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Type 2 diabetes (T2D) in youth is a growing healthcare and public health concern. It is costly, and youth suffer from disabling and deadly comorbid conditions at a faster pace than adult onset. However, T2D is preventable. The population of obese youth at greatest risk for T2D is of minority race/ethnicity and socioeconomically disadvantaged background, which creates barriers to health promoting lifestyles. Despite being the first line of prevention efforts for T2D, efficacious behavioral lifestyle interventions are still lacking at the community level. During the summers of 2016 and 2017, a study integrated obesity and diabetes prevention health education into TeenWorks summer employment program at Indy Urban Acres in Indianapolis, Indiana. Results were analyzed using paired sample t-tests. Participants (N = 168) had a mean age of 15.8 ± 0.7 years, 61% female, 13% Hispanic, 80% Black. By the end of the intervention, physical activity (p = 0.000) and prevention knowledge (p = 0.000) were significantly higher. Dietary intake (p = 0.204), self-efficacy (p = 0.58), food insecurity (p = 0.058) and depression screening scores (p = 0.809) were not significantly different. In light of the continuing childhood obesity epidemic and increasing prevalence of prediabetes and T2D in youth, there is a pressing need to understand and reduce barriers to obesity and diabetes prevention in high-risk populations. This study demonstrated the feasibility of integrating obesity and T2D prevention health education into a teen summer employment program.

We present an efficient simulation method for electronic transport and avalanche in single-photon avalanche diodes (SPAD). Carrier transport is simulated in the real space using a particle Monte Carlo approach based on the Fokker–Planck point of view on an advection-diffusion equation, that enables us to reproduce mobility models, including electric fields and doping dependencies. The avalanche process is computed thanks to impact ionization rates implemented using a modified Random Path Length algorithm. Both transport and impact ionization mechanisms are computed concurrently from a statistical point of view, which allows us to achieve a full multi-particle simulation. This method provides accurate simulation of transport and avalanche process suitable for realistic three-dimensional SPADs, including all relevant stochastic aspects of these devices, together with a huge reduction of the computational time required, compared to standard Monte Carlo methods for charge carrier transport. The efficiency of our method empowers the possibility to precisely evaluate SPADs figures of merit and to explore new features that were untrackable by conventional methods. An extensive series of comparisons with experimental data on state-of-the art SPADs shows a very good accuracy of the proposed approach.

Single Photon Avalanche Diodes (SPAD) are key optoelectronic detectors for medical imaging, camera ranging and automotive laser imaging detection and ranging (LiDAR) applications. Today, most of SPADs in the Time Of Flight (TOF) market are composed of a micrometric Silicon PN junction associated to a proximity CMOS electronics biasing the system above the breakdown voltage. These devices present low noise, high pixel-matrix integration capabilities, but their Photon Detection Efficiency (PDE) is relatively modest in the near infrared operating region (achieving typically only few percent at a wavelength of 940 nm). A considerable optimisation of the SPAD design is currently on going at an industrial level with a view of increasing the PDE without compromising the timing statistic response to avalanche (Jitter) and its quench probability. Within these perspectives, standard commercial Technology-Computer-Assisted-Design (TCAD) simulations can only provide a limited guidance for technological and design splits optimisation since they are based on deterministic solvers that are unable to capture these stochastic figures of merit. Since the seminal work from Spinelli [1] clearly showing that Monte Carlo simulations predictions can compare favourably with experimental measurements of PDE and timing resolution, the Monte Carlo method can be considered to be a useful one for the design of improved structures. It has been recently applied to optimize the PDE and Jitter of Silicon [3] and InGaAs SPADs [4],[5]. In this abstract we report a rigorous comparison between Monte Carlo predictions and measurements of PDE and Jitter. We also discuss in detail, the quench probability of these diodes once in avalanche. This latter point has rarely been discussed in literature and to the best of our knowledge never addressed within a Monte Carlo perspective.

International audience; Dark Count Rate (DCR) in Single-Photon Avalanche Diodes (SPAD) in Complementary Metal-Oxide Semiconductor technology is characterized and analyzed with a comprehensive simulation methodology. Based on a series of measurements of SPAD with various architectures, on an extended range of voltages and temperatures, the DCR measurements are correlated to the spatial localization of traps within the device and their parameters. To this aim, process and electrical simulations using Technology Computer-Aided Design (TCAD) tools are combined with an in-house McIntyre solver to compute the breakdown probability (Pt). The traps are accounted for using thermal SRH carrier generation-recombination mechanism which is coupled with the position-dependent breakdown probability. This rigorous methodology makes it possible to directly compare with DCR measurements, since only generated carriers with a non-negligible breakdown probability are considered

Traditional ghost imaging requires correlated but spatially separated photons and has been observed in many physical situations, spanning both the quantum and classical regimes. Here we observe ghost imaging in a new system—a system based on entanglement swapping, the key feature of a quantum network. We detail how the exact form of quantum interference between independent photons dictates the precise nature of the ghost imaging, for example, for an anti-symmetric projection, the recorded image is the contrast-reversed version of the object—where the object is bright, the image is dark, and vice versa. The results highlight the importance of state projection in this ghost-imaging process and provide a pathway for the teleportation of two-dimensional spatial states across a quantum network. Our results also indicate that ghost images with new image properties could be achieved in conventional settings through a variety of new signal processing procedures.

