共查询到20条相似文献,搜索用时 31 毫秒
1.
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
2.
We present an interesting monogamy equation for (2⊗2⊗n)-dimensional pure states, by which a quantity is found to characterize the tripartite entanglement with the GHZ type and W type entanglements as a whole. In particular, we, for the first time, reveals that for any quantum state of a pair of qubits, the difference between the two remarkable entanglement measures, concurrence and negativity, characterizes the W type entanglement of tripartite pure states with the two-qubit state as reduced density. 相似文献
3.
C. Sabín G. García-Alcaine 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,48(3):435-442
We present a classification of three-qubit states based in their three-qubit and reduced two-qubit entanglements. For
pure states these criteria can be easily implemented, and the different types can be related with sets of equivalence classes
under local unitary operations. For mixed states characterization of full tripartite entanglement is not yet solved in general;
some partial results will be presented here. 相似文献
4.
G. H. Yang L. Zhou 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(2):277-282
We investigate two identical Λ-type atoms in free space, and focus
on the entanglement between the two atoms. We derive a master equation for
the atomic subspace and solve it analytically to show how the spontaneous
emission from the two atoms system induces entanglement. The magnitude of
the entanglement and the steady state entanglement are found to be strongly
dependent on the initial states and the orientation of the dipoles of the
two atoms. 相似文献
5.
Polarization correlation in the two-photon decay of atomic hydrogen: nonlocality versus entanglement
T. Radtke A. Surzhykov S. Fritzsche 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(1):7-12
From the work by Perrie et al. [Phys. Rev. Lett. 54, 1790 (1985)], photon pairs from the 2s
1/2 → 1s
1/2 (two-photon) decay of atomic hydrogen are known to be quantum mechanically correlated. In these experiments, the polarization
states of the photons emitted in back-to-back geometry were shown to violate the Bell inequality as a qualitative sign of
nonlocality and entanglement. In the present contribution, we analyze how these nonlocal quantum correlations, as given by
the violation of the Bell inequality, differ from the concurrence as a true entanglement measure. Results are shown for both
quantifiers in dependence of the decay geometry and the initial polarization of the atoms for the 2s
1/2 → 1s
1/2 and 3d
5/2 → 1s
1/2 two-photon decay of atomic hydrogen. These results display the difference between nonlocality and entanglement and, hence,
may stimulate further experiments on nonlocal quantum correlations in atomic systems. 相似文献
6.
Indranil Chakrabarty Sovik Roy Nirman Ganguly Binayak S. Choudhury 《International Journal of Theoretical Physics》2009,48(6):1833-1840
In this work we describe a protocol by which two of three parties generate two bipartite entangled state among themselves
without involving third party, from a non maximal W-state or W-type state |X〉=α|001〉123+β|010〉123+γ|100〉123,α
2+β
2+γ
2=1 shared by three distant partners. Also we have considered the case β=γ, to obtain a range for α
2, for which the local output states are separable and non local output states are inseparable. We also find out the dependence
of the mixedness of inseparable states with their amount of inseparability, for that range of α
2. 相似文献
7.
F. Casagrande A. Lulli 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(1):165-172
We investigate the entanglement of an open tripartite
system where a cavity field mode in thermal equilibrium is
off-resonantly coupled with two atoms that are simultaneously driven
by a resonant coherent field. For moderately detuned atom-field
coupling and strong atomic driving we show the generation, at given
interaction times and for low enough cavity decay rates, of atomic
Bell states and of Bell state superpositions relevant for quantum
gates implementation. The system can oscillate between bi-separable
and fully separable states. Also we describe the distribution of
quantum correlations between the atom-atom and the two atom-field
subsystems. In the dispersive coupling regime with strongly driven
atoms we show the generation of nearly stationary Bell states which
remain protected from cavity dissipation. 相似文献
8.
Pawel Horodecki 《Central European Journal of Physics》2003,1(4):695-707
We consider the problem of invariance of distillable entanglement D and quantum capacities Q under erasure of information about single copy of quantum state or channel respectively. We argue that any 2 ⊗N two-way distillable state is still two-way distillable after erasure of single copy information. For some known distillation
protocols the obtained two-way distillation rate is the same as if Alice and Bob knew the state from the very beginning. The
isomorphism between quantum states and quantum channels is also investigated. In particular it is pointed out that any transmission
rate down the channel is equal to distillation rate with formal LOCC-like superoperator that uses in general nonphysical Alice
actions. This allows to we prove that if given channel Λ has nonzero capacity (Q
→ or Q
⟺) then the corresponding quantum state ϱ(Λ) has nonzero distillable entanglement (D
→ or D
⟺). Follwoing the latter arguments are provided that any channel mapping single qubit into N level system allows for reliable two-way transmission after erasure of information about single copy. Some open problems
are discussed. 相似文献
9.
A tripartite single-photon state shared through noisy quantum channels is considered for three different system configurations. The quantum teleportation of a single-photon state between two parties is investigated in cases with and without the assistance of a third party. The condition that the quantum teleportation is superior to the classical one is provided in terms of the damping rate and detector efficiency. 相似文献
10.
