, the physical realization of this scheme is not difficult.     

Faithful Teleportation of an Unknown Atomic-Entangled State Without Bell-State Measurement

An alternative scheme is proposed for teleportation of an unknown atomic-entangled state. The scheme is based on the resonant interaction of a two-mode cavity field with a A-type three-level atom. In contrast with the previously proposed scheme of [Commun. Theor. Phys. 47 （2007） 253], the present scheme is ascendant, since the fidelity is 1.0 in principle similarly without the Bell-state measurement. The scheme may be generalized to not only the teleportation of the cavity-mode-entangled-state but also the teleportation of the multi-atomic entangled states included in generalized GHZ states. And the scheme is experimentally feasible based on the current cavity QED technique.     

Teleportation of Unknown Atomic Entangled States Using GHZ Class States

We propose two physical schemes, which can teleport unknown atomic entangled states from user A （Alice） to user B （Bob） via GHZ class states as quantum channel The two schemes are both based on cavity QED techniques. In the two schemes, teleportation and distillation procedures can be realized simultaneously. The second teleportation scheme is more advantageous than the first one.     

Scheme for Implementing Quantum Dense Coding and Teleportation with Tripartite Entangled State in Cavity QED

In this paper, we present a peculiar tripartite entangled state that is inequivalent to both the GHZ state and the W state, and then propose to implement efficient quantum information processing such as quantum dense coding and teleportation with this entangled state in cavity QED. In this scheme the atoms interact with a highly detuned cavity field with the assistance of a strong classical driven field. It does not require the transfer of quantum information between the atomic system and the cavity, and then our scheme is insensitive to both the cavity decay and the thermal field.     

Teleportation Capability of Six-Qubit Cluster State

Recently Wei-Bo Gao et al. [Phys. Rev. Lett. 104 (2010) 020501]; reported on the creation of a 4-photon 6-qubit cluster state. It is shown this states can be utilized for perfect teleportation of arbitrary three qubit systems and controlled teleportation of an arbitrary two-qubit state. Therefore, the six-qubit cluster state as quantum channels is equivalent to that of maximally six-qubit entangled state.     

Concurrence, tangle and fully entangled fraction

We show that although we cannot distil a singlet from many pairs of bound entangled states, the concurrence and the tangle of two entangled quantum states are always strictly larger than those of one of them, even both entangled quantum states are bound entangled. We present a relation between the concurrence and the fidelity of optimal teleportation. We also give new upper and lower bounds for concurrence and tangle.     

Noisy teleportation of qubit states via the Greenberger-Horne-Zeilinger state or the W state

The effects of distributing entanglement through the amplitude damping channel or the phase damping channel on the teleportation of a single-qubit state via the Greenberger--Horne--Zeilinger state and the W state are discussed. It is found that the average fidelity of teleportation depends on the type and rate of the damping in the channel. For the one-qubit affected case, the Greenberger--Horne--Zeilinger state is as robust as the W state, i.e., the same quantum information is preserved through teleportation. For the two-qubit affected case, the W state is more robust when the entanglement is distributed via the amplitude damping channel; if the entanglement is distributed via the phase damping channel, the W state is more robust when the noisy parameter is small while the Greenberger--Horne--Zeilinger state becomes more robust when it is large. For the three-qubit affected case, the Greenberger--Horne--Zeilinger state is more robust than the W state.     

V型原子与光场拉曼相互作用传送未知原子态

未知量子态从一个地方到另一个地方的隐形传送在量子信息领域中有非常重要的作用,提出了一种利用简并V型三能级原子与振幅很大的单模相干态腔场的拉曼相互作用来传送未知原子态的方案。