168 research outputs found
Realization of two Fourier-limited solid-state single-photon sources
We demonstrate two solid-state sources of indistinguishable single photons.
High resolution laser spectroscopy and optical microscopy were combined at T =
1.4 K to identify individual molecules in two independent microscopes. The
Stark effect was exploited to shift the transition frequency of a given
molecule and thus obtain single photon sources with perfect spectral overlap.
Our experimental arrangement sets the ground for the realization of various
quantum interference and information processing experiments.Comment: 6 page
Molecules as Sources for Indistinguishable Single Photons
We report on the triggered generation of indistinguishable photons by
solid-state single-photon sources in two separate cryogenic laser scanning
microscopes. Organic fluorescent molecules were used as emitters and
investigated by means of high resolution laser spectroscopy. Continuous-wave
photon correlation measurements on individual molecules proved the isolation of
single quantum systems. By using frequency selective pulsed excitation of the
molecule and efficient spectral filtering of its emission, we produced
triggered Fourier-limited single photons. In a further step, local electric
fields were applied to match the emission wavelengths of two different
molecules via Stark effect. Identical single photons are indispensible for the
realization of various quantum information processing schemes proposed. The
solid-state approach presented here prepares the way towards the integration of
multiple bright sources of single photons on a single chip.Comment: Accepted for publication in J. Mod. Opt. This is the original
submitted versio
Diagnostic management and outcomes of pulmonary tuberculosis suspects admitted to a central hospital in Malawi
Quantum Interference of Tunably Indistinguishable Photons from Remote Organic Molecules
We demonstrate two-photon interference using two remote single molecules as
bright solid-state sources of indistinguishable photons. By varying the
transition frequency and spectral width of one molecule, we tune and explore
the effect of photon distinguishability. We discuss future improvements on the
brightness of single-photon beams, their integration by large numbers on chips,
and the extension of our experimental scheme to coupling and entanglement of
distant molecules
Spectroscopy of Small and Large Biomolecular Ions in Helium-Nanodroplets
A vast number of experiments have now shown that helium nanodroplets are an exemplary cryogenic matrix for spectroscopic investigations. The experimental techniques are well established and involve in most cases the pickup of evaporated neutral species by helium droplets. These techniques have been extended within our research group to enable nanodroplet pickup of anions or cations stored in an ion trap. By using electrospray ionization (ESI) in combination with modern mass spec- trometric methods to supply ions to the trap, an immense variety of mass-to-charge selected species can be doped into the droplets and spectroscopically investigated. We have combined this droplet doping methodology with IR action spectroscopy to investigate anions and cations ranging in size from a few atoms to proteins that consist of thousands of atoms. Herein, we show examples of small complexes of fluoride anions (F-) with CO2 and H2O and carbohydrate molecules. In the case of the small complexes, novel compounds could be identified, and quantum chemistry can in some instances quantitatively explain the results. For biologically relevant complex carbohydrate molecules, the IR spectra are highly diagnostic and allow the differentiation of species that would be difficult or impossible to identify by more conventional methods
New challenges in studying nutrition-disease interactions in the developing world.
Latest estimates indicate that nutritional deficiencies account for 3 million child deaths each year in less-developed countries. Targeted nutritional interventions could therefore save millions of lives. However, such interventions require careful optimization to maximize benefit and avoid harm. Progress toward designing effective life-saving interventions is currently hampered by some serious gaps in our understanding of nutrient metabolism in humans. In this Personal Perspective, we highlight some of these gaps and make some proposals as to how improved research methods and technologies can be brought to bear on the problems of undernourished children in the developing world
The impact of leaving group anomericity on the structure of glycosyl cations of protected galactosides
It has been reported that fragments produced by glycosidic bond breakage in mass spectrometry‐based experiments can retain a memory of their anomeric configuration, which has major implications for glycan sequencing. Herein, we use cryogenic vibrational spectroscopy and ion mobility‐mass spectrometry to study the structure of B‐type fragments of protected galactosides. Cationic fragments were generated from glycosyl donors carrying trichloroacetimidate or thioethyl leaving groups of different anomeric configuration. The obtained infrared signatures indicate that the investigated fragments exhibit an identical structure, which suggests that there is no anomeric memory in B‐type ions of fully protected monosaccharides
Tunable Indistinguishable Photons From Remote Quantum Dots
Single semiconductor quantum dots have been widely studied within devices
that can apply an electric field. In the most common system, the low energy
offset between the InGaAs quantum dot and the surrounding GaAs material limits
the magnitude of field that can be applied to tens of kVcm^-1, before carriers
tunnel out of the dot. The Stark shift experienced by the emission line is
typically 1 meV. We report that by embedding the quantum dots in a quantum well
heterostructure the vertical field that can be applied is increased by over an
order of magnitude whilst preserving the narrow linewidths, high internal
quantum efficiencies and familiar emission spectra. Individual dots can then be
continuously tuned to the same energy allowing for two-photon interference
between remote, independent, quantum dots
Micronutrient malnutrition and wasting in adults with pulmonary tuberculosis with and without HIV co-infection in Malawi
BACKGROUND: Wasting and micronutrient malnutrition have not been well characterized in adults with pulmonary tuberculosis. We hypothesized that micronutrient malnutrition is associated with wasting and higher plasma human immunodeficiency virus (HIV) load in adults with pulmonary tuberculosis. METHODS: In a cross-sectional study involving 579 HIV-positive and 222 HIV-negative adults with pulmonary tuberculosis in Zomba, Malawi, anthropometry, plasma HIV load and plasma micronutrient concentrations (retinol, α-tocopherol, carotenoids, zinc, and selenium) were measured. The risk of micronutrient deficiencies was examined at different severity levels of wasting. RESULTS: Body mass index (BMI), plasma retinol, carotenoid and selenium concentrations significantly decreased by increasing tertile of plasma HIV load. There were no significant differences in plasma micronutrient concentrations between HIV-negative individuals and HIV-positive individuals who were in the lowest tertile of plasma HIV load. Plasma vitamin A concentrations <0.70 μmol/L occurred in 61%, and zinc and selenium deficiency occurred in 85% and 87% respectively. Wasting, defined as BMI<18.5 was present in 59% of study participants and was independently associated with a higher risk of low carotenoids, and vitamin A and selenium deficiency. Severe wasting, defined as BMI<16.0 showed the strongest associations with deficiencies in vitamin A, selenium and plasma carotenoids. CONCLUSIONS: These data demonstrate that wasting and higher HIV load in pulmonary tuberculosis are associated with micronutrient malnutrition
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