11,525 research outputs found
On the tensor convolution and the quantum separability problem
We consider the problem of separability: decide whether a Hermitian operator
on a finite dimensional Hilbert tensor product is separable or entangled. We
show that the tensor convolution defined for certain mappings on an almost
arbitrary locally compact abelian group, give rise to formulation of an
equivalent problem to the separability one.Comment: 13 pages, two sections adde
Non-linear screening of spherical and cylindrical colloids: the case of 1:2 and 2:1 electrolytes
From a multiple scale analysis, we find an analytic solution of spherical and
cylindrical Poisson-Boltzmann theory for both a 1:2 (monovalent co-ions,
divalent counter-ions) and a 2:1 (reversed situation) electrolyte. Our approach
consists in an expansion in powers of rescaled curvature , where
is the colloidal radius and the Debye length of the electrolytic
solution. A systematic comparison with the full numerical solution of the
problem shows that for cylinders and spheres, our results are accurate as soon
as . We also report an unusual overshooting effect where the
colloidal effective charge is larger than the bare one.Comment: 9 pages, 11 figure
Electric field control and optical signature of entanglement in quantum dot molecules
The degree of entanglement of an electron with a hole in a vertically coupled
self-assembled dot molecule is shown to be tunable by an external electric
field. Using atomistic pseudopotential calculations followed by a configuration
interaction many-body treatment of correlations, we calculate the electronic
states, degree of entanglement and optical absorption. We offer a novel way to
spectroscopically detect the magnitude of electric field needed to maximize the
entanglement.Comment: 4 pages, 6 figure
Many-Body Approximation Scheme Beyond GW
We explore the combination of the extended dynamical mean field theory
(EDMFT) with the GW approximation (GWA); the former sums the local
contributions to the self-energies to infinite order in closed form and the
latter handles the non-local ones to lowest order. We investigate the different
levels of self-consistency that can be implemented within this method by
comparing to the exact QMC solution of a finite-size model Hamiltonian. We find
that using the EDMFT solution for the local self-energies as input to the GWA
for the non-local self-energies gives the best result.Comment: 4 pages, 8 figure
The distance between Inherent Structures and the influence of saddles on approaching the mode coupling transition in a simple glass former
We analyze through molecular dynamics simulations of a Lennard-Jones binary
mixture the statistics of the distances between inherent structures (IS)
sampled at temperatures above the mode coupling transition temperature T_MCT.
We take equilibrated configurations and randomly perturb the coordinates of a
given number of particles. After that we take the nearest IS of both the
original configuration and the perturbed one and evaluate the distance between
them. This distance presents an inflection point near T~1 with a strong
decrease below this temperature and goes to a small but nonzero value on
approaching T_MCT. In the low temperature region we study the statistics of
events which give zero distance, i.e. dominated by minima, and find evidence
that the number of saddles decreases exponentially near T_MCT. This implies
that saddles continue to exist even for T<=T_MCT. As at T_MCT the extrapolated
diffusivity goes to zero our results imply that there are saddles associated
with nondiffusional events at T<T_MCT.Comment: 5 pages, 5 ps figure
An Extensive Collection of Stellar Wind X-ray Source Region Emission Line Parameters,Temperatures, Velocities, and Their Radial Distributions as Obtained from Chandra Observations of 17 OB Stars
Chandra high energy resolution observations have now been obtained from
numerous non-peculiar O and early B stars. The observed X-ray emission line
properties differ from pre-launch predictions, and the interpretations are
still problematic. We present a straightforward analysis of a broad collection
of OB stellar line profile data to search for morphological trends. X-ray line
emission parameters and the spatial distributions of derived quantities are
examined with respect to luminosity class. The X-ray source locations and their
corresponding temperatures are extracted by using the He-like f/i line ratios
and the H-like to He-like line ratios respectively. Our luminosity class study
reveals line widths increasing with luminosity. Although the majority of the OB
emission lines are found to be symmetric, with little central line
displacement, there is evidence for small, but finite, blue-ward line-shifts
that also increase with luminosity. The spatial X-ray temperature distributions
indicate that the highest temperatures occur near the star and steadily
decrease outward. This trend is most pronounced in the OB supergiants. For the
lower density wind stars, both high and low X-ray source temperatures exist
near the star. However, we find no evidence of any high temperature X-ray
emission in the outer wind regions for any OB star. Since the temperature
distributions are counter to basic shock model predictions, we call this the
"near-star high-ion problem" for OB stars. By invoking the traditional OB
stellar mass loss rates, we find a good correlation between the fir-inferred
radii and their associated X-ray continuum optical depth unity radii. We
conclude by presenting some possible explanations to the X-ray source problems
that have been revealed by this study.Comment: Published in 2007, ApJ, 668, 456. An Erratum scheduled for
publication in 2008, ApJ, 680, is included as an Appendix. The Erratum
corrects some tabulated data in 5 tables and 2 figure
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Cas9+ conditionally-immortalized macrophages as a tool for bacterial pathogenesis and beyond.
