19,580 research outputs found
Population development of beet cyst nematodes and their damage potential to sugar beets under different temperature regimes
Chiral spin liquid and emergent anyons in a Kagome lattice Mott insulator
Topological phases in frustrated quantum spin systems have fascinated
researchers for decades. One of the earliest proposals for such a phase was the
chiral spin liquid put forward by Kalmeyer and Laughlin in 1987 as the bosonic
analogue of the fractional quantum Hall effect. Elusive for many years, recent
times have finally seen a number of models that realize this phase. However,
these models are somewhat artificial and unlikely to be found in realistic
materials. Here, we take an important step towards the goal of finding a chiral
spin liquid in nature by examining a physically motivated model for a Mott
insulator on the Kagome lattice with broken time-reversal symmetry. We first
provide a theoretical justification for the emergent chiral spin liquid phase
in terms of a network model perspective. We then present an unambiguous
numerical identification and characterization of the universal topological
properties of the phase, including ground state degeneracy, edge physics, and
anyonic bulk excitations, by using a variety of powerful numerical probes,
including the entanglement spectrum and modular transformations.Comment: 9 pages, 9 figures; partially supersedes arXiv:1303.696
Equivalence of critical scaling laws for many-body entanglement in the Lipkin-Meshkov-Glick model
We establish a relation between several entanglement properties in the
Lipkin-Meshkov-Glick model, which is a system of mutually interacting spins
embedded in a magnetic field. We provide analytical proofs that the single-copy
entanglement and the global geometric entanglement of the ground state close to
and at criticality behave as the entanglement entropy. These results are in
deep contrast to what is found in one- dimensional spin systems where these
three entanglement measures behave differently.Comment: 4 pages, 2 figures, published versio
Characterization of non-local gates
A non-local unitary transformation of two qubits occurs when some Hamiltonian
interaction couples them. Here we characterize the amount, as measured by time,
of interaction required to perform two--qubit gates, when also arbitrarily
fast, local unitary transformations can be applied on each qubit. The minimal
required time of interaction, or interaction cost, defines an operational
notion of the degree of non--locality of gates. We characterize a partial order
structure based on this notion. We also investigate the interaction cost of
several communication tasks, and determine which gates are able to accomplish
them. This classifies two--qubit gates into four categories, differing in their
capability to transmit classical, as well as quantum, bits of information.Comment: revtex, 14 pages, no pictures; proof of result 1 simplified
significantl
Pairing of Cooper Pairs in a Fully Frustrated Josephson Junction Chain
We study a one-dimensional Josephson junction chain embedded in a magnetic
field. We show that when the magnetic flux per elementary loop equals half the
superconducting flux quantum , a local \nbZ_2 symmetry arises.
This symmetry is responsible for a nematic Luttinger liquid state associated to
bound states of Cooper pairs. We analyze the phase diagram and we discuss some
experimental possibilities to observe this exotic phase.Comment: 4 pages, 4 EPS figure
Genralized Robustness of Entanglement
The robustness of entanglement results of Vidal and Tarrach considered the
problem whereby an entangled state is mixed with a separable state so that the
overall state becomes non-entangled. In general it is known that there are also
cases when entangled states are mixed with other entangled states and where the
sum is separable. In this paper, we treat the more general case where entangled
states can be mixed with any states so that the resulting mixture is
unentangled. It is found that entangled pure states for this generalized case
have the same robustness as the restricted case of Vidal and Tarrach.Comment: Final version. Editorial changes and references added to independent
wor
Transmission through quantum networks
We propose a simple formalism to calculate the conductance of any quantum
network made of one-dimensional quantum wires. We apply this method to analyze,
for two periodic systems, the modulation of this conductance with respect to
the magnetic field. We also study the influence of an elastic disorder on the
periodicity of the AB oscillations and we show that a recently proposed
localization mechanism induced by the magnetic field resists to such a
perturbation. Finally, we discuss the relevance of this approach for the
understanding of a recent experiment on GaAs/GaAlAs networks.Comment: 4 pages, 5 EPS figure
Symmetric Periodic Solutions of the Anisotropic Manev Problem
We consider the Manev Potential in an anisotropic space, i.e., such that the
force acts differently in each direction. Using a generalization of the
Poincare' continuation method we study the existence of periodic solutions
for weak anisotropy. In particular we find that the symmetric periodic orbits
of the Manev system are perturbed to periodic orbits in the anisotropic
problem.Comment: Late
Deuterium Toward WD1634-573: Results from the Far Ultraviolet Spectroscopic Explorer (FUSE) Mission
We use Far Ultraviolet Spectrocopic Explorer (FUSE) observations to study
interstellar absorption along the line of sight to the white dwarf WD1634-573
(d=37.1+/-2.6 pc). Combining our measurement of D I with a measurement of H I
from Extreme Ultraviolet Explorer data, we find a D/H ratio toward WD1634-573
of D/H=(1.6+/-0.5)e-5. In contrast, multiplying our measurements of D I/O
I=0.035+/-0.006 and D I/N I=0.27+/-0.05 with published mean Galactic ISM gas
phase O/H and N/H ratios yields D/H(O)=(1.2+/-0.2)e-5 and
D/H(N)=(2.0+/-0.4)e-5, respectively. Note that all uncertainties quoted above
are 2 sigma. The inconsistency between D/H(O) and D/H(N) suggests that either
the O I/H I and/or the N I/H I ratio toward WD1634-573 must be different from
the previously measured average ISM O/H and N/H values. The computation of
D/H(N) from D I/N I is more suspect, since the relative N and H ionization
states could conceivably vary within the LISM, while the O and H ionization
states will be more tightly coupled by charge exchange.Comment: 23 pages, 5 figures; AASTEX v5.0 plus EPSF extensions in mkfig.sty;
accepted by ApJ Supplemen
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