On-Chip Photonic Devices for Coupling to Color Centers in Silicon Carbide

Optical quantum networks are important for global use of quantum computers, and secure quantum communication. Those networks require storage devices for synchronizing or making queues of processing transferred quantum information. Practical quantum information networks should minimize loss of transmitted data (photons) and have high efficiency mapping when writing data on memories (solid state qubits). This requires strong light-matter interaction that is enabled by coupling qubits to optical cavities. The first half of the thesis focuses on emerging candidates for promising qubits in silicon carbide (SiC). The optical and quantum properties of these color centers are discussed with focus on divacancies in 4H-SiC due to their long spin coherence time. Optically detected magnetic resonance of divacancies is shown, an essential technique for reading out the qubit state using the intensity of optical emission. The second half of the thesis focuses on hybrid photonic devices for coupling to silicon carbide qubits. Hybrid devices are made of another layer of high refractive index material other than the qubit hosting material. Evanescent coupling to qubits close to the surface can be achieved without damaging the host material. Mainly the silicon (Si) on 4H-SiC hybrid ring resonator architecture is discussed starting from design, simulation to fabrication. The fabrication includes Si membrane transfer that is an important step to create a light confining layer on 4H-SiC. The final ring resonator device shows quality factors as high as 23000.</p

Hybrid silicon on silicon carbide integrated photonics platform

We demonstrate a hybrid on-chip photonics platform based on crystalline silicon resonators and waveguides patterned on top of silicon carbide. The devices were fabricated with membrane transfer followed by standard electron beam patterning procedures. The platform allows the integration of high quality silicon photonics with color centers in silicon carbide operating in the near infrared for spin-photon interfaces used in quantum information processing applications. We measure waveguide-coupled ring resonators with loaded quality factors up to 23 000 at cryogenic temperatures

Alterations of DNA Methylation at GDNF Gene Promoter in the Ventral Tegmental Area of Adult Depression-Like Rats Induced by Maternal Deprivation

Objective: To study the expression and DNA methylation of the Glial cell line-derived neurotrophic factor (GDNF) gene in the development of depression-like behaviors in rats experiencing maternal deprivation stress in early life.Methods: Newborn SD rats were randomly assigned to a normal control group (NOR) or maternal deprivation group (MD). An open field test (OPT), sucrose preference test (SPT), and a forced swimming test (FST) were used to evaluate rats' behaviors. Protein, mRNA, and methylation levels were measured by ELISA/Western blot, real-time PCR, and BiSulfte Amplicon sequencing PCR, respectively.Results: MD rats had significantly shorter total distance and more fecal pellets in OPT, a lower sucrose preference rate in SPT, and a longer immobility time in FST than NOR rats. Compared with NOR rats, MD rats showed a significantly higher plasma corticosterone (CORT) level. The levels of plasma dopamine (DA) and the GDNF were significantly lower in the MD rats than in NOR rats. In the ventral tegmental area (VTA) tissues, MD rats had a significantly higher level of methylation at the GDNF gene promoter than NOR rats. The expression of the GDNF mRNA and protein were significantly lower in MD rats than in NOR rats. The total distance was significantly correlated with plasma DA and GDNF, the DNA methylation level at the GDNF promoter and the GDNF mRNA level in the VTA. Fecal pellets showed a significant correlation with plasma CORT. The sucrose preference rate was significantly correlated with plasma DA, the DNA methylation level at the GDNF promoter and the GDNF mRNA level in the VTA. Immobility time showed a significant correlation with the plasma DA, the plasma GDNF and the GDNF mRNA level in the VTA.Conclusion: up-regulation of DNA methylation at the GDNF gene promotor and the subsequent down-regulation of the GDNF gene expression in the VTA, may be involved in the development of depression-like behaviors in rats experiencing MD in early life

Central and peripheral changes in the retina and choroid in patients with diabetes mellitus without clinical diabetic retinopathy assessed by ultra-wide-field optical coherence tomography angiography

BackgroundTo explore the central and peripheral retinal and choroidal changes in diabetic patients without clinical diabetic retinopathy (DM-NoDR) using ultra-wide-field swept-source optical coherence tomography angiography (UWF-SS-OCTA).Methods67 DM-NoDR eyes and 32 age-matched healthy eyes were recruited. Retinal and choroidal parameters, including qualitative retinal microangiopathy, vessel flow (VFD) and linear density (VLD), thickness, and volume, were measured in the central and peripheral areas of the 24 × 20 mm2 UWF-SS-OCTA images.ResultsDM-NoDR eyes had significantly more nonperfusion area and capillary tortuosity than controls in the central and peripheral areas (p &lt; 0.05). The presence of central capillary tortuosity was associated with higher levels of serum creatinine (OR 1.049, 95%CI 1.001–1.098; p = 0.044) and blood urea nitrogen (OR 1.775, 95%CI 1.051–2.998; p = 0.032) in DM-NoDR eyes. For DM-NoDR eyes versus controls, VFD in the 300-μm annulus around the foveal avascular zone, superficial capillary plexus (SCP), and full retina, and SCP-VLD significantly decreased, while VFD in the deep capillary plexus (DCP), retinal thickness, and retinal volume increased (p &lt; 0.05). Analysis in the central and peripheral areas recapitulated all these findings, except for decreased peripheral thickness and volume and no difference in peripheral DCP-VFD. In DM-NoDR eyes, choriocapillaris-VFD, choroidal thickness, and choroidal volume increased in the central area, while VFD in the large and medium choroidal vessel layer decreased in the whole image (p &lt; 0.05).ConclusionRetinal and choroidal changes already existed in the central and/or peripheral areas of DM-NoDR eyes. UWF-SS-OCTA, enabling the visualization of the peripheral fundus area, is a promising image technique for the early detection of fundus changes in DM-NoDR patients

Toward Microwave-to-Optical Conversion using Erbium Doped Crystals and Integrated Resonators

We present progress towards a bidirectional coherent microwave-to-optical photon converter using an ensemble of rare-earth ions coupled to integrated photonic and microwave resonators

Neural Network-Based Modeling for Risk Evaluation and Early Warning for Large-Scale Sports Events

[Problem] The risks of hosting large-scale sports events are very difficult to evaluate and often directly affected by natural environment risks, events management risks, and social environment risks. Before hosting the events, accurately assessing these risks can effectively minimize the occurrence of risks and reduce the subsequent losses. [Aim] In this article, we advocate the use of a back propagation neural network (BPNN) model for risk evaluation and early warning of large-scale sports events. [Methods] We first use expert surveys to assess the risks of 28 large-scale sports events using 12 indicators associated with climate conditions, events management, and natural disasters. We then apply the BPNN model to evaluate the risks of 28 large-scale sports events with sufficient samples by adding white noise with mean zero and small variance to the small actual samples. We provide a general rule to establish a BPNN model with insufficient and small samples. [Results] Our research results show that the recognition accuracy of the established BPNN model is 86.7% for the 15 simulation samples and 100% for the 28 actual samples. Based on this BPNN model, we determined and ranked the risk level of the events and the importance of each indicator. Thus, sample S8 had the highest risk and the second highest was sample S14, and indicator nine was the most important and indicator one the least important. [Conclusions] We can apply the established BPNN model to conveniently evaluate the risk of hosting a large-scale sports event. By analyzing the nonlinear relationship between each indicator and the risk of the sports event, and applying the established BPNN model, we can propose more targeted and effective measures and suggestions for eliminating and decreasing the risks of hosting a large-scale sports event, and ensure large-scale sports events can be successfully hosted