98 research outputs found
Proposal for an optical laser producing light at half the Josephson frequency
We describe a superconducting device capable of producing laser light in the
visible range at half of the Josephson generation frequency with the optical
phase of the light locked to the superconducting phase difference. It consists
of two single-level quantum dots embedded into a p-n semiconducting
heterostructure and surrounded by a cavity supporting a resonant optical mode.
We study decoherence and spontaneous switching in the device.Comment: 4+3 pages, 3+1 figure
Motivasi Rusia Menganeksasi Semenanjung Krimea Tahun 2014
This research describes Russias motivation on taking Crimea Peninsula byforce from Ukraine in March 2014 or internationally called as CrimeaAnnexation. After Ukraines Euromaidan Revolution ended in february 2014with the escape of President Viktor Yanukovych to Russia and the interimgovernment was formed, a new separatist conflict arise in the regions thatpredominantly Russian speakers and led by the Crimea secession which wasfollowed soon by Russias annexation. Russia has been violated manyinternational agreements and bring it to the condemnation by internationalcommunity and western countries were planned to impose sanctions. Thiscase will be analyzed within the framework of offensive realism with securityapproach. Under the assumptions of the thories, security dilemma andoffensive capabilities lead to the expansion by great powers, mainly territorialexpansion. Russia seeking to strengthening political influence and security inthe Black Sea Region, where Crimea, Ukraine, and Russia are located.Security dilemma comes from political and military expansion by NATO,European Union, and United States. Annexation of Crimea showed thatRussia has returned to a great power and the rivalry between Westerncountries and Russia actually continues even though cold war has ended morethan two decades ago.Keywords: Annexation, Black Sea Region, European Union, Territorial Expansion,NATO, Offensive Realism, Russia, Securit
Evolution of a localized electron spin in a nuclear spin environment
Motivated by recent interest in the role of the hyperfine interaction in
quantum dots we study the dynamics of a localized electron spin coupled to many
nuclei. An important feature of the model is that the coupling to an individual
nuclear spin depends on its position in the quantum dot. We introduce a
semi-classical description of the system valid in the limit of a large number
of nuclei and analyze the resulting classical dynamics. Contrary to a natural
assumption, the correlation functions of electron spin with an arbitrary
initial condition show no decay in time. Rather, they exhibit complicated
undamped oscillations. This may be attributed to the fact that the system has
many integrals of motion and is close to an integrable one. The ensemble
averaged correlation functions do exhibit a slow decay (1/ln(t)) for t ->
\infty.Comment: 11 pages, 11 figures, revtex4 styl
Full Counting Statistics of Non-Commuting Variables: the Case of Spin Counts
We discuss the Full Counting Statistics of non-commuting variables with the
measurement of successive spin counts in non-collinear directions taken as an
example. We show that owing to an irreducible detector back-action, the FCS in
this case may be sensitive to the dynamics of the detectors, and may differ
from the predictions obtained with using a naive version of the Projection
Postulate. We present here a general model of detector dynamics and
path-integral approach to the evaluation of FCS. We concentrate further on a
simple "diffusive" model of the detector dynamics where the FCS can be
evaluated with transfer-matrix method. The resulting probability distribution
of spin counts is characterized by anomalously large higher cumulants and
substantially deviates from Gaussian Statistics.Comment: 11 pages, 3 figure
Time dependent impurity in ultracold fermions: orthogonality catastrophe and beyond
Recent experimental realization of strongly imbalanced mixtures of ultracold
atoms opens new possibilities for studying impurity dynamics in a controlled
setting. We discuss how the techniques of atomic physics can be used to explore
new regimes and manifestations of Anderson's orthogonality catastrophe (OC),
which could not be accessed in solid state systems. We consider a system of
impurity atoms localized by a strong optical lattice potential and immersed in
a sea of itinerant Fermi atoms. Ramsey interference experiments with impurity
atoms probe OC in the time domain, while radio-frequency (RF) spectroscopy
probes OC in the frequency domain. The OC in such systems is universal for all
times and is determined by the impurity scattering length and Fermi wave vector
of itinerant fermions. We calculate the universal Ramsey response and RF
absorption spectra. In addition to the standard power-law contribution, which
corresponds to the excitation of multiple particle-hole pairs near the Fermi
surface, we identify a novel contribution to OC that comes from exciting one
extra particle from the bottom of the itinerant band. This gives rise to a
non-analytic feature in the RF absorption spectra, which evolves into a true
power-law singularity with universal exponent 1/4 at the unitarity.
Furthermore, we discuss the manifestations of OC in spin-echo experiments, as
well as in the energy counting statistic of the Fermi gas following a sudden
quench of the impurity state. Finally, systems in which the itinerant fermions
have two or more hyperfine states provide an even richer playground for
studying non-equilibrium impurity physics, allowing one to explore
non-equilibrium OC and to simulate quantum transport through nano-structures.
This provides a useful connection between cold atomic systems and mesoscopic
quantum transport.Comment: 15 pages, 7 figure
Effect of different 1-methylcyclopropene doses on the postharvest period of pitahaya fruits (Selenicereus megalanthus Haw.)
Colombia is one of the leading producers of yellow dragon fruit, but exports of this fruit is low when compared to the domestic production because most do not meet the requirements of international markets in terms of quality and preservation. As a result, this study aimed to determine the effect of theapplication of 1-methylcyclopropene (1-MCP) on the preservation and quality of dragon fruit, given that it has been effective in the conservation and postharvest quality of many agricultural species allowing longer life, using a completely randomized experiment design with three treatments: 0, 300 and 600 mg L-1 of 1-MCP, with four replications. The 600 mg L-1 of 1-MCP dose was able to maintain the quality of the dragon fruit longer (28 days after harvest (dah)) because it managed to reduce the respiratory rate. The application of 1-MCP did not affect the firmness, loss of mass, total soluble solids, total titratable acidity, or total carotenoids in the fruits. The application of 1-MCP slowed the loss of fruit quality in terms of color because the 600 mg L-1 dose maintained the lightness of the fruits longer, reduced the color changes as expressed in a* and b* values and decreased the chlorophyll degradation
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