8,469 research outputs found
Quantum random walk of two photons in separable and entangled state
We discuss quantum random walk of two photons using linear optical elements.
We analyze the quantum random walk using photons in a variety of quantum states
including entangled states. We find that for photons initially in separable
Fock states, the final state is entangled. For polarization entangled photons
produced by type II downconverter, we calculate the joint probability of
detecting two photons at a given site. We show the remarkable dependence of the
two photon detection probability on the quantum nature of the state. In order
to understand the quantum random walk, we present exact analytical results for
small number of steps like five. We present in details numerical results for a
number of cases and supplement the numerical results with asymptotic analytical
results
Synthesis of Nano-Crystalline Ceramic powders by Chemical Process
Several processes were developed by our research group to synthesise nanocrystalline ceramic materials. Amongst them, the im,estigation of the new, simple and versatile technique to generate ultra fine powders of advanced
ceramic oxides using a chemical pyrophoric reaction and sot-gel techniques are noteworthy. In the solution comb-ustion technique, the role of pH on the morphology of the synthesised powder was attributedto the redox reaction.
These pyrophoricallp generated precursors could also be utilised to synthesise nano-crystalline aluminium nitride powders at low temperatures using carbotherntic process. An economically feasible alkoxide based solgel process for the production of high purity nano-crystalline alumina
powders was established and several subsequent processes to generate nanospheres to micro spheres were investi-gated. This increased the potential of these high pure nano-crystalline spherical alumina powders for practical
applications in spray coating on industrial components, fabrication of envelope for sodium vapour lamp, hip joints and IC substrate
Spatial-temporal evolution of the current filamentation instability
The spatial-temporal evolution of the purely transverse current filamentation
instability is analyzed by deriving a single partial differential equation for
the instability and obtaining the analytical solutions for the spatially and
temporally growing current filament mode. When the beam front always encounters
fresh plasma, our analysis shows that the instability grows spatially from the
beam front to the back up to a certain critical beam length; then the
instability acquires a purely temporal growth. This critical beam length
increases linearly with time and in the non-relativistic regime it is
proportional to the beam velocity. In the relativistic regime the critical
length is inversely proportional to the cube of the beam Lorentz factor
. Thus, in the ultra-relativistic regime the instability
immediately acquires a purely temporal growth all over the beam. The analytical
results are in good agreement with multidimensional particle-in-cell
simulations performed with OSIRIS. Relevance of current study to recent and
future experiments on fireball beams is also addressed
Pump It Up: Predict Water Pump Status using Attentive Tabular Learning
Water crisis is a crucial concern around the globe. Appropriate and timely
maintenance of water pumps in drought-hit countries is vital for communities
relying on the well. In this paper, we analyze and apply a sequential attentive
deep neural architecture, TabNet, for predicting water pump repair status in
Tanzania. The model combines the valuable benefits of tree-based algorithms and
neural networks, enabling end-to-end training, model interpretability, sparse
feature selection, and efficient learning on tabular data. Finally, we compare
the performance of TabNet with popular gradient tree-boosting algorithms like
XGBoost, LightGBM,CatBoost, and demonstrate how we can further uplift the
performance by choosing focal loss as the objective function while training on
imbalanced data.Comment: 9 pages, 5 figures, 2 table
Magnetically assisted self-injection and radiation generation for plasma based acceleration
It is shown through analytical modeling and numerical simulations that
external magnetic fields can relax the self-trapping thresholds in plasma based
accelerators. In addition, the transverse location where self-trapping occurs
can be selected by adequate choice of the spatial profile of the external
magnetic field. We also find that magnetic-field assisted self-injection can
lead to the emission of betatron radiation at well defined frequencies. This
controlled injection technique could be explored using state-of-the-art
magnetic fields in current/next generation plasma/laser wakefield accelerator
experiments.Comment: 7 pages, 4 figures, accepted for publication in Plasma Physics and
Controlled Fusio
Analytical pair correlations in ideal quantum gases: Temperature-dependent bunching and antibunching
The fluctuation-dissipation theorem together with the exact density response
spectrum for ideal quantum gases has been utilized to yield a new expression
for the static structure factor, which we use to derive exact analytical
expressions for the temperature{dependent pair distribution function g(r) of
the ideal gases. The plots of bosonic and fermionic g(r) display "Bose pile"
and "Fermi hole" typically akin to bunching and antibunching as observed
experimentally for ultracold atomic gases. The behavior of spin-scaled pair
correlation for fermions is almost featureless but bosons show a rich structure
including long-range correlations near T_c. The coherent state at T=0 shows no
correlation at all, just like single-mode lasers. The depicted decreasing trend
in correlation with decrease in temperature for T < T_c should be observable in
accurate experiments.Comment: 8 pages, 1 figure, minor revisio
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