326 research outputs found
A Study on the Sudden Death of Entanglement
The dynamics of entanglement and the phenomenon of entanglement sudden death
(ESD) \cite{yu} are discussed in bipartite systems, measured by Wootters
Concurrence. Our calculation shows that ESD appears whenever the system is open
or closed and is dependent on the initial condition. The relation of the
evolution of entanglement and energy transfer between the system and its
surroundings is also studied.Comment: Comments and criticism are welcome. Accepted by Phys. Lett.
Magnetic Properties And Giant Magnetoresistance Of Magnetic Granular Co10cu90 Alloys Obtained By Direct-current Joule Heating
The direct-current (dc) joule heating technique was exploited to fabricate giant magnetoresistance (GMR) Co10Cu90 granular alloys. The Co cluster precipitation process was investigated by calorimetric and x-ray diffraction measurements. At T=10 K, the largest MR change of 25.0% has been observed for the melt-spun Co10Cu90 ribbon annealed at I=5 A. The magnetoresistance scales approximately as the inverse Co particle size. At room temperature, it was found that the dc joule-heated samples show relatively high GMR in comparison with furnace-annealed samples. Based on the phenomenological GMR model, we assumed that it is a consequence of smaller Co particles formed in dc joule-heated samples. © 1995 American Institute of Physics.7885062506
Magnetic properties and giant magnetoresistance of magnetic granular Co10 Cu90 alloys obtained by direct‐current joule heating
The direct-current (de) joule heating technique was exploited to fabricate giant magnetoresistance (GEAR) Co10Cu90 granular alloys. The Co cluster precipitation process was investigated by calorimetric and x-ray diffraction measurements. At T=10 K, the largest MR change of 25.0% has been observed for the melt-spun Co10Cu90 ribbon annealed at I=5 A. The magnetoresistance scales approximately as the inverse Co particle size. At room temperature, it was found that the de joule-heated samples show relatively high GMR in comparison with furnace-annealed samples. Based on the phenomenological GMR model, we assumed that it is a consequence of smaller Co particles formed in de joule-heated samples. (C) 1995 American Institute of Physics
Markov evolutions and hierarchical equations in the continuum I. One-component systems
General birth-and-death as well as hopping stochastic dynamics of infinite
particle systems in the continuum are considered. We derive corresponding
evolution equations for correlation functions and generating functionals.
General considerations are illustrated in a number of concrete examples of
Markov evolutions appearing in applications.Comment: 47 page
Interference between the halves of a double-well trap containing a Bose-Einstein condensate
Interference between the halves of a double-well trap containing a
Bose-Einstein condensate is studied. It is found that when the atoms in the two
wells are initially in the coherent state, the intensity exhibits collapses and
revivals, but it does not for the initial Fock states. Whether the initial
states are in the coherent states or in a Fock states, the fidelity time has
nothing to do with collision. We point out that interference and its fidelity
can be adjusted experimentally by properly preparing the number and initial
states of the system.Comment: 10 pages, 3 figures, accepted by Phy. rev.
Surface structure and solidification morphology of aluminum nanoclusters
Classical molecular dynamics simulation with embedded atom method potential
had been performed to investigate the surface structure and solidification
morphology of aluminum nanoclusters Aln (n = 256, 604, 1220 and 2048). It is
found that Al cluster surfaces are comprised of (111) and (001) crystal planes.
(110) crystal plane is not found on Al cluster surfaces in our simulation. On
the surfaces of smaller Al clusters (n = 256 and 604), (111) crystal planes are
dominant. On larger Al clusters (n = 1220 and 2048), (111) planes are still
dominant but (001) planes can not be neglected. Atomic density on cluster
(111)/(001) surface is smaller/larger than the corresponding value on bulk
surface. Computational analysis on total surface area and surface energies
indicates that the total surface energy of an ideal Al nanocluster has the
minimum value when (001) planes occupy 25% of the total surface area. We
predict that a melted Al cluster will be a truncated octahedron after
equilibrium solidification.Comment: 22 pages, 6 figures, 34 reference
Predicted robustness as QoS for Deep Neural Network Models
The adoption of deep neural network (DNN) model as the integral part of real-world software systems necessitates explicit consideration of their quality-of-service (QoS). It is well-known that DNN models are prone to adversarial attacks, and thus it is vitally important to be aware of how robust a model’s prediction is for a given input instance. A fragile prediction, even with high confidence, is not trustworthy in light of the possibility of adversarial attacks. We propose that DNN models should produce a robustness value as an additional QoS indicator, along with the confidence value, for each prediction they make. Existing approaches for robustness computation are based on adversarial searching, which are usually too expensive to be excised in real time. In this paper, we propose to predict, rather than to compute, the robustness measure for each input instance. Specifically, our approach inspects the output of the neurons of the target model and trains another DNN model to predict the robustness. We focus on convolutional neural network (CNN) models in the current research. Experiments show that our approach is accurate, with only 10%–34% additional errors compared with the offline heavy-weight robustness analysis. It also significantly outperforms some alternative methods. We further validate the effectiveness of the approach when it is applied to detect adversarial attacks and out-of-distribution input. Our approach demonstrates a better performance than, or at least is comparable to, the state-of-the-art techniques
Noise-assisted preparation of entangled atoms
We discuss the generation of entangled states of two two-level atoms inside
an optical cavity. The cavity mode is supposed to be coupled to a white noise
with adjustable intensity. We describe how the entanglement between the atoms
inside the cavity arise in such a situation. The entanglement is maximized for
intermediate values of the noise intensity, while it is a monotonic function of
the spontaneous rate. This resembles the phenomenon of stochastic resonance and
sheds more light on the idea to exploit white noise in quantum information
processing.Comment: 4 pages, 4 figure
Observation of thundercloud-related gamma rays and neutrons in Tibet
During the 2010 rainy season in Yangbajing (4300 m above sea level) in Tibet, China, a long-duration count enhancement associated with thunderclouds was detected by a solar-neutron telescope and neutron monitors installed at the Yangbajing Comic Ray Observatory. The event, lasting for ∼40 min, was observed on July 22, 2010. The solar-neutron telescope detected significant γ-ray signals with energies >40 MeV in the event. Such a prolonged high-energy event has never been observed in association with thunderclouds, clearly suggesting that electron acceleration lasts for 40 min in thunderclouds. In addition, Monte Carlo simulations showed that >10 MeV γ rays largely contribute to the neutron monitor signals, while >1 keV neutrons produced via a photonuclear reaction contribute relatively less to the signals. This result suggests that enhancements of neutron monitors during thunderstorms are not necessarily clear evidence for neutron production, as previously thought
State transfer in dissipative and dephasing environments
By diagonalization of a generalized superoperator for solving the master
equation, we investigated effects of dissipative and dephasing environments on
quantum state transfer, as well as entanglement distribution and creation in
spin networks. Our results revealed that under the condition of the same
decoherence rate , the detrimental effects of the dissipative
environment are more severe than that of the dephasing environment. Beside
this, the critical time at which the transfer fidelity and the
concurrence attain their maxima arrives at the asymptotic value
quickly as the spin chain length increases. The transfer
fidelity of an excitation at time is independent of when the system
subjects to dissipative environment, while it decreases as increases when
the system subjects to dephasing environment. The average fidelity displays
three different patterns corresponding to , and . For
each pattern, the average fidelity at time is independent of when the
system subjects to dissipative environment, and decreases as increases when
the system subjects to dephasing environment. The maximum concurrence also
decreases as increases, and when , it arrives at an
asymptotic value determined by the decoherence rate and the structure
of the spin network.Comment: 12 pages, 6 figure
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