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

Single-Photon Imaging and Efficient Coupling to Single Plasmons

We demonstrate strong coupling of single photons emitted by individual molecules at cryogenic and ambient conditions to individual nanoparticles. We provide images obtained both in transmission and reflection, where an efficiency greater than 55% was achieved in converting incident narrow-band photons to plasmon-polaritons (plasmons) of a silver nanoparticle. Our work paves the way to spectroscopy and microscopy of nano-objects with sub-shot noise beams of light and to triggered generation of single plasmons and electrons in a well-controlled manner

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

A planar dielectric antenna for directional single-photon emission and near-unity collection efficiency

Single emitters have been considered as sources of single photons in various contexts such as cryptography, quantum computation, spectroscopy, and metrology. The success of these applications will crucially rely on the efficient directional emission of photons into well-defined modes. To accomplish a high efficiency, researchers have investigated microcavities at cryogenic temperatures, photonic nanowires, and near-field coupling to metallic nano-antennas. However, despite an impressive progress, the existing realizations substantially fall short of unity collection efficiency. Here we report on a theoretical and experimental study of a dielectric planar antenna, which uses a layered structure for tailoring the angular emission of a single oriented molecule. We demonstrate a collection efficiency of 96% using a microscope objective at room temperature and obtain record detection rates of about 50 MHz. Our scheme is wavelength-insensitive and can be readily extended to other solid-state emitters such as color centers and semiconductor quantum dots

Chondroitin Sulfate Disaccharides in the Gas Phase: Differentiation and Conformational Constraints

Glycosaminoglycans (GAGs) are a family of complex carbohydrates vital to all mammalian organisms and involved in numerous biological processes. Chondroitin and dermatan sulfate, an important class of GAGs, are linear macromolecules consisting of disaccharide building blocks of N-acetylgalactosamine and two different uronic acids. The varying degree and the site of sulfation render their characterization challenging. Here, we combine mass spectrometry with cryogenic infrared spectroscopy in the wavenumber range from 1000 to 1800 cm-1. Fingerprint spectra were recorded for a comprehensive set of disaccharides bearing all known motifs of sulfation. In addition, state-of-the-art quantum chemical calculations were performed to aid the understanding of the differences in the experimental fingerprint spectra. The results show that the degree and position of charged sulfate groups define the size of the conformational landscape in the gas phase. The detailed understanding of cryogenic infrared spectroscopy for acidic and often highly sulfated glycans may pave the way to utilize the technique in fragment-based sequencing approaches

Anti-Retroviral Treatment Outcomes among Older Adults in Zomba District, Malawi

BACKGROUND: There are approximately 3 million people aged 50 and older in sub-Saharan Africa who are HIV-positive. Despite this, little is known about the characteristics of older adults who are on treatment and their treatment outcomes. METHODS: A retrospective cohort analysis was performed using routinely collected data with Malawi Ministry of Health monitoring tools from facilities providing antiretroviral therapy services in Zomba district. Patients aged 25 years and older initiated on treatment from July 2005 to June 2010 were included. Differences in survival, by age group, were determined using Kaplan-Meier survival plots and Cox proportional hazards regression models. RESULTS: There were 10,888 patients aged 25 and older. Patients aged 50 and older (N = 1419) were more likely to be male (P<0.0001) and located in rural areas (P = 0.003) than those aged 25-49. Crude survival estimates among those aged 50-59 were not statistically different from those aged 25-49 (P = 0.925). However, survival among those aged 60 and older (N = 345) was worse (P = 0.019) than among those 25-59. In the proportional hazards model, after controlling for sex and stage at initiation, survival in those aged 50-59 did not differ significantly from those aged 25-49 (hazard ratio 1.00 (95% CI: 0.79 to 1.27; P = 0.998) but the hazard ratio was 1.46 (95% CI: 1.03 to 2.06; P = 0.032) for those aged 60 and older compared to those aged 25-49. CONCLUSIONS: Treatment outcomes of those aged 50-59 are similar to those aged 25-49. A better understanding of how older adults present for and respond to treatment is critical to improving HIV services

Decoding the Fucose Migration Product during Mass-Spectrometric analysis of Blood Group Epitopes

Fucose is a signaling carbohydrate that is attached at the end of glycan processing. It is involved in a range of processes, such as the selectin-dependent leukocyte adhesion or pathogen-receptor interactions. Mass-spectrometric techniques, which are commonly used to determine the structure of glycans, frequently show fucose-containing chimeric fragments that obfuscate the analysis. The rearrangement leading to these fragments—often referred to as fucose migration—has been known for more than 25 years, but the chemical identity of the rearrangement product remains unclear. In this work, we combine ion-mobility spectrometry, radical-directed dissociation mass spectrometry, cryogenic IR spectroscopy of ions, and density-functional theory calculations to deduce the product of the rearrangement in the model trisaccharides Lewis x and blood group H2. The structural search yields the fucose moiety attached to the galactose with an α(1→6) glycosidic bond as the most likely product

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

Efficient coupling of photons to a single molecule and the observation of its resonance fluorescence

Single dye molecules at cryogenic temperatures display many spectroscopic phenomena known from free atoms and are thus promising candidates for fundamental quantum optical studies. However, the existing techniques for the detection of single molecules have either sacrificed the information on the coherence of the excited state or have been inefficient. Here we show that these problems can be addressed by focusing the excitation light near to the absorption cross section of a molecule. Our detection scheme allows us to explore resonance fluorescence over 9 orders of magnitude of excitation intensity and to separate its coherent and incoherent parts. In the strong excitation regime, we demonstrate the first observation of the Mollow triplet from a single solid-state emitter. Under weak excitation we report the detection of a single molecule with an incident power as faint as 150 attoWatt, paving the way for studying nonlinear effects with only a few photons.Comment: 6 figure