Towards coherent optical control of a single hole spin: rabi rotation of a trion conditional on the spin state of the hole

A hole spin is a potential solid-state q-bit, that may be more robust against nuclear spin induced dephasing than an electron spin. Here we propose and demonstrate the sequential preparation, control and detection of a single hole spin trapped on a self-assembled InGaAs/GaAs quantum dot. The dot is embedded in a photodiode structure under an applied electric field. Fast, triggered, initialization of a hole spin is achieved by creating a spin-polarized electron-hole pair with a picosecond laser pulse, and in an applied electric field, waiting for the electron to tunnel leaving a spin-polarized hole. Detection of the hole spin with picoseconds time resolution is achieved using a second picosecond laser pulse to probe the positive trion transition, where a trion is created conditional on the hole spin being detected as a change in photocurrent. Finally, using this setup we observe a Rabi rotation of the hole-trion transition that is conditional on the hole spin, which for a pulse area of 2 pi can be used to impart a phase shift of pi between the hole spin states, a non-general manipulation of the hole spin. (C) 2009 Elsevier Ltd. All rights reserved

Multi-scale ordering of self-assembled InAs/GaAs(001) quantum dots

Ordering phenomena related to the self-assembly of InAs quantum dots (QD) grown on GaAs(001) substrates are experimentally investigated on different length scales. On the shortest length-scale studied here, we examine the QD morphology and observe two types of QD shapes, i.e., pyramids and domes. Pyramids are elongated along the [1-10] directions and are bounded by {137} facets, while domes have a multi-facetted shape. By changing the growth rates, we are able to control the size and size homogeneity of freestanding QDs. QDs grown by using low growth rate are characterized by larger sizes and a narrower size distribution. The homogeneity of buried QDs is measured by photoluminescence spectroscopy and can be improved by low temperature overgrowth. The overgrowth induces the formation of nanostructures on the surface. The fabrication of self-assembled nanoholes, which are used as a template to induce short-range positioning of QDs, is also investigated. The growth of closely spaced QDs (QD molecules) containing 2–6 QDs per QD molecule is discussed. Finally, the long-range positioning of self-assembled QDs, which can be achieved by the growth on patterned substrates, is demonstrated. Lateral QD replication observed during growth of three-dimensional QD crystals is reported

Lateral Ordering of InAs Quantum Dots on Cross-hatch Patterned GaInP

We report the use of partially relaxed tensile as well as compressively strained GaInP layers for lateral ordering of InAs quantum dots with the aid of misfit dislocation networks. The strained layers and the InAs QDs were characterized by means of atomic force microscopy, scanning electron microscopy, and X-ray reciprocal space mapping. The QD-ordering properties of compressive GaInP are found to be very similar with respect to the use of compressive GaInAs, while a significantly stronger ordering of QDs was observed on tensile GaInP. Furthermore, we observed a change of the major type of dislocation in GaInP layers as the growth temperature was modified

Strategies for Controlled Placement of Nanoscale Building Blocks

The capability of placing individual nanoscale building blocks on exact substrate locations in a controlled manner is one of the key requirements to realize future electronic, optical, and magnetic devices and sensors that are composed of such blocks. This article reviews some important advances in the strategies for controlled placement of nanoscale building blocks. In particular, we will overview template assisted placement that utilizes physical, molecular, or electrostatic templates, DNA-programmed assembly, placement using dielectrophoresis, approaches for non-close-packed assembly of spherical particles, and recent development of focused placement schemes including electrostatic funneling, focused placement via molecular gradient patterns, electrodynamic focusing of charged aerosols, and others

Alterations in basal ganglia-cerebello-thalamo-cortical connectivity and whole brain functional network topology in Tourette's syndrome

Tourette Syndrome (TS) is a neuropsychiatric disorder characterized by the presence of motor and vocal tics. Major pathophysiological theories posit a dysfunction of the cortico-striato-thalamo-cortical circuits as being a representative hallmark of the disease. Recent evidence suggests a more widespread dysfunction of brain networks in TS including the cerebellum and going even beyond classic motor pathways.In order to characterize brain network dysfunction in TS, in this study we investigated functional and effective-like connectivity as well as topological changes of basal ganglia-thalamo-cortical and cortico-cerebellar brain networks. We collected resting-state fMRI data from 28 TS patients (age: 32 ± 11 years) and 28 age-matched, healthy controls (age: 31 ± 9 years). Region of interest based (ROI-ROI) bivariate correlation and ROI-ROI bivariate regression were employed as measures of functional and effective-like connectivity, respectively. Graph theoretical measures of centrality (degree, cost, betweenness centrality), functional segregation (clustering coefficient, local efficiency) and functional integration (average path length, global efficiency) were used to assess topological brain network changes.In this study, TS patients exhibited increased basal ganglia-cortical and thalamo-cortical connectivity, reduced cortico-cerebellar connectivity, and an increase in parallel communication through the basal ganglia, thalamus and cerebellum (increased global efficiency). Additionally, we observed a reduction in serial information transfer (reduction in average path length) within the default mode and the salience network.In summary, our findings show that TS is characterized by increased connectivity and functional integration of multiple basal ganglia-thalamo-cortical circuits, suggesting a predominance of excitatory neurotransmission and a lack of brain maturation. Moreover, topological changes of cortico-cerebellar and brain networks involved in interoception may be underestimated neural correlates of tics and the crucial premonitory urge feeling

