Solid state quantum emitters have shown strong potential for applications in quantum information, but spectral inhomogeneity of these emitters poses a significant challenge. We address this issue in a cavity-quantum dot system by demonstrating cavity-stimulated Raman spin flip emission. This process avoids populating the excited state of the emitter and generates a photon that is Raman shifted from the laser and enhanced by the cavity. The emission is spectrally narrow and tunable over a range of at least 125 GHz, which is two orders of magnitude greater than the natural linewidth. We obtain the regime in which the Raman emission is spin-dependent, which couples the photon to a long-lived electron spin qubit. This process can enable an efficient, tunable source of indistinguishable photons and deterministic entanglement of distant spin qubits in a photonic crystal quantum network.Controlled absorption and emission of single photons by quantum emitters are essential processes for quantum information technologies. Single photons can be used to transfer quantum information from one stationary qubit to another as part of a quantum network 1-4 , or they can be used as a qubit for photonic quantum computing 5 or secure communication 6 . Currently the largest challenge in achieving these goals is in scaling up the number of qubits. A promising approach is the integration of solid state quantum emitters into a photonic architecture [7][8][9] . Candidate materials include quantum dots 7,8 (QDs), QD molecules 10-13 , nitrogen-vacancy centers in diamond 9,14 , and other impurities or defects in solids 15,16 . These materials can take advantage of nanofabrication technologies to produce monolithic integrated structures that simplify the scaling-up problem 7,9 . Unfortunately, solid state quantum emitters suffer from spectral inhomogeneity, which greatly limits their usefulness for protocols that involve identical photons 5 or that involve the exchange of a photon between two qubits 1-4 .Here we demonstrate for the first time in a solid state system a cavity-stimulated Raman process [17][18][19] that can be used to overcome spectral inhomogeneity. We do this by coupling a negatively charged InAs/GaAs quantum dot (QD) that acts as a -type quantum emitter to a photonic crystal defect cavity 20 . Most previous work on QDs in cavities involves the coupling of 2 a 2-level exciton system to a cavity 7,[21][22][23] . In contrast, the three level -type system here provides a long-lived ground state electron spin coherence 24,25 , with ultrafast optical gates [25][26][27][28] and cavityenhanced initialization and readout 20 . The key feature of the Raman process (see Fig. 1a) is that the frequency of the emitted Raman photon is determined by the laser photon energy and the Zeeman energy, not by the excited state energy of the quantum emitter. The cavity strongly enhances this process when the Raman photon is resonant with the cavity mode. We measure cavity-stimulated Raman photons detuned from the QD over a range of at least 0.5 me...
BACKGROUND: Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the United States, yet little is known about NAFLD awareness in individuals with incidental fatty liver on imaging. OBJECTIVE: To assess the level of awareness of imagingdefined NAFLD among individuals with and without metabolic risk factors. DESIGN: Cross-sectional analysis within a prospective longitudinal population-based cohort study conducted in four U.S. cities. PARTICIPANTS: Adults age 43 to 55 years enrolled in the Coronary Artery Risk Development in Young Adults (CARDIA) Study who underwent computed tomography and a personal health questionnaire at the year 25 exam (2010-2011, n = 2788). MAIN MEASURES: NAFLD was defined as liver attenuation ≤ 51 Hounsfield units after exclusion of other causes of liver fat. Participants were considered "NAFLD aware" if they reported being told previously by a doctor or nurse that they had "fatty liver." KEY RESULTS: NAFLD prevalence was 23.9%. Only 16 of 667 (2.4%) participants with CT-defined NAFLD were aware of a NAFLD diagnosis. NAFLD aware participants were more likely to be white (81.3% vs. 53.5%, p = 0.03) and have the metabolic syndrome (87.5% vs. 59.3%, p = 0.02) and/or hypertension (75.0% vs. 50.2%, p = 0.05). In multivariable analyses adjusted for demographics, metabolic syndrome and hypertension remained predictive of NAFLD awareness. CONCLUSION: There is low awareness of NAFLD among individuals with hepatic steatosis on imaging, even among those with metabolic risk factors. These findings highlight an opportunity to raise public and practitioner awareness of NAFLD with the goal of increasing diagnosis and implementing early treatment strategies.
In this report, we study the effectiveness of hydrogen plasma surface treatments for improving the electrical properties of GaSb/Al2O3 interfaces. Prior to atomic layer deposition of an Al2O3 dielectric, p-GaSb surfaces were exposed to hydrogen plasmas in situ, with varying plasma powers, exposure times, and substrate temperatures. Good electrical interfaces, as indicated by capacitance-voltage measurements, were obtained using higher plasma powers, longer exposure times, and increasing substrate temperatures up to 250 °C. X-ray photoelectron spectroscopy reveals that the most effective treatments result in decreased SbOx, decreased Sb, and increased GaOx content at the interface. This in situ hydrogen plasma surface preparation improves the semiconductor/insulator electrical interface without the use of wet chemical pretreatments and is a promising approach for enhancing the performance of Sb-based devices.
A reagent-based treatment method was developed for the removal of sodium dodecyl sulfate (SDS) from aqueous dispersions of single-wall carbon nanotubes (SWCNTs). Based on a survey of various reagents, organic solvents emerged as the most effective at interrupting the SDS:SWCNT interaction without producing deleterious side reactions or causing precipitation of the surfactant. Specifically, treatment with acetone or acetonitrile allows for the facile isolation of SWCNTs with near complete removal of SDS through vacuum filtration, resulting in a 100x reduction in processing time. These findings were validated via quantitative analysis using thermogravimetric analysis, Raman spectroscopy, 4-point probe electrical measurement, and X-ray photoelectron spectroscopy. Subsequent thermal oxidation further enhances the purity of the reagent treated samples and yields bulk SWCNT samples with >95% carbonaceous purity. The proposed reagent treatment method thus demonstrates potential for large volume SWCNT processing.
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