Dissipation-assisted quantum gates with cold trapped ions

It is shown that a two-qubit phase gate and SWAP operation between ground states of cold trapped ions can be realised in one step by simultaneously applying two laser fields. Cooling during gate operations is possible without perturbing the computation and the scheme does not require a second ion species for sympathetic cooling. On the contrary, the cooling lasers even stabilise the desired time evolution of the system. This affords gate operation times of nearly the same order of magnitude as the inverse coupling constant of the ions to a common vibrational mode.Comment: 4 pages, 5 figures, substantially revised versio

4-Chloro­anilinium 3-carb­oxy­prop-2-enoate

In the title compound, C6H7ClN+·C4H3O4 −, the cations and anions lie on mirror planes and hence only half of the mol­ecules are present in the asymmeric unit. The 4-chloro­anilinium cation and hydrogen maleate anion in the asymmetric unit are each planar and are oriented at an angle of 15.6 (1)° to one another and perpendicular to the b axis. A characterestic intra­molecular O—H⋯O hydrogen bond, forming an S(7) motif, is observed in the maleate anion. In the crystal, the cations and anions are linked by N—H⋯O hydrogen bonds, forming layers in the ab plane. The aromatic rings of the cations are sandwiched between hydrogen-bonded chains and rings formed through the amine group of the cation and maleate anions, leading to alternate hydro­phobic (z = 0 or 1) and hydro­philic layers (z = 1/2) along the c axis

Doped two orbital chains with strong Hund's rule couplings - ferromagnetism, spin gap, singlet and triplet pairings

Different models for doping of two-orbital chains with mobile $S=1/2$ fermions and strong, ferromagnetic (FM) Hund's rule couplings stabilizing the S=1 spins are investigated by density matrix renormalization group (DMRG) methods. The competition between antiferromagnetic (AF) and FM order leads to a rich phase diagram with a narrow FM region for weak AF couplings and strongly enhanced triplet pairing correlations. Without a level difference between the orbitals, the spin gap persists upon doping, whereas gapless spin excitations are generated by interactions among itinerant polarons in the presence of a level difference. In the charge sector we find dominant singlet pairing correlations without a level difference, whereas upon the inclusion of a Coulomb repulsion between the orbitals or with a level difference, charge density wave (CDW) correlations decay slowest. The string correlation functions remain finite upon doping for all models.Comment: 9pages, 9figure

Entanglement of two-mode Bose-Einstein condensates

We investigate the entaglement characteristics of two general bimodal Bose-Einstein condensates - a pair of tunnel-coupled Bose-Einstein condensates and the atom-molecule Bose-Einstein condensate. We argue that the entanglement is only physically meaningful if the system is viewed as a bipartite system, where the subsystems are the two modes. The indistinguishibility of the particles in the condensate means that the atomic constituents are physically inaccessible and thus the degree of entanglement between individual particles, unlike the entanglement between the modes, is not experimentally relevant so long as the particles remain in the condensed state. We calculate the entanglement between the modes for the exact ground state of the two bimodal condensates and consider the dynamics of the entanglement in the tunnel-coupled case.Comment: 11 pages, 8 figures, submitted to Physical Review A, to be presented at the third UQ Mathematical Physics workshop, Oct. 4-6; changes made in response to referee comment

New Constraints on the Complex Mass Substructure in Abell 1689 from Gravitational Flexion

In a recent publication, the flexion aperture mass statistic was found to provide a robust and effective method by which substructure in galaxy clusters might be mapped. Moreover, we suggested that the masses and mass profile of structures might be constrained using this method. In this paper, we apply the flexion aperture mass technique to HST ACS images of Abell 1689. We demonstrate that the flexion aperture mass statistic is sensitive to small-scale structures in the central region of the cluster. While the central potential is not constrained by our method, due largely to missing data in the central 0.5$^\prime$ of the cluster, we are able to place constraints on the masses and mass profiles of prominent substructures. We identify 4 separate mass peaks, and use the peak aperture mass signal and zero signal radius in each case to constrain the masses and mass profiles of these substructures. The three most massive peaks exhibit complex small-scale structure, and the masses indicated by the flexion aperture mass statistic suggest that these three peaks represent the dominant substructure component of the cluster ($\sim 7\times 10^{14}h^{-1}M_\odot$). Their complex structure indicates that the cluster -- far from being relaxed -- may have recently undergone a merger. The smaller, subsidiary peak is located coincident with a group of galaxies within the cluster, with mass $\sim 1\times10^{14}h^{-1}M_\odot$. These results are in excellent agreement with previous substructure studies of this cluster.Comment: 18 pages, 10 figures, MNRAS accepted (7 Dec 2010

