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1.
Effect of excess noise on continuous variable entanglement sudden death and Gaussian quantum discord 下载免费PDF全文
A symmetric two-mode Gaussian entangled state is used to investigate the effect of excess noise on entanglement sudden death and Gaussian quantum discord with continuous variables. The results show that the excess noise in the channel can lead to entanglement sudden death of a symmetric two-mode Gaussian entangled state, while Gaussian quantum discord never vanishes. As a practical application, the security of a quantum key distribution (QKD) scheme based on a symmetric two-mode Gaussian entangled state against collective Gaussian attacks is analyzed. The calculation results show that the secret key cannot be distilled when entanglement vanishes and only quantum discord exists in such a QKD scheme. 相似文献
2.
Sudden birth versus sudden death of entanglement for the extended Werner-like state in a dissipative environment 下载免费PDF全文
In this paper, we investigate the dynamical behaviour of
entanglement in terms of concurrence in a bipartite system
subjected to an external magnetic field under the action of
dissipative environments in the extended Werner-like initial state.
The interesting phenomenon of entanglement sudden death as well as
sudden birth appears during the evolution process. We analyse in
detail the effect of the purity of the initial entangled state of two qubits
via Heisenberg XY interaction on the apparition time of entanglement
sudden death and entanglement sudden birth. Furthermore, the
conditions on the conversion of entanglement sudden death and
entanglement sudden birth can be generalized when the initial
entangled state is not pure. In particular, a critical purity of the
initial mixed entangled state exists, above which entanglement
sudden birth vanishes while entanglement sudden death appears. It is
also noticed that stable entanglement, which is independent of
different initial states of the qubits (pure or mixed state), occurs
even in the presence of decoherence. These results arising from the
combination of the extended Werner-like initial state and dissipative
environments suggest an approach to control and enhance the
entanglement even after purity induced sudden birth, death and
revival. 相似文献
3.
研究了初态为X态时Tavis-Cummings模型中具有偶极相互作用两原子的纠缠演化特性,在演化过程中,同时号码出现了两原子的纠缠突然死亡(ESD)与突然产生(ESB)两种有趣的现象.详细分析了两原子初始态的纯度、偶极相互作用、光场粒子数对这两种现象出现时间的影响,进一步给出了初始为混态时ESB与ESD的转换条件.计算结果表明,上述系统参量对两原子的纠缠演化、ESB与ESD有重要的影响,偶极相互作用会改变纠缠度的振荡周期,使出现ESD的时间间隔减少;随着初始两原子纠缠纯度的增大,纠缠突然产生以及纠缠突然死亡存在的时间缩短,并且可以提高两原子之间的纠缠;对于特殊的初态,产生了纠缠不变性以及固定的两原子纠缠,该定值受两原子初始状态的纯度控制。 相似文献
4.
A system of two initially entangled qubits interacting with a bosonic environment is considered. The interaction induces a loss of the initial entanglement of the two qubits, and for specific initial states it causes entanglement sudden death. An investigation of the modifications on the entanglement dynamics by a single pulse control field, performed in the two qubit system, shows that the control field can not only protect entangled states against sudden death but also induce a revival of entanglement in the two qubit system. 相似文献
5.
研究了两个初始处于纠缠相干态上的宏观场各自独立地与一个环境相互作用的系统, 环境对腔场的影响只体现在腔场光子数的泄漏上. 采用共生纠缠(concurrence)度量两个宏观场间的纠缠, 并给出宏观场纠缠的解析解, 以分析这种系统中宏观场纠缠的动力学特性. 研究表明当场的初始平均光子数较大时, 即使很小的光子泄漏率也会导致腔场间出现纠缠突然死亡现象. 同时研究结果也表明光子从腔场泄漏到环境后会导致两环境间的纠缠突然产生, 而这种纠缠产生的时机直接与腔场的初始光子数相关. 本文还进一步发现在大光子数的情况下, 在任何时刻任意一个腔场与任意一个环境间都不会产生纠缠.
关键词:
纠缠相干态
环境
纠缠突然死亡
纠缠突然产生 相似文献
6.
初始处于类贝尔纠缠态的完全一样的二能级原子A和B分别与空间分离的两处于真空场的腔场a和腔场b发生相互作用,利用双Jaynes-Cummings理论模型进行分析,我们采用部分转置矩阵的负本征值(negativity)的方法研究了两原子间纠缠度随时间演化的动力学特征,通过数值计算和理论分析发现在一定参数范围内原子间出现纠缠猝死现象;通过参数调整能有效缩小纠缠猝死区域,在一定的参数条件下能有效消除两原子间的纠缠猝死现象。 相似文献
7.
