177 research outputs found
Morphology Analysis of the Scale Formed on Crofer 22APU Steel in Atmospheres Containing SO2
Classical Equations for Quantum Systems
The origin of the phenomenological deterministic laws that approximately
govern the quasiclassical domain of familiar experience is considered in the
context of the quantum mechanics of closed systems such as the universe as a
whole. We investigate the requirements for coarse grainings to yield decoherent
sets of histories that are quasiclassical, i.e. such that the individual
histories obey, with high probability, effective classical equations of motion
interrupted continually by small fluctuations and occasionally by large ones.
We discuss these requirements generally but study them specifically for coarse
grainings of the type that follows a distinguished subset of a complete set of
variables while ignoring the rest. More coarse graining is needed to achieve
decoherence than would be suggested by naive arguments based on the uncertainty
principle. Even coarser graining is required in the distinguished variables for
them to have the necessary inertia to approach classical predictability in the
presence of the noise consisting of the fluctuations that typical mechanisms of
decoherence produce. We describe the derivation of phenomenological equations
of motion explicitly for a particular class of models. Probabilities of the
correlations in time that define equations of motion are explicitly considered.
Fully non-linear cases are studied. Methods are exhibited for finding the form
of the phenomenological equations of motion even when these are only distantly
related to those of the fundamental action. The demonstration of the connection
between quantum-mechanical causality and causalty in classical phenomenological
equations of motion is generalized. The connections among decoherence, noise,
dissipation, and the amount of coarse graining necessary to achieve classical
predictability are investigated quantitatively.Comment: 100pages, 1 figur
System komunikacji alternatywnej i wspomagającej wraz ze stosowanymi znakami oraz wykorzystanie urządzenia sterowanego za pomocą oczu w Polsce
Patients who do not communicate verbally or speak in an understandable way are a serious problem in providing appropriate care to patients due to a lack of understanding of their needs. Therefore, it is important that nursing staff have the knowledge and skills of alternative and assistive communication to communicate with patients with speech disorders. The purpose of article is to present the current state of knowledge of the alternative and augmentative communication with special consideration the signs used in Poland with a practicular emphasis laid to the revelant description of the eye tracking device. The literature has been reviewed, including also in this relation topics: alternative and augmentative communication, examples of signs used in alternative communication in Poland and communication and eye tracking. Not everyone has the ability to communicate verbally with the environment. In relation to this problem the solution is the alternative and augmentative communication which uses signs and devices to enable the patient to communicate with other people. (JNNN 2020;9(1):39–45)Pacjenci nie komunikujący się werbalnie lub mówiący w sposób niezrozumiały stanowią istotny problem w zapewnieniu właściwej opieki chorych w wyniku braku zrozumienia ich potrzeb. Z tego względu istotne jest posiadanie przez personel pielęgniarski wiedzy i umiejętności w zakresie komunikacji alternatywnej i wspomagającej by porozumieć się z pacjentami z zaburzeniami mowy. Celem pracy jest przedstawienie dotychczasowego stanu wiedzy na temat systemu komunikacji alternatywnej i wspomagającej ze szczególnym uwzgędnieniem wykorzystywanych znaków w Polsce oraz opis urządzenia sterowanego za pomocą oczu. Dokonano przeglądu literatury w zakresie tematów: komunikacja alternatywna i wspomagająca, przykłady znaków stosowanych w komunikacji alternatywnej w Polsce oraz komunikacja za pomocą oczu. Nie każdy człowiek posiada zdolność do komunikowania się werbalnie z otoczeniem. W odniesieniu do tego problemu rozwiązaniem jest komunikacja alternatywna i wspomagająca, która stosuje między innymi znaki oraz urządzenia, dające pacjentowi możliwość komunikowania się z ludźmi. (PNN 2020;9(1):39–45
Dynamical description of quantum computing: generic nonlocality of quantum noise
We develop dynamical non-Markovian description of quantum computing in weak
coupling limit, in lowest order approximation. We show that long range memory
of quantum reservoir produces strong interrelation between structure of noise
and quantum algorithm, implying nonlocal attacks of noise. We then argue that
the quantum error correction method fails to protect quantum computation
against electromagnetic or phonon vacuum which exhibit memory. This
shows that the implicit assumption of quantum error correction theory --
independence of noise and self-dynamics -- fails in long time regimes. We also
use our approach to present {\it pure} decoherence and decoherence accompanied
by dissipation in terms of spectral density of reservoir. The so-called {\it
dynamical decoupling} method is discussed in this context. Finally, we propose
