1,893 research outputs found
A Maxwell-vector p-wave holographic superconductor in a particular background AdS black hole metric
We study the p-wave holographic superconductor for AdS black holes with
planar event horizon topology for a particular Lovelock gravity, in which the
action is characterized by a self-interacting scalar field nonminimally coupled
to the gravity theory which is labeled by an integer . As the Lovelock
theory of gravity is the most general metric theory of gravity based on the
fundamental assumptions of general relativity, it is a desirable theory to
describe the higher dimensional spacetime geometry. The present work is devoted
to studying the properties of the p-wave holographic superconductor by
including a Maxwell field which nonminimally couples to a complex vector field
in a higher dimensional background metric. In the probe limit, we find that the
critical temperature decreases with the increase of the index of the
background black hole metric, which shows that a larger makes it harder for
the condensation to form. We also observe that the index affects the
conductivity and the gap frequency of the holographic superconductors.Comment: 14 pages, 6 figure
Simulating dynamical quantum Hall effect with superconducting qubits
We propose an experimental scheme to simulate the dynamical quantum Hall
effect and the related interaction-induced topological transition with a
superconducting-qubit array. We show that a one-dimensional Heisenberg model
with tunable parameters can be realized in an array of superconducting qubits.
The quantized plateaus, which is a feature of the dynamical quantum Hall
effect, will emerge in the Berry curvature of the superconducting qubits as a
function of the coupling strength between nearest neighbor qubits. We
numerically calculate the Berry curvatures of two-, four- and six-qubit arrays,
and find that the interaction-induced topological transition can be easily
observed with the simplest two-qubit array. Furthermore, we analyze some
practical conditions in typical experiments for observing such dynamical
quantum Hall effect.Comment: 9 pages, 6 figures, version accepted by PR
Demonstration of Geometric Landau-Zener Interferometry in a Superconducting Qubit
Geometric quantum manipulation and Landau-Zener interferometry have been
separately explored in many quantum systems. In this Letter, we combine these
two approaches to study the dynamics of a superconducting phase qubit. We
experimentally demonstrate Landau-Zener interferometry based on the pure
geometric phases in this solid-state qubit. We observe the interference caused
by a pure geometric phase accumulated in the evolution between two consecutive
Landau-Zener transitions, while the dynamical phase is canceled out by a
spin-echo pulse. The full controllability of the qubit state as a function of
the intrinsically robust geometric phase provides a promising approach for
quantum state manipulation.Comment: 5 pages + 3 pages supplemental Materia
Plant geographic phenotypic variation drives diversification in its associated community of a phytophagous insect and its parasitoids
International audienceBackground: While the communities constituted by phytophageous insects and their parasites may represent half of all terrestrial animal species, understanding their diversification remains a major challenge. A neglected idea is that geographic phenotypic variation in a host plant may lead to heterogeneous evolutionary responses of the different members of the associated communities. This could result in diversification on a host plant by ecological speciation in some species, leading to geographic variation in community composition. In this study we investigated geographic variation of inflorescence receptacle size in a plant, Ficus hirta, and how the hymenopteran community feeding in the inflorescences has responded. Our predictions were:1) Inflorescence size variation affects wasp species differently depending on how they access oviposition sites.2) In some affected lineages of wasps, we may observe vicariant, parapatric species adapted to different inflorescence sizes.Results: We show that fig (the enclosed inflorescence of Ficus) wall thickness varies geographically. The fig-entering pollinating wasp was not affected, while the parasites ovipositing through the fig wall were. Two parapatric species of Philotrypesis, exhibiting strikingly different ovipositor lengths, were recorded. One species of Sycoscapter was also present, and it was restricted, like the shorter-ovipositor Philotrypesis, to the geographic zone where fig walls were thinner.Conclusions: Previous work on fig wasps suggested that parapatric geographic ranges among congenerics were due to adaptation to variation in abiotic factors, complemented by interspecific competition. Our results show that parapatric ranges may also result from adaptation to variation in biotic factors. Within an insect community, differences among species in their response to geographic phenotypic variation of their host plant may result in geographically heterogeneous community structure. Such heterogeneity leads to heterogeneous interaction networks among sites. Our results support the hypothesis that plant geographic phenotypic variation can be a driver of diversification in associated insect communities, and can complement other diversification processes
Simulating the Kibble-Zurek mechanism of the Ising model with a superconducting qubit system
The Kibble-Zurek mechanism (KZM) predicts the density of topological defects
produced in the dynamical processes of phase transitions in systems ranging
from cosmology to condensed matter and quantum materials. The similarity
between KZM and the Landau-Zener transition (LZT), which is a standard tool to
describe the dynamics of some non-equilibrium physics in contemporary physics,
is being extensively exploited. Here we demonstrate the equivalence between KZM
in the Ising model and LZT in a superconducting qubit system. We develop a
time-resolved approach to study quantum dynamics of LZT with nano-second
resolution. By using this technique, we simulate the key features of KZM in the
Ising model with LZT, e.g., the boundary between the adiabatic and impulse
regions, the freeze-out phenomenon in the impulse region, especially, the
scaling law of the excited state population as the square root of the quenching
rate. Our results supply the experimental evidence of the close connection
between KZM and LZT, two textbook paradigms to study the dynamics of the
non-equilibrium phenomena.Comment: Title changed, authors added, and some experimental data update
Observation of coherent oscillation in single-passage Landau-Zener transitions
Landau-Zener transition (LZT) has been explored in a variety of physical
systems for coherent population transfer between different quantum states. In
recent years, there have been various proposals for applying LZT to quantum
information processing because when compared to the methods using ac pulse for
coherent population transfer, protocols based on LZT are less sensitive to
timing errors. However, the effect of finite range of qubit energy available to
LZT based state control operations has not been thoroughly examined. In this
work, we show that using the well-known Landau-Zener formula in the vicinity of
an avoided energy-level crossing will cause considerable errors due to coherent
oscillation of the transition probability in a single-passage LZT experiment.
The data agree well with the numerical simulations which take the transient
dynamics of LZT into account. These results not only provide a closer view on
the issue of finite-time LZT but also shed light on its effects on the quantum
state manipulation.Comment: 10 pages,5 figure
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