201 research outputs found
'Sawfish' Photonic Crystal Cavity for Near-Unity Emitter-to-Fiber Interfacing in Quantum Network Applications
Photon loss is one of the key challenges to overcome in complex photonic
quantum applications. Photon collection efficiencies directly impact the amount
of resources required for measurement-based quantum computation and
communication networks. Promising resources include solid-state quantum light
sources, however, efficiently coupling light from a single quantum emitter to a
guided mode remains demanding. In this work, we eliminate photon losses by
maximizing coupling efficiencies in an emitter-to-fiber interface. We develop a
waveguide-integrated 'Sawfish' photonic crystal cavity and use finite element
simulations to demonstrate that our system transfers, with 97.4% efficiency,
the zero-phonon line emission of a negatively-charged tin vacancy center in
diamond adiabatically to a single-mode fiber. A surrogate model trained by
machine learning provides quantitative estimates of sensitivities to
fabrication tolerances. Our corrugation-based design proves robust under
state-of-the-art nanofabrication parameters, maintaining an emitter-to-fiber
coupling efficiency of 88.6%. To demonstrate its potential in reducing resource
requirements, we apply the Sawfish cavity to a recent one-way quantum repeater
protocol.Comment: Main part: 16 pages, 7 figure
Visible wavelength spectral tuning of absorption and circular dichroism of DNA-assembled Au/Ag core-shell nanorod assemblies
Plasmonic nanoparticles have unique properties which can be harnessed to manipulate light at the nanoscale. With recent advances in synthesis protocols that increase their stability, gold-silver core-shell nanoparticles have become suitable building blocks for plasmonic nanostructures to expand the range of attainable optical properties. Here we tune the plasmonic response of gold-silver core-shell nanorods over the visible spectrum by varying the thickness of the silver shell. Through the chiral arrangement of the nanorods with the help of various DNA origami designs, the spectral tunability of the plasmon resonance frequencies is transferred into circular dichroism signals covering the spectrum from 400 nm to 700 nm. Our approach could aid in the construction of better sensors as well as metamaterials with a tunable optical response in the visible region
On the origin of chirality in plasmonic meta-molecules
Chirality is a fundamental feature in all domains of nature, ranging from
particle physics over electromagnetism to chemistry and biology. Chiral objects
lack a mirror plane and inversion symmetry and therefore cannot be spatially
aligned with their mirrored counterpart, their enantiomer. Both natural
molecules and artificial chiral nanostructures can be characterized by their
light-matter interaction, which is reflected in circular dichroism (CD). Using
DNA origami, we assemble model meta-molecules from multiple plasmonic
nanoparticles, representing meta-atoms accurately positioned in space. This
allows us to reconstruct piece by piece the impact of varying macromolecular
geometries on their surrounding optical near fields. Next to the emergence of
CD signatures in the instance that we architect a third dimension, we design
and implement sign flipping signals through addition or removal of single
particles in the artificial molecules. Our data and theoretical modelling
reveal the hitherto unrecognized phenomenon of chiral plasmonic-dielectric
coupling, explaining the intricate electromagnetic interactions within hybrid
DNA-based plasmonic nanostructures.Comment: Article and Supporting Informatio
Optimized diamond inverted nanocones for enhanced color center to fiber coupling
Nanostructures can be used for boosting the light outcoupling of color
centers in diamond; however, the fiber coupling performance of these
nanostructures is rarely investigated. Here, we use a finite element method for
computing the emission from color centers in inverted nanocones and the overlap
of this emission with the propagation mode in a single-mode fiber. Using
different figures of merit, the inverted nanocone parameters are optimized to
obtain maximal fiber coupling efficiency, free-space collection efficiency, or
rate enhancement. The optimized inverted nanocone designs show promising
results with 66% fiber coupling or 83% free-space coupling efficiency at the
tin-vacancy center zero-phonon line wavelength of 619 nm. Moreover, when
evaluated for broadband performance, the optimized designs show 55% and 76% for
fiber coupling and free-space efficiencies respectively, for collecting the
full tin-vacancy emission spectrum at room temperature. An analysis of
fabrication insensitivity indicates that these nanostructures are robust
against imperfections. For maximum emission rate into a fiber mode, a design
with a Purcell factor of 2.34 is identified. Finally, possible improvements
offered by a hybrid inverted nanocone, formed by patterning into two different
materials, are investigated, and increases the achievable fiber coupling
efficiency to 71%.Comment: The following article has been accepted by Applied Physics Letters.