We present a Verilog-A model accounting for the temporal avalanche buildup and its statistics in Single-Photon Avalanche Diodes (SPADs). This physics-based approach is compared to TCAD mixed-mode analyzing predictions, as well as measurements. The buildup that can be in the order of hundreds picoseconds, affects the statistical pulse width distribution, which is experimentally verified. Furthermore, we address in detail the voltage swing across the device during avalanche and its quenching, studying its impact on power consumption. This model can help a chip designer to optimize circuits for quenching the SPAD photodiode.

Since its first demonstration in 1995, ghost imaging has provided amazing insights into both classical and quantum physics as well as having found application in, for example, microscopy and imaging under low light conditions. Traditional ghost imaging uses correlations between two photons to reconstruct an image of an object from two systems which each individually know nothing about the object. In the quantum case, the state of the two photons is typically a symmetric, entangled state. Here we investigate the effect that changing the two-photon state's symmetry has on the reconstructed object, by using Dove prisms and a Hong-Ou-Mandel filter. Interestingly, it appears that post-selecting on the anti-symmetric Bell state results in a `double image': a juxtaposition of the original image rotated both clockwise and anti-clockwise. Furthermore, we consider a 4-photon experiment in which two photons, which originate from different entanglement sources and are hence completely independent initially, acquire correlations by way of entanglement swapping via appropriate post-selection on the remaining two photons. In such a setup, post-selecting on the symmetric Bell states results in the original object, but post-selecting on the anti-symmetric Bell state results in a contrast-reversed image of the object. These studies highlight the fundamental importance that state symmetry plays in quantum imaging.

It is impossible to distinguish between causal correlation and common cause based on classical correlations alone. An experiment now shows that for quantum variables it is sometimes possible to infer the causal structure just from observations.

Ascertaining the physical state of a system is vital in order to understand and predict its behaviour. Tomography is a standard approach used to determine the form of an unknown state. Here we show that an alternative approach, based on sequential weak and strong measurements, can be used to determine the density matrix in a simple, fast, and general style. We directly measure the probability amplitudes of a variety of pure polarisation states of light. We then generalise this experiment to directly measure the Dirac distribution and consequently determine the density matrix. Our work is the first to demonstrate the direct measurement of the full description of the state of a two-dimensional system, and it has applications to measurements in foundational quantum mechanics, quantum information, and physical chemistry., 10 pages, 6 figures; final version

We report an algorithm for reconstructing images when the average number of photons recorded per pixel is of order unity, i.e. photon-sparse data. The image optimisation algorithm minimises a cost function incorporating both a Poissonian log-likelihood term based on the deviation of the reconstructed image from the measured data and a regularization-term based upon the sum of the moduli of the second spatial derivatives of the reconstructed image pixel intensities. The balance between these two terms is set by a bootstrapping technique where the target value of the log-likelihood term is deduced from a smoothed version of the original data. When compared to the original data, the processed images exhibit lower residuals with respect to the true object. We use photon-sparse data from two different experimental systems, one system based on a single-photon, avalanche photo-diode array and the other system on a time-gated, intensified camera. However, this same processing technique could most likely be applied to any low photon-number image irrespective of how the data is collected.

We implement Poisson denoising algorithms that are fast enough to allow real-time processing of images produced by a single photon avalanche detector (SPAD) camera. This work has applications in low-light-level surveillance and medical imaging.

A simple approach to preparing high-dimensional entangled states by quantum interference., Many protocols in quantum science, for example, linear optical quantum computing, require access to large-scale entangled quantum states. Such systems can be realized through many-particle qubits, but this approach often suffers from scalability problems. An alternative strategy is to consider a lesser number of particles that exist in high-dimensional states. The spatial modes of light are one such candidate that provides access to high-dimensional quantum states, and thus they increase the storage and processing potential of quantum information systems. We demonstrate the controlled engineering of two-photon high-dimensional states entangled in their orbital angular momentum through Hong-Ou-Mandel interference. We prepare a large range of high-dimensional entangled states and implement precise quantum state filtering. We characterize the full quantum state before and after the filter, and are thus able to determine that only the antisymmetric component of the initial state remains. This work paves the way for high-dimensional processing and communication of multiphoton quantum states, for example, in teleportation beyond qubits.

We present an image reconstruction algorithm for producing grey-scale images derived from binary photon-sparse data. The algorithm is based upon a likelihood of Poissonian distribution combined with a measure of image smoothness.

