共查询到20条相似文献,搜索用时 46 毫秒
1.
The entanglement dynamics of two-qubit systems in different quantum noises are investigated by means of the operator-sum representation method.We find that,except for the amplitude damping and phase damping quantum noise,the sudden death of entanglement is always observed in different two-qubit systems with generalized amplitude damping and depolarizing quantum noise. 相似文献
2.
Rui-Hua Xiao Zhan-Ying Guo Shi-Qun Zhu Jian-Xing Fang 《International Journal of Theoretical Physics》2013,52(6):1721-1728
The dynamical behaviors of quantum discord between two atoms coupled with a vacuum cavity are investigated. If the two qubits are initially prepared in two extended Werner-like states, the quantum discord and entanglement can be numerically calculated. There are remarkable differences between the time evolutions of the quantum discord and entanglement under the same conditions. These results imply that quantum discord is not zero for some unentangled states and in some regions entanglement can disappear completely. A large amount of quantum discord exists between the two-qubit. Thus, the quantum discord is more robust than entanglement for the quantum system exposed to the environment. The quantum discord shows sudden change and its existence depends on the initial state of the system. This property of quantum discord may have important implications for experimental characterization of quantum phase transitions. 相似文献
3.
A simple two-qubit model showing quantum phase transitions as a consequence of ground-state-level crossings is studied in
detail. Using the system’s concurrence as an entanglement measure and heat capacity as a marker of thermodynamical properties,
we obtain an analytical expression giving the latter in terms of the former. A protocol allowing an experimental measure of
entanglement is then presented and compared with a related proposal recently reported by Wieśniak, Vedral, and Brukner. 相似文献
4.
SHAN Chuan-Jia LIU Ji-Bing CHEN Tao CHENG Wei-Wen LIU Tang-Kun HUANG Yan-Xia LI Hong 《理论物理通讯》2010,54(3):427-432
We investigate the sudden birth and sudden death of entanglement of two qubits interacting with uncorrelated structured reservoirs. The system is initially prepared in two-qubit extended Werner-like state. We work out the dependence of the entanglement dynamics on both non-Markovian environments and the purity of initial state, and show that non-Markovian environments and the purity can control the time of the two-qubit entanglement sudden death and the reservoirs' entanglement sudden birth.Furthermore, under the conditions of different purity and initial entanglement, the revival of qubits' entanglement can manifest before, simultaneously or even after the disentanglement of their corresponding reservoirs. 相似文献
5.
We consider the remote implementation of an arbitrary unitary operation on one qubit of a pure two-qubit entangled state with 100% efficiency via entanglement swapping in detail, then directly generalize this protocol from two-qubit to N-qubit entangled states. The overall classical information and distributed entanglement cost required for this quantum remote control protocol is less than the bi-directional quantum state teleportation method. 相似文献
6.
Xiu-Xing Zhang Guang-Hou Sun Xun-Chang Yin Chuan-Jia Shan 《International Journal of Theoretical Physics》2010,49(6):1212-1221
We investigate entanglement dynamics and transfer in a system of two identical independent qubits, each of them locally interacting
with a bosonic reservoir. Starting from two-qubit extended Werner-like states, we have shown that the degree of entanglement
of the initial states, Markovian environments and the purity can control the time of the two-qubit entanglement sudden death
and the reservoirs’ entanglement sudden birth. Moreover, the phenomenon of entanglement sudden death/birth may occur depending
on the values of parameters like purity or degree of entanglement of the initial state. When initial states are not pure,
entanglement sudden death/birth always occurs, this will permit us to link the occurrence time of entanglement sudden death/birth
and entanglement transfer to the purity or the degree of entanglement of the initial states. 相似文献
7.
Li-Tuo Shen Zhen-Biao Yang Mei Lu Rong-Xin Chen Huai-Zhi Wu 《Applied physics. B, Lasers and optics》2014,117(1):195-202
We study the ground states of the single- and two-qubit asymmetric Rabi models, in which the qubit–oscillator coupling strengths for the counterrotating-wave and corotating-wave interactions are unequal. We take the transformation method to obtain the approximately analytical ground states for both models and numerically verify its validity for a wide range of parameters under the near-resonance condition. We find that the ground-state energy in either the single- or two-qubit asymmetric Rabi model has an approximately quadratic dependence on the coupling strengths stemming from different contributions of the counterrotating-wave and corotating-wave interactions. For both models, we show that the ground-state energy is mainly contributed by the counterrotating-wave interaction. Interestingly, for the two-qubit asymmetric Rabi model, we find that, with the increase in the coupling strength in the counterrotating-wave or corotating-wave interaction, the two-qubit entanglement first reaches its maximum and then drops to zero. Furthermore, the maximum of the two-qubit entanglement in the two-qubit asymmetric Rabi model can be much larger than that in the two-qubit symmetric Rabi model. 相似文献
8.
