361 research outputs found
Adiabatic quantum simulations with driven superconducting qubits
We propose a quantum simulator based on driven superconducting qubits where
the interactions are generated parametrically by a polychromatic magnetic flux
modulation of a tunable bus element. Using a time-dependent Schrieffer-Wolff
transformation, we analytically derive a multi-qubit Hamiltonian which features
independently tunable and -type interactions as well as local bias
fields over a large parameter range. We demonstrate the adiabatic simulation of
the ground state of a hydrogen molecule using two superconducting qubits and
one tunable bus element. The time required to reach chemical accuracy lies in
the few microsecond range and therefore could be implemented on currently
available superconducting circuits. Further applications of this technique may
also be found in the simulation of interacting spin systems.Comment: 11 pages, 6 figure
A low-loss, broadband antenna for efficient photon collection from a coherent spin in diamond
We report the creation of a low-loss, broadband optical antenna giving highly
directed output from a coherent single spin in the solid-state. The device, the
first solid-state realization of a dielectric antenna, is engineered for
individual nitrogen vacancy (NV) electronic spins in diamond. We demonstrate a
directionality close to 10. The photonic structure preserves the high spin
coherence of single crystal diamond (T2>100us). The single photon count rate
approaches a MHz facilitating efficient spin readout. We thus demonstrate a key
enabling technology for quantum applications such as high-sensitivity
magnetometry and long-distance spin entanglement.Comment: 5 pages, 4 figures and supplementary information (5 pages, 8
figures). Comments welcome. Further information under
http://www.quantum-sensing.physik.unibas.c
Characterization and tomography of a hidden qubit
In circuit-based quantum computing, the available gate set typically consists
of single-qubit gates acting on each individual qubit and at least one
entangling gate between pairs of qubits. In certain physical architectures,
however, some qubits may be 'hidden' and lacking direct addressability through
dedicated control and readout lines, for instance because of limited on-chip
routing capabilities, or because the number of control lines becomes a limiting
factor for many-qubit systems. In this case, no single-qubit operations can be
applied to the hidden qubits and their state cannot be measured directly.
Instead, they may be controlled and read out only via single-qubit operations
on connected 'control' qubits and a suitable set of two-qubit gates. We first
discuss the impact of such restricted control capabilities on the quantum
volume of specific qubit coupling networks. We then experimentally demonstrate
full control and measurement capabilities in a superconducting two-qubit device
with local single-qubit control and iSWAP and controlled-phase two-qubit
interactions enabled by a tunable coupler. We further introduce an iterative
tune-up process required to completely characterize the gate set used for
quantum process tomography and evaluate the resulting gate fidelities
Rarity of figs (Ficus) on Madagascar and its relationship to a depauperate frugivore community
Bien que plusieurs auteurs aient remarquĂ© le faible nombre d'espĂšces frugivores prĂ©sentes Ă Madagascar, l'interprĂ©tation de cette observation n'a jusqu'Ă prĂ©sent fait l'objet que de quelques spĂ©culations. Si l'on compare la forĂȘt
malgache Ă celles des rĂ©gions tropicales de l'Ancien Monde, on y observe que le genre Ficus (gĂ©nĂ©ralement considĂ©rĂ© comme une ressource-clĂ© pour les frugivores des forĂȘts tropicales) prĂ©sente Ă la fois une faible diversitĂ© et une densitĂ© rĂ©duite. La productivitĂ© du groupe des Ficus y est
relativement basse et sa phénologie ne correspond pas aux séquences habituellement observées par ailleurs. Ces facteurs - dont certains pourraient résulter de la longue période au cours de laquelle Madagascar a été isolée des blocs continentaux - sont considérés comme des paramÚtres
importants pour expliquer le nombre réduit des frugivores sur cette ßle
Determinants of terrestrial feeding in an arboreal primate: the case of Hapalemur meridionalis
Objectives
The proximate and ultimate determinants that may have prompted some primates to shift from an arboreal to terrestrial feeding niche, whether due to environmental change, seasonality, and/or predation pressure, are poorly understood. Within a fragmented littoral forest in southeast Madagascar, an arboreal strepsirrhine population spends a large proportion of time on the ground, thus we aimed to identify which factors influence terrestrial feeding.
Methods
From January to December 2013, we conducted 103 full-day focal follows on three social groups of southern bamboo lemurs H. meridionalis. We continuously recorded feeding time on all arboreal and terrestrial items, as well as whether the focal individual was under the canopy or exposed, and the distance to their nearest conspecific neighbor. All observed food items were collected and analyzed for macronutrient content. Daily climatic variables (temperature, precipitation), resource seasonality, daily path length (DPL), along with dietary and predation risk proxies, were used as fixed effects in a linear mixed model, with the daily proportion of terrestrial feeding as the dependent variable.
Results
Our model indicated that daily terrestrial feeding increased at cooler temperature, was associated with reduced DPL, and the intake of dietary metabolizable energy increased as terrestrial feeding increased. All other fixed effects were not significant predictors.
Discussion
Our study provides a window into the ultimate determinants of niche expansion: ancestral primates, in absence of their primary resources, may have initially descended to the ground in peripheral population range areas where the benefits (e g., nutritional pay-off) out-weighed the costs
Plant secondary metabolites and primate food choices : a meta-analysis and future directions
The role of plant secondary metabolites (PSMs) in shaping the feeding decisions, habitat suitability, and reproductive success of herbivorous mammals has been a major theme in ecology for decades. Although primatologists were among the first to test these ideas, studies of PSMs in the feeding ecology of non-human primates have lagged in recent years, leading to a recent call for primatologists to reconnect with phytochemists to advance our understanding of the primate nutrition. To further this case, we present a formal meta-analysis of diet choice in response to PSMs based on field studies on wild primates. Our analysis of 155 measurements of primate feeding response to PSMs is drawn from 53 studies across 43 primate species which focussed primarily on the effect of three classes of PSMs tannins, phenolics, and alkaloids. We found a small but significant effect of PSMs on the diet choice of wild primates, which was largely driven by the finding that colobine primates showed a moderate aversion to condensed tannins. Conversely, there was no evidence that PSMs had a significant deterrent effect on food choices of non-colobine primates when all were combined into a single group. Furthermore, within the colobine primates, no other PSMs influenced feeding choices and we found no evidence that foregut anatomy significantly affected food choice with respect to PSMs. We suggest that methodological improvements related to experimental approaches and the adoption of new techniques including metabolomics are needed to advance our understanding of primate diet choice
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