Silicon is vital to the computing industry because of the high quality of its native oxide and well-established doping technologies. Isotopic purification has enabled quantum coherence times on the ...order of seconds, thereby placing silicon at the forefront of efforts to create a solid-state quantum processor. We demonstrate strong coupling of a single electron in a silicon double quantum dot to the photonic field of a microwave cavity, as shown by the observation of vacuum Rabi splitting. Strong coupling of a quantum dot electron to a cavity photon would allow for long-range qubit coupling and the long-range entanglement of electrons in semiconductor quantum dots.
Silicon is more than the dominant material in the conventional microelectronics industry: it also has potential as a host material for emerging quantum information technologies. Standard fabrication ...techniques already allow the isolation of single electron spins in silicon transistor-like devices. Although this is also possible in other materials, silicon-based systems have the advantage of interacting more weakly with nuclear spins. Reducing such interactions is important for the control of spin quantum bits because nuclear fluctuations limit quantum phase coherence, as seen in recent experiments in GaAs-based quantum dots. Advances in reducing nuclear decoherence effects by means of complex control still result in coherence times much shorter than those seen in experiments on large ensembles of impurity-bound electrons in bulk silicon crystals. Here we report coherent control of electron spins in two coupled quantum dots in an undoped Si/SiGe heterostructure and show that this system has a nuclei-induced dephasing time of 360 nanoseconds, which is an increase by nearly two orders of magnitude over similar measurements in GaAs-based quantum dots. The degree of phase coherence observed, combined with fast, gated electrical initialization, read-out and control, should motivate future development of silicon-based quantum information processors.
We measure the interdot charge relaxation time T1 of a single electron trapped in an accumulation mode Si/SiGe double quantum dot. The energy level structure of the charge qubit is determined using ...photon assisted tunneling, which reveals the presence of a low-lying excited state. We systematically measure T1 as a function of detuning and interdot tunnel coupling and show that it is tunable over four orders of magnitude, with a maximum of 45 μs for our device configuration.
Big data and extreme-scale computing Asch, M; Moore, T; Badia, R ...
The international journal of high performance computing applications,
07/2018, Letnik:
32, Številka:
4
Journal Article
Recenzirano
Over the past four years, the Big Data and Exascale Computing (BDEC) project organized a series of five international workshops that aimed to explore the ways in which the new forms of data-centric ...discovery introduced by the ongoing revolution in high-end data analysis (HDA) might be integrated with the established, simulation-centric paradigm of the high-performance computing (HPC) community. Based on those meetings, we argue that the rapid proliferation of digital data generators, the unprecedented growth in the volume and diversity of the data they generate, and the intense evolution of the methods for analyzing and using that data are radically reshaping the landscape of scientific computing. The most critical problems involve the logistics of wide-area, multistage workflows that will move back and forth across the computing continuum, between the multitude of distributed sensors, instruments and other devices at the networks edge, and the centralized resources of commercial clouds and HPC centers. We suggest that the prospects for the future integration of technological infrastructures and research ecosystems need to be considered at three different levels. First, we discuss the convergence of research applications and workflows that establish a research paradigm that combines both HPC and HDA, where ongoing progress is already motivating efforts at the other two levels. Second, we offer an account of some of the problems involved with creating a converged infrastructure for peripheral environments, that is, a shared infrastructure that can be deployed throughout the network in a scalable manner to meet the highly diverse requirements for processing, communication, and buffering/storage of massive data workflows of many different scientific domains. Third, we focus on some opportunities for software ecosystem convergence in big, logically centralized facilities that execute large-scale simulations and models and/or perform large-scale data analytics. We close by offering some conclusions and recommendations for future investment and policy review.
Genome-wide association studies (GWAS) have laid the foundation for investigations into the biology of complex traits, drug development and clinical guidelines. However, the majority of discovery ...efforts are based on data from populations of European ancestry
. In light of the differential genetic architecture that is known to exist between populations, bias in representation can exacerbate existing disease and healthcare disparities. Critical variants may be missed if they have a low frequency or are completely absent in European populations, especially as the field shifts its attention towards rare variants, which are more likely to be population-specific
. Additionally, effect sizes and their derived risk prediction scores derived in one population may not accurately extrapolate to other populations
. Here we demonstrate the value of diverse, multi-ethnic participants in large-scale genomic studies. The Population Architecture using Genomics and Epidemiology (PAGE) study conducted a GWAS of 26 clinical and behavioural phenotypes in 49,839 non-European individuals. Using strategies tailored for analysis of multi-ethnic and admixed populations, we describe a framework for analysing diverse populations, identify 27 novel loci and 38 secondary signals at known loci, as well as replicate 1,444 GWAS catalogue associations across these traits. Our data show evidence of effect-size heterogeneity across ancestries for published GWAS associations, substantial benefits for fine-mapping using diverse cohorts and insights into clinical implications. In the United States-where minority populations have a disproportionately higher burden of chronic conditions
-the lack of representation of diverse populations in genetic research will result in inequitable access to precision medicine for those with the highest burden of disease. We strongly advocate for continued, large genome-wide efforts in diverse populations to maximize genetic discovery and reduce health disparities.
