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Defect engineering is foundational to classical electronic device development and for emerging quantum devices. Here, we report on defect engineering of silicon with ion pulses from a laser accelerator in the laser intensity range of 1019 W cm−2 and ion flux levels of up to 1022 ions cm−2 s−1, about five orders of magnitude higher than conventional ion implanters. Low energy ions from plasma expansion of the laser-foil target are implanted near the surface and then diffuse into silicon samples locally pre-heated by high energy ions from the same laser-ion pulse. Silicon crystals exfoliate in the areas of highest energy deposition. Color centers, predominantly W and G-centers, form directly in response to ion pulses without a subsequent annealing step. We find that the linewidth of G-centers increases with high ion flux faster than the linewidth of W-centers, consistent with density functional theory calculations of their electronic structure. Intense ion pulses from a laser-accelerator drive materials far from equilibrium and enable direct local defect engineering and high flux doping of semiconductors.

There is a notable correlation between Eurosceptic and populist political actors, discourses and agendas across Europe. Since 2015, the ongoing conflict between Poland and the European Commission concerning the rule of law has brought European integration to the centre of Polish politics. The main focus of this article is on the relationship and interaction between populism and Euroscepticism, as analysed through the example of Polish political parties. To this end, the article investigates the different forms of EU contestation by Polish populist right-wing parties and assesses the extent to which these are expressed through populist discourse. We find a strong correlation between populist and Eurosceptic attitudes of Polish political parties. With the growing number of populist parties entering the mainstream and 'uncivil society' actors transforming into political parties, the anti-elitist discourse generates a need to locate the 'corrupted elites' outside of the national power structures. [ABSTRACT FROM AUTHOR]

Effective methods to generate colour centres in diamond and other wide band-gap materials are essential to the realisation of solid state quantum technologies based on such systems. Such methods have been the subject of intensive research effort in recent years. In this review, we bring together the various techniques used in the generation and positioning of colour centres in diamond: ion implantation, delta-doping, electron irradiation, laser writing and thermal annealing. We assess the roles and merits of each of these techniques in the formation of colour centres for different quantum technologies and consider future combinations of the techniques to meet the requirements of the most demanding applications.

Here, we investigate the magnetic field dependent photoluminescence (PL) of a fiber-coupled diamond single crystal with a high density of nitrogen vacancy (NV) centers. Angle-dependent magnetic field sweep measurements between 0 and 111 mT were performed using an oscillating illumination combined with lock-in techniques. Besides the expected superposed PL of differently oriented NV centers, a zoo of features in the PL are found. These features can be associated with level anti-crossings and cross relaxations. In particular, PL measurements allowed us to detect auto-cross relaxation between coupled NV centers. Moreover, the PL measurements at low magnetic fields show dips suggesting an interaction of NV centers with additional spin defects. The results presented here are not only a study for NV-based fiber-coupled sensors made of diamond, but also show a way to investigate with manageable effort and purely an optical multispin interaction with at least one NV center as a constituent. [ABSTRACT FROM AUTHOR]

Nuclear magnetic resonance techniques are widely used in the natural sciences but they lack sensitivity. Therefore, large sample volumes or long measurement times are necessary. In this work, we investigate the polarization of bulk 13 C nuclei in a diamond above the thermal equilibrium at room temperature. Previously studied mechanisms utilize direct coupling to nitrogen vacancy centers or the additional assistance of substitutional nitrogen impurities for this purpose. We exploit strongly coupled nitrogen vacancy centers as polarization sources. We study two approaches to transfer the optically induced polarization of the electron spins of the nitrogen vacancy centers to nearby nuclear spins. First, the electron-nuclear polarization transfer is achieved by energy matching conditions or, second, by magnetic field sweeps inducing Landau–Zener-like transitions. Simulations according to a quantum mechanical system consisting of two coupled nitrogen vacancy centers and a weakly coupled 13 C spin show an excellent agreement with the experimental data. Both approaches allow a reduction of the measurement time by roughly three orders of magnitude. [ABSTRACT FROM AUTHOR]