After it is published, it will be found at https://doi.org/10.1063/5.005033
Josephson parametric amplifier with Chebyshev gain profile and high saturation
We demonstrate a Josephson parametric amplifier design with a band-pass
impedance matching network based on a third-order Chebyshev prototype. We
measured eight amplifiers operating at 4.6 GHz that exhibit gains of 20 dB with
less than 1 dB gain ripple and up to 500 MHz bandwidth. The amplifiers further
achieve high output saturation powers around -73 dBm based on the use of
rf-SQUID arrays as their nonlinear element. We characterize the system readout
efficiency and its signal-to-noise ratio near saturation using a Sycamore
processor, finding the data consistent with near quantum limited noise
performance of the amplifiers. In addition, we measure the amplifiers'
intermodulation distortion in two-tone experiments as a function of input power
and inter-tone detuning, and observe excess distortion at small detuning with a
pronounced dip as a function of signal power, which we interpret in terms of
power-dependent dielectric losses.Comment: 14 pages, 10 figure
Disruption of the TCA cycle reveals an ATF4-dependent integration of redox and amino acid metabolism.
The Tricarboxylic Acid (TCA) Cycle is arguably the most critical metabolic cycle in physiology and exists as an essential interface coordinating cellular metabolism, bioenergetics, and redox homeostasis. Despite decades of research, a comprehensive investigation into the consequences of TCA cycle dysfunction remains elusive. Here, we targeted two TCA cycle enzymes, fumarate hydratase (FH) and succinate dehydrogenase (SDH), and combined metabolomics, transcriptomics, and proteomics analyses to fully appraise the consequences of TCA cycle inhibition (TCAi) in murine kidney epithelial cells. Our comparative approach shows that TCAi elicits a convergent rewiring of redox and amino acid metabolism dependent on the activation of ATF4 and the integrated stress response (ISR). Furthermore, we also uncover a divergent metabolic response, whereby acute FHi, but not SDHi, can maintain asparagine levels via reductive carboxylation and maintenance of cytosolic aspartate synthesis. Our work highlights an important interplay between the TCA cycle, redox biology, and amino acid homeostasis
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Disruption of the TCA cycle reveals an ATF4-dependent integration of redox and amino acid metabolism.
The Tricarboxylic Acid (TCA) Cycle is arguably the most critical metabolic cycle in physiology and exists as an essential interface coordinating cellular metabolism, bioenergetics, and redox homeostasis. Despite decades of research, a comprehensive investigation into the consequences of TCA cycle dysfunction remains elusive. Here, we targeted two TCA cycle enzymes, fumarate hydratase (FH) and succinate dehydrogenase (SDH), and combined metabolomics, transcriptomics, and proteomics analyses to fully appraise the consequences of TCA cycle inhibition (TCAi) in murine kidney epithelial cells. Our comparative approach shows that TCAi elicits a convergent rewiring of redox and amino acid metabolism dependent on the activation of ATF4 and the integrated stress response (ISR). Furthermore, we also uncover a divergent metabolic response, whereby acute FHi, but not SDHi, can maintain asparagine levels via reductive carboxylation and maintenance of cytosolic aspartate synthesis. Our work highlights an important interplay between the TCA cycle, redox biology, and amino acid homeostasis
Optimizing Pediatric Dosing Recommendations and Treatment Management of Antiretroviral Drugs Using Therapeutic Drug Monitoring Data in Children Living With HIV.
INTRODUCTION: This review summarizes the current dosing recommendations for antiretroviral (ARV) drugs in the international pediatric guidelines of the World Health Organization (WHO), US Department of Health and Human Services (DHHS), and Pediatric European Network for Treatment of AIDS (PENTA), and evaluates the research that informed these approaches. We further explore the role of data generated through therapeutic drug monitoring in optimizing the dosing of ARVs in children. METHODS: A PubMed search was conducted for the literature on ARV dosing published in English. In addition, the registration documentation of European Medicines Agency and the US Food and Drug Administration for currently used ARVs and studies referenced by the WHO, DHHS, and EMA guidelines were screened. Resulting publications were screened for papers containing data on the area under the concentration-time curve, trough concentration, and peak concentration. Studies with enrolled participants with a median or mean age of ?18 years were excluded. No restriction on publishing date was applied. DISCUSSION AND CONCLUSION: Pediatric ARV dosing is frequently based on data obtained from small studies and is often simplified to facilitate dosing in the context of a public health approach. Pharmacokinetic parameters of pediatric ARVs are subject to high interpatient variation and this leads to a potential risk of underdosing or overdosing when drugs are used in real life. To ensure optimal use of ARVs and validate dosing recommendations for children, it is essential to monitor ARV dosing more thoroughly with larger sample sizes and to include diverse subpopulations. Therapeutic drug monitoring data generated in children, where available and affordable, have the potential to enhance our understanding of the appropriateness of simplified pediatric dosing strategies recommended using a public health approach and to uncover suboptimal dosing or other unanticipated issues postmarketing, further facilitating the ultimate goal of optimizing pediatric ARV treatment
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