16,552 research outputs found
Treating some solid state problems with the Dirac equation
The ambiguity involved in the definition of effective-mass Hamiltonians for
nonrelativistic models is resolved using the Dirac equation. The multistep
approximation is extended for relativistic cases allowing the treatment of
arbitrary potential and effective-mass profiles without ordering problems. On
the other hand, if the Schrodinger equation is supposed to be used, our
relativistic approach demonstrate that both results are coincidents if the
BenDaniel and Duke prescription for the kinetic-energy operator is implemented.
Applications for semiconductor heterostructures are discussed.Comment: 06 pages, 5 figure
Quantum key distribution with higher-order alphabets using spatially-encoded qudits
We propose and demonstrate a quantum key distribution scheme in higher-order
-dimensional alphabets using spatial degrees of freedom of photons. Our
implementation allows for the transmission of 4.56 bits per sifted photon,
while providing improved security: an intercept-resend attack on all photons
would induce an error rate of 0.47. Using our system, it should be possible to
send more than a byte of information per sifted photon.Comment: 4 pages, 5 figures. Replaced with published versio
Experimental Observation of Environment-induced Sudden Death of Entanglement
We demonstrate the difference between local, single-particle dynamics and
global dynamics of entangled quantum systems coupled to independent
environments. Using an all-optical experimental setup, we show that, while the
environment-induced decay of each system is asymptotic, quantum entanglement
may suddenly disappear. This "sudden death" constitutes yet another distinct
and counter-intuitive trait of entanglement.Comment: 4 pages, 4 figure
e-Termos: a computer-supported collaborative work system for terminological management.
The e-Termos is a Web Collaborative Environment composed of six working modules to automatize tasks for managing terminological products. Each module is responsible for tasks inherent to the process of creating terminologies having different tools that assist the Natural Language Processing activities and also collaborative tools for supporting the communication and interaction needs of team members. The main contributions of e-Termos are the collaborative aspect instantiated in terminological practice, the flexible creation of Terminological Records and the possibility of being used for teaching terminology, lexicography and translation.Propor 2010. Demonstration
An extended-phase-space dynamics for the generalized nonextensive thermostatistics
We apply a variant of the Nose-Hoover thermostat to derive the Hamiltonian of
a nonextensive system that is compatible with the canonical ensemble of the
generalized thermostatistics of Tsallis. This microdynamical approach provides
a deterministic connection between the generalized nonextensive entropy and
power law behavior. For the case of a simple one-dimensional harmonic
oscillator, we confirm by numerical simulation of the dynamics that the
distribution of energy H follows precisely the canonical q-statistics for
different values of the parameter q. The approach is further tested for
classical many-particle systems by means of molecular dynamics simulations. The
results indicate that the intrinsic nonlinear features of the nonextensive
formalism are capable to generate energy fluctuations that obey anomalous
probability laws. For q<1 a broad distribution of energy is observed, while for
q>1 the resulting distribution is confined to a compact support.Comment: 4 pages, 5 figure
Methods for Reliable Teleportation
Recent experimental results and proposals towards implementation of quantum
teleportation are discussed. It is proved that reliable (theoretically, 100%
probability of success) teleportation cannot be achieved using the methods
applied in recent experiments, i.e., without quantum systems interacting one
with the other. Teleportation proposal involving atoms and electro-magnetic
cavities are reviewed and the most feasible methods are described. In
particular, the language of nonlocal measurements has been applied which has
also been used for presenting a method for teleportation of quantum states of
systems with continuous variables.Comment: 11 pages, 5eps figure
Avaliação de genótipos de feijoeiro comum dos grupos carioca e preto na região Oeste de Mato Grosso.
O objetivo desse trabalho é obter cultivares mais tolerantes a altas temperaturas, menores altitudes e apropriadas para a agricultura familiar que atendam essas condições no estado de Mato Grosso
- …