Adverse events in patients treated with Jak-inhibitors for alopecia areata: A systematic review

Recently, the impressive efficacy of JAK-inhibitors (JAK-I) in alopecia areata (AA) has been described in several studies; however, to date, there is limited information on the safety of JAK-I in AA patients. For this reason, on 18 August 2022, a systematic review was performed to collect the premarketing and postmarketing data on the safety of JAK-I in patients treated for AA, evaluating for each molecule the reported adverse events (AEs) in indexed literature and their frequency. The keywords ‘alopecia areata’ AND ‘Jak-inhibitors OR Janus-kinase Inhibitors’ were searched on PubMed, Embase and Cochrane databases. Of 407 studies retrieved, 28 papers met the requirements and were used in our review, including five RCTs and 23 case series; overall, 1719 patients were included, and the safety of 6 JAK-I was assessed (baricitinib, brepocitinib, deuruxolitinib, ritlecitinib, ruxolitinib and tofacitinib). Systemic JAK-I were well-tolerated, most of the AEs were mild, and the withdrawal rate for AEs was very low and inferior to placebo in controlled studies (1.6% vs. 2.2%). Laboratory abnormalities represented 40.1% of AEs associated with oral JAK-I, which mostly included the rise in cholesterol, transaminase, triglycerides, creatine phosphokinase (CPK) and sporadic cases of neutro/lymphocytopenia. The remaining AEs involved the respiratory tract (20.8%), the skin (17.2%), the urogenital (3.8%), or the gastroenterological (3.4%) tract. Increased rates of infections involved not only the upper (19.0%) and lower (0.3%) respiratory tract, but also the urogenital system (3.6%) and the skin (4.6%). Isolated cases of grade 3 to 4 AEs have been reported, including myocardial infarction, hypertensive urgencies, cellulitis, rhabdomyolysis, neutropenia and high elevation of creatinine kinase. No fatal outcomes were reported. AEs reported with topical formulation included scalp irritation and folliculitis. The main limit of this review is the lack of data related to postmarketing surveillance, which should be maintained on a long-term basis

Adverse events in patients treated with Jak-inhibitors for alopecia areata: a systematic review.

Recently, the impressive efficacy of JAK-inhibitors (JAK-I) in alopecia areata (AA) has been described in several studies; however, to date, there is limited information on the safety of JAK-I in AA patients. For this reason, on the August 18th 2022, a systematic review was performed to collect the pre-marketing and post-marketing data on the safety of JAK-I in patients treated for AA, evaluating for each molecule the reported adverse events (AEs) in indexed literature and their frequency. The keywords "alopecia areata" AND "Jak-inhibitors OR Janus-kinase Inhibitors" were searched on PubMed, Embase, and Cochrane databases. Of 407 studies retrieved, 28 papers met the requirements and were used in our review, including 5 RCTs and 23 case series, overall 1719 patients were included and the safety of 6 JAK-I was assessed (baricitinib, brepocitinib, deuruxolitinib, ritlecitinib, ruxolitinib, tofacitinib). Systemic JAK-I were well tolerated, most of the AEs were mild, and the withdrawal rate for AEs was very low and inferior to placebo in controlled studies (1.6% vs. 2.2%). Laboratory abnormalities represented 40.1% of AEs associated with oral JAK-I, which mostly included the rise in cholesterol, transaminase, triglycerides, creatine phosphokinase (CPK), and sporadic cases of neutro/lymphocytopenia. The remaining AEs involved the respiratory tract (20.8%), the skin (17.2%), the urogenital (3.8%), or the gastroenterological (3.4%) tract. Increased rates of infections involved not only the upper (19.0%) and lower (0.3%) respiratory tract, but also the urogenital system (3.6%), and the skin (4.6%). Isolated cases of grade 3 to 4 AEs have been reported, including myocardial infarction, hypertensive urgencies, cellulitis, rhabdomyolysis, neutropenia, and high elevation of creatinine kinase. No fatal outcomes were reported. AEs reported with topical formulation included scalp irritation and folliculitis. The main limit of this review is the lack of data related to post-marketing surveillance, which should be maintained on a long-term basis