67 research outputs found
Effects of Raman scattering and attenuation in silica fiber-based parametric frequency conversion
Four-wave mixing in the form of Bragg scattering (BS) has been predicted to
enable quantum noise less frequency conversion by analytic quantum approaches.
Using a semi-classical description of quantum noise that accounts for loss and
stimulated and spontaneous Raman scattering, which are not currently described
in existing quantum approaches, we quantify the impacts of these effects on the
conversion efficiency and on the quantum noise properties of BS in terms of an
induced noise figure (NF). We give an approximate closed-form expression for
the BS conversion efficiency that includes loss and stimulated Raman
scattering, and we derive explicit expressions for the Raman-induced NF from
the semi-classical approach used here.Comment: 14 single col pages, 11 figure
Spectrally pure heralded single photons by spontaneous four-wave mixing in a fiber: reducing impact of dispersion fluctuations
We model the spectral quantum-mechanical purity of heralded single photons
from a photon-pair source based on nondegenerate spontaneous four-wave mixing
taking the impact of distributed dispersion fluctuations into account. The
considered photon-pair-generation scheme utilizes pump-pulse walk-off to
produce pure heralded photons and phase matching is achieved through the
dispersion properties of distinct spatial modes in a few-mode silica step-index
fiber. We show that fiber-core-radius fluctuations in general severely impact
the single-photon purity. Furthermore, by optimizing the fiber design we show
that generation of single photons with very high spectral purity is feasible
even in the presence of large core-radius fluctuations. At the same time,
contamination from spontaneous Raman scattering is greatly mitigated by
separating the single-photon frequency by more than 32 THz from the pump
frequency
Detailed phase matching characterization of inter-modal four-wave mixing in a two-mode fiber
We experimentally characterize the phase matching properties of two inter-modal four-wave mixing processes in a graded index fiber guiding the LP01 and LP11 mode-groups
Cutavirus in cutaneous malignant melanoma
A novel human protoparvovirus related to human bufavirus and preliminarily named cutavirus has been discovered. We detected cutavirus in a sample of cutaneous malignant melanoma by using viral enrichment and high-throughput sequencing. The role of cutaviruses in cutaneous cancers remains to be investigated
âThe people who are out of ârightâ Englishâ: Japanese university students' social evaluations of English language diversity and the internationalisation of Japanese higher education
Previous research indicates that evaluations of speech forms reflect stereotypes of, and attitudes towards, the perceived group(s) of speakers of the language/variety under consideration. This study, employing both implicit and explicit attitude measures, investigates 158 Japanese university students' perceptions of forms of UK, US, Japanese, Chinese, Thai and Indian English speech. The results show a general convergence between students' explicit and implicit attitudes, for instance, regarding US and UK English as the most correct, and solidarity with Japanese speakers of English. The findings are discussed in relation to intergroup relations between the traditional Japanese cohort and specific groups of overseas students, particularly in light of recent internationalisation policies adopted by many Japanese universities, and the resultant increase in international students from South and East Asia
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