共查询到20条相似文献,搜索用时 15 毫秒
1.
M. A. Jafarizadeh Y. Akbari N. Behzadi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(2):283-293
The Gell-Mann λ matrices for Lie algebra su(3) are the
natural basis for the Hilbert space of Hermitian operators acting
on the states of a three-level system(qutrit). So the
construction of EWs for two-qutrit states by using these matrices
may be an interesting problem. In this paper, several two-qutrit
EWs are constructed based on the Gell-Mann matrices by using the
linear programming (LP) method exactly or approximately. The
decomposability and non-decomposability of constructed EWs are
also discussed and it is shown that the λ-diagonal EWs
presented in this paper are all decomposable but by adding
λ-non-diagonal terms, one can obtain various
non-decomposable EWs. 相似文献
2.
Quantum state sharing of an arbitrary two-qubit state
with two-photon entanglements and Bell-state measurements 总被引:4,自引:0,他引:4
F.-G. Deng X.-H. Li C.-Y. Li P. Zhou H.-Y. Zhou 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(3):459-464
Two schemes for sharing an arbitrary two-qubit state based on
entanglement swapping are proposed with Bell-state measurements
and local unitary operations. One is based on the quantum channel
with four Einstein-Podolsky-Rosen (EPR) pairs shared in advance.
The other is based on a circular topological structure, i.e., each
user shares an EPR pair with his neighboring one. The advantage of
the former is that the construction of the quantum channel between
the agents is controlled by the sender Alice, which will improve
the security of the scheme. The circular scheme reduces the
quantum resource largely when the number of the agents is large.
Both of those schemes have the property of high efficiency as
almost all the instances can be used to split the quantum
information. They are more convenient in application than the
other schemes existing as they require only two-qubit
entanglements and two-qubit joint measurements for sharing an
arbitrary two-qubit state. 相似文献
3.
Quantum state sharing of an arbitrary
multiqubit state using nonmaximally entangled GHZ states 总被引:1,自引:0,他引:1
Z.-X. Man Y.-J. Xia N. B. An 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(2):333-340
We explicitly present a scheme for quantum
state sharing of an arbitrary multiqubit state using nonmaximally
entangled GHZ states as the quantum channel and generalized Bell
states as the measurement basis. The scheme succeeds only
probabilistically with its total success probability depending on
the degree of entanglement matching between the quantum channel and
the generalized Bell states. Security of the scheme is guaranteed by
the fact that attacks of an outside eavesdropper or/and an inside
dishonest party will inevitably introduce detectable errors. 相似文献
4.
M. A. Jafarizadeh G. Najarbashi Y. Akbari H. Habibian 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(2):233-255
One of the problems concerning entanglement witnesses (EWs) is the
construction of them by a given set of operators. Here several
multi-qubit EWs called stabilizer EWs are constructed by using the
stabilizer operators of some given multi-qubit states such as GHZ,
cluster and exceptional states. The general approach to manipulate
the multi-qubit stabilizer EWs by exact(approximate) linear
programming (LP) method is described and it is shown that the
Clifford group play a crucial role in finding the hyper-planes
encircling the feasible region. The optimality, decomposability and
non-decomposability of constructed stabilizer EWs are discussed. 相似文献
5.
X. Wang K. Mølmer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(3):385-391
For pairs of particles extracted from a symmetric state of N two-level systems, the two-particle density matrix is expressed in terms of expectation values of collective spin operators
for the large system. Results are presented for experimentally relevant examples of pure states: Dicke states | S, M>, spin coherent, and spin squeezed states, where only the symmetric subspace, S = N/2 is populated, and for thermally entangled mixed states populating also lower S values. The entanglement of the extracted pair is then quantified by a calculation of the concurrence, which provides directly
the entanglement of formation of the pair.
Received 9 May 2001 and Received in final form 16 November 2001 相似文献
6.
