Implementation of Quantum Gates via Optimal Control

Starting with the basic control system model often employed in NMR pulse design, we derive more realistic control system models taking into account effects such as off-resonant excitation for systems with fixed inter-qubit coupling controlled by globally applied electromagnetic fields, as well as for systems controlled by a combination of a global fields and local control electrodes. For both models optimal control is used to find controls that implement a set of two- and three-qubit gates with fidelity greater than 99.99%. While in some cases the optimal pulses obtained appear to be surprisingly simple and experimentally realistic, the results also show that the "optimal" pulses obtained in other cases are experimentally infeasible, and more sophisticated parametrization of the control fields and numerical algorithms are needed.Comment: 10 pages, 4 figure

Visualization of facet-dependent pseudo-photocatalytic behavior of TiO2 nanorods for water splitting using In situ liquid cell TEM

We report an investigation of the pseudo-photocatalytic behavior of rutile TiO2 nanorods for water splitting observed with liquid cell transmission electron microscopy (TEM). The electron beam serves as a “light” source to initiate the catalytic reaction and a “water-in-salt” aqueous solution is employed as the electrolyte. The observation reveals that bubbles are generated preferentially residing near the {110} facet of a rutile TiO2 nanorod under a low electron dose rate (9.3–18.6 e-/Å2·s). These bubbles are ascribed to hydrogen gas generated from the pseudo-photocatalytic water splitting. As the electron beam current density increases to 93 e-/Å2 ·s, bubbles are also found at the {001} and {111} facets as well as in the bulk liquid solution, demonstrating the dominant effects of water electrolysis by electron beam under higher dose rates. The facet-dependent pseudo-photocatalytic behavior of rutile TiO2 nanorods is further validated using density functional theory (DFT)calculation. Our work establishes a facile liquid cell TEM setup for the study of pseudo-photocatalytic water splitting and it may also be applied to investigation of other photo-activated phenomena occurring at the solid-liquid interfaces

Chronological Lifespan in Yeast Is Dependent on the Accumulation of Storage Carbohydrates Mediated by Yak1, Mck1 and Rim15 Kinases

Upon starvation for glucose or any other macronutrient, yeast cells exit from the mitotic cell cycle and acquire a set of characteristics that are specific to quiescent cells to ensure longevity. Little is known about the molecular determinants that orchestrate quiescence entry and lifespan extension. Using starvation-specific gene reporters, we screened a subset of the yeast deletion library representing the genes encoding 'signaling' proteins. Apart from the previously characterised Rim15, Mck1 and Yak1 kinases, the SNF1/AMPK complex, the cell wall integrity pathway and a number of cell cycle regulators were shown to be necessary for proper quiescence establishment and for extension of chronological lifespan (CLS), suggesting that entry into quiescence requires the integration of starvation signals transmitted via multiple signaling pathways. The CLS of these signaling mutants, and those of the single, double and triple mutants of $\textit{RIM15}$, $\textit{YAK1}$ and $\textit{MCK1}$ correlates well with the amount of storage carbohydrates but poorly with transition-phase cell cycle status. Combined removal of the glycogen and trehalose biosynthetic genes, especially $\textit{GSY2}$ and $\textit{TPS1}$, nearly abolishes the accumulation of storage carbohydrates and severely reduces CLS. Concurrent overexpression of $\textit{GSY2}$ and $\textit{TSL1}$ or supplementation of trehalose to the growth medium ameliorates the severe CLS defects displayed by the signaling mutants ($\textit{rim15Δyak1Δ}$ or $\textit{rim15Δmck1Δ}$). Furthermore, we reveal that the levels of intracellular reactive oxygen species are cooperatively controlled by Yak1, Rim15 and Mck1, and the three kinases mediate the $\textit{TOR1}$-regulated accumulation of storage carbohydrates and CLS extension. Our data support the hypothesis that metabolic reprogramming to accumulate energy stores and the activation of anti-oxidant defence systems are coordinated by Yak1, Rim15 and Mck1 kinases to ensure quiescence entry and lifespan extension in yeast.This work was sponsored by a scholarship awarded by National University of Defense Technology of China (to LC) and a scholarship from Lucy Cavendish College, Cambridge (to ZQ). Reagents and tools were supported by the UNICELLSYS Collaborative Project (No. 201142) of the European Commission (awarded to SGO). NZ is grateful to the Wellcome Trust and the University of Cambridge for support and facilities

Free-standing graphene films embedded in epoxy resin with enhanced thermal properties

The poor thermal conductivity of polymer composites has long been a deterrent to their increased use in high-end aerospace or defence applications. This study describes a new approach for the incorporation of graphene in an epoxy resin, through the addition of graphene as free-standing film in the polymeric matrix. The electrical and thermal conductivity of composites embedding two different free-standing graphene films was compared to composites with embedded carbon nanotube buckypapers (CNT-BP). Considerably higher thermal conductivity values than those achieved with conventional dispersing methods of graphene or CNTs in epoxy resins were obtained. The characterisation was complemented with a study of the structure at the microscale by cross-sectional scanning electron microscopy (SEM) images and a thermogravimetric analysis (TGA). The films are preconditioned in order to incorporate them into the composites, and the complete manufacturing process proposed allows the production and processing of these materials in large batches. The high thermal conductivity obtained for the composites opens the way for their use in demanding thermal management applications, such as electronic enclosures or platforms facing critical temperature loads.European Defence Agency tender No 17.ESI.OP.066. Study on the Impact of Graphene on Defence Application

Movements of genes between populations: are pollinators more effective at transferring their own or plant genetic markers?