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
11.
Sudden Death of Entanglement between Two Atoms with Initial Tripartite Entangled State in the Tavis--Cummings Model 下载免费PDF全文
We study the entanglement dynamics of two atoms with initial tripartite entangled W-like state in the Tavis-Cummings model. We find that the entanglement evolvement is sensitive not only to the entanglement degree of the initial state but also to the concrete form of the initial state. The so-called sudden death effect occurs only for some initial states. 相似文献
12.
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
13.
S.-B. Li J.-B. Xu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):377-383
We investigate the concurrence and Bell violation of the standard
Werner state or Werner-like states in the presence of collective
dephasing. It is shown that the standard Werner state and certain
kinds of Werner-like states are robust against the collective
dephasing, and some kinds of Werner-like states is fragile and
becomes completely disentangled in a finite-time. The threshold
time of complete disentanglement of the fragile Werner-like states
is given. The influence of external driving field on the
finite-time disentanglement of the standard Werner state or
Werner-like states is discussed. Furthermore, we present a simple
method to control the stationary state entanglement and Bell
violation of two qubits. Finally, we show that the theoretical
calculations of fidelity based on the initial Werner state
assumption well agree with previous experimental results. 相似文献
14.
Y. Z. Wu C. H. Shi X. Hao T. Pan X. F. Jiang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(2):253-257
The evolution of entanglement in a one-dimensional Ising chain with both two-body and three-body interactions, under two types
of initial states, is numerically simulated. We analyse three problems concerning the dynamics of pairwise entanglement: (i)
the possibility of generating large entanglement from an initial separable state by the use of a selective irradiation scheme;
(ii) the effect of three-body interaction on the generation of entanglement from an initial separable state; (iii) the effect
of three-body interaction on the decay of the entanglement from a state with only (m,n)-pair maximal entangled, and the rest
in product form. It is shown that a large pairwise concurrence Cmn can be obtained when the resonant, transverse radio-frequency fields are selectively switched on from the mth to nth spins.
Three-body interaction will decrease the oscillation amplitude of the nearest neighbour concurrence, while the oscillation
amplitude of remote pairwise concurrence will be greatly increased with the consideration of three-body interactions. For
an initial (m,n)-pair maximal entangled state, a slow decay of the pairwise concurrence Cmn is found with the introduction of three-body interactions. 相似文献
15.
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
16.
A. R.R. Carvalho F. Mintert S. Palzer A. Buchleitner 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):425-432
We investigate the time evolution of entanglement for bipartite systems of
arbitrary dimensions under the influence of decoherence. For qubits, we
determine the precise entanglement decay rates under different
system-environment couplings, including finite temperature effects. For qudits, we show how
to obtain upper bounds for the decay rates and also present exact solutions
for various classes of states. 相似文献
17.
F. Michelot M. Rey 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(3):467-495
Effective vibronic Hamiltonian models are built for E ⊗e Jahn-Teller systems and analytical solutions are
obtained through Lie algebraic methods. Although approximate, we show that these models allow in particular to recover the
possible ground state crossover when quadratic couplings are present. The equivalence of E ⊗e and G' ⊗e
vibronic systems in cubic symmetry is precisely established through a particular realization of the electronic operators for
an
orbital quadruplet. We show how this equivalence is broken by a rovibronic interaction which, for a G' ⊗e system, still
gives an exactly solvable model. 相似文献
18.
J. Dong J. F. Teng 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(1):129-134
In this paper, we explicitly present a general scheme for controlled quantum teleportation of an arbitrary multi-qudit state
with unit fidelity and non-unit successful probability using d-dimensional nonmaximally entangled GHZ states as the quantum channel and generalized d-dimensional Bell states as the measurement basis. The expression of successful probability for controlled teleportation is
present depending on the degree of entanglement matching between the quantum channel and the generalized Bell states. And
the formulae for the selection of operations performed by the receiver are given according to the results measured by the
sender and the controller.
相似文献
19.
Given a bipartite quantum state (in arbitrary dimension) and a decomposition of it as a superposition of two others, we find bounds on the entanglement of the superposition state in terms of the entanglement of the states being superposed. In the case that the two states being superposed are biorthogonal, the answer is simple, and, for example, the entanglement of the superposition cannot be more than one ebit more than the average of the entanglement of the two states being superposed. However, for more general states, the situation is very different. 相似文献
20.
Xi-Wen Hou Jing-Hua Chen Ming-Fang Wan Zhong-Qi Ma 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(1):37-41
The dynamical comparison of entanglement, measured by linear entropy and negativity, is carried out for initial pure separable
states in vibrations of H2O and SO2. It is shown that both measures of an initial state with local-mode character have the same period for H2O, while those of an initial state with normal-mode character are no longer identical in period. When the total quantum number
of the initial state is one, both measures rise and lower together with the period for H2O being larger than that for SO2. For a suitable state in H2O, both measures exhibit a beat phenomenon with a long period. 相似文献