302 research outputs found
Focusing of laser-generated ion beams by a plasma cylinder: similarity theory and the thick lens formula
It is shown that plasma-based optics can be used to guide and focus highly
divergent laser-generated ion beams. A hollow cylinder is considered, which
initially contains a hot electron population. Plasma streaming toward the
cylinder axis maintains a focusing electrostatic field due to the positive
radial pressure gradient. The cylinder works as thick lens, whose parameters
are obtained from similarity theory for freely expanding plasma in cylindrical
geometry. Because the lens parameters are energy dependent, the lens focuses a
selected energy range of ions and works as a monochromator. Because the
focusing is due to the quasineutral part of the expanding plasma, the lens
parameters depend on the hot electron temperature only, and not their
density
Relativistic Doppler effect: universal spectra and zeptosecond pulses
We report on a numerical observation of the train of zeptosecond pulses
produced by reflection of a relativistically intense femtosecond laser pulse
from the oscillating boundary of an overdense plasma because of the Doppler
effect. These pulses promise to become a unique experimental and technological
tool since their length is of the order of the Bohr radius and the intensity is
extremely high W/cm. We present the physical mechanism,
analytical theory, and direct particle-in-cell simulations. We show that the
harmonic spectrum is universal: the intensity of th harmonic scales as
for , where is the largest --factor
of the electron fluid boundary, and for the broadband and
quasimonochromatic laser pulses respectively.Comment: 4 figure
Measurement-assisted non-Gaussian gate for Schr\"odinger cat states preparation: Fock resource state versus cubic phase state
In this paper, we consider the preparation of Schr\"odinger cat states using
a measurement-assisted gate based on the Fock resource state, the quantum
non-demolition (QND) entangling operation, and the homodyne measurement.
Previously we have investigated the gate, which for the same goal uses the
ancillary non-Gaussian cubic phase state generated from quadrature squeezed
states at realistic (finite) squeezing. It is of evident interest to compare
the efficiency of both schemes, that is, their ability to produce cat-like
superpositions with high fidelity and probability of success. We introduce, in
parallel with the exact theoretical description of the gate operation, a clear
visual interpretation of the output state based on the semiclassical mapping of
the input field variables. The emergence of the superpositions of copies of the
input state in both schemes is due to the fact that such mapping is compatible
with two (or, in general, more) sets of values of the output field observables.
We demonstrate that even fine details of the output of both gates are
effectively predicted and interpreted in our approach. We examine the fidelity
and success probability and reveal the ranges of physical parameters where the
Fock state-based and the cubic phase state-based gates demonstrate comparable
fidelity and (or) probability of success.Comment: 11 pages, 9 figure
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