Efficient orthogonal control of tunnel couplings in a quantum dot array

Electrostatically-defined semiconductor quantum dot arrays offer a promising platform for quantum computation and quantum simulation. However, crosstalk of gate voltages to dot potentials and inter-dot tunnel couplings complicates the tuning of the device parameters. To date, crosstalk to the dot potentials is routinely and efficiently compensated using so-called virtual gates, which are specific linear combinations of physical gate voltages. However, due to exponential dependence of tunnel couplings on gate voltages, crosstalk to the tunnel barriers is currently compensated through a slow iterative process. In this work, we show that the crosstalk on tunnel barriers can be efficiently characterized and compensated for, using the fact that the same exponential dependence applies to all gates. We demonstrate efficient calibration of crosstalk in a quadruple quantum dot array and define a set of virtual barrier gates, with which we show orthogonal control of all inter-dot tunnel couplings. Our method marks a key step forward in the scalability of the tuning process of large-scale quantum dot arrays.Comment: 8 pages, 7 figure

How Much Does Money Matter in a Direct Democracy?

The fine-structure splitting of quantum confined InxGa1-x Nexcitons is investigated using polarization-sensitive photoluminescence spectroscopy. The majority of the studied emission lines exhibits mutually orthogonal fine-structure components split by 100-340 mu eV, as measured from the cleaved edge of the sample. The exciton and the biexciton reveal identical magnitudes but reversed sign of the energy splitting.Original Publication:Supaluck Amloy, Y T Chen, K F Karlsson, K H Chen, H C Hsu, C L Hsiao, L C Chen and Per-Olof Holtz, Polarization-resolved fine-structure splitting of zero-dimensional InxGa1-xN excitons, 2011, PHYSICAL REVIEW B, (83), 20, 201307.http://dx.doi.org/10.1103/PhysRevB.83.201307Copyright: American Physical Societyhttp://www.aps.org

Equivalent SU(3)fSU(3)_f approaches for two-body anti-triplet charmed baryon decays

For the two-body anti-triplet charmed baryon decays, there exist two theoretical analyses based on the $SU(3)$ flavor ($SU(3)_f$) symmetry. One is the irreducible $SU(3)_f$ approach (IRA), which depends on the irreducible $SU(3)_f$ representation of the effective Hamiltonian. The other is the topological-diagram approach (TDA), where the decays are drawn to consist of $W$-boson emission and $W$-boson exchange topologies. We demonstrate that IRA and TDA can be equivalent, such that the IRA parameters can be seen to mix with the TDA topologies. The current observations of $\Xi_c^0\to \Xi^-\pi^+,\Xi^- K^+,\Lambda^0\bar K^0$ might cause theoretical difficulties. With the $SU(3)_f$ symmetry breaking, we explain ${\cal B}(\Xi_c^0\to\Xi^-\pi^+,\Xi^-K^+)$. It is found that a specific $W$-boson exchange topology denoted by $E_M$ only appears in $\Xi_c^0\to{\bf B}M$, by which we explain ${\cal B}(\Xi_c^0\to\Lambda^0\bar K^0)$. In addition, we predict ${\cal B}(\Xi_c^0\to\Sigma^0\bar K^0,\Sigma^+ K^-)= (5.8^{+4.7}_{-3.5},5.4^{+4.9}_{-3.4})\times 10^{-3}$ for future measurements to test if $E_M$ can be a significant contribution.Comment: 13 pages, 7 tables, 1 figure, introduction rephrased, reference added, typos correcte

Pictorial SU(3)fSU(3)_f approach for two-body Ωc\Omega_c weak decays

We explore two-body non-leptonic weak decays of $\Omega_c^0$ into final states ${\bf B}^{(*)}M$ and ${\bf B}^{(*)}V$, where ${\bf B}^{(*)}$ denotes an octet (a decuplet) baryon, and $M(V)$ represents a pseudoscalar (vector) meson. Based on the $SU(3)$ flavor $[SU(3)_f]$ symmetry, we depict and parameterize the $W$-emission and $W$-exchange processes using the topological diagram approach, establishing strict $SU(3)_f$ relations for possible decay channels. We identify dominant topological parameters, determined by available data, allowing us to explain the experimental ratios ${\cal B}(\Omega_c^0\to\Xi^{*0}\bar K^{*0})/{\cal B}(\Omega_c^0\to\Omega^-\rho^+)=0.28\pm 0.11$, ${\cal B}(\Omega_c^0\to\Xi^-\pi^+)/{\cal B}(\Omega_c^0\to\Xi^{0}\bar K^{0})=0.10\pm 0.02$, and ${\cal B}(\Omega_c^0 \to \Omega^- K^+)/{\cal B}(\Omega_c^0 \to \Omega^- \pi^+)=0.06\pm 0.01$. We also calculate the branching fractions of the Cabibbo-allowed decays, such as ${\cal B}(\Omega_c^0 \to \Xi^{* 0} \bar{K}^{0})=(9.8\pm1.3)\times 10^{-4}$. In particular, we establish approximate isospin relations: ${\cal B}(\Omega_c^0 \to \Xi^{(*)-} \pi^+)\simeq 2{\cal B}(\Omega_c^0 \to \Xi^{(*)0} \pi^0)$ and ${\cal B}(\Omega_c^0 \to \Xi^{(*)-} \rho^+)\simeq 2{\cal B}(\Omega_c^0 \to \Xi^{(*)0} \rho^0)$, where ${\cal B}(\Omega_c^0 \to \Xi^0 \pi^0)=(2.3\pm0.2)\times 10^{-4}$ is accessible to the Belle and LHCb experiments.Comment: 16 pages, 3 tables, 2 figure