Light‐emitting complex defects in silicon have been considered a potential platform for quantum technologies based on spin and photon degrees of freedom working at telecom wavelengths. Their integration in complex devices is still in its infancy and has been mostly focused on light extraction and guiding. Here the control of the electronic states of carbon‐related impurities (G‐centers) is addressed via strain engineering. By embedding them in patches of silicon on insulator and topping them with SiN, symmetry breaking along [001] and [110] directions is demonstrated, resulting in a controlled splitting of the zero phonon line (ZPL), as accounted for by the piezospectroscopic theoretical framework. The splitting can be as large as 18 meV, and it is finely tuned by selecting patch size or by moving in different positions on the patch. Some of the split, strained ZPLs are almost fully polarized, and their overall intensity is enhanced up to 7 times with respect to the flat areas, whereas their recombination dynamics is slightly affected accounting for the lack of Purcell effect. This technique can be extended to other impurities and Si‐based devices such as suspended bridges, photonic crystal microcavities, Mie resonators, and integrated photonic circuits. [ABSTRACT FROM AUTHOR]

The application of transparent conducting oxides in electronic devices like solar cells or displays is common. By transferring this technology to quantum sensing and computing in the form of microwave conductors, it is possible to benefit from the advantages of these materials. By using indium tin oxide (ITO), it is demonstrated that at an arbitrary position below the conductor, an arbitrary elliptical microwave polarization can be produced by two independent sources. This is independent of the geometry and size of the ITO, whereby a non-resonant microwave approach can be chosen. Using single nitrogen vacancy (NV) centers in diamond in combination with a cross-like ITO structure, each NV center can be addressed with an ideal (clockwise or anticlockwise) microwave polarization. By optimizing the coupling of the microwave field to the NV centers and minimizing the conductor size, the creation of smaller devices compared to common approaches is possible. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate the feasibility of detecting low energy single ions using nanometer-thick and few-micrometer-wide graphite flakes at room temperature. We used electrically contacted samples of highly oriented pyrolytic graphite and measured in situ the change in electrical resistance upon ion irradiation using a self-made nanovoltmeter. Eight samples of different dimensions were prepared and subjected to ion irradiation from various species. A fluence as low as 5 × 10 8 cm − 2 corresponding to a few hundreds of ions irradiated was sufficient to produce a signal significantly above the noise level. Furthermore, we used a model to describe the dependence of the change in electrical resistance on the defect concentration induced by ion irradiation. By extrapolating this model to the level of single ions, our findings support the feasibility of detecting single ions at room temperature using thin graphite as a detector material. [ABSTRACT FROM AUTHOR]

The non-invasively measured initial systolic time interval (ISTI) reflects a time difference between the electrical and pumping activity of the heart and depends on cardiac preload, afterload, autonomic nervous control and training level. However, the duration of the ISTI has not yet been compared to other time markers of the heart cycle. The present study gauges the duration of the ISTI by comparing the end point of this interval, the C-point, with heart cycle markers obtained by echocardiography. The heart rate of 16 healthy subjects was varied by means of an exercise stimulus. It was found that the C-point, and therefore the end point of ISTI, occurred around the moment of the maximum diameter of the aortic arch in all subjects and at all heart rates. However, while the time difference between the opening of the aortic valves and the maximum diameter of the aortic arch decreased significantly with decreasing RR-interval, the time difference with respect to the moment of the C-point remained constant within the subjects. This means that the shortening of the ISTI with increasing heart rate in response to an exercise stimulus was caused by a shortening of the pre-ejection period (PEP). It is concluded that the ISTI can be used as a non-invasive parameter indicating the time difference between the electrical and mechanical pumping activity of the heart, both inside and outside the clinic.

The authors report on the characterization at the single‐defect level of germanium‐vacancy (GeV) centers in diamond produced upon Ge− ion implantation and different subsequent annealing processes, with a specific focus on the effect of high‐pressure‐high‐temperature (HPHT) processing on their quantum‐optical properties. Different post‐implantation annealing conditions are explored for the optimal activation of GeV centers, namely, 900 °C 2 h, 1000 °C 10 h, 1500 °C 1 h under high vacuum, and 2000 °C 15 min at 6 GPa pressure. A systematic analysis of the relevant emission properties, including the emission intensity in saturation regime and the excited state radiative lifetime, is performed on the basis of a set of ion‐implanted samples, with the scope of identifying the most suitable conditions for the creation of GeV centers with optimal quantum‐optical emission properties. The main performance parameter adopted here to describe the excitation efficiency of GeV centers as single‐photon emitters is the ratio between the saturation optical excitation power and the emission intensity at saturation. The results show an up to eightfold emission efficiency increase in HPHT‐treated samples with respect to conventional annealing in vacuum conditions, suggesting a suitable thermodynamic pathway toward the repeatable fabrication of ultra‐bright GeV centers for single‐photon generation purposes. [ABSTRACT FROM AUTHOR]

