2,802 research outputs found
Linear optical Fredkin gate based on partial-SWAP gate
We propose a scheme for linear optical quantum Fredkin gate based on the
combination of recently experimentally demonstrated linear optical partial SWAP
gate and controlled-Z gates. Both heralded gate and simplified postselected
gate operating in the coincidence basis are designed. The suggested setups have
a simple structure and require stabilization of only a single Mach-Zehnder
interferometer. A proof-of-principle experimental demonstration of the
postselected Fredkin gate appears to be feasible and within the reach of
current technology.Comment: 6 pages, 3 figures, RevTeX
Collective behavior of heterogeneous neural networks
We investigate a network of integrate-and-fire neurons characterized by a
distribution of spiking frequencies. Upon increasing the coupling strength, the
model exhibits a transition from an asynchronous regime to a nontrivial
collective behavior. At variance with the Kuramoto model, (i) the macroscopic
dynamics is irregular even in the thermodynamic limit, and (ii) the microscopic
(single-neuron) evolution is linearly stable.Comment: 4 pages, 5 figure
Collective chaos in pulse-coupled neural networks
We study the dynamics of two symmetrically coupled populations of identical
leaky integrate-and-fire neurons characterized by an excitatory coupling. Upon
varying the coupling strength, we find symmetry-breaking transitions that lead
to the onset of various chimera states as well as to a new regime, where the
two populations are characterized by a different degree of synchronization.
Symmetric collective states of increasing dynamical complexity are also
observed. The computation of the the finite-amplitude Lyapunov exponent allows
us to establish the chaoticity of the (collective) dynamics in a finite region
of the phase plane. The further numerical study of the standard Lyapunov
spectrum reveals the presence of several positive exponents, indicating that
the microscopic dynamics is high-dimensional.Comment: 6 pages, 5 eps figures, to appear on Europhysics Letters in 201
From anomalous energy diffusion to Levy walks and heat conductivity in one-dimensional systems
The evolution of infinitesimal, localized perturbations is investigated in a
one-dimensional diatomic gas of hard-point particles (HPG) and thereby
connected to energy diffusion. As a result, a Levy walk description, which was
so far invoked to explain anomalous heat conductivity in the context of
non-interacting particles is here shown to extend to the general case of truly
many-body systems. Our approach does not only provide a firm evidence that
energy diffusion is anomalous in the HPG, but proves definitely superior to
direct methods for estimating the divergence rate of heat conductivity which
turns out to be , in perfect agreement with the dynamical
renormalization--group prediction (1/3).Comment: 4 pages, 3 figure
Time evolution of wave-packets in quasi-1D disordered media
We have investigated numerically the quantum evolution of a wave-packet in a
quenched disordered medium described by a tight-binding Hamiltonian with
long-range hopping (band random matrix approach). We have obtained clean data
for the scaling properties in time and in the bandwidth b of the packet width
and its fluctuations with respect to disorder realizations. We confirm that the
fluctuations of the packet width in the steady-state show an anomalous scaling
and we give a new estimate of the anomalous scaling exponent. This anomalous
behaviour is related to the presence of non-Gaussian tails in the distribution
of the packet width. Finally, we have analysed the steady state probability
profile and we have found finite band corrections of order 1/b with respect to
the theoretical formula derived by Zhirov in the limit of infinite bandwidth.
In a neighbourhood of the origin, however, the corrections are .Comment: 19 pages, 9 Encapsulated Postscript figures; submitted to ``European
Physical Journal B'
Modified Kuramoto-Sivashinsky equation: stability of stationary solutions and the consequent dynamics
We study the effect of a higher-order nonlinearity in the standard
Kuramoto-Sivashinsky equation: \partial_x \tilde G(H_x). We find that the
stability of steady states depends on dv/dq, the derivative of the interface
velocity on the wavevector q of the steady state. If the standard nonlinearity
vanishes, coarsening is possible, in principle, only if \tilde G is an odd
function of H_x. In this case, the equation falls in the category of the
generalized Cahn-Hilliard equation, whose dynamical behavior was recently
studied by the same authors. Instead, if \tilde G is an even function of H_x,
we show that steady-state solutions are not permissible.Comment: 4 page
Coupled transport in rotor models
Acknowledgement One of us (AP) wishes to acknowledge S. Flach for enlightening discussions about the relationship between the DNLS equation and the rotor model.Peer reviewedPublisher PD
- âŠ