共查询到20条相似文献,搜索用时 31 毫秒
1.
S. Parida 《Physics letters. A》2009,373(21):1852-1855
We theoretically show that the process of inner-shell photoionization in an atom A, followed by the spontaneous sequential emission of two Auger electrons, produces various kinds of spin-entangled states of three flying electronic qubits. All properties of these states are completely pre-determined by the total spin quantum numbers of the electronic states of four atomic species (i.e., A, A+∗, A2+∗, A3+) participating in this process in the Russell-Saunders coupling. These tripartite states are readily characterized experimentally by measuring only energies of the three emitted electrons, without requiring any entanglement witness or other such protocols. 相似文献
2.
Kaveenga Rasika Koswattage Iwao ShimoyamaYuji Baba Tetsuhiro SekiguchiKazumichi Nakagawa 《Applied Surface Science》2011,258(4):1561-1564
Adsorption behavior of atomic deuterium on a hexagonal boron nitride (h-BN) thin film is studied by photon-stimulated ion desorption (PSID) of D+ and near edge X-ray absorption fine structure (NEXAFS) at the B and N K-edges. After the adsorption of atomic deuterium, D+ desorption yield η(hν) shows clear enhancement at the B K-edge and almost no enhancement at the N K-edge. NEXAFS spectra show a large change in the B K-edge and a small change in the N K-edge after the adsorption. We propose selective adsorption of atomic deuterium on the h-BN thin film based on the experimental results, and mention the effectiveness of applying the PSID method with X-ray to study hydrogen storage materials. 相似文献
3.
Yan ZhangYu Zhang Xiao-Hang ZhangMiao Yu Cui-Li CuiJin-Hui Wu 《Physics letters. A》2012,376(4):656-661
We study the dynamic processes of reversible light storage in a double-Λ system of cold atoms by modulating two counter-propagating control fields in three successive stages. We find that stationary light pulses (SLPs) can be generated when we switch on both control fields to retrieve the stored light signal from a wave-packet of atomic spin coherence. But the two control fields should have equal Rabi frequencies for a symmetric structure of atomic levels while unequal Rabi frequencies for an asymmetric structure of atomic levels. That is, the generation of SLPs requires a special ratio between Rabi frequencies of the two control fields, which is determined by the spontaneous decay rates of relevant atomic transitions. We also show that phase modulation and profile reversal of the released light signal can be implemented by suitably manipulating the two control fields. The double-Λ system of cold atoms has the advantage of high efficiency and high fidelity, when compared to the Λ system of cold atoms, because SLPs generated therein suffer very slow decay and diffusion. 相似文献
4.
We address the question: “are weak right-handed non-singlet representations of quarks and leptons necessary?” An extension of the Weinberg-Salam model to SU(2) ? U(1) ? U(1) is found to adequately describe all existing weak interaction data including the lack of parity violation in atomic physics experiments. These data tightly constrain the additional parameters introduced by adding the second weak hypercharge. Although such a model may seem regressive when considered from the standpoint of “simple” unification schemes, we feel that it is aesthetics rather than experiment which leads to non-trivial right-handed multiplet structure. In contrast to most other models, ours predicts a substantial parity-violation effect in atomic experiments on hydrogen. We note that the second weak boson in our model is not constrained to be heavy by existing data and thus might already by accessable in pp → μ+μ?X or possibly in the next generation of colliding beam facilities through e+e? → μ+μ?. 相似文献
5.
We present several schemes for heralded storage of polarization states of single photons in single ions, using the 40Ca+ ion and photons at 854 nm wavelength as specific example. We compare the efficiencies of the schemes and the requirements for their implementation with respect to the preparation of the initial state of the ion, the absorption process and its analysis. These schemes may be used to create and herald entanglement of two distant ions through entanglement swapping; they are easily adapted to other atomic systems and wavelengths. 相似文献
6.
Quantum communication with terahertz (THz) frequency signals has many advantages like reduced attenuation and scintillation effects in certain atmospheric conditions along with very high level of data security. In this work, we propose a scheme to realize Quantum Memory (QM) for efficient storage of terahertz (THz) frequency signals using Electromagnetically Induced Transparency (EIT) in an ultracold atomic medium of 87Rb Rydberg atoms prepared in a Two Dimensional Magneto Optical Trap (2D-MOT). The uniqueness of our scheme lies in the choice of the energy levels involved in the EIT process, all three of which have been chosen to be the Rydberg levels (enabling signal beam to be in THz) in a lambda type arrangement. This first of its kind proposal reveals that atomic media are a potential candidate for devising QMs which can store THz frequency signals. We have estimated that the Optical Depth (OD) in our scheme can reach a very high value of 690, very high maximum obtainable storage efficiency (η) of ~99%, the group velocity () can be as low as 5.07 × 103 m/s, and the Delay Bandwidth Product (DBP) can be as high as 9.5. All of these estimates emphasize the feasibility of our scheme as a QM device for efficient storage of THz pulses. 相似文献
7.