Time-bin encoding is a robust form of optical quantum information, especially for transmission in optical fibers. To read out the information, the separation of the time bins must be larger than the detector time resolution, typically on the order of nanoseconds for photon counters. In the present work, we demonstrate a technique using a nonlinear interaction between chirped entangled time-bin photons and shaped laser pulses to perform projective measurements on arbitrary time-bin states with picosecond-scale separations. We demonstrate a tomographically-complete set of time-bin qubit projective measurements and show the fidelity of operations is sufficiently high to violate the CHSH-Bell inequality by more than 6 standard deviations., Comment: 5 pages main article, 5 pages supplementary, 5 main figures, 2 supplementary figures

The controlled generation of entangled states and their subsequent detection are integral aspects of quantum information science. In this Letter, we implement a simple and precise technique that produces any of the four Bell states in the orbital angular momentum degree of freedom. We then use these states to perform the first experimental demonstration of an accessible nonlinear entanglement witness. Such a witness determines entanglement by using the same measurements as required for a linear witness but can detect, in this case, twice as many states as a single linear witness can. We anticipate that our method of state preparation and nonlinear witnesses will have further uses in areas of quantum science, such as superdense coding and quantum key distribution.

Using shaped pulses and nonlinear optics, we have experimentally demonstrated coherent measurement of time-bin encoded photons with temporal separations two orders of magnitude smaller than detector resolution by converting timing information to frequency.

Nonlinear optical processes such as parametric down conversion and squeezed light generation are key elements of most quantum protocols, leading to crucial applications such as quantum imaging, sub-shot-noise metrology, and secure communication.

We produce all four Bell states in the orbital angular momentum degree of freedom and use a new class of accessible nonlinear entanglement witnesses to verify their entanglement.

Using an electron multiplying CCD camera we observe both image plane (position) and far field (momentum) correlations between photon pairs produced from spontaneous parametric down-conversion when using a 201 x 201 bi-dimensional array of pixels and a flux of around 0.02 photons/pixel. After background subtraction we characterize the strength of signal and idler correlations in both transverse dimensions by applying entanglement and EPR criteria, showing good agreement with the theoretical predictions. The application of such devices in quantum optics could have a wide range, including quantum computation with spatial degrees of freedom of single photons.

The methods of nonlinear optics lead to important capabilities within the field of quantum information science. Applications such as high-capacity quantum key distribution and enhanced measurement sensitivity are described.

The light produced by parametric down-conversion shows strong spatial entanglement that leads to violations of EPR criteria for separability. Historically, such studies have been performed by scanning a single-element, single-photon detector across a detection plane. Here we show that modern electron-multiplying charge-coupled device cameras can measure correlations in both position and momentum across a multi-pixel field of view. This capability allows us to observe entanglement of around 2,500 spatial states and demonstrate Einstein-Podolsky-Rosen type correlations by more than two orders of magnitude. More generally, our work shows that cameras can lead to important new capabilities in quantum optics and quantum information science., Comment: 5 pages, 4 figures

Entanglement witnesses provide an efficient means of determining the level of entanglement of a system using the minimum number of measurements. Here we demonstrate the observation of two-dimensional entanglement witnesses in the high-dimensional basis of orbital angular momentum (OAM). In this case, the number of potentially entangled subspaces scales as d(d − 1)/2, where d is the dimension of the space. The choice of OAM as a basis is relevant as each subspace is not necessarily maximally entangled, thus providing the necessary state for certain tests of nonlocality. The expectation value of the witness gives an estimate of the state of each two-dimensional subspace belonging to the d-dimensional Hilbert space. These measurements demonstrate the degree of entanglement and therefore the suitability of the resulting subspaces for quantum information applications.

We tomographically reconstruct the high-dimensionally entangled quantum state produced by parametric downconversion. Our results precisely characterize the entanglement, thus establishing the suitability of such states for applications in quantum information science.

Systems entangled in high dimensions have recently been proposed as important tools for various quantum information protocols, such as multibit quantum key distribution and loophole-free tests of nonlocality. It is thereforeimportanttohavepreciseknowledgeofthenatureofsuchentangledquantumstates.Wetomographically reconstruct the quantum state of the two photons produced by parametric downconversion that are entangled in a d-dimensional orbital angular momentum basis. We determine exactly the density matrix of the entangled two-qudit state with d ranging from 2 to 8. The recording of higher-dimensional states is limited only by the number of data points required and therefore the length of time needed to complete the measurements. We find all the measured states to have fidelities and linear entropies that satisfy the criteria required for a violation of the appropriate high-dimensional Bell inequality. Our results therefore precisely characterize the nature of the entanglement, thus establishing the suitability of such states for applications in quantum information science.

Orbital angular momentum (OAM) entanglement is investigated in the Bessel-Gaussian (BG) basis. Having a readily adjustable radial scale, BG modes provide an alternative basis for OAM entanglement over Laguerre-Gaussian modes. We show that the OAM bandwidth in terms of BG modes can be increased by selection of particular radial wavevectors and leads to a flattening of the spectrum, which allows for higher dimensionality in the entangled state. We demonstrate entanglement in terms of BG modes by performing a Bell-type experiment and showing a violation of the Clauser-Horne-Shimony-Holt inequality for the ℓ = ±1 subspace. In addition, we use quantum state tomography to indicate higher-dimensional entanglement in terms of BG modes.