Y. Cao A. M. Wang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(1):159-166
We classify 4-qubit pure states under the stochastic
local operation and classical communication (SLOCC). There exist
twenty three essentially different classes of states, giving rise to
a four-graded partially ordered structure. We also give the
criterion to judge which class an arbitrary 4-qubit state belongs
to. We re-classify the 4-qubit pure state into 2×2×4,
4×4 aspects. Finally, we give our analysis of the
classification difference of methods for the 3-qubit pure state. 相似文献
7.
M. Mirzaee M. Rezaei M. A. Jafarizadeh 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(2):193-201
In this study the intimate connection is established between the
Banach space wavelet reconstruction method on homogeneous spaces
with both singular and nonsingular vacuum vectors, and some of the
well known quantum tomographies, such as: Moyal-representation for a
spin, discrete phase space tomography, tomography of a free
particle, Homodyne tomography, phase space tomography and SU(1,1)
tomography. And both the atomic decomposition and the Banach frame
nature of these quantum tomographic examples are also revealed in
details. Finally the connection between the wavelet formalism on
Banach space and Q-function is discussed. 相似文献
8.
S. Tanzilli W. Tittel H. De Riedmatten H. Zbinden P. Baldi M. DeMicheli D.B. Ostrowsky N. Gisin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(2):155-160
We report on energy-time and time-bin entangled photon-pair sources based on a periodically poled lithium niobate (PPLN) waveguide.
Degenerate twin photons at 1 314 nm wavelength are created by spontaneous parametric down-conversion and coupled into standard
telecom fibers. Our PPLN waveguide features a very high conversion efficiency of about 10-6, roughly 4 orders of magnitude more than that obtained employing bulk crystals [#!Tanzilli01a!#]. Even if using low power
laser diodes, this engenders a significant probability for creating two pairs at a time - an important advantage for some
quantum communication protocols. We point out a simple means to characterize the pair creation probability in case of a pulsed
pump. To investigate the quality of the entangled states, we perform photon-pair interference experiments, leading to visibilities
of 97% for the case of energy-time entanglement and of 84% for the case of time-bin entanglement. Although the last figure
must still be improved, these tests demonstrate the high potential of PPLN waveguide based sources to become a key element
for future quantum communication schemes.
Received 13 July 2001 相似文献
9.
Y.-X. Ping B. Zhang Z. Cheng 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(1):175-180
The generation of continuous variable entanglement via
atomic coherence in a two-mode three-level cascade atomic system
is discussed according to the entanglement criterion proposed by
Duan et al. [Phys. Rev. Lett. 84, 2722 (2000)].
Atomic coherence between the top and bottom levels is induced with
two photons of a strong external pump field. It shows that
entanglement for the two-mode field in the cavity can be generated
under certain conditions. Moreover, by means of the input-output
theory, we show that the two-mode entanglement could also be
approached at the output. 相似文献
10.
P. F. Yu J. G. Cai J. M. Liu G. T. Shen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(1):151-158
We investigate the phase decoherence effects on
the entanglement of a two-qubit anisotropic Heisenberg
model
with a nonuniform magnetic field in the x–z-plane. As a
measure of the entanglement, the concurrence of the system is
calculated. It is shown that when the magnetic field is along the
z-axis, the nonuniform and uniform components of the field have
no influence on the entanglement for the cases of
and
, respectively. But when
the magnetic field is not along the z-axis, both the uniform and
the nonuniform components of the field will introduce the
decoherence effects. It is found that the effects of the
Heisenberg chain's anisotropy in the Z-direction on the
entanglement are dependent on the direction of the field.
Moreover, the larger the initial concurrence is, the higher value
it will exhibit during the time evolution of the system for a
proper set of the parameters ν, Δ, θ, γ
, B and b. 相似文献
11.
M.-M. He C.-T. Xu G. Chen J.-Q. Liang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(2):313-320
In this paper, we investigate the entanglement of a two-spin system with
Heisenberg exchange interaction in a quantized field. The pairwise
entanglement between bipartite subsystems is obtained. It is shown that the
entanglement exhibits a quantum phase transition due to the variation of
exchang coupling. Phase diagrams are obtained explicitly. The analogy of the
quantum phase transition compared to the case under a classical field are
addressed. 相似文献
12.