We investigate dynamics of pairwise entanglement between two atoms for various entangled initial states. The initial entanglement shows an interesting time evolution, including entanglement sudden death. The initial portion of the excited state is responsible for the sudden death of the entanglement. The initial portion of excited–ground–ground state or the initial photons in the system can induce pairwise entanglement. Meanwhile, we find that our model gives a concrete example to support the two theorems in [F. Verstraete, K. Audenaert, J. Dehaene and B. De Moor, J. Phys. A: Math. Gen. 34 (2001) 10327]. 相似文献
8.
Entanglement evolution of a two-qubit system with decay beyond the rotating-wave approximation 下载免费PDF全文
The entanglement property of two identical atoms,
initially entangled in Bell states, coupled to a single-mode cavity
is considered. Based on the reduced non-perturbative quantum master
equation method, the entanglement evolution of the two atoms with
decay is investigated beyond the conventional rotating-wave
approximation. We show that the counter-rotating wave terms,
usually neglected, have a great influence on the disentanglement
behaviour of the system. The phenomena of entanglement sudden death
and entanglement sudden birth will occur. In addition, we show that
the entanglement can be strengthened by introducing the
dipole--dipole interaction of the two atoms. 相似文献
9.
The sudden death of entanglement is investigated for non-Markovian dynamic process of a pair interacting flux qubits under
a thermal bath. The entangling evolution of the coupled qubits interacting with non-Markov environment is investigated in
terms of concurrence. The results show that, for initially two-qubit entangled states, the sudden death of entanglement (ESD)
always happens in the thermal reservoir, where the appearance of entanglement sudden death strongly depends on the environment.
Especially, ESD of the qubits is easier to occur for non-Markovian process than for Markovian one. 相似文献
10.
Entanglement evolution of three-qubit mixed states in multipartite cavity—reservoir systems 下载免费PDF全文
We analyze the multipartite entanglement evolution of three-qubit mixed states composed of a GHZ state and a W state.For a composite system consisting of three cavities interacting with independent reservoirs,it is shown that the entanglement evolution is restricted by a set of monogamy relations.Furthermore,as quantified by the negativity,the entanglement dynamical property of the mixed entangled state of cavity photons is investigated.It is found that the three cavity photons can exhibit the phenomenon of entanglement sudden death(ESD).However,compared with the evolution of a generalized three-qubit GHZ state which has the equal initial entanglement,the ESD time of mixed states is later than that of the pure state.Finally,we discuss the entanglement distribution in the multipartite system,and point out the intrinsic relation between the ESD of cavity photons and the entanglement sudden birth of reservoirs. 相似文献
11.
12.
We investigate the dynamics of entanglement for a two-parameter class of states in a hybrid qubit-qutrit system under the influence of various dissipative channels. Our results show that entanglement sudden death (ESD) is a general phenomenon and it usually takes place in a qubit-qutrit system interacting with various noisy channels, not only the case with dephasing and depolarizing channels observed by others. ESD can only be avoided for some initially entangled states under some particular noisy channels. Moreover, the environment affects the entanglement and the coherence of the system in very different ways. 相似文献
13.
J. S. Zhang L. Chen M. Abdel-Aty A. X. Chen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2012,66(1):2
We study the dynamics of quantum discord and entanglement of two entangled two-level
atoms within two isolated and dissipative cavities in the weak- or strong-coupling regime.
The quantum entanglement are measured by concurrence and relative entropy. The quantum
discord of two atoms based on quantum mutual information and relative entropy are also
calculated. In the weak-coupling regime, the sudden death of quantum discord and
entanglement of two atoms can occur simultaneously within a short interaction time. When
the interaction time is long, quantum discord and entanglement of two atoms could be
partially preserved due to the long-lived nature of quantum discord and entanglement.
However, in the strong-coupling regime, there is no sudden death of quantum discord though
the entanglement sudden death phenomenon occurs. In addition, we observe that entanglement
and discord will be destroyed eventually when the atom-field interactions are strong. We
also address the issue of experimental realization briefly. 相似文献
14.
