Static hybrid quarkonium potential with improved staggered quarks

We are studying the effects of light dynamical quarks on the excitation energies of a flux tube between a static quark and antiquark. We report preliminary results of an analysis of the ground state potential and the $\Sigma^{\prime+}_g$ and $\Pi_u$ potentials. We have measured these potentials on closely matched ensembles of gauge configurations, generated in the quenched approximation and with 2+1 flavors of Asqtad improved staggered quarks.Comment: Lattice2002(heavyquark

The preliminary lattice QCD calculation of κ\kappa meson decay width

We present a direct lattice QCD calculation of the $\kappa$ meson decay width with the s-wave scattering phase shift for the isospin $I=1/2$ pion-kaon ($\pi K$) system. We employ a special finite size formula, which is the extension of the Rummukainen-Gottlieb formula for the $\pi K$ system in the moving frame, to calculate the scattering phase, which indicates a resonance around $\kappa$ meson mass. Through the effective range formula, we extract the effective $\kappa \to \pi K$ coupling constant $g_{\kappa \pi K} = 4.54(76)$ GeV and decay width $\Gamma = 293 \pm 101$ MeV. Our simulations are done with the MILC gauge configurations with $N_f=2+1$ flavors of the "Asqtad" improved staggered dynamical sea quarks on a $16^3\times48$ lattice at $(m_\pi + m_K) / m_\kappa \approx 0.8$ and lattice spacing $a \approx 0.15$ fm.Comment: To make it concise. arXiv admin note: text overlap with arXiv:1110.1422, but much of v1 text overlap with articles by same and other authors remove

Experimental verification of the treatment of time-dependent flux in circuit quantization

Recent theoretical work has highlighted that quantizing a superconducting circuit in the presence of time-dependent flux $\Phi(t)$ generally produces Hamiltonian terms proportional to $d\Phi/dt$ unless a special allocation of the flux across inductive terms is chosen. Here, we present an experiment probing the effects of a fast flux ramp applied to a heavy-fluxonium circuit. The experiment confirms that na\"ive omission of the $d\Phi/dt$ term leads to theoretical predictions inconsistent with experimental data. Experimental data are fully consistent with recent theory that includes the derivative term or equivalently uses "irrotational variables" that uniquely allocate the flux to properly eliminate the $d\Phi/dt$ term

Tunable inductive coupler for high fidelity gates between fluxonium qubits

The fluxonium qubit is a promising candidate for quantum computation due to its long coherence times and large anharmonicity. We present a tunable coupler that realizes strong inductive coupling between two heavy-fluxonium qubits, each with $\sim50$MHz frequencies and $\sim5$ GHz anharmonicities. The coupler enables the qubits to have a large tuning range of $\textit{XX}$ coupling strengths ($-35$ to $75$ MHz). The $\textit{ZZ}$ coupling strength is $<3$kHz across the entire coupler bias range, and $<100$Hz at the coupler off-position. These qualities lead to fast, high-fidelity single- and two-qubit gates. By driving at the difference frequency of the two qubits, we realize a $\sqrt{i\mathrm{SWAP}}$ gate in $258$ns with fidelity $99.72\%$, and by driving at the sum frequency of the two qubits, we achieve a $\sqrt{b\mathrm{SWAP}}$ gate in $102$ns with fidelity $99.91\%$. This latter gate is only 5 qubit Larmor periods in length. We run cross-entropy benchmarking for over $20$ consecutive hours and measure stable gate fidelities, with $\sqrt{b\mathrm{SWAP}}$ drift ($2 \sigma$) $< 0.02\%$ and $\sqrt{i\mathrm{SWAP}}$ drift $< 0.08\%$.Comment: 16 pages, 14 figure

Viscosity and Interfacial Tension of Ternary Mixtures Consisting of Linear Alkanes, Alcohols, and/or Dissolved Gases Using Surface Light Scattering and Equilibrium Molecular Dynamics Simulations

Ternary mixtures consisting of liquids and dissolved gases with either two solvents or solutes are characterized by determining their liquid dynamic viscosity ηL and interfacial tension σ using surface light scattering (SLS) and equilibrium molecular dynamics (EMD) simulations in the temperature range between (298 and 573) K and for mole fractions of the dissolved gas up to 0.20. The four ternary mixtures of interest are n-hexadecane + n-octacosane + carbon dioxide (CO2), n-hexadecane + nitrogen (N2) + CO2, as well as 1-hexadecanol + n-octacosane with CO2 or water (H2O). With SLS, ηL and σ of the two ternary mixtures containing n-hexadecane are accessed with average relative expanded experimental uncertainties (coverage factor k = 2) of ur(ηL) = 0.021 and ur(σ) = 0.019. EMD simulations are performed for all four ternary mixtures and give access to ηL and σ with average relative expanded statistical uncertainties (k = 2) of ur(ηL) = 0.15 and ur(σ) = 0.061. The influence of the dissolved gases is investigated by comparing the thermophysical properties of the ternary mixtures to those of the pure solvent or the binary subsystems. The results for the ternary mixture consisting of n-hexadecane, n-octacosane, and CO2, which include a variation of the composition of the binary subsystem, i.e. the solvent mixture, have shown the reduction of both properties, due to dissolving CO2, to be independent of the solvent composition. For the ternary mixture consisting of n-hexadecane, N2, and CO2, the reduction in both properties can be estimated by adding up the reduction determined for the binary subsystems, i.e. n-hexadecane with dissolved N2 or CO2, which suggest that the presence of a further solute does not influence the impact of a dissolved gas.Open Access funding enabled and organized by Projekt DEAL.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659Friedrich-Alexander-Universität Erlangen-Nürnberg (1041

Imaging and spectroscopic observations of extreme-ultraviolet brightenings using EUI and SPICE on board Solar Orbiter

