共查询到20条相似文献,搜索用时 15 毫秒
1.
Guo Hui Yang Xiang Yang Miao Jun Feng Zhang 《International Journal of Theoretical Physics》2010,49(4):766-776
We report possibility of generating entanglement and steady entanglement between two identical atoms in free space with a
very natural way when their spatial separation is on the order of wavelength or less. We show a dynamical creation of entanglement
and steady entanglement due to the radiative coupling with different separable initial atomic states and study the entanglement
properties about this atomic subsystem. Not only the creation of steady state entanglement is decided by the initial atomic
states, but also the magnitude of the entanglement and the steady state entanglement are found to be strongly dependent on
the initial states. 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 and steady entanglement, the crossing coupling terms in master equation
can enhance the entanglement value. 相似文献
2.
Ying Xu Hosho Katsura Takaaki Hirano Vladimir E. Korepin 《Journal of statistical physics》2008,133(2):347-377
We study a 1-dimensional AKLT spin chain, consisting of spins S in the bulk and S/2 at both ends. The unique ground state of this AKLT model is described by the Valence-Bond-Solid (VBS) state. We investigate
the density matrix of a contiguous block of bulk spins in this ground state. It is shown that the density matrix is a projector
onto a subspace of dimension
. This subspace is described by non-zero eigenvalues and corresponding eigenvectors of the density matrix. We prove that for
large block the von Neumann entropy coincides with Renyi entropy and is equal to
.
NSF Grant DMS-0503712. 相似文献
3.
Dynamic evolution of entanglement is studied for coupling two-qubit system in non-Markov environment in terms of concurrence.
We find that the degree of entanglement depends on the initial quantum state of the system and the interaction between the
two-qubit system and the environment. When the interaction between the qubits and the environment is completely symmetric,
especially, the environment has no effect on the entanglement, where the decoherence is entirely resulted from the interaction
between qubits. By controlling the coupling way of the interaction, thus, one may avoid the entanglement sudden death (ESD). 相似文献
4.
This paper presents a comprehensive analysis of the degree statistics in models for growing networks where new nodes enter one at a time and attach to one earlier node according to a stochastic rule. The models with uniform attachment, linear attachment (the Barabási-Albert model), and generalized preferential attachment with initial attractiveness are successively considered. The main emphasis is on finite-size (i.e., finite-time) effects, which are shown to exhibit different behaviors in three regimes of the size-degree plane: stationary, finite-size scaling, large deviations. 相似文献
5.
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
6.
Creation of Multipartite Entanglement and Entanglement Transfer via Heisenberg Interaction 总被引:5,自引:0,他引:5 下载免费PDF全文
We discuss how to create multipartite entanglement. By coupling a new particle with entangled particles via Heisenberg interaction between two particles, we can prepare three-particle entangled states. For some special coupling strength, entanglement transfer can be achieved from entangled pair AB to particles A and C that never interact by coupling particle C with particle B, which can be used to create entanglement between two separated particles. 相似文献
7.
T. Calligaro Y. Coquinot I. Reiche J. Castaing J. Salomon G. Ferrand Y. Le Fur 《Applied Physics A: Materials Science & Processing》2009,94(4):871-878
Two artefacts made of rock crystal (quartz) from the collection of the Musée du
quai Branly in Paris, France, a skull approximately half of the size of a real cranium and a smaller anthropomorphic head, purportedly
attributed to pre-Columbian Mesoamerican cultures, were studied to assess their authenticity. The surface of the artefacts
were examined by means of optical microscopy and scanning electron microscopy (SEM) and were analyzed nondestructively by
ERDA (Elastic Recoil Detection Analysis), an ion beam analytical method that can measure hydrogen concentration profiles in
depth. Optical and SEM imaging of tool marks indicates that the skull has been cut from a rock crystal block using machine
lapidary techniques unavailable to pre-Columbian artisans, whereas the anthropomorphic head has more likely been carved and
polished with manual techniques comparable to ancient ones. Hydrogen depth profiles in the first micron below the surface
of the artefacts have been measured by ERDA with a 3-MeV He beam in a controlled helium atmosphere. Recently the progressive
penetration of water at the surface of a quartz sample exposed to the natural environment has been proposed as a dating method
(labeled quartz hydration dating or QHD) applicable to archaeological artefacts made of this material. The shallower penetration
of H clearly indicates that the rock crystal skull was manufactured more recently than the reference quartz sample cut in
1740. As for the anthropomorphic head, the deep penetration profiles indicate an older artefact. Thus the converging micro-topographical
examinations and hydrogen profiles of the samples surfaces indicate that the skull is probably not a pre-Columbian artefact
but has been carved in the 18th or 19th century. The anthropomorphic head, on the other hand, could have been carved in the
pre-Columbian period. In addition, the ERDA method carried out with an external beam presented here provides a new and simple
approach for the nondestructive authentication of quartz-based archaeological artefacts by QHD. 相似文献
8.
