877 research outputs found
Outcomes of the webinar: Potential of O&G projects in the Far East in new economic realities
As a preamble to the 5th Annual International East Russia Oil and Gas Forum, which is scheduled to take place in Vladivostok on 7-8 July 2021, British consultancy Vostock Capital hosted a free webinar “Potential of O&G projects in the Far East in new economic realities”
Post-pandemic Prospects of O&G Projects
A presentation that was held on the webinar: Potential of O&G Projects of the Far East in New Economic Realities in May 2020 by Vostock Capita
Quantum repeater via entangled phase modulated multimode coherent states
We present a scheme of quantum repeater that uses entangled multimode
coherent states which are obtained by electro-optic modulation of symmetric and
antisymmetric Schr\"odinger cat states. In this method subcarrier modes of the
phase modulated states generated by the remote parties are sent to a symmetric
beam splitter at the central node. The entangled coherent states are heraldedly
prepared by photon counting measurements at the output channels of the beam
splitter. We study how the effects of decoherence in the quantum channel affect
statistics of photocounts and corresponding fidelity. We show how the proposed
scheme can be useful for extending range of quantum key distribution with sub
carrier wave encoding by exploiting quantum teleportation with the generated
entanglement.Comment: 14 pages, 8 figure
Single- and coupled-channel radial inverse scattering with supersymmetric transformations
The present status of the coupled-channel inverse-scattering method with
supersymmetric transformations is reviewed. We first revisit in a pedagogical
way the single-channel case, where the supersymmetric approach is shown to
provide a complete solution to the inverse-scattering problem. A special
emphasis is put on the differences between conservative and non-conservative
transformations. In particular, we show that for the zero initial potential, a
non-conservative transformation is always equivalent to a pair of conservative
transformations. These single-channel results are illustrated on the inversion
of the neutron-proton triplet eigenphase shifts for the S and D waves. We then
summarize and extend our previous works on the coupled-channel case and stress
remaining difficulties and open questions. We mostly concentrate on two-channel
examples to illustrate general principles while keeping mathematics as simple
as possible. In particular, we discuss the difference between the
equal-threshold and different-threshold problems. For equal thresholds,
conservative transformations can provide non-diagonal Jost and scattering
matrices. Iterations of such transformations are shown to lead to practical
algorithms for inversion. A convenient technique where the mixing parameter is
fitted independently of the eigenphases is developed with iterations of pairs
of conjugate transformations and applied to the neutron-proton triplet S-D
scattering matrix, for which exactly-solvable matrix potential models are
constructed. For different thresholds, conservative transformations do not seem
to be able to provide a non-trivial coupling between channels. In contrast, a
single non-conservative transformation can generate coupled-channel potentials
starting from the zero potential and is a promising first step towards a full
solution to the coupled-channel inverse problem with threshold differences.Comment: Topical review, 84 pages, 7 figures, 93 reference
Feshbach projection-operator formalism to resonance scattering on Bargmann-type potentials
The projection-operator formalism of Feshbach is applied to resonance
scattering in a single-channel case. The method is based on the division of the
full function space into two segments, internal (localized) and external
(infinitely extended). The spectroscopic information on the resonances is
obtained from the non-Hermitian effective Hamilton operator
appearing in the internal part due to the coupling to the external part. As
well known, additional so-called cut-off poles of the -matrix appear,
generally, due to the truncation of the potential. We study the question of
spurious matrix poles in the framework of the Feshbach formalism. The
numerical analysis is performed for exactly solvable potentials with a finite
number of resonance states. These potentials represent a generalization of
Bargmann-type potentials to accept resonance states. Our calculations
demonstrate that the poles of the matrix obtained by using the Feshbach
projection-operator formalism coincide with both the complex energies of the
physical resonances and the cut-off poles of the -matrix.Comment: 12 pages, 9 figure
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