998 research outputs found
Transient Cherenkov radiation from an inhomogeneous string excited by an ultrashort laser pulse at superluminal velocity
An optical response of one-dimensional string made of dipoles with a
periodically varying density excited by a spot of light moving along the string
at the superluminal (sub-luminal) velocity is theoretically studied. The
Cherenkov radiation in such system is rather unusual, possessing both transient
and resonant character. We show that under certain conditions, in addition to
the resonant Cherenkov peak another Doppler-like frequency appears in the
radiation spectrum. Both linear (small-signal) and nonlinear regimes as well as
different string topologies are considered.Comment: accepted to Phys. Rev.
Effect of the superconducting wiggler on the DELSY beam dynamics
The project DELSY is being under development at JINR, Dubna, Russia. This
synchrotron radiation source is dedicated to the investigation on condensed
matter physics, atomic physics, biology, medicine, chemistry, micromechanics,
lithography and others. The storage ring DELSY is an electron storage ring with
the beam energy 1.2 GeV and 4 straight sections to accommodate accelerator
equipment and insertion devices. One of the straight sections is intended for a
10 T superconducting wiggler (wavelength shifter) and one for the undulator
with 150 periods and a magnetic field of 0.75 T. The wiggler will influence
many aspects of beam dynamics: linear motion, dynamic aperture, emittance,
damping times etc. The problem is rather serious for the DELSY machine because
the energy of the electron beam is small while the wiggler's magnetic field is
strong. In this paper we consider two models of the wiggler's magnetic field
with and without the focusing caused by the sextupolar field of the wiggler as
we need to develop the requirements to the wiggler design. We study the
influence of the 10 T wiggler on the beam dynamics in the DELSY storage ring
and propose a possible scheme to cure it. The combined work of the insertion
device is presented too.Comment: 17 pages, submitted to journal NIM
Enhancing entanglement detection of quantum optical frequency combs via stimulated emission
We investigate the performance of a certain nonclassicality identifier,
expressed via integrated second-order intensity moments of optical fields, in
revealing bipartite entanglement of quantum-optical frequency combs (QOFCs),
which are generated in both spontaneous and stimulated parametric
down-conversion processes. We show that, by utilizing that nonclassicality
identifier, one can well identify the entanglement of the QOFC directly from
the experimentally measured intensity moments without invoking any state
reconstruction techniques or homodyne detection. Moreover, we demonstrate that
the stimulated generation of the QOFC improves the entanglement detection of
these fields with the nonclassicality identifier. Additionally, we show that
the nonclassicality identifier can be expressed in a factorized form of
detectors quantum efficiencies and the number of modes, if the QOFC consists of
many copies of the same two-mode twin beam. As an example, we apply the
nonclassicality identifier to two specific types of QOFC, where: (i) the QOFC
consists of many independent two-mode twin beams with non-overlapped spatial
frequency modes, and (ii) the QOFC contains entangled spatial frequency modes
which are completely overlapped, i.e., each mode is entangled with all the
remaining modes in the system. We show that, in both cases, the nonclassicality
identifier can reveal bipartite entanglement of the QOFC including noise, and
that it becomes even more sensitive for the stimulated processes.Comment: 11 p., 8 fig
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