M. A. Majeed?Khan M. Wasi?Khan Mansour Alhoshan M. S. AlSalhi A. S. Aldwayyan 《Applied Physics A: Materials Science & Processing》2010,100(1):45-51
Pure and Co-doped ZnO nanostructured samples have been synthesized by a chemical route. We have studied the structural and
optical properties of the samples by using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), field-emission
transmission electron microscope (FETEM), energy-dispersive X-ray (EDX) analysis and UV–VIS spectroscopy. The XRD patterns
show that all the samples are hexagonal wurtzite structures. Changes in crystallite size due to mechanical activation were
also determined from X-ray measurements. These results were correlated with changes in particle size followed by SEM and TEM.
The average crystallite sizes obtained from XRD were between 20 to 25 nm. The TEM images showed the average particle size
of undoped ZnO nanostructure was about 20 nm whereas the smallest average grain size at 3% Co was about 15 nm. Optical parameters
such as absorption coefficient (α), energy band gap (E
g
), the refractive index (n), and dielectric constants (σ) have been determined using different methods. 相似文献
9.
Celine Nadal Satya N. Majumdar Massimo Vergassola 《Journal of statistical physics》2011,142(2):403-438
We compute analytically the statistics of the Renyi and von Neumann entropies (standard measures of entanglement), for a random
pure state in a large bipartite quantum system. The full probability distribution is computed by first mapping the problem
to a random matrix model and then using a Coulomb gas method. We identify three different regimes in the entropy distribution,
which correspond to two phase transitions in the associated Coulomb gas. The two critical points correspond to sudden changes
in the shape of the Coulomb charge density: the appearance of an integrable singularity at the origin for the first critical
point, and the detachment of the rightmost charge (largest eigenvalue) from the sea of the other charges at the second critical
point. Analytical results are verified by Monte Carlo numerical simulations. A short account of part of these results appeared
recently in Nadal et al. (Phys. Rev. Lett. 104:110501, 2010). 相似文献
10.
Ji-Hui Teng Hong-Fu Wang Lin-Na Qi Shou Zhang 《International Journal of Theoretical Physics》2009,48(10):2818-2825
We investigate the influence of Kerr medium on atomic population probability and residual entanglement of the system which consists of cascade-type three-level atoms and a bimodal cavity field filled with Kerr medium. The results show that the period of residual entanglement is shortened and the value of residual entanglement is enhanced by appropriately adjusting the nonlinear Kerr constant. Furthermore, we also study the influence of Kerr medium on entanglement evolution of the two atoms, and find that it decreases the value of entanglement between two atoms. 相似文献
11.
Koji Nagata 《International Journal of Theoretical Physics》2009,48(12):3353-3357
We show that there is a contradiction within quantum mechanics. We derive a proposition concerning a quantum expectation value
under the assumption of the existence of the directions in a spin-1/2 system. The quantum predictions within the formalism
of von Neumann’s projective measurement cannot coexist with the proposition concerning the existence of the directions. Therefore,
we have to give up either the existence of the directions or the formalism of von Neumann’s projective measurement. Hence
there is a contradiction within the Hilbert space formalism of the quantum theory. This implies that there is no axiomatic
system for the quantum theory. We need new physical theories in order to explain mathematically the handing of raw experimental
data. 相似文献
12.
Z. Fleischman C. Munasinghe A. J. Steckl A. Wakahara J. Zavada V. Dierolf 《Applied physics. B, Lasers and optics》2009,97(3):607-618
Using combined excitation emission spectroscopy, we performed a comparative study of europium ions in GaN in samples that
have been in situ doped during interrupted growth epitaxy (IGE) or conventional molecular beam epitaxy (MBE) as well as samples
that were grown using organometallic vapor phase epitaxy (OMVPE) and subsequently ion implanted with Eu ions. Through site-selective
resonant excitation, we are able to unambiguously assign all major observed transitions to a combination of different incorporation
sites and electron–phonon coupled transitions. We identified at least nine different incorporation sites of Eu ions in GaN
and studied how these sites behave under different excitation conditions and how their relative number is modified by different
growth and doping conditions. The coupling to phonons has also been studied for a series of Al
x
Ga1−x
N samples with x=0…1. We find that a main site most resembling an unperturbed Eu ion on Ga site is always dominant, while the minority sites
are changing substantially in relative numbers and can occur in some samples fairly close in emission intensity to the main
site. In terms of the excitation pathway after the creation of electron-hole pairs, we found three types of centers: (1) sites
that are dominantly excited through shallow defect traps; (2) sites that are excited through a deep defect trap; (3) sites
that cannot be excited at all including the majority of the main sites. We interpret this finding to indicate that the ion
in this environment is not very efficient in trapping excitation and that the indirect excitation involving other traps depends
on the ion/trap distance. Many of the main sites are far away from these traps and cannot be excited through this channel
at all. The efficiency of excitation is highest for the deep traps, indicating that it would be desirable to enrich the respective
site, as has been done with some success in the IGE grown samples. 相似文献
13.
