12,542 research outputs found
Modulation instability and solitary wave formation in two-component Bose-Einstein condensates
We investigate nonlinear dynamics induced by the modulation instability of a
two-component mixture in an atomic Bose-Einstein condensate. The nonlinear
dynamics is examined using numerical simulations of the time-dependent coupled
Gross-Pitaevskii equations. The unstable modulation grows from initially
miscible condensates into various types of vector solitary waves, depending on
the combinations of the sign of the coupling constants (intracomponent and
intercomponent). We discuss the detailed features of the modulation
instability, dynamics of solitary wave formation, and an analogy with the
collapsing dynamics in a single-component condensate with attractive
interactions.Comment: 15 pages, 10 figure
Matter wave switching in Bose-Einstein condensates via intensity redistribution soliton interactions
Using time dependent nonlinear (s-wave scattering length) coupling between
the components of a weakly interacting two component Bose-Einstein condensate
(BEC), we show the possibility of matter wave switching (fraction of atoms
transfer) between the components via shape changing/intensity redistribution
(matter redistribution) soliton interactions. We investigate the exact
bright-bright N-soliton solution of an effective one-dimensional (1D) two
component BEC by suitably tailoring the trap potential, atomic scattering
length and atom gain or loss. In particular, we show that the effective 1D
coupled Gross-Pitaevskii (GP) equations with time dependent parameters can be
transformed into the well known completely integrable Manakov model described
by coupled nonlinear Schr\"odinger (CNLS) equations by effecting a change of
variables of the coordinates and the wave functions under certain conditions
related to the time dependent parameters. We obtain the one-soliton solution
and demonstrate the shape changing/matter redistribution interactions of two
and three soliton solutions for the time independent expulsive harmonic trap
potential, periodically modulated harmonic trap potential and kink-like
modulated harmonic trap potential. The standard elastic collision of solitons
occur only for a specific choice of soliton parameters.Comment: 11 pages, 14 figures, 1 tabl
Multicomputer communication system
A local area network is provided for a plurality of autonomous computers which operate at different rates and under different protocols coupled by network bus adapters to a global bus. A host computer (HC) divides a message file to be transmitted into blocks, each with a header that includes a data type identifier and a trailer. The associated network bus adapter (NBA) then divides the data into packets, each with a header to which a transport header and trailer is added with frame type code which specifies one of three modes of addressing in the transmission of data, namely a physical address mode for computer to computer transmission using two bytes for source and destination addresses, a logical address mode and a data type mode. In the logical address mode, one of the two addressing bytes contains a logical channel number (LCN) established between the transmitting and one or more receiving computers. In the data type mode, one of the addressing bytes contains a code identifying the type of data
Stationary scattering from a nonlinear network
Transmission through a complex network of nonlinear one-dimensional leads is
discussed by extending the stationary scattering theory on quantum graphs to
the nonlinear regime. We show that the existence of cycles inside the graph
leads to a large number of sharp resonances that dominate scattering. The
latter resonances are then shown to be extremely sensitive to the nonlinearity
and display multi-stability and hysteresis. This work provides a framework for
the study of light propagation in complex optical networks.Comment: 4 pages, 4 figure
Propagation of temporal entanglement
The equations that govern the temporal evolution of two photons in the
Schr{\"o}dinger picture are derived, taking into account the effects of loss,
group-velocity dispersion, temporal phase modulation, linear coupling among
different optical modes, and four-wave mixing. Inspired by the formalism, we
propose the concept of quantum temporal imaging, which uses dispersive elements
and temporal phase modulators to manipulate the temporal correlation of two
entangled photons. We also present the exact solution of a two-photon vector
soliton, in order to demonstrate the ease of use and intuitiveness of the
proposed formulation.Comment: 8 pages, 4 figure
Consequences of self-consistency violations in Hartree-Fock random-phase approximation calculations of the nuclear breathing mode energy
We provide for the first time accurate assessments of the consequences of
violations of self-consistency in the Hartree-Fock based random phase
approximation (RPA) as commonly used to calculate the energy of the
nuclear breathing mode. Using several Skyrme interactions we find that the
self-consistency violated by ignoring the spin-orbit interaction in the RPA
calculation causes a spurious enhancement of the breathing mode energy for spin
unsaturated systems. Contrarily, neglecting the Coulomb interaction in the RPA
or performing the RPA calculations in the TJ scheme underestimates the
breathing mode energy. Surprisingly, our results for the Zr and
Pb nuclei for several Skyrme type effective nucleon-nucleon
interactions having a wide range of nuclear matter incompressibility ( MeV) and symmetry energy ( MeV) indicate that
the net uncertainty ( MeV) is comparable to the
experimental one.Comment: Revtex file (11 pages), Accepted for the publication in Phys. Rev.
Distilling Quantum Entanglement via Mode-Matched Filtering
We propose a new avenue towards distillation of quantum entanglement that is
implemented by directly passing the entangled qubits through a mode-matched
filter. This approach can be applied to a common class of entanglement
impurities appearing in photonic systems where the impurities inherently occupy
different spatiotemporal modes than the entangled qubits. As a specific
application, we show that our method can be used to significantly purify the
telecom-band entanglement generated via the Kerr nonlinearity in single-mode
fibers where a substantial amount of Raman-scattering noise is concomitantly
produced.Comment: 6 pages, 2 figures, to appear in Phys. Rev.
Asymmetric partially coherent solitons in saturable nonlinear media
We investigate theoretically properties of partially coherent solitons in optical nonlinear media with slow
saturable nonlinearity. We have found numerically that such a medium can support spatial solitons which are
asymmetric in shape and are composed of only a finite number of modes associated with the self-induced
waveguide. It is shown that these asymmetric spatial solitons can propagate many diffraction lengths without
changes, but that collisions change their shape and may split them apart. [S1063-651X(99)12808-3
The refractive index and wave vector in passive or active media
Materials that exhibit loss or gain have a complex valued refractive index
. Nevertheless, when considering the propagation of optical pulses, using a
complex is generally inconvenient -- hence the standard choice of
real-valued refractive index, i.e. n_s = \RealPart (\sqrt{n^2}). However, an
analysis of pulse propagation based on the second order wave equation shows
that use of results in a wave vector \emph{different} to that actually
exhibited by the propagating pulse. In contrast, an alternative definition n_c
= \sqrt{\RealPart (n^2)}, always correctly provides the wave vector of the
pulse. Although for small loss the difference between the two is negligible, in
other cases it is significant; it follows that phase and group velocities are
also altered. This result has implications for the description of pulse
propagation in near resonant situations, such as those typical of metamaterials
with negative (or otherwise exotic) refractive indices.Comment: Phys. Rev. A, to appear (2009
- …