The transfer of genes between populations is increasingly important in a world where pollinators are declining, plant and animal populations are increasingly fragmented and climate change is forcing shifts in distribution. The distances that pollen can be transported by small insects are impressive, as is the extensive gene flow between their own populations. We compared the relative ease by which small insects introduce genetic markers into their own and host-plant populations. Gene flow via seeds and pollen between populations of an Asian fig species were evaluated using cpDNA and nuclear DNA markers, and between-population gene flow of its pollinator fig wasp was determined using microsatellites. This insect is the tree's only pollinator locally, and only reproduces in its figs. The plant's pollen-to-seed dispersal ratio was 9.183-9.437, smaller than that recorded for other Ficus. The relative effectiveness of the pollinator at introducing markers into its own populations was higher than the rate it introduced markers into the plant's populations (ratio = 14 : 1), but given the demographic differences between plant and pollinator, pollen transfer effectiveness is remarkably high. Resource availability affects the dispersal of fig wasps, and host-plant flowering phenology here and in other plant-pollinator systems may strongly influence relative gene flow rates

Mode Transition and Symmetry-Breaking in the Wake of a Flapping Foil

A numerical model for two-dimensional flows around a pitching foil in a viscous flow is presented. The model is numerically solved using the immersed boundary method and used to investigate the flow patterns of the foil pitching sinusoidally over a range of frequencies and amplitudes. A transition from the Karman vortex streets to the reverse Karman vortex streets are found, as the amplitudes of pitching motions increase. In the transition, the vortex streets undergo symmetry-breaking to the central lines of vortex streets. Those observations are in agreement with the previous experiment (Phys. Rev. E. 77 016308 2008). Furthermore, we examine the wake of the foils pitching with different frequencies. The transition from the Karman vortex streets to the reverse Karman vortex streets is also observed. An explanation is presented to the mechanism of the transition

Can the salt-advection feedback be detected in internal variability of the atlantic meridional overturning circulation?

Evidence for the assumptions of the salt-advection feedback in box models is sought by studying the Atlantic meridional overturning circulation (AMOC) internal variability in the long preindustrial control runs of two Earth system models. The first assumption is that AMOC strength is proportional to the meridional density difference between the North Atlantic and the Southern Oceans. The model simulations support this assumption, with the caveat that nearly all the long time-scale variability occurs in the North Atlantic density. The second assumption is that the freshwater transport variability by the overturning at the Atlantic southern boundary is controlled by the strength of AMOC. Only one of the models shows some evidence that AMOC variability at 45°N leads variability in the overturning freshwater transport at the southern boundary by about 30 years, but the other model shows no such coherence. In contrast, in both models this freshwater transport variability is dominated by local salinity variations. The third assumption is that changes in the overturning freshwater transport at the Atlantic southern boundary perturb the north-south density difference, and thus feed back on AMOC strength in the north. No evidence for this assumption is found in either model at any time scale, although this does not rule out that the salt-advection feedback may be excited by a strong enough freshwater perturbation

Complex Faulting and Triggered Rupture During the 2018 MW 7.9 Offshore Kodiak, Alaska, Earthquake

We combine aftershock relocations, source mechanisms, teleseismic P wave backprojection, and Global Positioning System data inversion to constrain complex faulting geometry of the 2018 MW 7.9 offshore Kodiak earthquake. Relocated aftershocks delineate several N‐S trends including a prominent 110‐km‐long segment, as well as broad NE‐SW trends. Global Positioning System modeling and backprojection indicate that the NE‐SW trending left‐lateral strike‐slip segments released most energy dominating far‐field crustal deformation and radiated wavefield. Backprojection infers fast E‐to‐W rupture propagations superimposed on a slower S‐to‐N migration. We propose a five‐segment model of the rupture that was partially driven by dynamic triggering

Monotone iterative procedure and systems of a finite number of nonlinear fractional differential equations

The aim of the paper is to present a nontrivial and natural extension of the comparison result and the monotone iterative procedure based on upper and lower solutions, which were recently established in (Wang et al. in Appl. Math. Lett. 25:1019-1024, 2012), to the case of any finite number of nonlinear fractional differential equations.The author is very grateful to the reviewers for the remarks, which improved the final version of the manuscript. This article was financially supported by University of Łódź as a part of donation for the research activities aimed at the development of young scientists, grant no. 545/1117