42 research outputs found
Deterministic entanglement between a propagating photon and a singlet--triplet qubit in an optically active quantum dot molecule
Two-electron charged self-assembled quantum dot molecules exhibit a
decoherence-avoiding singlet-triplet qubit subspace and an efficient
spin-photon interface. We demonstrate quantum entanglement between emitted
photons and the spin-qubit after the emission event. We measure the overlap
with a fully entangled state to be , exceeding the threshold of
required to prove the non-separability of the density matrix of the
system. The photonic qubit is encoded in two photon states with an energy
difference larger than the timing resolution of existing detectors. We devise a
novel heterodyne detection method, enabling projective measurements of such
photonic color qubits along any direction on the Bloch sphere
Geometric matrix midranges
We define geometric matrix midranges for positive definite Hermitian matrices and study the midrange problem from a number of perspectives. Special attention is given to the midrange of two positive definite matrices before considering the extension of the problem to matrices. We compare matrix midrange statistics with the scalar and vector midrange problem and note the special significance of the matrix problem from a computational standpoint. We also study various aspects of geometric matrix midrange statistics from the viewpoint of linear algebra, differential geometry and convex optimization.ECH2020 EUROPEAN RESEARCH COUNCIL (ERC) (670645
Quantum nature of a strongly-coupled single quantum dot-cavity system
Cavity quantum electrodynamics (QED) studies the interaction between a
quantum emitter and a single radiation-field mode. When an atom is in strong
coupling with a cavity mode1,2, it is possible to realize key quantum
information processing (QIP) tasks, such as controlled coherent coupling and
entanglement of distinguishable quantum systems. Realizing these tasks in the
solid state is clearly desirable, and coupling semiconductor self-assembled
quantum dots (QDs) to monolithic optical cavities is a promising route to this
end. However, validating the efficacy of QDs in QIP applications requires
confirmation of the quantum nature of the QD-cavity system in the strong
coupling regime. Here we find a confirmation by observing quantum correlations
in photoluminescence (PL) from a photonic crystal (PC) nanocavity3-5
interacting with one, and only one, QD located precisely at the cavity electric
field maximum. When off-resonance, photon emission from the cavity mode and QD
excitons is anti-correlated at the level of single quanta, proving that the
mode is driven solely by the QD despite an energy mis-match between cavity and
excitons. When tuned into resonance, the exciton and photon enter the
strong-coupling regime of cavity-QED and the QD lifetime reduces by a factor of
120. The photon stream from the cavity becomes anti-bunched, proving that the
coupled exciton/photon system is in the quantum anharmonic regime. Our
observations unequivocally show that QIP tasks requiring the quantum nonlinear
regime are achievable in the solid state.Comment: 14 pages 4 figure
Dioxin Induces Genomic Instability in Mouse Embryonic Fibroblasts
Ionizing radiation and certain other exposures have been shown to induce genomic instability (GI), i.e., delayed genetic damage observed many cell generations later in the progeny of the exposed cells. The aim of this study was to investigate induction of GI by a nongenotoxic carcinogen, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Mouse embryonic fibroblasts (C3H10T1/2) were exposed to 1, 10 or 100 nM TCDD for 2 days. Micronuclei (MN) and expression of selected cancer-related genes were assayed both immediately and at a delayed point in time (8 days). For comparison, similar experiments were done with cadmium, a known genotoxic agent. TCDD treatment induced an elevated frequency of MN at 8 days, but not directly after the exposure. TCDD-induced alterations in gene expression were also mostly delayed, with more changes observed at 8 days than at 2 days. Exposure to cadmium produced an opposite pattern of responses, with pronounced effects immediately after exposure but no increase in MN and few gene expression changes at 8 days. Although all responses to TCDD alone were delayed, menadione-induced DNA damage (measured by the Comet assay), was found to be increased directly after a 2-day TCDD exposure, indicating that the stability of the genome was compromised already at this time point. The results suggested a flat dose-response relationship consistent with dose-response data reported for radiation-induced GI. These findings indicate that TCDD, although not directly genotoxic, induces GI, which is associated with impaired DNA damage response
The effect of maternal deprivation between 6 and 10 weeks of age upon the behaviour of alsatian puppies
Improvement of the transport properties of a high-mobility electron system by intentional parallel conduction
Heterogeneity of islet pathology in two infants with recent onset diabetes mellitus
The mechanisms by which the beta cells of pancreatic islets are destroyed in insulin-dependent diabetes mellitus (IDDM) are poorly understood. In this report the pancreatic histo- and immunopathology of two children, both HLA-DR 3/4, DQ 2/8 positive and who both died from cerebral oedema within a day of clinical diagnosis of IDDM, were investigated. Patient 1, a 14-month-old girl, had a 4-week history of polydipsia and polyuria. Patient 2, a 3-year-old boy, had 2 days of illness. Both patients had a similarly severe loss of insulin cells but differed markedly as to the extent of lymphocytic islet infiltration (insulitis). Apart from insulitis, marked islet macrophage infiltration was demonstrated in both patients with the HAM-56 monoclonal antibody. Neither patient showed aberrant expression of HLA class II antigens on insulin-immunoreactive cells, but allele-specific HLA-DQ8 expression was evident on endothelial cells. Glutamic acid decarboxylase immunoreactivity was detected in both insulin- and glucagon-immunoreactive cells. It is concluded that the heterogeneity of islet pathology, especially insulitis, may reflect different dynamics and extent rather than different pathomechanisms of immune destruction of islets in IDDM