Entanglement and decoherence of coupled superconductor qubits in a non-Markovian environment 下载免费PDF全文
The sudden death of entanglement is investigated for
the non-Markovian dynamic process of a pair of interacting flux qubits
under a thermal bath. The results show that, for initially two-qubit
entangled states, entanglement sudden death (ESD) always
happens in the thermal reservoir, where its appearance
strongly depends on the environment.
In particular, ESD of the qubits occurs more easily for the non-Markovian
process than for the Markovian one. 相似文献
15.
SHAN Chuan-Jia LIU Ji-Bing CHENG Wei-Wen LIU Tang-Kun HUANG Yan-Xia LI Hong 《理论物理通讯》2009,51(6):1013-1016
In this paper, we study entanglement dynamics of a two-qubit extended Werner-like state locally, interacting with independent noisy channels, i.e., amplitude damping, phase damping, and depolarizing channels. We show that the purity of initial entangled state has direct impacts on the entanglement robustness in each noisy channel. That is, if the initial entangled state is prepared in mixed instead of pure form, the state may exhibit entanglement sudden death (ESD) and/or be decreased for the critical probability at which the entanglement disappear. 相似文献
16.
Synthesis of maximally entangled mixed states and disentanglement in
coupled Josephson charge qubits 总被引:1,自引:0,他引:1
Mahmoud Abdel-Aty 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(3):537-543
We analyze a controllable generation of maximally entangled mixed states of
a circuit containing two-coupled superconducting charge qubits. Each qubit
is based on a Cooper pair box connected to a reservoir electrode through a
Josephson junction. Illustrative variational calculations were performed to
demonstrate the effect on the two-qubits entanglement. At sufficiently
deviation between the Josephson energies of the qubits and/or strong
coupling regime, maximally entangled mixed states at certain instances of
time is synthesized. We show that entanglement has an interesting subsequent
time evolution, including the sudden death effect. This enables us to
completely characterize the phenomenon of entanglement sharing in the
coupling of two superconducting charge qubits, a system of both theoretical
and experimental interest. 相似文献
17.
Entanglement dynamics of two non-interacting atoms in a squeezed vacuum reservoir is studied. Several examples with different initial entangled states are investigated, and it is found that entangled atoms become disentangled faster in squeezed vacuum than in ordinary vacuum, and larger squeezing results in faster entanglement decay. The time evolution of the concurrence and the separability "distance" A can be used to explain this novel entanglement sudden death phenomenon. 相似文献
18.
Three-Qubit Entanglement Sudden Death 总被引:1,自引:0,他引:1
GE Min ZHU Lin-Fan QIU Liang 《理论物理通讯》2008,49(6):1443-1448
We study entanglement dynamics of three-qubit system via negativity. Three atoms A, B, and C interact isolatedly with their own Jaynes-Cummings cavities a, b, and c. Aa system is prepared entangled with Bb and Cc, however, their mutual isolations forbid Aa interacting with system Bb and Cc. It is the same for system Bb and Cc. We show entanglement evolution of different three-qubit systems ABC, abc, Abc, and aBC and find entanglement sudden death effect. 相似文献
19.
A system consisting of two atoms interacting with a
two-mode vacuum is considered, where each atom is resonant with the
two cavity modes through two different competing transitions. The
effect of mode--mode competition on the atom--atom entanglement is
investigated. We find that the entanglement between the two atoms
can be induced by the mode--mode competition. For the initial atomic
state |\varPsi(0)\rangle, whether the atoms are initially
separated or entangled, a large or even maximal entanglement between
them can be obtained periodically by introducing the mode--mode
competition. For the initial atomic state |\varPhi(0)\rangle, the
strong mode--mode competition can prevent the two atoms entangled
initially from suffering entanglement sudden death; besides, it
makes them in a more stable and longer-lived entanglement than in
the non-competition case. 相似文献
20.
N. Metwally 《International Journal of Theoretical Physics》2010,49(7):1571-1579
The sensitivity of entanglement to the thermal and squeezed reservoirs’ parameters is investigated regarding entanglement
decay and what is called sudden-death of entanglement, for a system of two qubit pairs. The dynamics of information is investigated
by means of the information disturbance and exchange information. We show that for squeezed reservoir, we can keep both of
the entanglement and information survival for a long time. However the sudden death of information is depicted clearly when
the entangled qubit system interacts with thermal reservoir. By controlling the environmental parameters, one can reduces
the lose of the encrypted information. 相似文献