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We analyze entanglement dynamics and transfer in a system composed of two initially correlated two-level atoms, in which each atom is coupled with another atom interacting with its own reservoir. Considering atomic dipole-dipole interactions, the results show that dipole-dipole interactions restrain the entanglement birth of the reservoirs, and a parametric region of dipole-dipole interaction strength exists in which the maximal entanglement of two initially uncorrelated atoms is reduced. The transfer of entanglement shows obvious different behaviors in two initial Bell-like states. 相似文献
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Controlled Bidirectional Quantum Direct Communication by Using a GHZ State 总被引:5,自引:0,他引:5 下载免费PDF全文
A controlled bidirectional quantum secret direct communication scheme is proposed by using a Greenberger- Horne-Zeilinger (GHZ) state. In the scheme, two users can exchange their secret messages simultaneously with a set of devices under the control of a third party. The security of the scheme is analysed and confirmed. 相似文献
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Improvement of Security of Three-Party Quantum Secure Direct Communication Based on GHZ States 总被引:2,自引:0,他引:2 下载免费PDF全文
A protocol for three-party quantum secure direct communication based on Greenberger-Horne-Zeilinger (GHZ) states was recently proposed by 3in et al. [Phys. Lett. A 354 (2006) 67] By analysing the protocol we find some security loopholes, e.g. one bit of secret messages of a party (Alice in the original paper) can always be leaked straight to the public without any eavesdropping. These problems suggested previously are discussed and possible solutions are presented to improve the security of the original protocol. 相似文献
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In this paper, we consider the entanglement dynamics of a four-qubit model [2006 Phys. Rev. A 74 042328] where two entangled qubits a and b locally interact with separate qubits A and B via the spin-exchange-like Hamiltonian. We study the effect of purity of initial entangled state of qubits a, b on the entanglement evolution and its relation with energy transfer. Also, we find that the total bipartite entanglement of qubits a, b plus A, B is not a constant any longer when the initial entangled state of a, b is not pure, which is a complement to the result in the paper [2007 J. Phys. B 40 S45] for the pure case. 相似文献
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采用多参考组态相互作用(MRCI)方法,结合aug-cc-pV6Z(AV6Z)基组,计算了C2+(X4Σg-,14Σu+)的势能曲线,计算过程中考虑了Davidson修正和相对论效应,并将结果外推至完备基组(CBS)的极限.基于得到的单点能量,用最小二乘法方法进行了Murrell-Sorbie函数拟合,得到了势能函数解析式(APEF).基于APEF,计算了C2+(X4Σg-,14Σu+)离子体系的离解能De,平衡核间距Re,光谱常数ωe,ωeχe,Be,αe,结果与实验和其他理论计算值符合... 相似文献
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In this paper,we study the quantum phase transition and the effect of impurity on the thermal entanglement between any two lattices in three-qubit Heisenberg XX chain in a uniform magnetic field.We show that the quantum phase transition always appears when impurity parameter is an arbitrary constant and unequal to zero,the external magnetic field and impurity parameters have a great effect on it.Also,there exists a relation between the quantum phase transition and the entanglement.By modulating the temperature,magnetic field and the impurity parameters,the entanglement between any two lattices can exhibit platform-like behaviour,which can be used to realize entanglement switch. 相似文献
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量子直接通讯是最近提出的一种不需要事先制备共享密钥而直接进行信息传递的通讯方式。在大多数的量子直接通讯方案中必须进行联合Bell基或多粒子GHZ态的测量,但是在实验中实现联合基矢的测量是非常困难的。为了解决这个问题,我们提出一个不需要联合基矢测量的通讯方案一控制的N体同时量子直接通讯方案,该方案只需要对单量子比特进行测量就可以实现。我们考虑如下通讯模型:通讯的控制者Alice希望控制N个用户Bob1,Bob2,…,和BobN之间的秘密通讯。这意味着只有在Alice(前提条件是她是可靠的和合作的)的允许下这些用户才能从对方那里获得信息。同时,各用户之间的通讯是秘密进行的,也就是说通讯的内容对其他人包括控制者Alice来说同样是秘密的。我们提出的方案可以实现该模型,在控制者Alice的控制下,各用户不需要进行联合基矢测量就可以同时交换他们的秘密信息。该方案包括两个安全检测过程,可以探测到窃听者经常使用的攻击方法,因此我们的方案是安全的。 相似文献
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An efficient quantum secure direct communication protocol with one-sender versus N-receiver is proposed. The secret bits can be encoded in the N + 1-particle GHZ states and can be decoded by the N receivers with a classical information of the sender plus their own measurement outcomes. Any attacks can be detected by comparing measurement results on the detecting states. 相似文献