Masashi Ban 《Optics Communications》2008,281(14):3943-3946
The relation between entanglement and phase correlation of two-qubit states is studied. Decoherence of entanglement and phase correlation caused by correlated classical noises is also investigated. It is found that the decay of the phase correlation is quite different from that of the entanglement when the finite-time disentanglement occurs. 相似文献
9.
We investigate quantum control of the dissipation of entanglement under environmental decoherence. We show by means of a simple
two-qubit model that standard control methods – coherent or openloop control – will not in general prevent entanglement loss
induced by a Markovian environment. However, we propose a control method utilizing a Wiseman–Milburn feedback/measurement
control scheme which will effectively negate environmental entanglement dissipation. 相似文献
10.
The effects of atmospheric turbulence on the entanglement of spatial two-qubit states that are prepared using the signal and idler photons produced by parametric down-conversion are studied. Utilizing the non-Kolmogorov model for atmospheric turbulence and Rytov approximation method, we quantify the effects of atmospheric turbulence on the entanglement of the two-qubit state in terms of Wootters's concurrence. Our results show that the effects of the zenith angle of communication channel and the outer scale of turbulence on the concurrence of a spatial two-qubit state can be ignored and the smaller inner scale of turbulence, the smaller refractive-index power α, the shorter wavelength of beams and the longer propagation distance will lead to the larger fluctuations of the concurrence of a spatial two-qubit state. 相似文献
11.
The entanglement between two stationary qubits is a kind of valuable quantum resources in quantum information or quantum network. This paper investigates the time evolution of the entanglement between two atoms, which are initially prepared in the Bell states and each of which interacts with its own cavity field in the identical and non-identical double damping Jaynes-Cummings (J-C) system. It mainly considers the effect of the atomic spontaneous decay Γ and the decay of cavity field κ on the two-qubit entanglement in such system. While causing the decay of entanglement, Γ and κ can also play a positive role in the entanglement evolution, which may imply a way to better control and maintain the entanglement. What is more, the rules governing the transfer of entanglement between two-qubit subsystems in strong coupling regime are finally studied by taking Γ and κ into consideration. 相似文献
12.
De-Chao Li 《Physics letters. A》2009,373(40):3610-3613
Based on a new set of entanglement monotones of two-qubit pure states, we give sufficient and necessary conditions that one two-qubit mixed state is transformed into another one by local operations and classical communication (LOCC). This result can be viewed as a generalization of Nielsen's theorem Nielsen (1999) [1]. However, we find that it is more difficult to manipulate the entanglement transformation between single copy of two-qubit mixed states than to do between single copy of two-qubit pure ones. 相似文献
13.
Yao-Hua Hu Ya-Ping Tao Yong-Gang Tan Hai-Feng Yang 《International Journal of Theoretical Physics》2017,56(5):1504-1516
Considering X-states the density matrixes of which look like the letter X, we propose a weak measurement-based entanglement protection protocol of two-qubit X-states under local amplitude damping channels using weak measurement and reversal operation. It is shown that, with increase of the decoherence parameter, the entanglement attenuates rapidly owing to the amplitude damping noise and even experiences entanglement sudden death (ESD). However, the entanglement under the weak measurement and reversal operation is always much stronger than the entanglement undergoing the amplitude damping decoherence. These results reflect that entanglement of two-qubit X-states from amplitude damping decoherence can be protected, and ESD can be circumvented by increasing the weak measurement strength. 相似文献
14.
Application of quantum algorithms to direct measurement of concurrence of a two-qubit pure state
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This paper proposes a method to measure directly the concurrence of an arbitrary two-qubit pure state based on a generalized Grover quantum iteration algorithm and a phase estimation algorithm. The concurrence can be calculated by applying quantum algorithms to two available copies of the bipartite system, and a final measurement on
the auxiliary working qubits gives a better estimation of the concurrence. This method opens new prospects of entanglement measure by the application of quantum algorithms. The implementation of the protocol would be an important step toward quantum information processing and more complex entanglement measure of the finite-dimensional quantum system with an arbitrary number of qubits. 相似文献
15.
