6,994 research outputs found
Self-focusing threshold of Gaussian-elliptic light beams
There is now substantial evidence to indicate
that the long damage filaments
created by laser beams passing through
solid materials are due to self-focusing
Adiabatic Control of the Electron Phase in a Quantum Dot
A Berry phase can be added to the wavefunction of an isolated quantum dot by
adiabatically modulating a nonuniform electric field along a time-cycle. The
dot is tuned close to a three-level degeneracy, which provides a wide range of
possibilities of control. We propose to detect the accumulated phase by
capacitively coupling the dot to a double-path inteferometer. The effective
Hamiltonian for the phase-sensitive coupling is discussed in detail.Comment: 14 pages, 2 .eps figure
Optimal purification of a generic n-qudit state
We propose a quantum algorithm for the purification of a generic mixed state
of a -qudit system by using an ancillary -qudit system. The
algorithm is optimal in that (i) the number of ancillary qudits cannot be
reduced, (ii) the number of parameters which determine the purification state
exactly equals the number of degrees of freedom of , and (iii)
is easily determined from the density matrix . Moreover, we
introduce a quantum circuit in which the quantum gates are unitary
transformations acting on a -qudit system. These transformations are
determined by parameters that can be tuned to generate, once the ancillary
qudits are disregarded, any given mixed -qudit state.Comment: 8 pages, 9 figures, remarks adde
Quantum interference of electrons in a ring: tuning of the geometrical phase
We calculate the oscillations of the DC conductance across a mesoscopic ring,
simultaneously tuned by applied magnetic and electric fields orthogonal to the
ring. The oscillations depend on the Aharonov-Bohm flux and of the spin-orbit
coupling. They result from mixing of the dynamical phase, including the Zeeman
spin splitting, and of geometric phases. By changing the applied fields, the
geometric phase contribution to the conductance oscillations can be tuned from
the adiabatic (Berry) to the nonadiabatic (Ahronov-Anandan) regime. To model a
realistic device, we also include nonzero backscattering at the connection
between ring and contacts, and a random phase for electron wavefunction,
accounting for dephasing due to disorder.Comment: 4 pages, 3 figures, minor change
Spatial and performance optimality in power distribution networks
(c) 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.Complex network theory has been widely used in vulnerability analysis of power networks, especially for power transmission ones. With the development of the smart grid concept, power distribution networks are becoming increasingly relevant. In this paper, we model power distribution systems as spatial networks. Topological and spatial properties of 14 European power distribution networks are analyzed, together with the relationship between geographical constraints and performance optimization, taking into account economic and vulnerability issues. Supported by empirical reliability data, our results suggest that power distribution networks are influenced by spatial constraints which clearly affect their overall performance.Peer ReviewedPostprint (author's final draft
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