A Study on Knowledge Sharing in Vietnamese Organizations

Knowledge sharing is very much a sign for the atmosphere of social interactions in the organizations, it depends on the quality of the conversation, formally or informally. In other words, for more effective knowledge sharing, communication competence is required in order to have appropriate conversation. During the past decades, most theories of communication competence have been developed on the basis of “western” conceptualization. This empirical research is conducted in order to study the organizational communication competence in a non-western country, Vietnam, and the effect of such competence to the employees’ knowledge sharing behavior respectively. Base on the data collected from 11 organizations, the effects of three culture dimensions, namely individualism, power distance, and uncertainty avoidance to the communication competence were statistically analyzed; then, stemming from the certain level of communication competence, the behavior of organizational members towards knowledge sharing was explaine

Probing the ISM Near Star Forming Regions with GRB Afterglow Spectroscopy: Gas, Metals, and Dust

We study the chemical abundances of the interstellar medium surrounding high z gamma-ray bursts (GRBs) through analysis of the damped Lya systems (DLAs) identified in afterglow spectra. These GRB-DLAs are characterized by large HI column densities N(HI) and metallicities [M/H] spanning 1/100 to nearly solar, with median [M/H]>-1. The majority of GRB-DLAs have [M/H] values exceeding the cosmic mean metallicity of atomic gas at z>2, i.e. if anything, the GRB-DLAs are biased to larger metallicity. We also observe (i) large [Zn/Fe] values (>+0.6) and sub-solar Ti/Fe ratios which imply substantial differential depletion, (ii) large a/Fe ratios suggesting nucleosynthetic enrichment by massive stars, and (iii) low C^0/C^+ ratios (<10^{-4}). Quantitatively, the observed depletion levels and C^0/C^+ ratios of the gas are not characteristic of cold, dense HI clouds in the Galactic ISM. We argue that the GRB-DLAs represent the ISM near the GRB but not gas directly local to the GRB (e.g. its molecular cloud or circumstellar material). We compare these observations with DLAs intervening background quasars (QSO-DLAs). The GRB-DLAs exhibit larger N(HI) values, higher a/Fe and Zn/Fe ratios, and have higher metallicity than the QSO-DLAs. We argue that the differences primarily result from galactocentric radius-dependent differences in the ISM: GRB-DLAs preferentially probe denser, more depleted, higher metallicity gaslocated in the inner few kpc whereas QSO-DLAs are more likely to intersect the less dense, less enriched, outer regions of the galaxy. Finally, we investigate whether dust obscuration may exclude GRB-DLA sightlines from QSO-DLA samples; we find that the majority of GRB-DLAs would be recovered which implies little observational bias against large N(HI) systems.Comment: 16 pages, 9 figures. Submitted to Ap

Critical behavior of the 3-state Potts model on Sierpinski carpet

We study the critical behavior of the 3-state Potts model, where the spins are located at the centers of the occupied squares of the deterministic Sierpinski carpet. A finite-size scaling analysis is performed from Monte Carlo simulations, for a Hausdorff dimension $d_{f}$ $\simeq 1.8928$. The phase transition is shown to be a second order one. The maxima of the susceptibility of the order parameter follow a power law in a very reliable way, which enables us to calculate the ratio of the exponents $\gamma /\nu$. We find that the scaling corrections affect the behavior of most of the thermodynamical quantities. However, the sequence of intersection points extracted from the Binder's cumulant provides bounds for the critical temperature. We are able to give the bounds for the exponent $1/\nu$ as well as for the ratio of the exponents $\beta/\nu$, which are compatible with the results calculated from the hyperscaling relation.Comment: 13 pages, 4 figure