Type 2 diabetes mellitus (T2DM) is associated with risk for chronic kidney disease (CKD), which is associated with a decrease in renal myogenic tone - part of renal autoregulatory mechanisms. Novel ...class of drugs used for the treatment of T2DM, dipeptidyl peptidase-4 (DPP-4) inhibitors, have protective effects on the cardiovascular system. A Zucker Diabetic Fatty (ZDF) rat is an animal model of T2DM that displays progressive nephropathy in which inflammation leads to initiation of renal fibrosis and CKD. We hypothesized that CKD in the ZDF rat is related to decrease in myogenic constriction (MC) of intrarenal arteries and that treatment with the DPP-4 inhibitor, vildagliptin, prevents such changes. Renal arteries isolated from 25 weeks old lean, ZDF and ZDF treated with vildagliptin (n=7 in each group) were transferred to an arteriograph to assess agonist and pressure induced contractile responses. Furthermore, blood glucose, proteinuria, focal glomerulosclerosis (FGS) and p22phox mRNA expression of renal tissue were measured. Compared to lean controls, ZDF had significantly increased plasma glucose and cholesterol levels, focal glomerulosclerosis and interstitial α-SMA expression, and urinary protein excretion. ZDF rats also had impaired MC of renal arteries and increased renal p22phox expression. Vildagliptin did not affect plasma glucose levels or proteinuria, but effectively decreased glomerulosclerosis and restored MC and p22phox expression to the levels found in lean rats. Based on these data, it can be suggested that vildagliptin treatment protects diabetic rats from the loss of renal vascular reactivity and the development of glomerulosclerosis perhaps secondary to a reduction in oxidative stress.
The lithium complexes Li{N(SiMe3)C(R1)C(R2)(C5H4N-2)}2 (1a, 2a, and 3a) were each treated with MCl4 to afford the racemic complexes M{N(SiMe3)C(R1)C(R2)(C5H4N-2)}2Cl2 (M = Zr, R1 = Ph, R2 = H (1b); M ...= Zr, R1 = But, R2 = H (2b); M = Hf, R1 = But, R2 = H (2c); M = Zr, R1 = Ph, R2 = SiMe3 (3b)). Similarly, Li{N(SiMe3)C(Ph)C(R)(C9H6N-2)} (4a and 5a) afforded the racemic complexes Zr{N(SiMe3)C(Ph)C(R)(C9H6N-2)}2Cl2 (R = H (4b); R = SiMe3 (5b)). X-ray structural analysis of 2b, 2c, and 3b revealed that these complexes have C 2 octahedral geometries with their chloride ligands in cis positions. Molecular orbital calculations on model systems of the bis{3-(2-pyridyl)-1-azaallyl}zirconium system Zr(LL)22+ (LL = N(H)C(H)C(H)(2-C5H4N) demonstrate that (i) the frontier orbitals are similar to those of Zr(η5-C5H5)22+ and (ii) the bis{3-(2-pyridyl)-1-azaallyl} ligand environment is more electron-donating, making the zirconium system less electrophilic. Conproportionation of ZrCl4 with Zr{N(SiMe3)C(R1)C(R2)(C5H4N-2)}2Cl2 or Zr{N(SiMe3)C(Ph)C(SiMe3)(C9H6N-2)}2Cl2 afforded the mono(1-azaallyl)zirconium complexes Zr{N(SiMe3)C(R1)C(R2)(C5H4N-2)}Cl3 (R1 = But, R2 = H (2d); R1 = Ph, R2 = SiMe3 (3d)) and Zr{N(SiMe3)C(Ph)C(SiMe3)(C9H6N-2)}Cl3 (5d), respectively. When activated with methylaluminoxane (MAO), these compounds were highly active in ethylene polymerization. Compound 3d also showed modest activity in the polymerization of 1-hexene and the copolymerization of ethylene and 1-hexene.
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