Cerebral perfusion changes in acute subdural hematoma.

INTRODUCTION: Acute subdural hematoma (aSDH) is one of the main causes of high mortality and morbidity in traumatic brain injury. Prognosis is poor due to the rapid volume shift and mass effect. Cerebral perfusion is likely affected in this condition. This study quantifies perfusion changes in aSDH using early ER polytrauma CT with perfusion imaging (CTP). METHODS: Data of 54 patients with traumatic aSDH were retrospectively collected. Glasgow Coma scale (GCS), perfusion parameters, therapeutic decisions and imaging data including hematoma thickness, midline shift, and hematoma localization were analyzed. The cortical perfusion parameters of each hemisphere, the area anterior to the hematoma (AAH), area below the hematoma (ABH), area posterior to the hematoma (PAH), and corresponding mirrored contralateral regions were determined. RESULTS: We found a significant difference in Tmax in affected and unaffected whole-hemisphere data (mean 4.0 s vs. 3.3 s, p < 0.05) and a significantly different mean for Tmax in ABH and for the corresponding mirrored area (mABH) (mean 3.8 s vs. 3.1 s, p < 0.05). No significant perfusion changes in cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) were found. CONCLUSION: There was a significant elevation of time to maximum (Tmax) values in the underlying cortical area of aSDH. Possible pathophysiological explanations, the influence on immediate surgical decision-making and further therapeutic consequences have to be evaluated.

Observation of non-Hermitian degeneracies in a chaotic exciton-polariton billiard.

Exciton-polaritons are hybrid light-matter quasiparticles formed by strongly interacting photons and excitons (electron-hole pairs) in semiconductor microcavities. They have emerged as a robust solid-state platform for next-generation optoelectronic applications as well as for fundamental studies of quantum many-body physics. Importantly, exciton-polaritons are a profoundly open (that is, non-Hermitian) quantum system, which requires constant pumping of energy and continuously decays, releasing coherent radiation. Thus, the exciton-polaritons always exist in a balanced potential landscape of gain and loss. However, the inherent non-Hermitian nature of this potential has so far been largely ignored in exciton-polariton physics. Here we demonstrate that non-Hermiticity dramatically modifies the structure of modes and spectral degeneracies in exciton-polariton systems, and, therefore, will affect their quantum transport, localization and dynamical properties. Using a spatially structured optical pump, we create a chaotic exciton-polariton billiard--a two-dimensional area enclosed by a curved potential barrier. Eigenmodes of this billiard exhibit multiple non-Hermitian spectral degeneracies, known as exceptional points. Such points can cause remarkable wave phenomena, such as unidirectional transport, anomalous lasing/absorption and chiral modes. By varying parameters of the billiard, we observe crossing and anti-crossing of energy levels and reveal the non-trivial topological modal structure exclusive to non-Hermitian systems. We also observe mode switching and a topological Berry phase for a parameter loop encircling the exceptional point. Our findings pave the way to studies of non-Hermitian quantum dynamics of exciton-polaritons, which may uncover novel operating principles for polariton-based devices.

The Visual Analog Scale detects exercise-induced bronchoconstriction in children with asthma.

Objective: Exercise-induced bronchoconstriction (EIB) is a specific morbidity of childhood asthma and an important sign of uncontrolled asthma. The occurrence of EIB is insufficiently identified by the Childhood Asthma Control Test (C-ACT) and Asthma Control Test (ACT). This study aimed to (1) evaluate the Visual Analog Scale (VAS) for dyspnea as a tool to detect EIB in asthmatic children and (2) assess the value of combining (C-)ACT outcomes with VAS scores. Methods: We measured EIB in 75 asthmatic children (mean age 10.8 years) with a standardized exercise challenge test (ECT) performed in cold and dry air. Children and parents reported VAS dyspnea scores before and after the ECT. Asthma control was assessed by the (C-)ACT. Results: Changes in VAS scores (ΔVAS) of children and parents correlated moderately with fall in forced expiratory volume in 1 second (FEV1), respectively rs=0.57 (p < .001) and rs=0.58 (p < .001). At a ΔVAS cutoff value of ≥3 in children, sensitivity and specificity for EIB were 80% and 79% (AUC 0.82). Out of 38 children diagnosed with EIB, 37 had a (C-)ACT score of ≤19 and/or a ΔVAS of ≥3, corresponding with a sensitivity of 97% and a negative predictive value of 96%. Conclusion: This study shows that the VAS could be an effective additional tool for diagnosing EIB in children. A reported difference in VAS scores of ≥3 after a standardized ECT combined with low (C-)ACT scores was highly effective in detecting and excluding EIB.

