520 research outputs found
Time course and robustness of ERP object and face differences
Conflicting results have been reported about the earliest “true” ERP differences related to face processing, with the bulk of the literature focusing on the signal in the first 200 ms after stimulus onset. Part of the discrepancy might be explained by uncontrolled low-level differences between images used to assess the timing of face processing. In the present experiment, we used a set of faces, houses, and noise textures with identical amplitude spectra to equate energy in each spatial frequency band. The timing of face processing was evaluated using face–house and face–noise contrasts, as well as upright-inverted stimulus contrasts. ERP differences were evaluated systematically at all electrodes, across subjects, and in each subject individually, using trimmed means and bootstrap tests. Different strategies were employed to assess the robustness of ERP differential activities in individual subjects and group comparisons. We report results showing that the most conspicuous and reliable effects were systematically observed in the N170 latency range, starting at about 130–150 ms after stimulus onset
Teleportation of bipartite states using a single entangled pair
A class of quantum protocols to teleport bipartite (entangled) states of two
qubits is suggested. Our schemes require a single entangled pair shared by the
two parties and the transmission of three bits of classical information, as
well as a two-qubit gate with an additional qubit at the receiver' location.
Noisy quantum channels are considered and the effects on both the teleportation
fidelity and the entanglement of the replica are evaluated.Comment: 11 pages, 4 figures, to appear on Phys. Lett.
On Bures fidelity of displaced squeezed thermal states
Fidelity plays a key role in quantum information and communication theory.
Fidelity can be interpreted as the probability that a decoded message possesses
the same information content as the message prior to coding and transmission.
In this paper, we give a formula of Bures fidelity for displaced squeezed
thermal states directly by the displacement and squeezing parameters and
birefly discuss how the results can apply to quantum information theory.Comment: 10 pages with RevTex require
Optimized teleportation in Gaussian noisy channels
We address continuous variable quantum teleportation in Gaussian quantum
noisy channels, either thermal or squeezed-thermal. We first study the
propagation of twin-beam and evaluate a threshold for its separability. We find
that the threshold for purely thermal channels is always larger than for
squeezed-thermal ones. On the other hand, we show that squeezing the channel
improves teleportation of squeezed states and, in particular, we find the class
of squeezed states that are better teleported in a given noisy channel.
Finally, we find regimes where optimized teleportation of squeezed states
improves amplitude-modulated communication in comparison with direct
transmission
Generation of atom-photon entangled states in atomic Bose-Einstein condensate via electromagnetically induced transparency
In this paper, we present a method to generate continuous-variable-type
entangled states between photons and atoms in atomic Bose-Einstein condensate
(BEC). The proposed method involves an atomic BEC with three internal states, a
weak quantized probe laser and a strong classical coupling laser, which form a
three-level Lambda-shaped BEC system. We consider a situation where the BEC is
in electromagnetically induced transparency (EIT) with the coupling laser being
much stronger than the probe laser. In this case, the upper and intermediate
levels are unpopulated, so that their adiabatic elimination enables an
effective two-mode model involving only the atomic field at the lowest internal
level and the quantized probe laser field. Atom-photon quantum entanglement is
created through laser-atom and inter-atomic interactions, and two-photon
detuning. We show how to generate atom-photon entangled coherent states and
entangled states between photon (atom) coherent states and atom-(photon-)
macroscopic quantum superposition (MQS) states, and between photon-MQS and
atom-MQS states.Comment: 9 pages, 1 figur
Parity Violating Measurements of Neutron Densities
Parity violating electron nucleus scattering is a clean and powerful tool for
measuring the spatial distributions of neutrons in nuclei with unprecedented
accuracy. Parity violation arises from the interference of electromagnetic and
weak neutral amplitudes, and the of the Standard Model couples primarily
to neutrons at low . The data can be interpreted with as much confidence
as electromagnetic scattering. After briefly reviewing the present theoretical
and experimental knowledge of neutron densities, we discuss possible parity
violation measurements, their theoretical interpretation, and applications. The
experiments are feasible at existing facilities. We show that theoretical
corrections are either small or well understood, which makes the interpretation
clean. The quantitative relationship to atomic parity nonconservation
observables is examined, and we show that the electron scattering asymmetries
can be directly applied to atomic PNC because the observables have
approximately the same dependence on nuclear shape.Comment: 38 pages, 7 ps figures, very minor changes, submitted to Phys. Rev.
Local Hidden Variables Underpinning of Entanglement and Teleportation
Entangled states whose Wigner functions are non-negative may be viewed as
being accounted for by local hidden variables (LHV). Recently, there were
studies of Bell's inequality violation (BIQV) for such states in conjunction
with the well known theorem of Bell that precludes BIQV for theories that have
LHV underpinning. We extend these studies to teleportation which is also based
on entanglement. We investigate if, to what extent, and under what conditions
may teleportation be accounted for via LHV theory. Our study allows us to
expose the role of various quantum requirements. These are, e.g., the
uncertainty relation among non-commuting operators, and the no-cloning theorem
which forces the complete elimination of the teleported state at its initial
port.Comment: 24 pages, 1 figure, accepted Found. Phy
Creating the cultures of the future: cultural strategy, policy and institutions in Gramsci. Part one: Gramsci and cultural policy studies: some methodological reflections
Gramsci’s writings have rarely been discussed and used systematically by scholars in cultural policy studies, despite the fact that in cultural studies, from which the field emerged, Gramsci has been a major source of theoretical concepts. Cultural policy studies were, in fact, theorised as an anti-Gramscian project between the late 1980s and the early 1990s, when a group of scholars based in Australia advocated a major political and theoretical reorientation of cultural studies away from hegemony theory and radical politicisation, and towards reformist-technocratic engagement with the policy concerns of contemporary government and business. Their criticism of the ‘Gramscian tradition’ as inadequate for the study of cultural policy and institutions has remained largely unexamined in any detail for almost twenty years and seems to have had a significant role in the subsequent neglect of Gramsci’s contribution in this area of study. This essay, consisting of three parts, is an attempt to challenge such criticism and to provide an analysis of Gramsci’s writings, with the aim of proposing a more systematic contribution of his work to the theoretical development of cultural policy studies.
In Part One, I question the use of the notion of ‘Gramscian tradition’ made by its critics and challenge the claim that it was inadequate for the study of cultural policy and institutions.
In parts Two and Three, I consider Gramsci’s specific writings on questions of cultural strategy, policy and institutions, which have so far been overlooked by scholars, arguing that they provide further analytical insights to those offered by his more general concepts. More specifically, in Part Two, I consider Gramsci’s pre-prison writings and political practice in relation to questions of cultural strategy and institutions. I argue that the analysis of these early texts, which were written in the years in which Gramsci was active in party organisation and leadership, is fundamental not only for understanding the nature of Gramsci’s early and continued involvement with questions of cultural strategy and institutions, but also as a key for deciphering and interpreting cultural policy themes that he later developed in the prison notebooks, and which originated in earlier debates.
Finally, in Part Three, I carry out a detailed analysis of Gramsci’s prison notes on questions of cultural strategy, policy and institutions, which enrich the theoretical underpinnings for critical frameworks of analysis as well as for radical practices of cultural strategy, cultural policy-making and cultural organisation. I then answer the question of whether Gramsci’s insights amount to a theory of cultural policy
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