The smallest extreme-ultraviolet (EUV) brightening events that were detected so far, called campfires, have recently been uncovered by the High Resolution EUV telescope (HRIEUV), which is part of the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter. HRIEUV has a broad bandpass centered at 17.4 nm that is dominated by Fe ix and Fe x emission at about 1 MK. We study the thermal properties of EUI brightening events by simultaneously observing their responses at different wavelengths using spectral data from the Spectral Imaging of the Coronal Environment (SPICE) also on board Solar Orbiter and imaging data from EUI. We studied three EUI brightenings that were identified in HRIEUV data that lie within the small areas covered by the slit of the SPICE EUV spectrometer. We obtained the line intensities of the spectral profiles by Gaussian fitting. These diagnostics were used to study the evolution of the EUI brightenings over time at the different line-formation temperatures. We find that (i) the detection of these EUI brightenings is at the limit of the SPICE capabilities. They could not have been independently identified in the data without the aid of HRIEUV observations. (ii) Two of these EUI brightenings with longer lifetimes are observed up to Ne viii temperatures (0.6 MK). (iii) All of the events are detectable in O vi (0.3 MK), and the two longer-lived events are also detected in other transition region (TR) lines. (iv) In one case, we observe two peaks in the intensity light curve of the TR lines that are separated by 2.7 min for C iii and 1.2 min for O vi. The Ne viii intensity shows a single peak between the two peak times of the TR line intensity. Spectral data from SPICE allow us to follow the thermal properties of EUI brightenings. Our results indicate that at least some EUI brightenings barely reach coronal temperatures.Comment: 13 pages, 16 figures, language editing, accepted in A&

Sequence differences between BAX and BAK core domains manifest as differences in their interactions with lipids

The B-cell lymphoma 2 (BCL2) family members, BCL2-associated protein X (BAX) and BCL2 homologous antagonist killer (BAK), are required for programmed cell death via the mitochondrial pathway. When cells are stressed, damaged or redundant, the balance of power between the BCL2 family of proteins shifts towards BAX and BAK, allowing their transition from an inactive, monomeric state to a membrane-active oligomeric form that releases cytochrome c from the mitochondrial intermembrane space. That oligomeric state has an essential intermediate, a symmetric homodimer of BAX or BAK. Here we describe crystal structures of dimers of the core domain of BAX, comprising its helices α2–α5. These structures pro-vide an atomic resolution description of the interactions that drive BAX homo-dimerisation and insights into potential interaction between core domain dimers and membrane lipids. The previously identified BAK lipid-interacting sites are not conserved with BAX and are likely to determine the differences between them in their interactions with lipids. We also describe structures of heterodimers of BAK/BAX core domains, yielding further insight into the differences in lipid binding between BAX and BAK

Sequence differences between BAX and BAK core domains manifest as differences in their interactions with lipids

The B-cell lymphoma 2 (BCL2) family members, BCL2-associated protein X (BAX) and BCL2 homologous antagonist killer (BAK), are required for programmed cell death via the mitochondrial pathway. When cells are stressed, damaged or redundant, the balance of power between the BCL2 family of proteins shifts towards BAX and BAK, allowing their transition from an inactive, monomeric state to a membrane-active oligomeric form that releases cytochrome c from the mitochondrial intermembrane space. That oligomeric state has an essential intermediate, a symmetric homodimer of BAX or BAK. Here we describe crystal structures of dimers of the core domain of BAX, comprising its helices α2–α5. These structures pro-vide an atomic resolution description of the interactions that drive BAX homo-dimerisation and insights into potential interaction between core domain dimers and membrane lipids. The previously identified BAK lipid-interacting sites are not conserved with BAX and are likely to determine the differences between them in their interactions with lipids. We also describe structures of heterodimers of BAK/BAX core domains, yielding further insight into the differences in lipid binding between BAX and BAK

Viscosity and Interfacial Tension of Binary Mixtures Consisting of Linear, Branched, Cyclic, or Oxygenated Hydrocarbons with Dissolved Gases Using Surface Light Scattering and Equilibrium Molecular Dynamics Simulations

In the present study, the influence of the molecular characteristics of the solvent and solute on the dynamic viscosity and interfacial tension of binary mixtures consisting of a liquid with a dissolved gas is investigated using surface light scattering (SLS) and equilibrium molecular dynamics (EMD) simulations. In detail, binary mixtures consisting of linear, branched, cyclic, or oxygenated hydrocarbons and the solutes hydrogen, helium, methane, water, carbon monoxide, or carbon dioxide are studied in the temperature range between (298 and 573) K and for solute mole fractions up to 0.2. With SLS, the liquid dynamic viscosity and interfacial tension of the binary mixtures could be accessed in macroscopic thermodynamic equilibrium with average expanded uncertainties (coverage factor k  = 2) of (2.4 and 2.3)%, respectively. While EMD simulations were able to predict the influence of the dissolved gases on the interfacial tension of the binary mixtures, the simulations fail to represent the influence of the dissolved gas on the viscosity. Due to the systematic variation of the solvent and solute molecules, the influence of the molecular characteristics, e.g., in the form of size, shape, or polarity, on the thermophysical properties of the mixtures is discussed. Dissolving carbon dioxide, e.g., leads to a reduction of both properties by up to 60% compared to the properties of the pure solvent. Dissolved helium, on the other hand, has only a small influence on the properties of the pure solvent. The influence of dissolved water was found to be negligible in mixtures with an alkane but strongly increases both properties when dissolved in an alcohol, which may be explained by the formation of hydrogen bonds.Open Access funding enabled and organized by Projekt DEAL.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659Friedrich-Alexander-Universität Erlangen-Nürnberg (1041