共查询到20条相似文献,搜索用时 781 毫秒
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Wei Cheng Fang Xu Hua Li Gang Wang 《International Journal of Theoretical Physics》2013,52(4):1061-1074
We discuss entanglement and distillability in qutrit-qutrit systems by convex linear combination. Inspired by the seminal Horodecki quantum states, we explicitly construct three pairs of qutrit-qutrit systems. We find that convex linear combination states can evolve from entangled into non-entangled states and from distillable into non-distillable states, and vice versa. The new and different angle from convex linear combination states can be helpful for us to understand entanglement and distillability. 相似文献
3.
How the Hawking effect and the prepared states influence the entanglement distillability of Dirac fields in the Schwarzschild spacetime is studied by using the Werner states which are composed of the maximum or generic entangled states. It is found that the states are entangled when the parameter of the Werner states, F , satisfies τ<F?1 in which τ is influenced both by the Hawking temperature of the black hole and energy of the fields. It is also shown that although the parameter of the generic entangled states, α, affects the entanglement, it does not change the range of the parameter, F, where the states are entangled for the case of generic entangled states. 相似文献
4.
We study entanglement distillability of bipartite mixed spin states under Wigner rotations induced by Lorentz transformations. We define weak and strong criteria for relativistic isoentangled and isodistillable states to characterize relative and invariant behavior of entanglement and distillability. We exemplify these criteria in the context of Werner states, where fully analytical methods can be achieved and all relevant cases presented. 相似文献
5.
The effect of stochastic dephasing on the dynamics of entanglement of qutrit-qutrit states is investigated by using negativity and bound entanglement defined with realignment criterion. From the analysis, we find that the time evolution of quantum free entanglement and bound entanglement depends on the fluctuations of the stochastic variables and the parameters of the particular initial states of concern. Our results imply that some qutrits states display both distillability sudden death and entanglement sudden death, while some states do not display distillability sudden death but onlyentanglement sudden death. 相似文献
6.
We characterize the set of shared quantum states which contain a cryptographically private key. This allows us to recast the theory of privacy as a paradigm closely related to that used in entanglement manipulation. It is shown that one can distill an arbitrarily secure key from bound entangled states. There are also states that have less distillable private keys than the entanglement cost of the state. In general, the amount of distillable key is bounded from above by the relative entropy of entanglement. Relationships between distillability and distinguishability are found for a class of states which have Bell states correlated to separable hiding states. We also describe a technique for finding states exhibiting irreversibility in entanglement distillation. 相似文献
7.
We investigate the entanglement dynamics in a bipartite atomic system subjected to thermal environment with arbitrary initial pure entangled states. We consider the atoms close together and study the effect of temperature of the reservoir and the interatomic distance on the evolution of entanglement for both initially entangled and unentangled states. We find that we can have long time entanglement even in thermal environment. 相似文献
8.
Quantum Entanglement in a System of Two Spatially Separated Atoms Coupled to the Thermal Reservoir
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We study quantum entanglement between two spatially separated atoms coupled to the thermal reservoir. The influences of the initial state of the system, the atomic frequency difference and the mean number of the thermal field on the entanglement are examined. The results show that the maximum of the entanglement obtained with nonidentical atoms is greater than that obtained with identical atoms. The degree of entanglement is progressively decreased with the increase of the thermal noise. Interestingly, the two atoms can be easily entangled even when the two atoms are initially prepared in the most mixed states. 相似文献
9.
DiGuglielmo J Samblowski A Hage B Pineda C Eisert J Schnabel R 《Physical review letters》2011,107(24):240503
Among the possibly most intriguing aspects of quantum entanglement is that it comes in free and bound instances. The existence of bound entangled states certifies an intrinsic irreversibility of entanglement in nature and suggests a connection with thermodynamics. In this Letter, we present a first unconditional, continuous-variable preparation and detection of a bound entangled state of light. We use convex optimization to identify regimes rendering its bound character well certifiable, and continuously produce a distributed bound entangled state with an extraordinary and unprecedented significance of more than 10 standard deviations away from both separability and distillability. Our results show that the approach chosen allows for the efficient and precise preparation of multimode entangled states of light with various applications in quantum information, quantum state engineering, and high precision metrology. 相似文献
10.
We study the effect of a thermal reservoir on the squeezing transfer and entanglement between two identical harmonic oscillators, caused by a bilinear coupling of the RWA type. We analyze the evolution of the invariant squeezing coefficients of each mode for arbitrary initially factorized mixed states, as well as the separability coefficient based on Simon's criterion for Gaussian states. We show the importance of initial squeezing for the emergence of entanglement and the existence of critical temperatures above which no squeezing transfer or entanglement are possible. 相似文献
11.
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
12.
Xiang-Ping Liao Jian-Shu Fang Mao-Fa Fang Zhong Huang 《International Journal of Theoretical Physics》2011,50(9):2631-2643
We study the dynamics of quantum discord between two qubits coupled collectively to a thermal reservoir. For comparison, we
also consider the dynamics of quantum entanglement. It is shown that we can obtain a stable quantum discord induced by the
thermal environment when the discord of the initial state is zero. The thermal environment can also induce a stable amplification
of the initially prepared quantum discord for certain X-type states. It is very valuable that the quantum discord is more
resistant against the thermal environment than quantum entanglement. And, we have demonstrated that the sudden death of discord
in a Markovian regime is impossible even at high temperature. It provides us a feasible way to create and protect quantum
correlation in the case of a high-temperature thermal environment for various physical system such as trapped ions, quantum
dots or Josephson junctions. 相似文献
13.