L.R. Carlson S.A. Johnson E.F. Worden C.A. May R.W. Solarz J.A. Paisner 《Optics Communications》1977,21(1):116-120
We describe a method of determining atomic transition probabilities by independently measuring branching ratios and radiative lifetimes. These quantities are directly determined by time resolved optical pumping. The technique has been applied to the measurement of gA values for particular transitions in 238U I. 相似文献
8.
《Physics letters. [Part B]》1999,471(1):45-52
We describe the generalization of spherical field theory to other modal expansion methods. The main approach remains the same, to reduce a d-dimensional field theory into a set of coupled one-dimensional systems. The method we discuss here uses an expansion with respect to periodic-box modes. We apply the method to φ4 theory in two dimensions and compute the critical coupling and critical exponents. We compare with lattice results and predictions via universality and the two-dimensional Ising model. 相似文献
9.
《Nuclear Physics B》1988,305(2):199-218
A model of “planar random surfaces without spikes” on hypercubical lattices was introduced some years ago as a discretization of quantum string theory. We review some general properties of this model and present results from a Monte Carlo study of its critical behaviour in d = 4, 8 and 10 dimensions. In d = 4 dimensions we find a Hausdorff dimension dH ≈ 4 and an anomalous dimensions η ≈ 1. These critical exponents imply a deviation from mean field theory in contrast to other lattice random surface models. Furthermore, we find evidence for mean field behaviour in 8 and 10 dimensions, indicating an upper critical dimension dcu ⩽ 8. 相似文献
10.
《Journal of magnetism and magnetic materials》2010,322(13):1706-1709
In this study, we have considered the three dimensional mixed ferro-ferrimagnetic ternary alloy model of the type ABpC1-p where the A and X (X=B or C) ions are alternately connected and have different Ising spins SA=3/2, SB=1 and SC=5/2, respectively. We have investigated the dependence of the critical and compensation temperatures of the model on concentration and interaction parameters by using MC simulation method. We have shown that the behavior of the critical temperature and the existence of compensation points strongly depend on interaction and concentration parameters. In particular, we have found that the critical temperature of the model is independent on concentration of different types of spins at a special interaction value and the model has one or two compensation temperature points in a certain range of values of the concentration of the different spins. 相似文献
11.
P. Mikheenko A. Sarkar V.-S. Dang J.L. Tanner J.S. Abell A. Crisan 《Physica C: Superconductivity and its Applications》2009,469(14):798-804
We report measurements of critical current in YBa2Cu3Ox films deposited on SrTiO3 substrates decorated with silver and gold nanodots. An increase in critical current in these films, in comparison with the films deposited on non-decorated substrates, has been achieved. We argue that this increase comes from the c-axis correlated extended defects formed in the films and originated from the nanodots. Additionally to creating extended defects, the nanodots pin them and prevent their exit from the sample during the film growth, thus keeping a high density of defects and providing a lower rate of decrease of the critical current with the thickness of the films. The best pinning is achieved in the samples with silver nanodots by optimising their deposition temperature. The nanodots grown at a temperature of a few hundred °C have a small diameter of a few nanometres and a high surface density of 1011–1012 particles/cm2. We give evidence of c-axis correlated extended defects in YBa2Cu3Ox films by planar and cross-sectional atomic force microscopy, transmission electron microscopy and angle-dependent transport measurements of critical current. 相似文献
12.
M. Sebawe Abdalla M. M. A. Ahmed E. M. Khalil A. S.-F. Obada 《Journal of Russian Laser Research》2014,35(2):169-181
We consider the problem of two two-level atoms interacting with N-level atom. We obtain the exact solution for the wave function for the case where both atoms are identical and the system is treated at exact resonance. We use the results obtained for discussing the temporal evolution of the atomic inversion, in particular, the collapse and revival phenomena. We build up our discussion on the variation of the atomic number j and the atomic angle θ. For small j, the system exhibits a small period of collapse, and for large j we observe a long period of revival. We employ the linear entropy in the discussion of entanglement. We show that the atomic angle θ influences the system in such a way that the period of partial entanglement increases with increase in the value of θ. In addition to the variance squeezing, we also examine the entanglement between the spinors and show that the squeezing phenomenon occurs in the second quadrature, being absent in the first quadrature. Also we realize that the squeezing phenomenon reaches its maximum and gets more pronounced for a small value of the atomic number and a large value of the atomic angle. 相似文献
13.
