LT11557AR
Recovering entanglement from environmental noise
Quantum entanglement, a fundamental property
ensuring security of key distribution and
efficiency of quantum computing, is extremely
sensitive to noise. The presence of noise alters
or even invalidates the transmission of quantum
information through communication channel, by
spoiling entanglement. In this paper we report
the proposal and the first realization of a
method which allows to restore entanglement after
its propagation over a strongly noisy channel.
In fact, up today different procedures have been
developed in order to recover entanglement but,
besides a certain amount of noise, entanglement
is anyhow completely lost, since all the present
techniques require a certain amount of
entanglement left after the transmission over the
noisy channel that is, the channel has not to be
an “entanglement-breaking” one. Here we report
the experimental realization of a new protocol,
the entanglement localization, which restores
entanglement from an entanglement breaking
channel. This method is based on the measurement
of environmental light (noise) which interacts
with the entangled signal leading to the loss of
entanglement and a quantum feed-forward
correction, revealing entanglement even if this
one completely disappeared. A direct application
of this entanglement localization can be
envisaged to improve in-line quantum communication, and in quantum computation.
***
EA10480
Human group formation in online guilds and offline gangs driven by a
common team dynamic
Quantifying human group dynamics represents a unique challenge. Unlike
animals and other biological systems, humans form groups in both real
(offline) and virtual (online) spaces - from potentially dangerous
street gangs populated mostly by disaffected male youths, through to
the massive global guilds in online role-playing games for which
membership currently exceeds tens of millions of people from all
possible backgrounds, age-groups and genders. We have compiled and
analyzed data for these two seemingly unrelated offline and online
human activities, and have uncovered an unexpected quantitative link
between them. Although their overall dynamics differ visibly, we find
that a common team-based model can accurately reproduce the
quantitative features of each simply by adjusting the average
tolerance level and attribute range for each population. By contrast,
we find no evidence to support a version of the model based on
like-seeking-like (i.e. kinship or `homophily').
***
LC12134
Graphene pseudospintronics: A new twist on spin-based electronics
In an article appearing in Physical Review Letters, we propose a new electronic device based upon a unique property of graphene.
Graphene is a conducting material made up of a single layer of carbon atoms
which supports a new quantum number called pseudospin. Pseudospin is
manifested in many exotic properties of graphene, including the unusual
sequencing of plateaus in the quantum Hall effect, suppression of
backscattering, and Klein tunneling at interfaces.
The presence of pseudospin in graphene draws parallels with the physical
spin of electrons, including the possibility of exploiting the pseudospin
degree of freedom in a similar way as physical spin in spintronics and
quantum computing applications. So far, this has proved elusive because of
chirality in graphene: the orientation of an electron's pseudospin is
inextricably linked to the direction of its momentum, preventing its use as
an independently-tuneable degree of freedom.
We propose that "pseudospintronics" can be realized in
two coupled layers of graphene by applying external gate potentials. Their
numerical calculations demonstrate the performance of two devices: a
pseudospin-based version of a spin valve and a pseudospin-based spin-valve
transistor with a large on-off ratio.
***
BDR1159
Hybrid light-matter 'particles' created in films of silver nanostructures
New modes of light called polaritons can be created when there is a
very strong interaction between light and matter. Control and
manipulation of these new 'particles' is of considerable interest for
the development of novel devices including lasers, sensors and fast
optical switches which could one day replace electronic transistors.
In this paper we have created films of silver nanostructures which
capture and strongly confine light. This trapped light then interacts
with electrons in a surrounding layer of dye molecules, resulting in
the formation of new coupled electromagnetic modes. By controlling the
energy and strength of these hybrid particles, we have observed a
massive enhancement in Raman scattering from the dye molecules. Raman
scattering is a normally weak optical emission which provides a
spectroscopic fingerprint from molecules, and is therefore an important
analytical tool for molecular sensors.
***
LB12391
IS SUPERCONDUCTIVITY IN THE IRON AGE DRIVEN BY
SCHIZOPHRENIA OF FRUSTRATED ELECTRONS?
Superconductivity recently entered the "iron age" with discovery
of ferropnictides, where magnetism gives way to a superconductor
upon carrier doping. This unexpected finding is reinforced by an
equally unusual causal connection: the non-superconductive metal
lies outside the scope of the "standard model" of metals, where
long-lived electronic states carry the current. Thus, ferropnictides
resemble the famous cuprates in this respect.
