3,620 research outputs found
Entanglement purification of multi-mode quantum states
An iterative random procedure is considered allowing an entanglement
purification of a class of multi-mode quantum states. In certain cases, a
complete purification may be achieved using only a single signal state
preparation. A physical implementation based on beam splitter arrays and
non-linear elements is suggested. The influence of loss is analyzed in the
example of a purification of entangled N-mode coherent states.Comment: 6 pages, 3 eps-figures, using revtex
Changes in intracellular ion activities induced by adrenaline in human and rat skeletal muscle
To study the stimulating effect of adrenaline (ADR) on active Na+/K+ transport we used double-barrelled ion-sensitive micro-electrodes to measure the activities of extracellular K+ (aKe) and intracellular Na+ (aNai) in isolated preparations of rat soleus muscle, normal human intercostal muscle and one case of hyperkalemic periodic paralysis (h.p.p.). In these preparations bath-application of ADR (10−6 M) resulted in a membrane hyperpolarization and transient decreasesaKe andaNai which could be blocked by ouabain (3×10−4 M). In the h.p.p. muslce a continuous rise ofaNai induced by elevation ofaKe to 5.2 mM could be stopped by ADR. In addition, the intracellular K+ activity (aKi), the free intracellular Ca2+ concentration (pCai) and intracellular pH (pHi) were monitored in rat soleus muscle. During ADRaKi increased, pHi remained constant and intracellular Ca2+ apparently decreased. In conclusion, our data show that ADR primarily stimulates the Na+/K+ pump in mammalian skeletal muscle. This stimulating action is not impaired in the h.p.p. muscle
Production of superpositions of coherent states in traveling optical fields with inefficient photon detection
We develop an all-optical scheme to generate superpositions of
macroscopically distinguishable coherent states in traveling optical fields. It
non-deterministically distills coherent state superpositions (CSSs) with large
amplitudes out of CSSs with small amplitudes using inefficient photon
detection. The small CSSs required to produce CSSs with larger amplitudes are
extremely well approximated by squeezed single photons. We discuss some
remarkable features of this scheme: it effectively purifies mixed initial
states emitted from inefficient single photon sources and boosts negativity of
Wigner functions of quantum states.Comment: 13 pages, 9 figures, to be published in Phys. Rev.
Heralded single-photon generation using imperfect single-photon sources and a two-photon-absorbing medium
We propose a setup for a heralded, i.e. announced generation of a pure
single-photon state given two imperfect sources whose outputs are represented
by mixtures of the single-photon Fock state with the vacuum
. Our purification scheme uses beam splitters, photodetection and a
two-photon-absorbing medium. The admixture of the vacuum is fully eliminated.
We discuss two potential realizations of the scheme.Comment: 22 pages, 8 figures (LaTeX). In version v2 we have slightly modified
our setup so as to increase the success probability of single-photon
generation by a factor of two. In addition, in an appendix we discuss
alternative realizations of single-photon generation without a Mach-Zehnder
interferometer. Three new figures have been added. Version v3 is a revised
version published in Phys. Rev. A. It contains numerous minor corrections and
clarifications. A new figure has been added in order to clarify our
convention regarding labelling the field modes. The action of the beam
splitters in the Schroedinger picture is introduced. A new reference has been
include
Complete Set of Polarization Transfer Observables for the Reaction at 296 MeV and 0
A complete set of polarization transfer observables has been measured for the
reaction at and . The total spin transfer and the observable
deduced from the measured polarization transfer observables indicate that
the spin--dipole resonance at has greater
strength than strength, which is consistent with recent experimental and
theoretical studies. The results also indicate a predominance of the spin-flip
and unnatural-parity transition strength in the continuum. The exchange tensor
interaction at a large momentum transfer of is
discussed.Comment: 4 pages, 4 figure
Knowledge of learning disabilities: the relationship with choice, duty of care and non-aversive approaches
The present study examines the relationship between the knowledge of the diagnostic criteria for a learning disability (based on DSM IV criteria), care practices and experience in health care and social care staff. Responses to a questionnaire were analysed in terms of participants emphasis on: recognizing duty of care; enabling choice; non-aversive and aversive strategies. Results indicated that the knowledge of the criteria for a learning disability was limited, with only I6% of the sample correctly identifying all three criteria. There were no significant differences between the two groups in relation to experience or level of knowledge. No clear cut differences were found between the groups in relation to tendency to emphasize a particular management approach, with the strategies adopted appearing to be influenced by vignettes used in this study. Participants tended to give responses that identified both a recognition of their duty of care to clients and the need to enable choice. Limitations of this study are discussed
Dragging a polymer chain into a nanotube and subsequent release
We present a scaling theory and Monte Carlo (MC) simulation results for a
flexible polymer chain slowly dragged by one end into a nanotube. We also
describe the situation when the completely confined chain is released and
gradually leaves the tube. MC simulations were performed for a self-avoiding
lattice model with a biased chain growth algorithm, the pruned-enriched
Rosenbluth method. The nanotube is a long channel opened at one end and its
diameter is much smaller than the size of the polymer coil in solution. We
analyze the following characteristics as functions of the chain end position
inside the tube: the free energy of confinement, the average end-to-end
distance, the average number of imprisoned monomers, and the average stretching
of the confined part of the chain for various values of and for the number
of monomers in the chain, . We show that when the chain end is dragged by a
certain critical distance into the tube, the polymer undergoes a
first-order phase transition whereby the remaining free tail is abruptly sucked
into the tube. This is accompanied by jumps in the average size, the number of
imprisoned segments, and in the average stretching parameter. The critical
distance scales as . The transition takes place when
approximately 3/4 of the chain units are dragged into the tube. The theory
presented is based on constructing the Landau free energy as a function of an
order parameter that provides a complete description of equilibrium and
metastable states. We argue that if the trapped chain is released with all
monomers allowed to fluctuate, the reverse process in which the chain leaves
the confinement occurs smoothly without any jumps. Finally, we apply the theory
to estimate the lifetime of confined DNA in metastable states in nanotubes.Comment: 13pages, 14figure
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