The coherent interaction of electromagnetic fields with solid-state two-level systems can yield deterministic quantum light sources for photonic quantum technologies. To date, the performance of semiconductor single-photon sources based on three-level systems is limited mainly due to a lack of high photon indistinguishability. Here we tailor the cavity-enhanced spontaneous emission from a ladder-type three-level system in a single epitaxial quantum dot through stimulated emission. After populating the biexciton (XX) of the quantum dot through two-photon resonant excitation, we use another laser pulse to selectively depopulate the XX state into an exciton (X) state with a predefined polarization. The stimulated XX-X emission modifies the X decay dynamics and improves the characteristics of a polarized single-photon source, such as a source brightness of 0.030(2), a single-photon purity of 0.998(1) and an indistinguishability of 0.926(4). Our method can be readily applied to existing quantum dot single-photon sources and expands the capabilities of three-level systems for advanced quantum photonic functionalities.
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http://dx.doi.org/10.1038/s41565-022-01092-6 | DOI Listing |
Front Neurosci
December 2024
Intramural Research Program, National Institute on Drug Abuse National Institutes of Health, Baltimore, MD, United States.
Miniature fluorescence microscopes (miniscopes) are one of the most powerful and versatile tools for recording large scale neural activity in freely moving rodents with single cell resolution. Recent advances in the design of genetically encoded calcium indicators (GECIs) allow to target distinct neuronal populations with non-overlapping emission spectral profiles. However, conventional miniscopes are limited to a single excitation, single focal plane imaging, which does not allow to compensate for chromatic aberration and image from two spectrally distinct calcium indicators.
View Article and Find Full Text PDFACS Appl Nano Mater
December 2024
Walter Schottky Institut, Technical University of Munich, Garching 85748, Germany.
InAs semiconductor quantum dots (QDs) emitting in the near-infrared are promising platforms for on-demand single-photon sources and spin-photon interfaces. However, the realization of quantum-photonic nanodevices emitting in the telecom windows with similar performance remains an open challenge. In particular, nanophotonic devices incorporating quantum light emitting diodes in the telecom C-band based on GaAs substrates are still lacking due to the relaxation of the lattice constant along the InGaAs graded layer which makes the implementation of electrically contacted devices challenging.
View Article and Find Full Text PDFFluorescence interference is a pervasive challenge in Raman spectroscopy, often limiting its broader application. Time-gated Raman spectroscopy offers a more universal solution by temporally separating Raman signals from fluorescence; however, it faces significant challenges when dealing with samples that exhibit short fluorescence lifetimes. Achieving high time resolution to effectively distinguish these signals typically requires advanced detectors that are not only costly but also difficult to source commercially, often resulting in substantial residual fluorescence that diminishes overall signal quality.
View Article and Find Full Text PDFNeurol Med Chir (Tokyo)
December 2024
Department of Neurosurgery, Graduate School of Biomedical and Health Sciences, Hiroshima University.
In focal epilepsy cases, precise identification and resection of the epileptogenic zone increase the likelihood of achieving a seizure-free outcome. Nevertheless, localizing the source of epilepsy in magnetic resonance imaging-negative epilepsy cases presents significant challenges for clinicians. In this study, we evaluated the diagnostic efficacy and impact on the seizure outcome by using 4 noninvasive modalities, including scalp video electroencephalography, magnetoencephalography, fluorodeoxyglucose-positron emission tomography, and iomazenil single-photon emission computed tomography, in a cohort of patients with magnetic resonance imaging-negative focal epilepsy who underwent resective surgery.
View Article and Find Full Text PDFAnn Nucl Cardiol
October 2024
Department of Radiology, Sakakibara Heart Institute, Tokyo, Japan.
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