938 research outputs found
Study of Electromagnetically Induced Transparency using long-lived Singlet States
The long-lived singlet states are useful to study a variety of interesting
quantum phenomena. In this work we study electromagnetically induced
transparency using a two-qubit system. The singlet state acts as a `dark state'
which does not absorb a probe radiation in the presence of a control radiation.
Further we demonstrate that the simultaneous irradiation of probe and control
radiations acts as a dynamical decoupling preserving the singlet state at
higher correlation for longer durations.Comment: 4 pages, 4 figure
A non-destructive analytic tool for nanostructured materials : Raman and photoluminescence spectroscopy
Modern materials science requires efficient processing and characterization
techniques for low dimensional systems. Raman spectroscopy is an important
non-destructive tool, which provides enormous information on these materials.
This understanding is not only interesting in its own right from a physicist's
point of view, but can also be of considerable importance in optoelectronics
and device applications of these materials in nanotechnology. The commercial
Raman spectrometers are quite expensive. In this article, we have presented a
relatively less expensive set-up with home-built collection optics attachment.
The details of the instrumentation have been described. Studies on four classes
of nanostructures - Ge nanoparticles, porous silicon (nanowire), carbon
nanotubes and 2D InGaAs quantum layers, demonstrate that this unit can be of
use in teaching and research on nanomaterials.Comment: 32 pages, 13 figure
Evolution of Quantum Discord and its Stability in Two-Qubit NMR Systems
We investigate evolution of quantum correlations in ensembles of two-qubit
nuclear spin systems via nuclear magnetic resonance techniques. We use discord
as a measure of quantum correlations and the Werner state as an explicit
example. We first introduce different ways of measuring discord and geometric
discord in two-qubit systems and then describe the following experimental
studies: (a) We quantitatively measure discord for Werner-like states prepared
using an entangling pulse sequence. An initial thermal state with zero discord
is gradually and periodically transformed into a mixed state with maximum
discord. The experimental and simulated behavior of rise and fall of discord
agree fairly well. (b) We examine the efficiency of dynamical decoupling
sequences in preserving quantum correlations. In our experimental setup, the
dynamical decoupling sequences preserved the traceless parts of the density
matrices at high fidelity. But they could not maintain the purity of the
quantum states and so were unable to keep the discord from decaying. (c) We
observe the evolution of discord for a singlet-triplet mixed state during a
radio-frequency spin-lock. A simple relaxation model describes the evolution of
discord, and the accompanying evolution of fidelity of the long-lived singlet
state, reasonably well.Comment: 9 pages, 7 figures, Phys. Rev. A (in press
Stable CoO Nanoscrolls With Outstanding Electrical Properties
Layered CoO is of great interest for its promising properties but is
meta-stable in its bulk form. CoO was synthesized in a long-term stable
nanotubular or scrolled form by converting the quasi-one-dimensional crystal
structure of bulk CaCoO via a hydrothermal treatment. The resulting
one-dimensional nanostructures with very thin walls are investigated in detail.
The CoO_ is found to crystallize in monoclinic form, similar to the related
CaCoO-CoO misfit structure. Individual nanoscrolls are characterized
electrically and show a p-type semiconducting nature with a high
current-carrying capacity of A/cm and an extremely high
breakdown voltage of 27 kV/cm. The results demonstrate the possibility to
stabilize meta-stable materials in low-dimensional forms and a promising
application of the nanoscrolls as interconnect in high-voltage electronic
circuitry
Storing entanglement of nuclear spins via Uhrig Dynamical Decoupling
Stroboscopic spin flips have already been shown to prolong the coherence
times of quantum systems under noisy environments. Uhrig's dynamical decoupling
scheme provides an optimal sequence for a quantum system interacting with a
dephasing bath. Several experimental demonstrations have already verified the
efficiency of such dynamical decoupling schemes in preserving single qubit
coherences. In this work we describe the experimental study of Uhrig's
dynamical decoupling in preserving two-qubit entangled states using an ensemble
of spin-1/2 nuclear pairs in solution state. We find that the performance of
odd-order Uhrig sequences in preserving entanglement is superior to both
even-order Uhrig sequences and periodic spin-flip sequences. We also find that
there exists an optimal length of the Uhrig sequence at which the decoherence
time gets boosted from a few seconds to about 30 seconds.Comment: 6 pages, 7 figure
Large diamagnetic persistent currents
In multichannel rings, evanescent modes will always co-exist with propagating
modes. The evanescent modes can carry a very large diamagnetic persistent
current that can oscillate with energy and are very sensitive to impurity
scattering. This provides a natural explanation for the large diamagnetic
persistent currents observed in experiments.Comment: 5 figure
Non-invasive biomarkers and pulmonary function in smokers
Limited information exists regarding measurement, reproducibility and interrelationships of non-invasive biomarkers in smokers. We compared exhaled breath condensate (EBC) leukotriene B4 (LTB4) and 8-isoprostane, exhaled nitric oxide, induced sputum, spirometry, plethysmography, impulse oscillometry and methacholine reactivity in 18 smokers and 10 non-smokers. We assessed the relationships between these measurements and within-subject reproducibility of EBC biomarkers in smokers. Compared to non-smokers, smokers had significantly lower MMEF % predicted (mean 64.1 vs 77.7, p = 0.003), FEV1/FVC (mean 76.2 vs 79.8 p = 0.05), specific conductance (geometric mean 1.2 vs 1.6, p = 0.02), higher resonant frequency (mean 15.5 vs 9.9, p = 0.01) and higher EBC 8-isoprostane (geometric mean 49.9 vs 8.9 pg/ml p = 0.001). Median EBC pH values were similar, but a subgroup of smokers had airway acidification (pH < 7.2) not observed in non-smokers. Smokers had predominant sputum neutrophilia (mean 68.5%). Repeated EBC measurements showed no significant differences between group means, but Bland Altman analysis showed large individual variability. EBC 8-isoprostane correlated with EBC LTB4 (r = 0.78, p = 0.0001). Sputum supernatant IL-8 correlated with total neutrophil count per gram of sputum (r = 0.52, p = 0.04) and with EBC pH (r = −0.59, p = 0.02). In conclusion, smokers had evidence of small airway dysfunction, increased airway resistance, reduced lung compliance, airway neutrophilia and oxidative stress
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