WEARCON: wearable home monitoring in children with asthma reveals a strong association with hospital based assessment of asthma control.

BACKGROUND: Asthma is one of the most common chronic diseases in childhood. Regular follow-up of physiological parameters in the home setting, in relation to asthma symptoms, can provide complementary quantitative insights into the dynamics of the asthma status. Despite considerable interest in asthma home-monitoring in children, there is a paucity of scientific evidence, especially on multi-parameter monitoring approaches. Therefore, the aim of this study is to investigate whether asthma control can be accurately assessed in the home situation by combining parameters from respiratory physiology sensors. METHODS: Sixty asthmatic and thirty non-asthmatic children were enrolled in the observational WEARCON-study. Asthma control was assessed according to GINA guidelines by the paediatrician. All children were also evaluated during a 2-week home-monitoring period with wearable devices; a physical activity tracker, a handheld spirometer, smart inhalers, and an ambulatory electrocardiography device to monitor heart and respiratory rate. Multiple logistic regression analysis was used to determine which diagnostic measures were associated with asthma control. RESULTS: 24 of the 27 uncontrolled asthmatic children and 29 of the 32 controlled asthmatic children could be accurately identified with this model. The final model showed that a larger variation in pre-exercise lung function (OR = 1.34 95%-CI 1.07-1.68), an earlier wake-up-time (OR = 1.05 95%-CI 1.01-1.10), more reliever use (OR = 1.11 95%-CI 1.03-1.19) and a longer respiratory rate recovery time (OR = 1.12 95%-CI 1.05-1.20) were significant contributors to the probability of having uncontrolled asthma. CONCLUSIONS: Home-monitoring of physiological parameters correlates with paediatrician assessed asthma control. The constructed multivariate model identifies 88.9% of all uncontrolled asthmatic children, indicating a high potential for monitoring of asthma control. This may allow healthcare professionals to assess asthma control at home. TRIAL REGISTRATION: Netherlands Trail Register, NL6087 . Registered 14 February 2017.

Quantum Interference between Light Sources Separated by 150 Million Kilometers.

We report an experiment to test quantum interference, entanglement, and nonlocality using two dissimilar photon sources, the Sun and a semiconductor quantum dot on the Earth, which are separated by ∼150 million kilometers. By making the otherwise vastly distinct photons indistinguishable in all degrees of freedom, we observe time-resolved two-photon quantum interference with a raw visibility of 0.796(17), well above the 0.5 classical limit, providing unambiguous evidence of the quantum nature of thermal light. Further, using the photons with no common history, we demonstrate postselected two-photon entanglement with a state fidelity of 0.826(24) and a violation of Bell inequality by 2.20(6). The experiment can be further extended to a larger scale using photons from distant stars and open a new route to quantum optics experiments at an astronomical scale.

Controlled Ordering of Topological Charges in an Exciton-Polariton Chain.

We demonstrate, experimentally and theoretically, controlled loading of an exciton-polariton vortex chain into a 1D array of trapping potentials. Switching between two types of vortex chains, with topological charges of the same or alternating signs, is achieved by appropriately shaping an off-resonant pump beam that drives the system to the regime of bosonic condensation. In analogy to spin chains, these vortex sequences realize either a "ferromagnetic" or an "antiferromagnetic" order, whereby the role of spin is played by the orbital angular momentum. The ferromagnetic ordering of vortices is associated with the formation of a persistent chiral current. Our results pave the way for the controlled creation of nontrivial distributions of orbital angular momentum and topological order in a periodic exciton-polariton system.