Macrophages play critical roles in immunity, development, tissue repair, and cancer, but studies of their function have been hampered by poorly-differentiated tumor cell lines and genetically-intractable primary cells. Here we report a facile system for genome editing in non-transformed macrophages by differentiating ER-Hoxb8 myeloid progenitors from Cas9-expressing transgenic mice. These conditionally immortalized macrophages (CIMs) retain characteristics of primary macrophages derived from the bone marrow yet allow for easy genetic manipulation and a virtually unlimited supply of cells. We demonstrate the utility of this system for dissection of host genetics during intracellular bacterial infection using two important human pathogens: Listeria monocytogenes and Mycobacterium tuberculosis
Simulating noisy quantum protocols with quantum trajectories
The theory of quantum trajectories is applied to simulate the effects of
quantum noise sources induced by the environment on quantum information
protocols. We study two models that generalize single qubit noise channels like
amplitude damping and phase flip to the many-qubit situation. We calculate the
fidelity of quantum information transmission through a chaotic channel using
the teleportation scheme with different environments. In this example, we
analyze the role played by the kind of collective noise suffered by the quantum
processor during its operation. We also investigate the stability of a quantum
algorithm simulating the quantum dynamics of a paradigmatic model of chaos, the
baker's map. Our results demonstrate that, using the quantum trajectories
approach, we are able to simulate quantum protocols in the presence of noise
and with large system sizes of more than 20 qubits.Comment: 11 pages, 7 fig
Relative multiplexing for minimizing switching in linear-optical quantum computing
Many existing schemes for linear-optical quantum computing (LOQC) depend on
multiplexing (MUX), which uses dynamic routing to enable near-deterministic
gates and sources to be constructed using heralded, probabilistic primitives.
MUXing accounts for the overwhelming majority of active switching demands in
current LOQC architectures. In this manuscript, we introduce relative
multiplexing (RMUX), a general-purpose optimization which can dramatically
reduce the active switching requirements for MUX in LOQC, and thereby reduce
hardware complexity and energy consumption, as well as relaxing demands on
performance for various photonic components. We discuss the application of RMUX
to the generation of entangled states from probabilistic single-photon sources,
and argue that an order of magnitude improvement in the rate of generation of
Bell states can be achieved. In addition, we apply RMUX to the proposal for
percolation of a 3D cluster state in [PRL 115, 020502 (2015)], and we find that
RMUX allows a 2.4x increase in loss tolerance for this architecture.Comment: Published version, New Journal of Physics, Volume 19, June 201
Morphology, dynamics and plasma parameters of plumes and inter-plume regions in solar coronal holes
Coronal plumes, which extend from solar coronal holes (CH) into the high
corona and - possibly - into the solar wind (SW), can now continuously be
studied with modern telescopes and spectrometers on spacecraft, in addition to
investigations from the ground, in particular, during total eclipses. Despite
the large amount of data available on these prominent features and related
phenomena, many questions remained unanswered as to their generation and
relative contributions to the high-speed streams emanating from CHs. An
understanding of the processes of plume formation and evolution requires a
better knowledge of the physical conditions at the base of CHs, in plumes and
in the surrounding inter-plume regions (IPR). More specifically, information is
needed on the magnetic field configuration, the electron densities and
temperatures, effective ion temperatures, non-thermal motions, plume
cross-sections relative to the size of a CH, the plasma bulk speeds, as well as
any plume signatures in the SW. In spring 2007, the authors proposed a study on
"Structure and dynamics of coronal plumes and inter-plume regions in solar
coronal holes" to the International Space Science Institute (ISSI) in Bern to
clarify some of these aspects by considering relevant observations and the
extensive literature. This review summarizes the results and conclusions of the
study. Stereoscopic observations allowed us to include three-dimensional
reconstructions of plumes. Multi-instrument investigations carried out during
several campaigns led to progress in some areas, such as plasma densities,
temperatures, plume structure and the relation to other solar phenomena, but
not all questions could be answered concerning the details of plume generation
process(es) and interaction with the SW.Comment: To appear on: The Astronomy and Astrophysics Review. 72 pages, 30
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