Single-experiment-detectable multipartite entanglement witness for ensemble quantum computing

In this paper we provide an operational method to detect multipartite entanglement in ensemble-based quantum computing. This method is based on the concept of entanglement witness. We decompose the entanglement witness for each class of multipartite entanglement into nonlocal operations in addition to local measurements. Individual single qubit measurements are performed simultaneously, hence complete detection of entanglement is performed in a single run experiment. This approach is particularly important for experiments where it is operationally difficult to prepare several copies of an unknown quantum state and in this sense the introduced scheme in this work is superior to the generally used entanglement witnesses that require a number of experiments and preparation of copies of quantum state.Comment: 9 pages, 5 figures, minor changes have been mad

Damped orbital excitations in the titanates

A possible mechanism for the removal of the orbital degeneracy in RTiO3 (where R=La, Y, ...) is considered. The calculation is based on the Kugel-Khomskii Hamiltonian for electrons residing in the t2g orbitals of the Ti ions, and uses a self-consistent pe rturbation expansion in the interaction between the orbital and the spin degrees of freedom. The latter are assumed to be ordered in a Neel state, brought about by delicate interactions that are not included in the Kugel-Khomskii Hamiltonian. Within our model calculations, each of the t2g bands is found to acquire a finite, temperature-dependent dispersion, that lifts the orbital degeneracy. The orbital excitations are found to be heavily damped over a rather wide band. Consequently, they do not participate as a separate branch of excitations in the low-temperature thermodynamics.eComment: 6 pages, 3 figure

Electronic Structures of Fe3−xV_{3-x}V_x$Si Probed by Photoemission Spectroscopy

The electronic structures of the Heusler type compounds Fe$_{3-x}V$_x$Si in the concentration range between x = 0 and x = 1 have been probed by photoemission spectroscopy (PES). The observed shift of Si 2p core- level and the main valence band structres indicate a chemical potential shift to higher energy with increasing x. It is also clarified that the density of state at Fermi edge is owing to the collaboration of V 3d and Fe 3d derived states. Besides the decrease of the spectral intensity near Fermi edge with increasing x suggests the formation of pseudo gap at large x.Comment: 4 pages, 5 figures, 5 reference

Adsorption of Xe and Ar on Quasicrystalline Al-Ni-Co

An interaction potential energy between and adsorbate (Xe and Ar) and the 10-fold Al-Ni-Co quasicrystal is computed by summing over all adsorbate-substrate interatomic interactions. The quasicrystal atoms' coordinates are obtained from LEED experiments and the Lennard-Jones parameters of Xe-Al, Xe-Ni and Xe-Co are found using semiempirical combining rules. The resulting potential energy function of position is highly corrugated. Monolayer adsorption of Xe and Ar on the quasicrystal surface is investigated in two cases: 1) in the limit of low coverage (Henry's law regime), and 2) at somewhat larger coverage, when interactions between adatoms are considered through the second virial coefficient, C_{AAS}. A comparison with adsorption on a flat surface indicates that the corrugation enhances the effect on Xe-Xe (Ar-Ar) interactions. The theoretical results for the low coverage adsorption regime are compared to experimental (LEED isobar) data.Comment: 12 pages, 8figure

High-resolution Ce 3d-edge resonant photoemission study of CeNi_2

Resonant photoemission (RPES) at the Ce 3d -> 4f threshold has been performed for alpha-like compound CeNi_2 with extremely high energy resolution (full width at half maximum < 0.2 eV) to obtain bulk-sensitive 4f spectral weight. The on-resonance spectrum shows a sharp resolution-limited peak near the Fermi energy which can be assigned to the tail of the Kondo resonance. However, the spin-orbit side band around 0.3 eV binding energy corresponding to the f_{7/2} peak is washed out, in contrast to the RPES spectrum at the Ce 3d -> 4f RPES threshold. This is interpreted as due to the different surface sensitivity, and the bulk-sensitive Ce 3d -> 4f RPES spectra are found to be consistent with other electron spectroscopy and low energy properties for alpha-like Ce-transition metal compounds, thus resolves controversy on the interpretation of Ce compound photoemission. The 4f spectral weight over the whole valence band can also be fitted fairly well with the Gunnarsson-Schoenhammer calculation of the single impurity Anderson model, although the detailed features show some dependence on the hybridization band shape and (possibly) Ce 5d emissions.Comment: 4 pages, 3 figur

Dopant-dependent impact of Mn-site doping on the critical-state manganites: R0.6Sr0.4MnO3 (R=La, Nd, Sm, and Gd)

Versatile features of impurity doping effects on perovskite manganites, $R_{0.6}$Sr$_{0.4}$MnO$_{3}$, have been investigated with varying the doing species as well as the $R$-dependent one-electron bandwidth. In ferromagnetic-metallic manganites ($R$=La, Nd, and Sm), a few percent of Fe substitution dramatically decreases the ferromagnetic transition temperature, leading to a spin glass insulating state with short-range charge-orbital correlation. For each $R$ species, the phase diagram as a function of Fe concentration is closely similar to that for $R_{0.6}$Sr$_{0.4}$MnO$_{3}$ obtained by decreasing the ionic radius of $R$ site, indicating that Fe doping in the phase-competing region weakens the ferromagnetic double-exchange interaction, relatively to the charge-orbital ordering instability. We have also found a contrastive impact of Cr (or Ru) doping on a spin-glass insulating manganite ($R$=Gd). There, the impurity-induced ferromagnetic magnetization is observed at low temperatures as a consequence of the collapse of the inherent short-range charge-orbital ordering, while Fe doping plays only a minor role. The observed opposite nature of impurity doping may be attributed to the difference in magnitude of the antiferromagnetic interaction between the doped ions.Comment: 7 pages, 6 figure

Avian malaria is absent in juvenile colonial herons (Ardeidae) but not Culex pipiens mosquitoes in the Camargue, Southern France

Apicomplexan blood parasites Plasmodium and Haemoproteus (together termed “Avian malaria”) and Leucocytozoon are widespread, diverse vector-transmitted blood parasites of birds, and conditions associated with colonial nesting in herons (Ardeidae) and other waterbirds appear perfect for their transmission. Despite studies in other locations reporting high prevalence of parasites in juvenile herons, juvenile Little Egrets (Egretta garzetta) previously tested in the Camargue, Southern France, had a total absence of malaria parasites. This study tested the hypotheses that this absence was due to insufficient sensitivity of the tests of infection; an absence of infective vectors; or testing birds too early in their lives. Blood was sampled from juveniles of four species shortly before fledging: Little Egret (n = 40), Cattle Egret (Bubulcus ibis; n = 40), Black-crowned Night-Heron (Nycticorax nycticorax, n = 40), and Squacco Heron (Ardeola ralloides; n = 40). Sensitive nested-Polymerase Chain Reaction was used to test for the presence of parasites in both birds and host-seeking female mosquitoes captured around the colonies. No malaria infection was found of in any of the heron species. Four different lineages of Plasmodium were detected in pooled samples of female Culex pipiens mosquitoes, including two in potentially infective mosquitoes. These results confirm that the absence of malaria parasites previously demonstrated in Little Egret is not due to methodological limitations. Although the prevalence of infection in mosquitoes was low, conditions within the colonies were suitable for transmission of Plasmodium. These colonial heron species may have evolved strategies for resisting malaria infection through physiological or behavioral mechanisms