Toward Scalable Boson Sampling with Photon Loss.

Boson sampling is a well-defined task that is strongly believed to be intractable for classical computers, but can be efficiently solved by a specific quantum simulator. However, an outstanding problem for large-scale experimental boson sampling is the scalability. Here we report an experiment on boson sampling with photon loss, and demonstrate that boson sampling with a few photons lost can increase the sampling rate. Our experiment uses a quantum-dot-micropillar single-photon source demultiplexed into up to seven input ports of a 16×16 mode ultralow-loss photonic circuit, and we detect three-, four- and fivefold coincidence counts. We implement and validate lossy boson sampling with one and two photons lost, and obtain sampling rates of 187, 13.6, and 0.78 kHz for five-, six-, and seven-photon boson sampling with two photons lost, which is 9.4, 13.9, and 18.0 times faster than the standard boson sampling, respectively. Our experiment shows an approach to significantly enhance the sampling rate of multiphoton boson sampling.

Nanoscale Tipping Bucket Effect in a Quantum Dot Transistor-Based Counter.

Electronic circuits composed of one or more elements with inherent memory, that is, memristors, memcapacitors, and meminductors, offer lower circuit complexity and enhanced functionality for certain computational tasks. Networks of these elements are proposed for novel computational paradigms that rely on information processing and storage on the same physical platform. We show a nanoscaled memdevice able to act as an electronic analogue of tipping buckets that allows reducing the dimensionality and complexity of a sensing problem by transforming it into a counting problem. The device offers a well adjustable, tunable, and reliable periodic reset that is controlled by the amounts of transferred quantum dot charges per gate voltage sweep. When subjected to periodic voltage sweeps, the quantum dot (bucket) may require up to several sweeps before a rapid full discharge occurs thus displaying period doubling, period tripling, and so on between self-governing reset operations.

Exciton-polariton trapping and potential landscape engineering.

Exciton-polaritons in semiconductor microcavities have become a model system for the studies of dynamical Bose-Einstein condensation, macroscopic coherence, many-body effects, nonclassical states of light and matter, and possibly quantum phase transitions in a solid state. These low-mass bosonic quasiparticles can condense at comparatively high temperatures up to 300 K, and preserve the fundamental properties of the condensate, such as coherence in space and time domain, even when they are out of equilibrium with the environment. Although the presence of a confining potential is not strictly necessary in order to observe Bose-Einstein condensation, engineering of the polariton confinement is a key to controlling, shaping, and directing the flow of polaritons. Prototype polariton-based optoelectronic devices rely on ultrafast photon-like velocities and strong nonlinearities exhibited by polaritons, as well as on their tailored confinement. Nanotechnology provides several pathways to achieving polariton confinement, and the specific features and advantages of different methods are discussed in this review. Being hybrid exciton-photon quasiparticles, polaritons can be trapped via their excitonic as well as photonic component, which leads to a wide choice of highly complementary trapping techniques. Here, we highlight the almost free choice of the confinement strengths and trapping geometries that provide powerful means for control and manipulation of the polariton systems both in the semi-classical and quantum regimes. Furthermore, the possibilities to observe effects of the polariton blockade, Mott insulator physics, and population of higher-order energy bands in sophisticated lattice potentials are discussed. Observation of such effects could lead to realization of novel polaritonic non-classical light sources and quantum simulators.

Temporally versatile polarization entanglement from Bragg reflection waveguides.

Bragg reflection waveguides emitting broadband parametric downconversion (PDC) have been proven to be well suited for the on-chip generation of polarization entanglement in a straightforward fashion [Sci. Rep.3, 2314 (2013)SRWSDA2045-232210.1038/srep02314]. Here, we investigate how the properties of the created states can be modified by controlling the relative temporal delay between the pair of photons created via PDC. Our results offer an easily accessible approach for changing the coherence of the polarization entanglement, in other words, to tune the phase of the off-diagonal elements of the density matrix. Furthermore, we provide valuable insight into the engineering of these states directly at the source.