YE Liu GUO GuangcanLaboratory of Quantum Communication Quantum Computation University of Science Technology of China Hefei ChinaDepartment of Physics Anhui University Hefei China 《Chinese Journal of Lasers》2002,11(2):96-98
A scheme is proposed for the generation of entangled atomic states and a method is presented to produce entangled photon states. It is shown that entanglement can be swapped from atoms to cavities via atom-cavity interaction. 相似文献
14.
Economic and Deterministic Quantum Teleportation of Arbitrary Bipartite Pure and Mixed State with Shared Cluster Entanglement 总被引:1,自引:0,他引:1
We present a novel protocol for teleportation of arbitrary bipartite pure and mixed state with shared cluster entanglement
in this paper. By employing Bell-state measurement on the teleported state and the shared cluster state twice, a sender could
transmit the arbitrary bipartite state to a distant receiver. We show the good feature of the cluster state channel, with
which it can realize the deterministic teleportation rather than probabilistic one. Moreover, since we require less particles
to be shared and need no auxiliary qubit in our protocol, it is more efficient and applicable than the previous schemes. 相似文献
15.
This paper investigates the entanglement dynamics of two-spin Ising model with the Dzialoshinskii-Moriya (DM) interaction
in an inhomogeneous magnetic field. The system is initially prepared in the Werner state.It is found that the phenomenon of
the entanglement sudden death (ESD) appears during the evolution process. We also analyze in detail the effects of the DM
interaction, the degree of inhomogeneous magnetic field and the purity of the initial state on the time of ESD. These effects
indicate that one can control the entanglement of the system. It is helpful for quantum information processing. 相似文献
16.
Masaki Oba Yoichiro Maruyama Katsuaki Akaoka Masabumi Miyabe Ikuo Wakaida 《Applied Physics A: Materials Science & Processing》2010,101(3):545-549
Emission characteristics of gadolinium (Gd) oxide are studied, using ns and fs laser pulses for ablation in double-pulse laser
induced breakdown spectroscopy (LIBS). In the current conditions of pulse energy and signal detection timing, emission intensity
enhancement in the reheating mode is 25-fold, but little effect can be observed in a pre-pulse mode. It is shown that the
optimum focus position of the ablation pulse is about 5 mm apart from the sample surface in the reheating mode. Although little
emission can be observed in the single-pulse configuration with fs ablation pulses, the intense emission can be observed in
the reheating mode in the double-pulse configuration. 相似文献
17.
The evolution of the field entropy and the entanglement between the atom and the field for the system of a single-mode vacuum
field interacting with a Ξ-type three-level atom have been studied by using the reduced quantum entropy. The influences of the detuning of the light
field and the setting of the initial state of the atom on the field entropy and entanglement of the system under consideration
are discussed emphatically. It is showed that the detuning of the light field and the setting of the initial state of the
atom play an important role for the evolution of the field entropy and the entanglement between the atom and the field. The
general conclusions reached are illustrated by numerical results. 相似文献
18.
We consider three two-level atoms (A, B, and C) initially in the W entanglement state, then one of them, C, is injected into a high-Q cavity to make resonant interaction to entangle with the other two atoms A and 13 that are far away from the cavity. The entanglement swapping or disentanglement can be realized by carrying out measurements on C and selecting appropriate interaction time of C with the coherent field. 相似文献
19.
In many-particle spin-half systems with exchange symmetry, we find that the spin squeezing is related to two types of entanglement, the bipartite and the pairwise entanglement. A quantitative relationship is revealed for the spin squeezing parameter, the tangle, and the concurrence. We find that a class of states is spin squeezed if the pairwise entanglement is stronger than the bipartite entanglement. 相似文献
20.
Probabilistic Preparation of N—particle Cat States via Entanglement Swapping and Entanglement Concentration 下载免费PDF全文
We discuss two different schemes for the probabilistic preparation of N-particle cat states using pure multiparticle entangled states via entanglement swapping and entanglement concentration.At the centre of distribution A,Alice performs all of the operations required to achieve our goal. 相似文献