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991.
This paper proposes a simple scheme for generating a three-atom GHZ
state via cavity quantum electrodynamics (QED). The task can be
achieved through the interaction between two EPR states, which can be
prepared easily with current technology. In this scheme, the cavity
field is only virtually excited during the interaction process, and
no quantum information transfer between the atoms and the cavity is
required. Thus it greatly prolongs the efficient decoherent time.
Moreover, this scheme is also applicable for generating an N-atom
GHZ state. 相似文献
992.
Considering two identical two-level atoms interacting
with a single-mode thermal
field through two-photon processes,
this paper studies the atomic coherence control on the
entanglement between two two-level atoms,
and finds that the entanglement is greatly
enhanced due to the initial atomic coherence. The results show
that the entanglement can be manipulated
by changing the initial
parameters of the system, such as the superposition coefficients
and the relative phases
of the initial atomic coherent state and the mean photon
number of the cavity field. 相似文献
993.
We consider a one-dimensional
array of L identical coupled cavities, and each cavity is doped
with a two-level qubit. Experimentally, it has been developed in
several varieties by the newest technology. We find that the one-qubit
quantum state can be perfectly transferred through the cavity array, and the
entanglement between the first two qubits can also be transferred
to the last two qubits. In addition, we successfully realized the
entangling gate and swap gate in the coupled cavity array. 相似文献
994.
CHEN Chang-Yong LI Shao-Hua 《理论物理通讯》2008,49(3):625-628
A scheme has been proposed for generating the macroscopic entanglement between the mesoscopic squeezed vacuum states and mesoscopic coherent states by considering both the two-photon interaction and the single photon interaction of N two-level atoms in cavities with high quality factor assisted by a strong driving field. Moreover, we derive the dissipative interaction models for single photon interaction and two-photon interaction, respectively. The corresponding analytical expressions of the fidelities can be given. Our scheme can be realized in the current techniques on the cavity QED. 相似文献
995.
LIU Dan ZHAO Xin LONG Gui-Lu 《理论物理通讯》2008,49(2):329-332
Four-qubit entanglement has been investigated using a recent proposed entanglement measure, multiple entropy measures (MEMS). We have performed optimization for the nine different families of states of four-qubit system. Some extremal entangled states have been found. 相似文献
996.
SHAN Chuan-Jia CHENG Wei-Wen LIU Tang-Kun GUO De-Jun XIA Yun-Jie 《理论物理通讯》2008,49(6):1505-1514
Considering the dipole-dipole coupling intensity between two atoms and the field in the Fock state, the entanglement dynamics between two atoms that are initially entangled in the system of two two-level atoms coupled to a single mode cavity in the presence of phase decoherence has been investigated. The two-atom entanglement appears with periodicity without considering phase decoherence, however, the phase decoherence causes the decay of entanglement between two atoms, with the increasing of the phase decoherence coefficient, the entanglement will quickly become a constant value, which is affected by the two-atom initial state. Meanwhile the two-atom quantum state will forever stay in the maximal entangled state when the initial state is proper even in the presence of phase decoherence. On the other hand, the Bell violation and the entanglement do not satisfy the monotonous relation, a large Bell violation implies the presence of a large amount of entanglement under certain conditions, while a large Bell violation corresponds to a little amount of entanglement in certain situations. However, the violation of Bell-CHSH inequality can reach the maximal value if two atoms are in the maximal entangled state, or vice versa. 相似文献
997.
CHEN Chang-Yong 《理论物理通讯》2008,49(5):1187-1190
We propose an etticient scheme for generating the macroscopic superpositions and the entanglement between the high-order squeezed vacuum states by considering the multi-photon interaction of N two-level atoms in a cavity with high quality factor, assisted by a strong driving field. Through specific choices of the cavity detuning, a number of multi-party entangled states between the atoms and the high-order squeezed vacuum states and among the high-order squeezed vacuum states of the cavities can be prepared, including also the macroscopic "Schrodinger cats" of the high- order squeezed vacuum states, the entangled states of the macroscopic "Schrodinger cats", and so on. Possible extension and application of our scheme are discussed. Our scheme is reachable within the current techniques in the cavity QED. 相似文献
998.
LIN Gong-Wei CHEN Li-Bo DU Qian-Hua LAN Jie-Qin LIN Xiu-Min 《理论物理通讯》2008,49(6):1483-1486
Based on the input-output relation of a one-sided cavity, we propose an experimental scheme to implement entanglement swapping with photons. In the ideal case, the successful probability of the scheme approaches unity. In addition, the protocol can be extended to establish multiphoton entanglement among distant users in a communication network. 相似文献
999.
We present a (t,n) threshold multiparty controlled quantum teleportation protocol of an arbitrary m-qubit quantum state between two remote parties. The unknown m-qubit quantum state can be recovered by the receiver under control of a subset of the n controllers if the number of the subset is larger than or equal to a threshold, say, t, but not for any t-1 or fewer controllers. Our scheme seems to be more practical and more flexible than otherexisting protocols. The quantum resource required is just mEinstein-Podolsky-Rosen (EPR) pairs plus some single photons. Thetechniques required are only Bell state measurement, single-qubitunitary operation and von Neumann measurement. So our scheme is alsofeasible with present-day technique. 相似文献
1000.
A quantum secure direct communication scheme using dense coding is proposed. At first, the sender (Alice) prepares four-particle genuine entangled states and shares them with the receiver (Bob) by sending two particles in each entangled state to him. Secondly, Alice encodes secret information by performing the unitarytransformations on her particles and transmits them to Bob. Finally, Bob performs the joint measurements on his particles to decode the secret information. The two-step security test guarantees the security of communication. 相似文献