共查询到20条相似文献,搜索用时 15 毫秒
1.
Effects of photon addition on quantum nonlocality of squeezed entangled coherent states for Bell-inequality tests are studied theoretically. By utilizing the method of photon-parity measurement, it is found that photon addition can always increase the degrees of Bell violations within a certain parameter range. A possible scheme for generating photon-added squeezed entangled coherent states is proposed. 相似文献
2.
Shao-Hua Xiang Zhen-Gang Shi Wei Wen De-Hua Lu Xi-Xiang Zhu Ke-Hui Song 《Optics Communications》2011,284(9):2402-2407
We propose a protocol to concentrate partially entangled states of photons using entanglement reflector, which consists of a single electron spin confined in a charged quantum dot inside a single-sided microcavity. The outstanding advantage of the proposed scheme is its experimental simplicity and feasibility since it only needs to perform a single local measurement on electronic spins rather than a joint Bell-state measurement on photons. We then extend this scheme to concentrate N-photon Greenberger-Horne-Zeilinger state. Finally, we analyze the influence of various imperfections on the scheme. 相似文献
3.
Probabilistic teleportation scheme of two-mode entangled photon states by using linear optic element
XIANG Shao-hua 《原子与分子物理学报》2003,20(3):425-428
A scheme for teleporting two-mode entangled photon states with the successful probability 33.3% is Proposed. In the sehane, the tdeported qubit is two-mode photon entangled states, and two pairs of EPR pair are usedas quantum channel between a sender and a recciver. This procedure is achieved by using two 50/50 symmetric beam aplitters and four photon number detectors with the help of classical information. 相似文献
4.
M. Genovese 《The European Physical Journal C - Particles and Fields》2008,55(4):683-686
Entangled states of pseudoscalar mesons represent a very interesting tool for studying the foundations of quantum mechanics,
e.g. for testing the Bell inequalities. Recently, they also emerged as a test bench for quantum information protocols. On
the other hand, from a quantum information point of view, the characterization of the distance between two quantum states
is a topic of the utmost importance. In this work, with the purpose of providing a useful tool for further investigations,
we address the problem of which distance allows for a better discrimination between density matrices appearing in pseudoscalar
phenomenology.
PACS 13.20.Eb; 03.65.Bz; 03.65.Ta; 03.67.-a 相似文献
5.
We introduce a new entangled quantum state generated by applying single-mode coherent superposition of photon subtraction and addition (a† cos θ + a sin θ)m to the entangled coherent state |Ψ±(α,0)〉, and then investigate the entanglement properties affected by coherent superposition operation. It is shown that this operation can be applied to enhance the entanglement of the state |Ψ+(α,0)〉. In addition, the effects of the coherent operation is better to improve the entanglement than that of the creation operation (a†m) for |Ψ+(α,0)〉 in a small-amplitude regime and for |Ψ−(α,0)〉 in any regime. 相似文献
6.
Nuri Ünal 《Annals of Physics》2012,327(9):2177-2183
In this study, we derive the quasi-coherent states for a photon in a medium with time varying dielectric permittivity . We introduce a new kind of holomorphic coordinates and solve the Schrödinger equation for a harmonic oscillator with the time dependent parameters by reducing it to the Riccati equation for which the nonstationary solution gives the squeezed states of a photon with non-minimum uncertainties. We also derive the quasi-coherent states and discrete, nonstationary quantum states in the configuration space of a photon. 相似文献
7.
8.
We show how to design families of operational criteria that distinguish entangled from separable quantum states. The simplest of these tests corresponds to the well-known Peres-Horodecki positive partial transpose (PPT) criterion, and the more complicated tests are strictly stronger. The new criteria are tractable due to powerful computational and theoretical methods for the class of convex optimization problems known as semidefinite programs. We successfully applied the results to many low-dimensional states from the literature where the PPT test fails. As a by-product of the criteria, we provide an explicit construction of the corresponding entanglement witnesses. 相似文献
9.
D. Rodriguez-Mendez 《Optics Communications》2011,284(13):3345-3347
We show how NOON states may be generated entangling two cavities by passing atoms through them. The atoms interact with each cavity via two-photon resonant transitions. We take advantage of the fact that depending on the state the atom enter (excite or ground), it leaves or takes two photons per interaction and leaves the cavities in a pure state. 相似文献
10.
We discuss the entanglement properties of bipartite states with Gaussian Wigner functions. For the separability, and the positivity of the partial transpose, we establish explicit necessary and sufficient criteria in terms of the covariance matrix of the state. It is shown that, for systems composed of a single oscillator for Alice and an arbitrary number for Bob, positivity of the partial transpose implies separability. However, this implication fails with two oscillators on each side, as we show by constructing a five parameter family of bound entangled Gaussian states. 相似文献
11.
