3,429 research outputs found
Experimental entanglement distribution by separable states
The distribution of entanglement between macroscopically separated parties
represents a crucial protocol for future quantum information networks.
Surprisingly, it has been theoretically shown that two distant systems can be
entangled by sending a third mediating system that is not entangled with either
of them. Such a possibility seems to contradict the intuition that to
distribute entanglement, the transmitted system always needs to be entangled
with the sender. Here, we experimentally distribute entanglement by exchanging
a subsystem and successfully prove that this subsystem is not entangled with
either of the two parties. Our implementation relies on the preparation of a
specific three-mode Gaussian state containing thermal noise that demolishes the
entanglement in two of the three bipartite splittings. After transmission of a
separable mode this noise can be removed by quantum interference. Our work
demonstrates an unexpected variant of entanglement distribution and improves
the understanding necessary to engineer multipartite quantum information
networks.Comment: 9 pages, 6 figure
In situ observation of single-molecule surface reactions from low to high affinities
This is the author accepted manuscript. The final version is available from the publisher via the DOI in this recordUnderstanding reactions occurring between ligand molecules and nanomaterial surfaces is essential in the field of nanoscience. The conventional methods for characterizing
such surface-based reactions allow only for the analysis of the end product of a reaction,
although the reaction path proceeds through the transient interaction of reactants and
with kinetics dependent on environmental parameters. Here we study single molecule
reaction kinetics associated with gold nanoparticle surfaces in an aqueous medium by
utilizing whispering-gallery-mode microcavity sensors. Our approach resolves transient
as well as permanent interaction kinetics of ligand molecules at the nanoparticle interface in situ, over a broad range of affinities and even under conditions where no net
product is formed. This enables us to monitor and characterize reactions during the
entire procedure of a bottom-up surface modification, ranging from the deposition of
ligands to the confirmation of their functionality. We demonstrate this prospect by
studying surface reaction kinetics with respect to the species of ligand head groups,
tethered molecules, and inhibitors in addition to subsequent bio-specific reactions between tethered molecules and analytes.Max Planck Societ
The GALEX Ultraviolet Virgo Cluster Survey (GUViCS). II. Constraints on star formation in ram-pressure stripped gas
Context: Several galaxies in the Virgo cluster are known to have large HI gas
tails related to a recent ram-pressure stripping event. The Virgo cluster has
been extensively observed at 1539 A in the far-ultraviolet for the GALEX
Ultraviolet Virgo Cluster Survey (GUViCS), and in the optical for the Next
Generation Virgo Survey (NGVS), allowing a study of the stellar emission
potentially associated with the gas tails of 8 cluster members. On the
theoretical side, models of ram-pressure stripping events have started to
include the physics of star formation. Aim: We aim to provide quantitative
constraints on the amount of star formation taking place in the ram-pressure
stripped gas, mainly on the basis of the far-UV emission found in the GUViCS
images in relation with the gas content of the tails. Methods: We have
performed three comparisons of the young stars emission with the gas column
density: visual, pixel-by-pixel and global. We have compared our results to
other observational and theoretical studies. Results: We find that the level of
star formation taking place in the gas stripped from galaxies by ram-pressure
is low with respect to the available amount of gas. Star formation is lower by
at least a factor 10 compared to the predictions of the Schmidt Law as
determined in regular spiral galaxy disks. It is also lower than measured in
dwarfs galaxies and the outer regions of spirals, and than predicted by some
numerical simulations. We provide constraints on the star formation efficiency
in the ram-pressure stripped gas tails, and compare these with current models.Comment: Accepted in A&A, 17 pages (including the appendix and "on-line"
figures of the paper
Virgo Galaxies with Long One-Sided HI Tails
In a new HI imaging survey of Virgo galaxies (VIVA: VLA Imaging of Virgo
galaxies in Atomic gas), we find 7 spiral galaxies with long HI tails. The
morphology varies but all the tails are extended well beyond the optical radii
on one side. These galaxies are found in intermediate-low density regions
(0.6-1 Mpc in projection from M87). The tails are all pointing roughly away
from M87, suggesting that these tails may have been created by a global cluster
mechanism. While the tidal effects of the cluster potential are too small, a
rough estimate suggests that simple ram-pressure stripping indeed could have
formed the tails in all but two cases. At least three systems show HI
truncation to within the stellar disk, providing evidence for a gas-gas
interaction. Although most of these galaxies do not appear disturbed optically,
some have close neighbors, suggesting that tidal interactions may have moved
gas outwards making it more susceptible to the ICM ram-pressure or viscosity.
Indeed, a simulation study of one of the tail galaxies, NGC 4654, suggests that
the galaxy is most likely affected by the combined effect of a gravitational
interaction and ram-pressure stripping. We conclude that these one-sided HI
tail galaxies have recently arrived in the cluster, falling in on highly radial
orbits. It appears that galaxies begin to lose their gas already at
intermediate distances from the cluster center through ram-pressure or
turbulent viscous stripping and tidal interactions with neighbours, or a
combination of both.Comment: 4 pages, 3 figures (including 1 plate), accepted for accepted for
publication in ApJ Letter (vol. 659, L115), a version with full resolution
Plate 1 is available from
http://www.astro.umass.edu/~achung/astro-ph/viva_tail.pd
Order and nFl Behavior in UCu4Pd
We have studied the role of disorder in the non-Fermi liquid system UCu4Pd
using annealing as a control parameter. Measurement of the lattice parameter
indicates that this procedure increases the crystallographic order by
rearranging the Pd atoms from the 16e to the 4c sites. We find that the low
temperature properties depend strongly on annealing. Whereas the non-Fermi
liquid behavior in the specific heat can be observed over a larger temperature
range after annealing, the clear non-Fermi liquid behavior of the resistivity
of the unannealed sample below 10 K disappears. We come to the conclusion that
this argues against the Kondo disorder model as an explanation for the
non-Fermi liquid properties of both as-prepared and annealed UCu4Pd
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