The Initial Systolic Time Interval (ISTI) has been defined as the time difference between the peak electrical and peak mechanical activity of the heart. ISTI is obtained from the electro-cardiogram and the impedance cardiogram. The response of ISTI while breathing at rest and to a deep breathing stimulus was studied in a group of patients suffering from Parkinson’s disease (PD) and a group of healthy control subjects. ISTI showed substantial variability during these manoeuvres. The tests showed that the variability of RR and ISTI was substantially different between PD patients and controls. It is hypothesized that in PD patients the sympathetic nervous system compensates for the loss of regulatory control function of the blood-pressure by the parasympathetic system. It is concluded that ISTI is a practical, additional and independent parameter that can be used to assist other tests in evaluating autonomic nervous control of the heart in PD patients.

The Initial Systolic Time Interval (ISTI), obtained from the electrocardiogram (ECG) and impedance cardiogram (ICG), is considered to be a measure for the time delay between the electrical and mechanical activity of the heart and reflects an early active period of the cardiac cycle. The clinical relevance of this time interval is subject of study. This paper introduces a method using ISTI to evaluate and predict the circulatory response to fluid administration in patients after coronary artery bypass graft surgery and presents preliminary results of a pilot study by comparing ISTI with cardiac output (CO) responsiveness. Also the use of the pulse transit time (PTT), earlier recommended for this purpose, was investigated. The results showed an inverse relationship between ISTI and CO at all moments of fluid administration and also an inverse relationship between the changes ΔISTI and ΔCO before and after full fluid administration. No relationships between PTT and CO or ΔPTT and ΔCO were found. It is concluded that ISTI is dependent upon preload, and that ISTI has the potential to be used as a clinical parameter assessing preload.

An integrated magnetic sensor is designed and tested that utilizes the negatively charged nitrogen vacancy centers (NVC) in diamond as a magnetic field‐sensitive quantum material, which is accessed and readout solely optically. The compact sensor device features a side length of 10 mm and includes a small HPHT diamond slab, light‐emitting diode (LED) for excitation, and integrated photodiodes. A microwave‐free approach is used. With the device, DC sensitivity to magnetic fields of 49 nA mT−1 in the range of 5–50 mT is achieved. The sensor device is also capable of detecting very small magnetic fields: Magnetic field dependencies at very low flux densities in the μT range (zero‐magnetic field) show a characteristic fluorescence behavior revealing a sensitivity of 4.8 pA μT−1. Additionally, a ray‐tracing model is applied, to identify loss mechanisms in the setup. Using this device, an ultracompact, reliable, and industry‐ready package is made available for sensor developments in industry and academia. [ABSTRACT FROM AUTHOR]

The detection of physiological activity at the microscopic level is key for understanding the function of biosystems and relating this to their physical structure. Current sensing methods for in vitro study of living tissue often rely on invasive probes to stimulate and detect activity, bearing the risk of inducing damage in the target system. In recent years, a new type of quantum sensor based on color centers in diamond has begun to offer the possibility to instead passively sense and image living biological systems. Here, we use such a sensor to realize the recording of the biomagnetic field generated by tightly focused, high intensity pulsed laser optogenetic neuromuscular stimulation of extensor digitorum longus muscles, dissected from mice and kept alive in carbogenated solution. Recordings captured a compound action potential response and a slow signal component, which we seek to explain using a detailed model of the biological system. We show proof-of-principle experimental recording of localized neuromuscular activity from the laser stimulation site without photovoltaic or fluorescence artifacts associated with alternative techniques. Our work represents a further step toward passive sensing and imaging at the microscopic level with quantum sensing, enabling further research into mapping of neural activity and intracellular processes. [ABSTRACT FROM AUTHOR]

Silicon‐based micro‐ and nano‐structures for light management at near‐infrared and visible frequencies have been widely exploited for guided optics and metasurfaces. However, light emission with this material has been hampered by the indirect character of its bandgap. Here it is shown that, via ion beam implantation, light emitting G‐centers can be directly embedded within Si‐based Mie resonators previously obtained by solid state dewetting. Size‐ and position‐dependent, directional light emission at 120 K is demonstrated experimentally and confirmed by finite difference time domain simulations. It is estimated that, with an optimal coupling of the G‐centers emission with the resonant antennas, a collection efficiency of about 90% can be reached using a conventional objective lens. The integration of these telecom‐frequency emitters in resonant antennas is relevant for their efficient exploitation in quantum optics applications and more generally to Si‐based photonic metasurfaces. [ABSTRACT FROM AUTHOR]