Here, we propose a new mechanism for superconductivity in ferropnictides.
Previously, we showed how a combination of "frustrated" and "dualistic"
electrons unable to choose between localization and free motion gave
birth to an unusual metal. We explore how such a state contains the
seeds of the electronic glue that pairs electrons into cooper pairs in
these fascinating materials. This superconductive state is very unusual:
the pair amplitude switches sign between electron and hole-like fermi
sheets. In addition, we propose that the pair amplitude vanishes on
parts of the full Fermi surface. We also show how our work quantitatively
describes a wide range of experimental benchmarks in a natural way, and
reconciles apparently conflicting interpretations from different probes.
Seemingly, as opposed to normal human experience, dualistic
"schizophrenia"
and frustration in combination can lead to fascinating outcomes in
condensed
matter.
***
LA12438
Medium Modifications Resolve Anomalous NuTeV Result
A new calculation of nuclear medium effects may resolve
the NuTeV anomaly, a puzzling experimental result that
had indicated strong disagreement with the Standard Model
of particle physics.
The NuTeV anomaly came about when experimenters at
Fermilab's NuTeV (Neutrinos at the Tevatron) experiment
measured the ratio of two types of particles, neutrinos
and muons, emerging from high energy collisions of neutrinos
with an iron target. They found that about one percent
fewer collisions produced neutrinos than predicted by the
Standard Model.
One common assumption that was used in the analysis of the
NuTeV data involved a correction for an imbalance in the
number of protons and neutrons in the nucleus of iron. In
the NuTeV analysis, this correction was made by simply
subtracting the contribution of the excess neutrons.
In this Letter, a collaboration involving researchers
from Tokai University, the University of Washington and
the Department of Energy's Jefferson Lab has revealed a
novel EMC effect in which the isovector nuclear force
generated by those extra neutrons results in a subtle
change in the quark structure of every nucleon in the
nucleus.
The discovery of this isovector EMC effect implies that it
is not enough to simply subtract the scattering from the extra
neutrons, because the structure of the remaining nucleons is
still modified by their presence. This leads to a residual
correction, of a sign and magnitude which is essentially model
independent and which removes at least half of the NuTeV anomaly.
When this effect is combined with the well known correction for
charge symmetry violation in the nucleon itself, the NuTeV data
is in fact in excellent agreement with the Standard Model.
In this sense, the NuTeV anomaly may be seen as providing crucial
evidence for a conceptual change in our understanding of nuclear
structure in which the quark structure of the bound nucleon is
fundamentally modified by the medium -- a result arguably as
important as the original interpretation in terms of physics
beyond the Standard Model.
***
EC10577
Magnetic Drugs
Drugs attached to magnetic particles can be manipulated inside the
bloodstream by means of applied magnetic fields, making it possible to
greatly decrease the side-effects of e.g. chemotherapy. In this paper
we derive a scaling relation between the magnetic force and the amount
of particles that can be localized at a desired target location,
revealing that
a four times higher force is initially needed to double the efficiency
of a specific treatment. This result helps explaining a wide variety of
experimental results and follows naturally from the observation that the
blood
flow velocity close to the vessel wall increases approximately linearly
with
distance. For more accurate predictions, formulas are derived for the
particle
motion in idealized arterial flows. The obtained results can also be
useful for
the magnetic separation of materials in the laboratory, the testing of
numerical
codes, and a possible future application to the treatment of
atherosclerosis.
***
AE10616
Isotope effect in dissociative electron attachment to acetylene
"Towards the understanding of electron-driven
chemistry in polyatomic molecules"
Breaking molecules by hitting them with free
electrons is very important for a number of
technologies, such as plasma processing in the
manufacture of integrated circuits or for
radiotherapy in medicine. It is relatively easy
to determine that a molecule breaks when hit by
an electron, but much harder to measure exactly
how much they break, how many molecules are
broken by a given number of electrons. This
information is available for only few molecules,
particularly for only few molecules larger than
two atoms. In this paper, we present some
significant improvements of the instrumentation
required to obtain this information, and results
for the prototype molecule acetylene. We further
measured that acetylene where hydrogen is
replaced by heavy hydrogen (deuterium) is
15-times more resistant to breaking by electron
impact than normal acetylene. The importance of
the results lies also in the fact that theory has
advanced to the point where such reactions can be
studied. This allows an interplay between theory
and experiment, with experiment validating
the theory and theory helping to explain the mechanisms in the experiment.