Experimental Verification of the Very Strong Coupling Regime in a GaAs Quantum Well Microcavity.

The dipole coupling strength g between cavity photons and quantum well excitons determines the regime of light matter coupling in quantum well microcavities. In the strong coupling regime, a reversible energy transfer between exciton and cavity photon takes place, which leads to the formation of hybrid polaritonic resonances. If the coupling is further increased, a hybridization of different single exciton states emerges, which is referred to as the very strong coupling regime. In semiconductor quantum wells such a regime is predicted to manifest as a photon-mediated electron-hole coupling leading to different excitonic wave functions for the two polaritonic branches when the ratio of the coupling strength to exciton binding energy g/E_{B} approaches unity. Here, we verify experimentally the existence of this regime in magneto-optical measurements on a microcavity characterized by g/E_{B}≈0.64, showing that the average electron-hole separation of the upper polariton is significantly increased compared to the bare quantum well exciton Bohr radius. This yields a diamagnetic shift around 0 detuning that exceeds the shift of the lower polariton by 1 order of magnitude and the bare quantum well exciton diamagnetic shift by a factor of 2. The lower polariton exhibits a diamagnetic shift smaller than expected from the coupling of a rigid exciton to the cavity mode, which suggests more tightly bound electron-hole pairs than in the bare quantum well.

Picosecond Control of Quantum Dot Laser Emission by Coherent Phonons.

A picosecond acoustic pulse can be used to control the lasing emission from semiconductor nanostructures by shifting their electronic transitions. When the active medium, here an ensemble of (In,Ga)As quantum dots, is shifted into or out of resonance with the cavity mode, a large enhancement or suppression of the lasing emission can dynamically be achieved. Most interesting, even in the case when gain medium and cavity mode are in resonance, we observe an enhancement of the lasing due to shaking by coherent phonons. In order to understand the interactions of the nonlinearly coupled photon-exciton-phonon subsystems, we develop a semiclassical model and find an excellent agreement between theory and experiment.

Dimensionality-Driven Metal-Insulator Transition in Spin-Orbit-Coupled SrIrO_{3}.

Upon reduction of the film thickness we observe a metal-insulator transition in epitaxially stabilized, spin-orbit-coupled SrIrO_{3} ultrathin films. By comparison of the experimental electronic dispersions with density functional theory at various levels of complexity we identify the leading microscopic mechanisms, i.e., a dimensionality-induced readjustment of octahedral rotations, magnetism, and electronic correlations. The astonishing resemblance of the band structure in the two-dimensional limit to that of bulk Sr_{2}IrO_{4} opens new avenues to unconventional superconductivity by "clean" electron doping through electric field gating.

Time-Bin-Encoded Boson Sampling with a Single-Photon Device.

Boson sampling is a problem strongly believed to be intractable for classical computers, but can be naturally solved on a specialized photonic quantum simulator. Here, we implement the first time-bin-encoded boson sampling using a highly indistinguishable (∼94%) single-photon source based on a single quantum-dot-micropillar device. The protocol requires only one single-photon source, two detectors, and a loop-based interferometer for an arbitrary number of photons. The single-photon pulse train is time-bin encoded and deterministically injected into an electrically programmable multimode network. The observed three- and four-photon boson sampling rates are 18.8 and 0.2 Hz, respectively, which are more than 100 times faster than previous experiments based on parametric down-conversion.

Observation of the Transition from Lasing Driven by a Bosonic to a Fermionic Reservoir in a GaAs Quantum Well Microcavity.