{\it minimal decoherence model}, in which the only source of decoherence is
vacuum. We optimize fidelity of quantum information processing under the
trade-off between speed of gate and strength of decoherence.Comment: 12 pages, minor corrections, softened interpretation of the result
Classicality of quantum information processing
The ultimate goal of the classicality programme is to quantify the amount of
quantumness of certain processes. Here, classicality is studied for a
restricted type of process: quantum information processing (QIP). Under special
conditions, one can force some qubits of a quantum computer into a classical
state without affecting the outcome of the computation. The minimal set of
conditions is described and its structure is studied. Some implications of this
formalism are the increase of noise robustness, a proof of the quantumness of
mixed state quantum computing and a step forward in understanding the very
foundation of QIP.Comment: Minor changes, published in Phys. Rev. A 65, 42319 (2002
Quantum Superposition States of Bose-Einstein Condensates
We propose a scheme to create a macroscopic ``Sch\"odinger cat'' state formed
by two interacting Bose condensates. In analogy with quantum optics, where the
control and engineering of quantum states can be maintained to a large extend,
we consider the present scheme to be an example of quantum atom optics at work.Comment: 24 pages, 6 figure
Dynamics of quantum entanglement
A model of discrete dynamics of entanglement of bipartite quantum state is
considered. It involves a global unitary dynamics of the system and periodic
actions of local bistochastic or decaying channel. For initially pure states
the decay of entanglement is accompanied with an increase of von Neumann
entropy of the system. We observe and discuss revivals of entanglement due to
unitary interaction of both subsystems. For some mixed states having different
marginal entropies of both subsystems (one of them larger than the global
entropy and the other one one smaller) we find an asymmetry in speed of
entanglement decay. The entanglement of these states decreases faster, if the
depolarizing channel acts on the "classical" subsystem, characterized by
smaller marginal entropy.Comment: 10 pages, Revtex, 10 figures, refined versio
Phase Measurement for Driven Spin Oscillations in a Storage Ring
This paper reports the first simultaneous measurement of the horizontal and
vertical components of the polarization vector in a storage ring under the
influence of a radio frequency (rf) solenoid. The experiments were performed at
the Cooler Synchrotron COSY in J\"ulich using a vector polarized, bunched
deuteron beam. Using the new spin feedback system, we
set the initial phase difference between the solenoid field and the precession
of the polarization vector to a predefined value. The feedback system was then
switched off, allowing the phase difference to change over time, and the
solenoid was switched on to rotate the polarization vector. We observed an
oscillation of the vertical polarization component and the phase difference.
The oscillations can be described using an analytical model. The results of
this experiment also apply to other rf devices with horizontal magnetic fields,
such as Wien filters. The precise manipulation of particle spins in storage
rings is a prerequisite for measuring the electric dipole moment (EDM) of
charged particles
Charge Symmetry Breaking in dd->4He{\pi}0 with WASA-at-COSY
Charge symmetry breaking (CSB) observables are a suitable experimental tool
to examine effects induced by quark masses on the nuclear level. Previous high
precision data from TRIUMF and IUCF are currently used to develop a consistent
description of CSB within the framework of chiral perturbation theory. In this
work the experimental studies on the reaction dd->4He{\pi}0 have been extended
towards higher excess energies in order to provide information on the
contribution of p-waves in the final state. For this, an exclusive measurement
has been carried out at a beam momentum of p=1.2 GeV/c using the WASA-at-COSY
facility. The total cross section amounts to sigma(tot) = (118 +- 18(stat) +-
13(sys) +- 8(ext)) pb and first data on the differential cross section are
consistent with s-wave pion production.Comment: 14 pages, 5 figure
ABC Effect and Resonance Structure in the Double-Pionic Fusion to He
Exclusive and kinematically complete measurements of the double pionic fusion
to He have been performed in the energy region of the so-called ABC effect,
which denotes a pronounced low-mass enhancement in the -invariant mass
spectrum. The experiments were carried out with the WASA detector setup at
COSY. Similar to the observations in the basic reaction
and in the He reaction, the data reveal a correlation
between the ABC effect and a resonance-like energy dependence in the total
cross section. Differential cross sections are well described by the hypothesis
of resonance formation during the reaction process in addition to the
conventional -channel mechanism. The deduced resonance
width can be understood from collision broadening due to Fermi motion of the
nucleons in initial and final nuclei
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