I. Raptis P. Wallden R. R. Zapatrin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(1):185-188
The generalization of Schmidt decomposition due to
Cartelet-Higuchi-Sudbery applied to quantum register (a system of N
qubits) is shown to acquire direct geometrical meaning: any pure
state is canonically associated with a chain of a simplicial
complex. A leading vector method is presented to calculate the
values of the coefficients of appropriate chain. 相似文献
13.
Y. Xiang S. J. Xiong F. Y. Hong 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(2):257-260
A bipartite quantum state (for two systems in any dimensions) can be
decomposed as a superposition of many components. For a
superposition of more than two components we prove that there is a
bound of the entanglement of the superposition state which can be
expressed according to entanglements of its component states.
Especially, if the component states are mutually bi-orthogonal, the
entanglement of the superposition state can be exactly given in
terms of the entanglements of the states being superposed. 相似文献
14.
G.A. Barbosa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):433-440
Quantum states of twin photons entangled in angular momentum and polarization provide new degrees of freedom to researchers
in quantum information and imaging. This work discuss these states and also emphasizes differences between two proposed models
for twin photons entangled in angular momentum. Answers to the presented questions would contribute to a better understanding
of this nonlinear process.
Received 30 August 2002 / Received in final form 10 October 2002 Published online 21 January 2003 相似文献
15.
C.-S. Yu H.-S. Song 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(1):147-151
In this paper, an intuitive approach is employed to
generalize the full separability criterion of tripartite quantum
states of qubits to the higher-dimensional systems [Phys. Rev. A
72, 022333 (2005)]. A distinct characteristic of the
present generalization is that less restrictive conditions are
needed to characterize the properties of full separability.
Furthermore, the formulation for pure states can be conveniently
extended to the case of mixed states by utilizing the Kronecker
product approximate technique. As applications, we give the analytic
approximation of the criterion for weakly mixed tripartite quantum
states and investigate the full separability of some weakly mixed
states. 相似文献
16.
E. Santos 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(3):501-509
A family of local models containing two angles as hidden variables is
defined for experiments measuring polarization correlation of optical
photons. Searching for the best model of the family, that is giving
predictions most close to quantum mechanics, allows deriving Bell-type
inequalities which may be tested with relatively low detection efficiency. 相似文献
17.
Z.-Y. Wang H. Yuan S.-H. Shi Z.-J. Zhang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):371-375
A three-party scheme for securely sharing an
arbitrary unknown single-qutrit state is presented. Using a
generalized Greenberger-Horne-Zeilinger (GHZ) state as the quantum
channel among the three parties, the quantum information (i.e.
the qutrit state) from the sender can be split in such a way that
the information can be recovered if and only if both receivers
collaborate. A generalization of the scheme
to multi-party case is also sketched. 相似文献
18.
G. Chen M.-M. He J.-Q. Li J.-Q. Liang 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(1):25-27
In this paper we investigate entanglement between the nuclear
spin and field mode in a GaAs semiconductor. The eigenfuctions of nuclear spin
in the quantized external field are obtained and thus the von Neumann
entropy is evaluated explicitly. It is shown that the von Neumann entropy
monotonously increases with the spin-field coupling constant but
monotonously decreases with the anisotropy energy. 相似文献
19.
K.-H. Song W.-J. Zhang G.-C. Guo 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(2):267-269
A scheme for preparing entangled coherent states is presented. It is based on the atom-cavity-mode Raman interaction. We also
generalize this method for generating multi-mode entangled coherent states. Finally, our experimental feasibility is discussed.
Received 15 September 2001 and Received in final form 15 November 2001 相似文献
20.
E. Santos 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(3):531-536
A recent experiment by Brida et al. [Eur. Phys. J. D 44, 547 (2007)] is analyzed with the conclusion that the results disagree with standard quantum predictions but fit a simple
local hidden variables model. New experiments are proposed which might throw new light on the anomaly. 相似文献