125 research outputs found
On-chip resonantly-driven quantum emitter with enhanced coherence
Advances in nanotechnology provide techniques for the realisation of integrated quantum-optical circuits for on-chip quantum information processing(QIP). The indistinguishable single photons, required for such devices can be generated by parametric down-conversion, or from quantum emitters such as colour centres and quantum dots(QDs). Among these, semiconductor QDs offer distinctive capabilities including on-demand operation, coherent control, frequency tuning and compatibility with semiconductor nanotechnology. Moreover, the coherence of QD photons can be significantly enhanced in resonance fluorescence(RF) approaching at its best the coherence of the excitation laser. However, the implementation of QD RF in scalable on-chip geometries remains challenging due to the need to suppress stray laser photons. Here we report on-chip QD RF coupled into a single-mode waveguide with negligible resonant laser background and show that the coherence is enhanced compared to off-resonant excitation. The results pave the way to a novel class of integrated quantum-optical devices for on-chip QIP with embedded resonantly-driven quantum emitters
On-chip resonantly-driven quantum emitter with enhanced coherence
Advances in nanotechnology provide techniques for the realisation of integrated quantum-optical circuits for on-chip quantum information processing(QIP). The indistinguishable single photons, required for such devices can be generated by parametric down-conversion, or from quantum emitters such as colour centres and quantum dots(QDs). Among these, semiconductor QDs offer distinctive capabilities including on-demand operation, coherent control, frequency tuning and compatibility with semiconductor nanotechnology. Moreover, the coherence of QD photons can be significantly enhanced in resonance fluorescence(RF) approaching at its best the coherence of the excitation laser. However, the implementation of QD RF in scalable on-chip geometries remains challenging due to the need to suppress stray laser photons. Here we report on-chip QD RF coupled into a single-mode waveguide with negligible resonant laser background and show that the coherence is enhanced compared to off-resonant excitation. The results pave the way to a novel class of integrated quantum-optical devices for on-chip QIP with embedded resonantly-driven quantum emitters
Isolation and structural determination of non-racemic tertiary cathinone derivatives
The racemic tertiary cathinones N,N-dimethylcathinone (1), N,N-diethylcathinone (2) and 2-(1-pyrrolidinyl)-propiophenone (3) have been prepared in reasonable yield and characterized using NMR and mass spectroscopy. HPLC indicates that these compounds are isolated as the anticipated racemic mixture. These can then be co-crystallized with (+)-O,O′-di-p-toluoyl-D-tartaric, (+)-O,O′-dibenzoyl-D-tartaric and (−)-O,O′-dibenzoyl-L-tartaric acids giving the single enantiomers S and R respectively of 1, 2 and 3, in the presence of sodium hydroxide through a dynamic kinetic resolution. X-ray structural determination confirmed the enantioselectivity. The free amines could be obtained following basification and extraction. In methanol these are reasonably stable for the period of several hours, and their identity was confirmed by HPLC and CD spectroscopy
Redshifting Rings of Power
The cosmic microwave background (CMB) has provided a precise template for
features in the linear power spectrum: the matter-radiation turnover, sound
horizon drop, and acoustic oscillations. In a two dimensional power spectrum in
redshift and angular space, the features appear as distorted rings, and yield
simultaneous, purely geometric, measures of the Hubble parameter H(z) and
angular diameter distance D_A(z) via an absolute version of the
Alcock-Paczynski test. Employing a simple Fisher matrix tool, we explore how
future surveys can exploit these rings of power for dark energy studies. High-z
CMB determinations of H and D_A are best complemented at moderate to low
redshift (z < 0.5) with a population of objects that are at least as abundant
as clusters of galaxies. We find that a sample similar to that of the ongoing
SDSS Luminous Red Galaxy (LRG) survey can achieve statistical errors at the ~5%
level for D_A(z) and H(z) in several redshift bins. This, in turn, implies
errors of sigma(w)=0.03-0.05 for a constant dark energy equation of state in a
flat universe. Deep galaxy cluster surveys such as the planned South Pole
Telescope (SPT) survey, can extend this test out to z~1 or as far as redshift
followup is available. We find that the expected constraints are at the
sigma(w)=0.04-0.08 level, comparable to galaxies and complementary in redshift
coverage.Comment: 8 pages, 5 figures submitted to PR
Detectability of Tensor Perturbations Through CBR Anisotropy (final published version)
Detection of the tensor perturbations predicted in inflationary models is
important for testing inflation as well as for reconstructing the inflationary
potential. We show that because of cosmic variance the tensor contribution to
the square of the CBR quadrupole anisotropy must be greater than about 20\% of
the scalar contribution to ensure a statistically significant detection of
tensor perturbations. This sensitivity could be achieved by full-sky
measurements on angular scales of and .Comment: 10 pages, uu-encoded postscript file, FERMILAB-PUB-94/175-
Detector Description and Performance for the First Coincidence Observations between LIGO and GEO
For 17 days in August and September 2002, the LIGO and GEO interferometer
gravitational wave detectors were operated in coincidence to produce their
first data for scientific analysis. Although the detectors were still far from
their design sensitivity levels, the data can be used to place better upper
limits on the flux of gravitational waves incident on the earth than previous
direct measurements. This paper describes the instruments and the data in some
detail, as a companion to analysis papers based on the first data.Comment: 41 pages, 9 figures 17 Sept 03: author list amended, minor editorial
change
Characterization of optical properties and surface roughness profiles: The Casimir force between real materials
The Lifshitz theory provides a method to calculate the Casimir force between
two flat plates if the frequency dependent dielectric function of the plates is
known. In reality any plate is rough and its optical properties are known only
to some degree. For high precision experiments the plates must be carefully
characterized otherwise the experimental result cannot be compared with the
theory or with other experiments. In this chapter we explain why optical
properties of interacting materials are important for the Casimir force, how
they can be measured, and how one can calculate the force using these
properties. The surface roughness can be characterized, for example, with the
atomic force microscope images. We introduce the main characteristics of a
rough surface that can be extracted from these images, and explain how one can
use them to calculate the roughness correction to the force. At small
separations this correction becomes large as our experiments show. Finally we
discuss the distance upon contact separating two rough surfaces, and explain
the importance of this parameter for determination of the absolute separation
between bodies.}Comment: 33 pages, 14 figures, to appear in Springer Lecture Notes in Physics,
Volume on Casimir Physics, edited by Diego Dalvit, Peter Milonni, David
Roberts, and Felipe da Ros
Evaluation of electrophoretic profile and albumin quota in the cerebrospinal fluid of dogs with distemper showing or not neurvous signs
Entomopathogenic nematodes for the control of phorid and sciarid flies in mushroom crops
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