Quantum entanglement and information processing via excitons in optically-driven quantum dots

We show how optically-driven coupled quantum dots can be used to prepare maximally entangled Bell and Greenberger-Horne-Zeilinger states. Manipulation of the strength and duration of the selective light-pulses needed for producing these highly entangled states provides us with crucial elements for the processing of solid-state based quantum information. Theoretical predictions suggest that several hundred single quantum bit rotations and Controlled-Not gates could be performed before decoherence of the excitonic states takes place.Comment: 3 separate PostScript Figures + 7 pages. Typos corrected. Minor changes added. This updated version is to appear in PR

Digenic inheritance of human primary microcephaly delineates centrosomal and non-centrosomal pathways.

Primary microcephaly (PM) is characterized by a small head since birth and is vastly heterogeneous both genetically and phenotypically. While most cases are monogenic, genetic interactions between Aspm and Wdr62 have recently been described in a mouse model of PM. Here, we used two complementary, holistic in vivo approaches: high throughput DNA sequencing of multiple PM genes in human patients with PM, and genome-edited zebrafish modeling for the digenic inheritance of PM. Exomes of patients with PM showed a significant burden of variants in 75 PM genes, that persisted after removing monogenic causes of PM (e.g., biallelic pathogenic variants in CEP152). This observation was replicated in an independent cohort of patients with PM, where a PM gene panel showed in addition that the burden was carried by six centrosomal genes. Allelic frequencies were consistent with digenic inheritance. In zebrafish, non-centrosomal gene casc5 -/- produced a severe PM phenotype, that was not modified by centrosomal genes aspm or wdr62 invalidation. A digenic, quadriallelic PM phenotype was produced by aspm and wdr62. Our observations provide strong evidence for digenic inheritance of human PM, involving centrosomal genes. Absence of genetic interaction between casc5 and aspm or wdr62 further delineates centrosomal and non-centrosomal pathways in PM

Local optical spectroscopy of semiconductor nanostructures in the linear regime

We present a theoretical approach to calculate the local absorption spectrum of excitons confined in a semiconductor nanostructure. Using the density-matrix formalism, we derive a microscopic expression for the nonlocal susceptibility, both in the linear and nonlinear regimes, which includes a three-dimensional description of electronic quantum states and their Coulomb interaction. The knowledge of the nonlocal susceptibility allows us to calculate a properly defined local absorbed power, which depends on the electromagnetic field distribution. We report on explicit calculations of the local linear response of excitons confined in single and coupled T-shaped quantum wires with realistic geometry and composition. We show that significant interference effects in the interacting electron-hole wave function induce new features in the space-resolved optical spectra, particularly in coupled nanostructures. When the spatial extension of the electromagnetic field is comparable to the exciton Bohr radius, Coulomb effects on the local spectra must be taken into account for a correct assignment of the observed features

Učinak bakra na toksičnost i genotoksičnost kadmija u vodenoj leći (Lemna minor L.)

We investigated interactions between copper (in the concentrations of 2.5 μmol L-1 and 5 μmol L-1) and cadmium (5 μmol L-1) in common duckweed (Lemna minor L.) by exposing it to either metal or to their combinations for four or seven days. Their uptake increased with time, but it was lower in plants treated with combinations of metals than in plants treated with either metal given alone. In separate treatments, either metal increased malondialdehyde (MDA) level and catalase and peroxidase activity. Both induced DNA damage, but copper did it only after 7 days of treatment. On day 4, the combination of cadmium and 5 μmol L-1 copper additionally increased MDA as well as catalase and peroxidase activity. In contrast, on day 7, MDA dropped in plants treated with combinations of metals, and especially with 2.5 μmol L-1 copper plus cadmium. In these plants, catalase activity was higher than in copper treated plants. Peroxidase activity increased after treatment with cadmium and 2.5 μmol L-1 copper but decreased in plants treated with cadmium and 5 μmol L-1 copper. Compared to copper alone, combinations of metals enhanced DNA damage after 4 days of treatment but it dropped on day 7. In conclusion, either metal given alone was toxic/genotoxic and caused oxidative stress. On day 4 of combined treatment, the higher copper concentration was more toxic than either metal alone. In contrast, on day 7 of combined treatment, the lower copper concentration showed lower oxidative and DNA damage. These complex interactions can not be explained by simple antagonism and/or synergism. Further studies should go in that direction.U svrhu istraživanja interakcija između bakra kao esencijalnog elementa te kadmija kao neesencijalnog i toksičnog metala, vodenu leću Lemna minor L. uzgajali smo na podlogama s kadmijem (5 μmol L-1) odnosno s bakrom (2,5 μmol L-1 i 5 μmol L-1) te s njihovim kombinacijama. Unos metala u biljke povećavao se s trajanjem pokusa, a kod kombinacije metala u biljkama je izmjerena niža količina kadmija nego u onima uzgajanima samo na kadmiju. U biljkama tretiranim pojedinačnim metalom došlo je do povećanja sadržaja malondialdehida (MDA) te aktivnosti katalaze i peroksidaze u odnosu na kontrolne biljke. Također, primijećeno je oštećenje DNA iako kod bakra tek sedmog dana tretmana. Količina MDA i aktivnost obaju enzima dodatno se povećala na tretmanu kombinacijom kadmija i bakra (5 μmol L-1) nakon četvrtog dana pokusa, dok se količina MDA smanjila nakon sedmog dana kod kombinacije kadmija i 2,5 μmol L-1 bakra. U tim biljkama primijećena je i veća aktivnost katalaze, dok je aktivnost peroksidaze porasla na tretmanu kadmijem i 2,5 μmol L-1 bakrom, ali se smanjila na tretmanu kadmijem i 5 μmol L-1 bakrom. Oštećenje DNA koje je bilo veće kod kombinacije metala nakon četvrtog dana, osobito u usporedbi sa samim bakrom, smanjilo se nakon sedmog dana pokusa. Iz ovih rezultata može se zaključiti da su oba metala u istraživanim koncentracijama toksična i genotoksična za vodenu leću i da uzrokuju oksidacijski stres. Kadmij u kombinaciji s bakrom više koncentracije bio je toksičniji od pojedinačnih metala nakon četvrtog dana pokusa, dok su u biljaka tretiranih kombinacijom kadmija i bakra niže koncentracije toksični učinci bili manji. Budući da su primijećene interakcije vrlo kompleksne i ne uključuju samo antagonizam odnosno sinergizam potrebna su daljnja istraživanja