Schmid C Kiesel N Laskowski W Wieczorek W Zukowski M Weinfurter H 《Physical review letters》2008,100(20):200407
The variety of multipartite entangled states enables numerous applications in novel quantum information tasks. In order to compare the suitability of different states from a theoretical point of view, classifications have been introduced. Accordingly, here we derive criteria and demonstrate how to experimentally discriminate an observed state against the ones of certain other classes of multipartite entangled states. Our method, originating in Bell inequalities, adds an important tool for the characterization of multiparty entanglement. 相似文献
12.
We present the cluster-type entangled coherent states (CTECS) and discuss their properties. A cavity QED generation scheme using suitable choices of atom-cavity interactions, obtained via detunings adjustments and the application of classical external fields, is also presented. After the realization of simple atomic measurements, CTECS representing nonlocal electromagnetic fields in separate cavities can be generated. 相似文献
13.
Comparison between photon annihilation-then-creation and photon creation-then-annihilation thermal states:Non-classical and non-Gaussian properties
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We investigate the nonclassical properties of arbitrary number photon annihilation-then-creation operation(AC) and creation-then-annihilation operation(CA) to the thermal state(TS), whose normalization factors are related to the polylogarithm function. Then we compare their quantum characters, such as photon number distribution, average photon number,Mandel Q-parameter, purity and the Wigner function. Because of the noncommutativity between the annihilation operator and the creation operator, the ACTS and the CATS have different nonclassical properties. It is found that nonclassical properties are exhibited more strongly after AC than after CA. In addition we also examine their non-Gaussianity. The result shows that the ACTS can present a slightly bigger non-Gaussianity than the CATS. 相似文献
14.
《Physics Reports》2005,415(4):207-259
We develop an original approach for the quantitative characterisation of the entanglement properties of, possibly mixed, bi- and multipartite quantum states of arbitrary finite dimension. Particular emphasis is given to the derivation of reliable estimates which allow for an efficient evaluation of a specific entanglement measure, concurrence, for further implementation in the monitoring of the time evolution of multipartite entanglement under incoherent environment coupling. The flexibility of the technical machinery established here is illustrated by its implementation for different, realistic experimental scenarios. 相似文献
15.
Lancaster T Blundell SJ Baker PJ Brooks ML Hayes W Pratt FL Manson JL Conner MM Schlueter JA 《Physical review letters》2007,99(26):267601
The information accessible from a muon-spin relaxation experiment can be limited due to a lack of knowledge of the precise muon stopping site. We demonstrate here the possibility of localizing a spin polarized muon in a known stopping state in a molecular material containing fluorine. The muon-spin precession that results from the entangled nature of the muon spin and surrounding nuclear spins is sensitive to the nature of the stopping site. We use this property to identify three classes of sites that occur in molecular magnets and describe the extent to which the muon distorts its surroundings. 相似文献
16.
Nonlocal shaping effects in the time or spectral profiles of an entangled photon pair emerging from a pulsed parametric down-converter are observed by spectrally or temporally filtering one of the twin beams. In particular, we demonstrate the appearance of fourth-order ("ghost") interference fringes in the spectrum of one beam conditioned by photodetection at the output of an unbalanced Michelson interferometer placed in the path of the other beam. The coherence time of the pump is the limiting factor for the sharpness of the details in the shaped biphoton spectrum. 相似文献
17.
Yang T Zhang Q Chen TY Lu S Yin J Pan JW Wei ZY Tian JR Zhang J 《Physical review letters》2006,96(11):110501
We report the generation of independent entangled photon pairs from two synchronized but mutually incoherent laser sources. The quality of synchronization is confirmed by observing a violation of Bell's inequality with 3.2 standard deviations in an entanglement swapping experiment. The techniques developed in our experiment are not only important for realistic linear optical quantum-information processing, but also enable new tests of local realism. 相似文献
18.
We investigate time-modulated EPR entangled states and intensity quantum correlation of twin light beams in application to
time-resolved quantum communication. As a proper device generating such states, the nondegenerate optical parametric oscillator
driven by the time-modulated pump field is considered.
The text was submitted by the authors in English. 相似文献
19.
The dynamics of an ensemble of identically prepared two-qubit systems is investigated which is subjected to the iteratively applied measurements and conditional selection of a typical entanglement purification protocol. The resulting dynamics exhibits strong sensitivity to initial conditions. For one class of initial states two types of islands characterize the asymptotic limit. They correspond to a separable and a fully entangled two-qubit state, respectively, and their boundaries form fractal-like structures. In the presence of incoherent noise an additional stable asymptotic cycle appears. 相似文献
20.
G. Rigolin 《Foundations of Physics Letters》2002,15(3):293-298
A generalized uncertainty relation for an entangled pair of particles is obtained if we impose a symmetrization rule for all
operators that we should employ when doing any calculation using the entangled wave function of the pair. This new relation
reduces to Heisenberg’s uncertainty relation when the particles have no correlation and suggests that we can have new lower
bounds for the product of position and momentum dispersions. 相似文献