ABSTRACT
The excitonic fine structure plays a key role for the quantum light generated by semiconductor quantum dots, both for entangled photon pairs and single photons. Controlling the excitonic fine structure has been demonstrated using electric, magnetic, or strain fields, but not for quantum dots in optical cavities, a key requirement to obtain high source efficiency and near-unity photon indistinguishability. Here, we demonstrate the control of the fine structure splitting for quantum dots embedded in micropillar cavities. We propose and implement a scheme based on remote electrical contacts connected to the pillar cavity through narrow ridges. Numerical simulations show that such a geometry allows for a three-dimensional control of the electrical field. We experimentally demonstrate tuning and reproducible canceling of the fine structure, a crucial step for the reproducibility of quantum light source technology.
ABSTRACT
Semiconductor quantum dots in cavities are promising single-photon sources. Here, we present a path to deterministic operation, by harnessing the intrinsic linear dipole in a neutral quantum dot via phonon-assisted excitation. This enables emission of fully polarized single photons, with a measured degree of linear polarization up to 0.994±0.007, and high population inversion-85% as high as resonant excitation. We demonstrate a single-photon source with a polarized first lens brightness of 0.50±0.01, a single-photon purity of 0.954±0.001, and single-photon indistinguishability of 0.909±0.004.
ABSTRACT
Hong-Ou-Mandel interference is a cornerstone of optical quantum technologies. We explore both theoretically and experimentally how unwanted multiphoton components of single-photon sources affect the interference visibility, and find that the overlap between the single photons and the noise photons significantly impacts the interference. We apply our approach to quantum dot single-photon sources to access the mean wave packet overlap of the single-photon component. This study provides a consistent platform with which to diagnose the limitations of current single-photon sources on the route towards the ideal device.
ABSTRACT
Light states composed of multiple entangled photons-such as cluster states-are essential for developing and scaling-up quantum computing networks. Photonic cluster states can be obtained from single-photon sources and entangling gates, but so far this has only been done with probabilistic sources constrained to intrinsically low efficiencies, and an increasing hardware overhead. Here, we report the resource-efficient generation of polarization-encoded, individually-addressable photons in linear cluster states occupying a single spatial mode. We employ a single entangling-gate in a fiber loop configuration to sequentially entangle an ever-growing stream of photons originating from the currently most efficient single-photon source technology-a semiconductor quantum dot. With this apparatus, we demonstrate the generation of linear cluster states up to four photons in a single-mode fiber. The reported architecture can be programmed for linear-cluster states of any number of photons, that are required for photonic one-way quantum computing schemes.
ABSTRACT
The fluoranthene (Fluo) is one of the most abundant polycyclic aromatic hydrocarbons (PAHs) in human food and in marine compartments. However, the existing data on its genotoxicity is poor and controversial. The aim of this study was to assess in vitro the potential genotoxicity of Fluo in sole and its possible effect on CYP450 modulation. Freshly isolated hepatocytes were exposed for 24 h to a range of Fluo concentrations from 0.5 to 50 µM in both culture flasks and microplate wells. The ethoxyresorufin-O-deethylase (EROD) activity was measured as an indicator of the activity of the cytochrome P450 1A1 (CYP1A1). The genotoxic effects were evaluated by measuring both DNA strand breaks and DNA adducts by the alkaline comet assay and the postlabeling technique respectively. Calf thymus DNA was also exposed to Fluo in the presence of sole liver microsomes in order to check for Fluo DNA adduct formation. In sole hepatocytes, Fluo was shown to induce a decrease in the EROD activity in a concentration-dependent manner. A significant genotoxic effect was observed in terms of DNA strand breakage from an exposure concentration of 5 µM: despite a concentration-dependent effect was observed, it did not follow a linear dose-response. The response was similar whatever the way of exposure in flasks or in wells. One reproducible adduct was detected in the hepatocytes exposed to the highest concentrations of Fluo. The formation of Fluo adducts was confirmed by the detection of one reproducible adduct following in vitro exposure of calf thymus DNA to 100 and 200 µM of Fluo in the presence of sole microsomes. These results demonstrate the potential of sole hepatocytes to metabolize Fluo in 24 h into reactive species, able to induce genotoxicity by DNA strand breakage and DNA adduct formation. Moreover, a miniaturized cell exposure system was validated for further experiments using fewer amounts of hepatocytes and contaminants, and allowing exposure to PAH metabolites.
Subject(s)
Flatfishes/physiology , Fluorenes/toxicity , Hepatocytes/drug effects , Microsomes, Liver/drug effects , Water Pollutants, Chemical/toxicity , Animals , Cells, Cultured , Cytochrome P-450 CYP1A1/metabolism , DNA Adducts/drug effects , DNA Breaks/drug effects , Flatfishes/genetics , Flatfishes/metabolism , Hepatocytes/enzymology , Microsomes, Liver/enzymologyABSTRACT
Two patients presented parotid metastases from adenocarcinoma of kidney. These metastases are rare and may reveal or develop during the course of a cancer of kidney. In the former case diagnosis presents certain difficulties. Treatment of single metastases is by parotidectomy and nephrectomy, prognosis being similar to that of the renal adenocarcinoma.
Subject(s)
Adenocarcinoma/secondary , Kidney Neoplasms , Parotid Neoplasms/secondary , Aged , Humans , Male , Middle AgedABSTRACT
The authors report a case of a child Wilm's tumour with inferior vena cava obstruction. The diagnostic, technical and prognostic features are discussed. Ultrasonography appears to be the best diagnostic method to confirm thrombus in the vena cava and allows the choice of an appropriate surgical technique. The presence of vena cava thrombus does not alter the prognosis.
Subject(s)
Kidney Neoplasms/complications , Thrombosis/etiology , Vena Cava, Inferior , Wilms Tumor/complications , Child, Preschool , Humans , Kidney Neoplasms/surgery , Male , Prognosis , Thrombosis/diagnosis , Thrombosis/surgery , Ultrasonography , Wilms Tumor/surgeryABSTRACT
A 50-year-old man developed a cystadenocarcinoma on a large urachal cyst. Only 15 similar cases have been reported in the published literature, equivalent to less than 10 p. cent of cancers of the urachus. These tumours present certain clinical, radiological, endoscopic, ultrasonographic, and pathological characteristics. As against solid urachal tumours, there is little controversy as to their vestigial origin from the remains of the allantoid canal. Their prognosis is poor, regional recurrences and pulmonary metastases, and complicated or uncomplicated urachal cysts should therefore be systematically excised.