We show that, by monitoring the free carrier reservoir in a GaAs-based quantum well microcavity under nonresonant pulsed optical pumping, lasing supported by a fermionic reservoir (photon lasing) can be distinguished from lasing supported by a reservoir of bosons (polariton lasing). Carrier densities are probed by measuring the photocurrent between lateral contacts deposited directly on the quantum wells of a microcavity that are partially exposed by wet chemical etching. We identify two clear thresholds in the input-output characteristic of the photoluminescence signal which can be attributed to polariton and photon lasing, respectively. The power dependence of the probed photocurrent shows a distinct kink at the threshold power for photon lasing due to an increased radiative recombination of free carriers as stimulated emission into the cavity mode sets in. At the polariton lasing threshold, on the other hand, the nonlinear increase of the luminescence is caused by stimulated scattering of exciton polaritons to the ground state which do not contribute directly to the photocurrent.

Talbot Effect for Exciton Polaritons.

We demonstrate, experimentally and theoretically, a Talbot effect for hybrid light-matter waves-an exciton-polariton condensate formed in a semiconductor microcavity with embedded quantum wells. The characteristic "Talbot carpet" is produced by loading the exciton-polariton condensate into a microstructured one-dimensional periodic array of mesa traps, which creates an array of phase-locked sources for coherent polariton flow in the plane of the quantum wells. The spatial distribution of the Talbot fringes outside the mesas mimics the near-field diffraction of a monochromatic wave on a periodic amplitude and phase grating with the grating period comparable to the wavelength. Despite the lossy nature of the polariton system, the Talbot pattern persists for distances exceeding the size of the mesas by an order of magnitude. Thus, our experiment demonstrates efficient shaping of the two-dimensional flow of coherent exciton polaritons by a one-dimensional "flat lens."

Half adder capabilities of a coupled quantum dot device.

In this paper we demonstrate two realizations of a half adder based on a voltage-rectifying mechanism involving two Coulomb-coupled quantum dots. First, we examine the ranges of operation of the half adder's individual elements, the AND and XOR gates, for a single rectifying device. It allows a switching between the two gates by a control voltage and thus enables a clocked half adder operation. The logic gates are shown to be reliably operative in a broad noise amplitude range with negligible error probabilities. Subsequently, we study the implementation of the half adder in a combined double-device consisting of two individually tunable rectifiers. We show that this double device allows a simultaneous operation of both relevant gates at once. The presented devices draw their power solely from electronic fluctuations and are therefore an advancement in the field of energy efficient and autonomous electronics.

Uncovering dispersion properties in semiconductor waveguides to study photon-pair generation.

We investigate the dispersion properties of ridge Bragg-reflection waveguides to deduce their phasematching characteristics. These are crucial for exploiting them as sources of parametric down-conversion (PDC). In order to estimate the phasematching bandwidth we first determine the group refractive indices of the interacting modes via Fabry-Perot experiments in two distant wavelength regions. Second, by measuring the spectra of the emitted PDC photons, we gain access to their group index dispersion. Our results offer a simple approach for determining the PDC process parameters in the spectral domain, and provide important feedback for designing such sources, especially in the broadband case.

[Pain as the primary symptom of a malignant parotid tumour]. / Pijn als primair symptoom van een maligne parotistumor.

The differential diagnosis of peri-auricular pain is comprehensive and arriving at a correct diagnosis is not always easy, which may result in a delay of treatment or even malpractice. Two patients presented themselves with facial peri-auricular pain. After a period of follow-up and control this pain turned out to be related to a malignant tumor in the glandula parotidea. These two cases show the importance for the dentist to refer patients with peri-auricular pain, with or without concomitant facial nerve palsy, to a specialist in a timely manner.

Mode-resolved Fabry-Perot experiment in low-loss Bragg-reflection waveguides.

Based on the interaction between different spatial modes, semiconductor Bragg-reflection waveguides (BRWs) provide a highly functional platform for non-linear optics. For achieving any desired quantum optical functionality, we must control and engineer the properties of each spatial mode. To reach this purpose we extend the Fabry-Perot technique and achieve a detailed linear optical characterization of dispersive multimode semiconductor waveguides. With this efficient broadband spectral method we gain direct experimental access to the relevant modes of our BRWs and determine their group velocities. Furthermore, we show that our waveguides have lower than expected loss coefficients. This renders them suitable for integrated quantum optics applications.