2,925 research outputs found
Diamond chemical vapor deposition on optical fibers for fluorescence waveguiding
A technique has been developed for depositing diamond crystals on the
endfaces of optical fibers and capturing the fluorescence generated by
optically active defects in the diamond into the fiber. This letter details the
diamond growth on optical fibers and transmission of fluorescence through the
fiber from the nitrogen-vacancy (N-V) color center in diamond. Control of the
concentration of defects incorporated during the chemical vapor deposition
(CVD) growth process is also demonstrated. These are the first critical steps
in developing a fiber coupled single photon source based on optically active
defect centers in diamond.Comment: 10 pages, 3 figure
A highly efficient two level diamond based single photon source
An unexplored diamond defect centre which is found to emit stable single
photons at a measured rate of 1.6 MHz at room temperature is reported. The
novel centre, identified in chemical vapour deposition grown diamond crystals,
exhibits a sharp zero phonon line at 734 nm with a full width at half maximum
of ~ 4 nm. The photon statistics confirm the center is a single emitter and
provides direct evidence of the first true two-level single quantum system in
diamond.Comment: 3 pages, 4 figure
A wider Europe? The view from Russia, Belarus and Ukraine
On the evidence of national surveys conducted between 2000 and 2006, there is a declining sense of European self-identity in the three Slavic post-Soviet republics of Russia, Belarus and Ukraine. Attitudes towards the European Union and the possibility of membership are broadly supportive, but with a substantial proportion who find it difficult to express a view, and substantial proportions are poorly informed in comparison with the general public in EU member or prospective member countries. Those who are better informed are more likely to favour EU membership and vice versa. Generally, socioeconomic characteristics (except for age and region) are relatively poor predictors of support for EU membership as compared with attitudinal variables. But ‘Europeanness’ should not be seen as a given, and much will depend on whether EU member countries emphasize what is common to east and west or establish ‘new dividing lines’ in place of those of the cold war
Demonstration of the spatial separation of the entangled quantum side-bands of an optical field
Quantum optics experiments on "bright" beams typically probe correlations
between side-band modes. However the extra degree of freedom represented by
this dual mode picture is generally ignored. We demonstrate the experimental
operation of a device which can be used to separate the quantum side-bands of
an optical field. We use this device to explicitly demonstrate the quantum
entanglement between the side-bands of a squeezed beam
Three-dimensional device fabrication in monocrystalline diamond using FIB and a novel lift-off technique
Strong-field terahertz-optical mixing in excitons
Driving a double-quantum-well excitonic intersubband resonance with a
terahertz (THz) electric field of frequency \omega_{THz} generated terahertz
optical sidebands \omega=\omega_{THz}+\omega_{NIR} on a weak NIR probe. At high
THz intensities, the intersubband dipole energy which coupled two excitons was
comparable to the THz photon energy. In this strong-field regime the sideband
intensity displayed a non-monotonic dependence on the THz field strength. The
oscillating refractive index which gives rise to the sidebands may be
understood by the formation of Floquet states, which oscillate with the same
periodicity as the driving THz field.Comment: 4 pages, 6 figure
Unconditional Continuous Variable Dense Coding
We investigate the conditions under which unconditional dense coding can be
achieved using continuous variable entanglement. We consider the effect of
entanglement impurity and detector efficiency and discuss experimental
verification. We conclude that the requirements for a strong demonstration are
not as stringent as previously thought and are within the reach of present
technology
A Bright Spatially-Coherent Compact X-ray Synchrotron Source
Each successive generation of x-ray machines has opened up new frontiers in
science, such as the first radiographs and the determination of the structure
of DNA. State-of-the-art x-ray sources can now produce coherent high brightness
keV x-rays and promise a new revolution in imaging complex systems on nanometre
and femtosecond scales. Despite the demand, only a few dedicated synchrotron
facilities exist worldwide, partially due the size and cost of conventional
(accelerator) technology. Here we demonstrate the use of a recently developed
compact laser-plasma accelerator to produce a well-collimated,
spatially-coherent, intrinsically ultrafast source of hard x-rays. This method
reduces the size of the synchrotron source from the tens of metres to
centimetre scale, accelerating and wiggling a high electron charge
simultaneously. This leads to a narrow-energy spread electron beam and x-ray
source that is >1000 times brighter than previously reported plasma wiggler and
thus has the potential to facilitate a myriad of uses across the whole spectrum
of light-source applications.Comment: 5 pages, 4 figure
Pregnancy is associated with elevation of liver enzymes in HIV-positive women on antiretroviral therapy.
The objective of this study is to assess whether pregnancy is associated with an increased risk of liver enzyme elevation (LEE) and severe LEE in HIV-positive women on antiretroviral therapy (ART)
Uncoupling of Genomic and Epigenetic Signals in the Maintenance and Inheritance of Heterochromatin Domains in Fission Yeast
Many essential aspects of genome function, including gene expression and chromosome segregation, are mediated throughout development and differentiation by changes in the chromatin state. Along with genomic signals encoded in the DNA, epigenetic processes regulate heritable gene expression patterns. Genomic signals such as enhancers, silencers, and repetitive DNA, while required for the establishment of alternative chromatin states, have an unclear role in epigenetic processes that underlie the persistence of chromatin states throughout development. Here, we demonstrate in fission yeast that the maintenance and inheritance of ectopic heterochromatin domains are independent of the genomic sequences necessary for their de novo establishment. We find that both structural heterochromatin and gene silencing can be stably maintained over an ∼10-kb domain for up to hundreds of cell divisions in the absence of genomic sequences required for heterochromatin establishment, demonstrating the long-term persistence and stability of this chromatin state. The de novo heterochromatin, despite the absence of nucleation sequences, is also stably inherited through meiosis. Together, these studies provide evidence for chromatin-dependent, epigenetic control of gene silencing that is heritable, stable, and self-sustaining, even in the absence of the originating genomic signals
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