Da-Chuang Li 《Optics Communications》2009,282(6):1226-1636
Thermal entanglement is investigated in a two-qubit Heisenberg XYZ system with different inhomogeneous magnetic fields. It is found that different magnetic fields have different entanglement and critical values. In addition, according to the relation of spin-spin coupling coefficients, a more efficient control parameter of magnetic field can be obtained by adjusting the direction of external magnetic field. 相似文献
16.
Hui-Zhi Xia Chao Li Qing Yang Ming Yang Zhuo-Liang Cao 《Brazilian Journal of Physics》2012,42(3-4):167-171
The operator entanglement of two-qubit joint unitary operations is revisited. The Schmidt number, an important attribute of a two-qubit unitary operation, may have connection with the entanglement measure of the unitary operator. We find that the entanglement measure of a two-qubit unitary operators is classified by the Schmidt number of the unitary operators. We also discuss the exact relation between the operator entanglement and the parameters of the unitary operator. 相似文献
17.
Two closest single-qubit states could be diagonalised by the same unitary matrix,which helps to find the relative entropy of entanglement of a two-qubit ’X’ state.We formulate two binary equations for the relative entropy of entanglement and the corresponding closest separable state of a given two-qubit ’X’ state.This approach can be applied to get the relative entropy of entanglement of many widely-discussed two-qubit states,such as pure states,Werner states,and so on. 相似文献
18.
We study the dynamics of entanglement in a two-qubit system interacting with a squeezed thermal bath via a dissipative system-reservoir interaction with the system and reservoir assumed to be in a separable initial state. The resulting entanglement is studied by making use of concurrence as well as a recently introduced measure of mixed state entanglement via a probability density function which gives a statistical and geometrical characterization of entanglement by exploring the entanglement content in the various subspaces spanning the two-qubit Hilbert space. We also make an application of the two-qubit dissipative dynamics to a simplified model of quantum repeaters. 相似文献
19.
G. Lagmago Kamta A. Y. Istomin A. F. Starace 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(2):389-400
We study systematically the entanglement of a two-qubit
Heisenberg XY model in thermal equilibrium in the presence of an
external arbitrarily-directed static magnetic field, thereby
generalizing our prior work [G. Lagmago Kamta, A.F. Starace, Phys.
Rev. Lett. 88, 107901 (2002)]. We show that a magnetic field
having a component in the xy-plane containing the spin-spin
interaction components produces different entanglement for
ferromagnetic (FM) and antiferromagnetic (AFM) couplings. In
particular, quantum phase transitions induced by the magnetic
field-driven level crossings always occur for the AFM-coupled
qubits, but only occur in FM-coupled qubits when the coupling is of
Ising type or when the magnetic field has a component perpendicular
to the xy-plane. When the magnetic field has a component in the
xy-plane, the cut-off temperature above which the entanglement of
both the FM- and AFM-coupled qubits vanishes can always be
controlled using the magnetic field for any value of the XY coupling
anisotropy parameter. Thus, by adjusting the magnetic field, an
entangled state of two spins can be produced at any finite
temperature. Finally, we find that a higher level of entanglement is
achieved when the in-plane component of the magnetic field is
parallel to the direction in which the XY exchange coupling is
smaller. 相似文献
20.
Jing Ma Li-Nan Jiang Si-Yuan Yu Qi-Wen Ran Li-Ying Tan 《International Journal of Theoretical Physics》2014,53(11):3843-3855
We investigate the entanglement dynamics of the two-qubit entanglement quantum system when they transmitted through the Pauli channels and the depolarizing channel both independently or collectively. Making use of the concurrence we found that the entanglement of a kind of mixed two-qubit system defined in this paper can be preserved in the collective Pauli σ y noise channel, but the entanglement of the other kind of mixed two-qubit system can be preserved in the collective Pauli σ z noise channel. Meanwhile, our quantum systems will undergoing the entanglement sudden death (ESD) in collective depolarizing channel when they return to the maximally entangled Bell states. The reason is the Landblad operators in depolarizing channel are non-commuting operators and this finding is in accord with the previous study. 相似文献