B. Budick 《Nuclear Physics A》1979,329(3):331-338
We have calculated the momenta of the decay products from a hypothetical Σ?n hyperfragment, including final-state interaction between the two neutrons. We have also examined the cascade of exotic atoms that incorporate Σ?n as a satellite. We find that a large fraction of dibaryons that stop in insulators of low atomic number will decay before being absorbed. 相似文献
14.
《Nuclear Physics B》1996,468(3):514-540
We apply the Monte Carlo Renormalization group to the crumpling transition in random surface models of fixed connectivity. This transition is notoriously difficult to treat numerically. We employ here a Fourier accelerated Langevin algorithm in conjunction with a novel blocking procedure in momentum space which has proven extremely successful in λφ4. We perform two successive renormalizations in lattices with up to 642 sites. We obtain a result for the critical exponent ν in general agreement with previous estimates and similar error bars, but with much less computational effort. We also measure with great accuracy η. As a by-product we are able to determine the fractal dimension dH of random surfaces at the crumpling transition. 相似文献
15.
A radiative interaction in a collective two-atom system forms subradiant and superradiant states when the distance between neighboring atoms is less than half a wavelength of resonant radiation. We calculate the G (2) function depending on the atomic separation and detection angle and show that it oscillates with a time delay between two successively emitted photons. These oscillations are the signature of coherent effects due to the periodic emission and absorption of photons by each atom. 相似文献
16.
Substantial progress has been made in recent years on the 2D critical percolation scaling limit and its conformal invariance properties. In particular, chordal SLE 6(the Stochastic Loewner Evolution with parameter κ=6) was, in the work of Schramm and of Smirnov, identified as the scaling limit of the critical percolation “exploration process.” In this paper we use that and other results to construct what we argue is the fullscaling limit of the collection of allclosed contours surrounding the critical percolation clusters on the 2D triangular lattice. This random process or gas of continuum nonsimple loops in Bbb R2is constructed inductively by repeated use of chordal SLE 6. These loops do not cross but do touch each other—indeed, any two loops are connected by a finite “path” of touching loops. 相似文献
17.
A systematic study is made of the plane wave modes of a nonlinear c-number field (λφ4 model) and interesting features of the behavior of such fields, which do not seem to have been observed before, are brought out. These relate to the case λ < 0, wherein there are different regimes characterized by different kinds of elliptic-function forms for the waves. We show that when the amplitude of the elliptic function waves approaches critical values corresponding to “phase transition” from one regime to another, the energy density in the field increases without limit (though the amplitude is finite). In two of the regimes which are “tachyonic” in nature, there are frozen wave modes which are spatially periodic but time independent. These turn out however to be unstable against perturbations. Finally we observe that in one of these regimes there exist a lower bound on the energy density in the wave field. The case of fields with higher nonlinearities is briefly considered. 相似文献
18.
We have studied by grazing incidence X-ray diffraction the self-ordering of the Cu-CuO stripe pattern. By comparing the experimental results to molecular dynamics simulations and anisotropic linear elastic calculations, we have been able to determine the atomic relaxations within the Cu substrate. The results show the importance of the crystalline anisotropy in the relaxation field. These relaxations are due to the surface stress difference Δσ between oxygen-covered and bare Cu(1 1 0) regions. For the different oxygen coverages studied, we have always found Δσ=1.0±0.1 N m−1. This surface stress difference is shown to be the origin of the self-ordering. 相似文献
19.
J. H. Eberly 《Hyperfine Interactions》1987,37(1-4):33-47
20.
Quantum networks are distributed many-body quantum systems with tailored topology and controlled information exchange. We present two schemes to generate remote entanglement, in atomic external degrees of freedom and between cavities. In the first scheme, we entangle two atoms with their cavities in momentum space through Bragg diffraction. Thereafter, in order to trace out the cavities, we let resonantly interact an auxiliary atom with each cavity. In the last, we perform quantum measurement on two auxiliary atoms and get remote entangled state in atomic external degrees of freedom. In the second scheme, we have a three cavities system. The other two cavities, A and B, are entangled with indistinguishable modes of cavity, C. Performing quantum measurement on third cavity, C, we disentangle it from the system and the cavities, A and B, become entangled. 相似文献