Entanglement and decoherence of coupled superconductor qubits in a non-Markovian environment
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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
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15.
Masanes L 《Physical review letters》2006,97(5):050503
A multipartite quantum state violates a Bell inequality asymptotically if, after jointly processing by general local operations an arbitrarily large number of copies of it, the result violates the inequality. In the bipartite case we show that asymptotic violation of the Clauser-Horne-Shimony-Holt inequality is equivalent to distillability. Hence, bound entangled states do not violate it. In the multipartite case we consider the complete set of full-correlation Bell inequalities with two dichotomic observables per site. We show that asymptotic violation of any of these inequalities by a multipartite state implies that pure-state entanglement can be distilled from it, although the corresponding distillation protocol may require that some of the parties join into several groups. We also obtain the extreme points of the set of distributions generated by measuring N quantum systems with two dichotomic observables per site. 相似文献
16.
Bing Wang Shao-hua Xu Yao-hua Meng 《International Journal of Theoretical Physics》2013,52(10):3604-3607
We study the entanglement dynamics of two-level atoms interacting in independent structured non-Markovian reservoirs. The atoms are initially prepared in a pure W state and the reservoir is in the vacuum. We have shown that the degree of entanglement of the initial states, Markovian environments can control the time of the two qubit entanglement sudden death and the reservoirs’ entanglement sudden birth. We show the dependence of entanglement dynamics on the non-Markovianity. When the initial state of atoms is in a pure W state, the entanglement will decay asymptotically. 相似文献
17.
Entanglement and coherence of a three-level atom in Λ configuration interacting with two fields
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We investigate the entanglement of a three-level atom in λ
configuration interacting with two quantized field modes by using
logarithmic negativity. Then, we study the relationship of the
atomic coherence and the entanglement between two fields which are
initially prepared in vacuum or thermal states. We find that if the
two fields are prepared in thermal states, the atomic coherence can
induce the entanglement between two thermal fields. However, there
is no coherence-induced entanglement between two vacuum fields. 相似文献
18.
M. Popp F. Verstraete M.A. Martin-Delgado I. Cirac 《Applied physics. B, Lasers and optics》2006,82(2):225-235
We present an introduction to the concept of localizable entanglement (LE) with special focus on its numerical computation.
LE is an entanglement measure for multipartite systems, which leads naturally to notions like entanglement length and entanglement
fluctuations. After briefly reviewing basic properties of LE we present a scheme for the numerical calculation of LE. It is
based on the matrix-product state representation of many-body quantum states and the Monte Carlo method. It can be applied
both to pure and mixed states. Using this method we calculate the LE of ground and thermal states for various spin systems.
PACS 03.67.Mn; 03.65.Ud; 75.10.Pq; 73.43.Nq 相似文献
19.
We present studies of thermal entanglement of a three-spin system in triangular symmetry. Spin correlations are described within an effective Heisenberg Hamiltonian, derived from the Hubbard Hamiltonian, with super-exchange couplings modulated by an effective electric field. Additionally a homogenous magnetic field is applied to completely break the degeneracy of the system. We show that entanglement is generated in the subspace of doublet states with different pairwise spin correlations for the ground and excited states. For the doublets with the same spin orientation one can observe nonmonotonic temperature dependence of entanglement due to competition between entanglement encoded in the ground state and the excited state. The mixing of the states with an opposite spin orientation or with quadruplets (unentangled states) always monotonically destroys entanglement. Pairwise entanglement is quantified using concurrence for which analytical formulae are derived in various thermal mixing scenarios. The electric field plays a specific role – it breaks the symmetry of the system and changes spin correlations. Rotating the electric field can create maximally entangled qubit pairs together with a separate spin (monogamy) that survives in a relatively wide temperature range providing robust pairwise entanglement generation at elevated temperatures. 相似文献
20.
Chuan-Jia Shan Tao Chen Ji-Bing Liu Wei-Wen Cheng Tang-Kun Liu Yan-Xia Huang Hong Li 《International Journal of Theoretical Physics》2010,49(4):717-727
The decoherence and the decay of quantum entanglement due to both population relaxation and thermal effects are investigated
for the two qubits initially prepared in the extended Werner-like state by solving the Lindblad form of the master equation,
where each qubit is interacting with an independent reservoir at finite temperature T. Entanglement sudden death (ESD) and entanglement sudden birth (ESB) are observed during the evolution process. We analyze
in detail the effects of the mixedness, the degree of entanglement of the initial states and finite temperature on the time
of entanglement sudden death and entanglement sudden birth. We also obtain an analytic formula for the steady state concurrence
that shows its dependence on both the system parameters, the decoherence rate and finite temperature. These results arising
from the combination of extended Werner-like initial state and independent thermal reservoirs suggest an approach to control
the maximum possible concurrence even after the purity and finite temperature induce sudden birth, death and revival. 相似文献