9,617 research outputs found
Coherent-state phase concentration by quantum probabilistic amplification
We propose novel coherent-state phase concentration by probabilistic
measurement-induced ampli- fication. The amplification scheme uses novel
architecture, thermal noise addition (instead of single photon addition)
followed by feasible multiple photon subtraction using realistic photon-number
resolving detector. It allows to substantially amplify weak coherent states and
simultaneously reduce their phase uncertainty, contrary to the deterministic
amplifier
Experimentally feasible quantum erasure-correcting code for continuous variables
We devise a scheme that protects quantum coherent states of light from
probabilistic losses, thus achieving the first continuous-variable quantum
erasure-correcting code. If the occurrence of erasures can be probed, then the
decoder enables, in principle, a perfect recovery of the original light states.
Otherwise, if supplemented with postselection based on homodyne detection, this
code can be turned into an efficient erasure-filtration scheme. The
experimental feasibility of the proposed protocol is carefully addressed
Phase fluctuations in atomic Bose gases
We improve on the Popov theory for partially Bose-Einstein condensed atomic
gases by treating the phase fluctuations exactly. As a result, the theory
becomes valid in arbitrary dimensions and is able to describe the
low-temperature crossover between three, two and one-dimensional Bose gases,
which is currently being explored experimentally. We consider both homogeneous
and trapped Bose gases.Comment: 4 pages. Title changed Major changes involve extension of theory to
include trapped Bose gases. Deletion of reference to and comparison with
hydrogen experiment. Due to these changes, second author added. Modified
manuscript accepted for PR
Editorial: Toward a Minor Tech
This journal issue addresses what we are calling "minor tech" making reference to Gilles Deleuze and FeÌlix Guattari's essay "Kafka: Toward a Minor Literature" (written in 1975). They propose the concept of minor literature as opposed to great or established literature â the use of a major language that subverts it from within. "Becoming-minitorian" in this sense â to use a related concept from A Thousand Plateaus â involves the recognition of particular instances of power and the ability of the repressed minority to gain some degree of autonomy of expression. For our purpose, this notion of the minor is a relative position to major (or big) tech
Before and After the Network - Editorial
How do we think about networks under post- digital conditions? What does this imply for research?
This journal issue takes as its outset, the call of the transmediale festival to â[leave] be- hind a decade marked by a backlash against the Internet and the network societyâ in order to re-evaluate the limits of ânetworksâ. It refers to Robert Filliouâs âThe Eternal Network,â an idealistic notion from the 1960s, pointing to the interconnectedness of everyday-life actions across an emerging global world at that time. This is a good reminder that network cultures exist beyond the technical reality of network culture as we now know it despite our primary identification of networks with social media and planetary computation. By drawing on the legacies of critical and autonomous network cultures, the aim was to make the limits of Internet-based networks visible but also highlight alternatives. Is there a conceivable counter-power to networks? Which alternative technological models and cultural narratives are needed to construct the principles of end-to-end communication anew? How might the critique of networks extend to non-western contexts and reflect the limits in a global perspective?
To answer such complex questions, this editorial begins by reflecting on the periodizing logic that invites us to leave behind âthe backlash against the Internet.â What comes before and after the network
EEG source imaging assists decoding in a face recognition task
EEG based brain state decoding has numerous applications. State of the art
decoding is based on processing of the multivariate sensor space signal,
however evidence is mounting that EEG source reconstruction can assist
decoding. EEG source imaging leads to high-dimensional representations and
rather strong a priori information must be invoked. Recent work by Edelman et
al. (2016) has demonstrated that introduction of a spatially focal source space
representation can improve decoding of motor imagery. In this work we explore
the generality of Edelman et al. hypothesis by considering decoding of face
recognition. This task concerns the differentiation of brain responses to
images of faces and scrambled faces and poses a rather difficult decoding
problem at the single trial level. We implement the pipeline using spatially
focused features and show that this approach is challenged and source imaging
does not lead to an improved decoding. We design a distributed pipeline in
which the classifier has access to brain wide features which in turn does lead
to a 15% reduction in the error rate using source space features. Hence, our
work presents supporting evidence for the hypothesis that source imaging
improves decoding
Efficient calculation of local dose distribution for response modelling in proton and ion beams
We present an algorithm for fast and accurate computation of the local dose
distribution in MeV beams of protons, carbon ions or other heavy-charged
particles. It uses compound Poisson-process modelling of track interaction and
succesive convolutions for fast computation. It can handle mixed particle
fields over a wide range of fluences. Since the local dose distribution is the
essential part of several approaches to model detector efficiency or cellular
response it has potential use in ion-beam dosimetry and radiotherapy.Comment: 9 pages, 3 figure
Squeezed state purification with linear optics and feed forward
A scheme for optimal and deterministic linear optical purification of mixed
squeezed Gaussian states is proposed and experimentally demonstrated. The
scheme requires only linear optical elements and homodyne detectors, and allows
the balance between purification efficacy and squeezing degradation to be
controlled. One particular choice of parameters gave a ten-fold reduction of
the thermal noise with a corresponding squeezing degradation of only 11%. We
prove optimality of the protocol, and show that it can be used to enhance the
performance of quantum informational protocols such as dense coding and
entanglement generation.Comment: 4 pages, 3 figure
Infrared Spectra of Meteoritic SiC Grains
We present here the first infrared spectra of meteoritic SiC grains. The
mid-infrared transmission spectra of meteoritic SiC grains isolated from the
Murchison meteorite were measured in the wavelength range 2.5--16.5 micron, in
order to make available the optical properties of presolar SiC grains. These
grains are most likely stellar condensates with an origin predominately in
carbon stars. Measurements were performed on two different extractions of
presolar SiC from the Murchison meteorite. The two samples show very different
spectral appearance due to different grain size distributions. The spectral
feature of the smaller meteoritic SiC grains is a relatively broad absorption
band found between the longitudinal and transverse lattice vibration modes
around 11.3 micron, supporting the current interpretation about the presence of
SiC grains in carbon stars. In contrast to this, the spectral feature of the
large (> 5 micron) grains has an extinction minimum around 10 micron. The
obtained spectra are compared with commercially available SiC grains and the
differences are discussed. This comparison shows that the crystal structure
(e.g., beta-SiC versus alpha-SiC) of SiC grains plays a minor role on the
optical signature of SiC grains compared to e.g. grain size.Comment: 7 pages, 6 figures. To appear in A&
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