We report the fabrication of isolated G centers in silicon with single photon emission at optical telecommunication wavelengths. Our sample is made from a silicon-on-insulator wafer, which is locally implanted with carbon ions and protons at various fluences. Decreasing the implantation fluences enables us to gradually switch from large ensembles to isolated single defects, reaching areal densities of G centers down to ∼0.2 μm−2. Single defect creation is demonstrated by photon antibunching in intensity-correlation experiments, thus establishing our approach as an effective procedure for generating single artificial atoms in silicon for future quantum technologies. [ABSTRACT FROM AUTHOR]

Meanders formed where the Antarctic Circumpolar Current (ACC) interacts with topography have been identified as dynamical hot spots, characterized by enhanced eddy energy, momentum transfer, and cross-front exchange. However, few studies have used observations to diagnose the dynamics of ACC standing meanders. We use a synoptic hydrographic survey and satellite altimetry to explore the momentum and vorticity balance of a Subantarctic Front standing meander, downstream of the Southeast Indian Ridge. Along-stream anomalies of temperature in the upper ocean (150–600 m) show along-stream cooling entering the surface trough and along-stream warming entering the surface crest, while warming is observed from trough to crest in the deeper ocean (600–1500 m). Advection of relative vorticity is balanced by vortex stretching, as found in model studies of meandering currents. Meander curvature is sufficiently large that the flow is in gradient wind balance, resulting in ageostrophic horizontal divergence. This drives downwelling of cooler water along isopycnals entering the surface trough and upwelling of warmer water entering the surface crest, consistent with the observed evolution of temperature anomalies in the upper ocean. Progressive along-stream warming observed between 600 and 1500 m likely reflects cyclogenesis in the deep ocean. Vortex stretching couples the upper and lower water column, producing a low pressure at depth between surface trough and crest and cyclonic flow that carries cold water equatorward in the surface trough and warm water poleward in the surface crest (poleward heat flux). The results highlight gradient–wind balance and cyclogenesis as central to dynamics of standing meanders and their critical role in the ACC momentum and vorticity balance. Significance Statement: The Antarctic Circumpolar Current (ACC) in the Southern Ocean is a nearly zonal current that encircles Antarctica. It acts as a barrier between warmer water equatorward and colder water poleward. In a few regions where the current encounters strong topographic changes, the current meanders and opens a pathway for heat to travel across the ACC toward Antarctica. We surveyed a meander in the ACC and examined the along-stream change of temperature. In the upper ocean, temperature changes are caused by a vertical circulation, bringing cool water down when entering the surface trough (the part of the meander closest to the equator), and warm water up when exiting the surface trough and entering the surface crest. At depth, cold water is transported equatorward in the surface trough and warm water poleward in the surface crest, leading to a net transport of heat poleward. This study highlights the importance of the secondary circulation within a meander for generating cross-ACC flows and moving heat toward Antarctica. [ABSTRACT FROM AUTHOR]

Background: An important focus of post-stroke physical therapy is to improve walking and walking capacity. However, many people after stroke experience difficulties with gait-related participation, which includes more than walking capacity alone. Gait-related participation involves walking with a participation goal and requires to deal with changes in the environment during walking and perform dual tasks, for example. Objective: To explore barriers and facilitators for gait-related participation from the perspective of people after stroke. This knowledge can contribute to the development of effective interventions to improve gait-related participation. Methods: Semi-structured interviews were conducted to investigate how people after stroke experience gait-related participation. Audio-recorded interviews were transcribed, anonymized, and analyzed thematically. Barriers and facilitators were categorized according to the International Classification of Functioning, Disability and Health (ICF) framework. Results: Twenty-one people after stroke participated. Median age was 65 years, median time since stroke 16 weeks. Barriers were reported in movement-related functions, cognitive functions, mobility, personal factors, and environmental factors. Facilitators were found on participation level and in personal and environmental factors, such as motivation and family support. Conclusion: People after stroke who were physically able to walk independently still described multiple barriers to gait-related participation in all components of the ICF framework. [ABSTRACT FROM AUTHOR]