Stability of Repulsive Bose-Einstein Condensates in a Periodic Potential

The cubic nonlinear Schr\"odinger equation with repulsive nonlinearity and an elliptic function potential models a quasi-one-dimensional repulsive dilute gas Bose-Einstein condensate trapped in a standing light wave. New families of stationary solutions are presented. Some of these solutions have neither an analog in the linear Schr\"odinger equation nor in the integrable nonlinear Schr\"odinger equation. Their stability is examined using analytic and numerical methods. All trivial-phase stable solutions are deformations of the ground state of the linear Schr\"odinger equation. Our results show that a large number of condensed atoms is sufficient to form a stable, periodic condensate. Physically, this implies stability of states near the Thomas-Fermi limit.Comment: 12 pages, 17 figure

Exposure to aircraft and road traffic noise and associations with heart disease and stroke in six European countries: a cross-sectional study

This work was supported by the Economic and Social Research Council (grant ES/F038763/1) with additional funding from the European Network for Noise and Health (ENNAH, EU FP7 grant number 226442)

Entanglement and nonlocality in multi-particle systems

Entanglement, the Einstein-Podolsky-Rosen (EPR) paradox and Bell's failure of local-hidden-variable (LHV) theories are three historically famous forms of "quantum nonlocality". We give experimental criteria for these three forms of nonlocality in multi-particle systems, with the aim of better understanding the transition from microscopic to macroscopic nonlocality. We examine the nonlocality of N separated spin J systems. First, we obtain multipartite Bell inequalities that address the correlation between spin values measured at each site, and then we review spin squeezing inequalities that address the degree of reduction in the variance of collective spins. The latter have been particularly useful as a tool for investigating entanglement in Bose-Einstein condensates (BEC). We present solutions for two topical quantum states: multi-qubit Greenberger-Horne-Zeilinger (GHZ) states, and the ground state of a two-well BEC

CD32+CD4+ T cells are enriched in HIV-1 DNA

Background: CD32 was reported to mark the HIV-1 reservoir harboring replication-competentproviruses, but several recent reports challenged this finding. We aimed to confirm or deny theusefulness of CD32 as a marker of the latent reservoir and to further characterize the phenotype of theseCD32+CD4+ T cells, as well as the transcriptional activity of HIV-1 residing in this reservoir.Methods: CD32 expression was measured by flow cytometry on PBMCs from ART-treated HIV-1 infectedpatients and uninfected controls. Co-expression of HLA-DR, immune checkpoint receptors (PD-1, TIGIT,LAG-3) and CD2 was measured by flow cytometry. HIV-1 DNA and unspliced RNA were quantified in bulkPBMC samples and in CD32+ and CD32- fractions of CD4+ T cells sorted with magnetic beads.Results: The median frequency of CD32+CD4+ T cells in HIV-infected individuals (n=18) was 0.07% whichwas significantly higher than in the controls (0.01%, p=0.016). We found a positive correlation betweenthe percentage of CD32+CD4+ T cells and total HIV-1 DNA load in PBMCs (rho=0.58; p=0.012).CD32+CD4+ T cells demonstrated increased expression of LAG-3 (p=0.016), TIGIT (p=0.016) and HLA-DR(p< 0.0001) compared with CD32-CD4+ T cells in HIV-infected patients. In the full sample, CD32+CD4+ Tcells were not enriched for HIV-1 DNA or RNA compared with CD32-CD4+ cells. However, in a subgroupof patients with smaller (and presumably purer) CD32+CD4+ T-cell fractions (n=9), we observed asignificant enrichment for HIV-1 DNA in this fraction (average of 6-fold, p=0.012). We thereforeoptimized our assay to isolate a purer fraction of CD32+CD4+ T cells and found a positive enrichment forHIV-1 DNA in the CD32+CD4+ fraction in all the additional patients (n=7) tested (average of 14-fold,p=0.016).Conclusions: We confirmed that CD32+CD4+ T cells are enriched for HIV-1 DNA, although the level ofenrichment was less pronounced than previously reported. Our results also highlight the importance ofgetting a sufficiently pure CD32+CD4+ T cells fraction for analysis and might explain the negative resultsobtained by others. Our data further indicate that these CD32+CD4+ T cells are activated cells, and thatthey often co-express the immune checkpoint receptors TIGIT and LAG-3.info:eu-repo/semantics/publishe