Visible-to-telecom quantum frequency conversion of light from a single quantum emitter

Quantum frequency conversion (QFC), a nonlinear optical process in which the frequency of a quantum light field is altered while conserving its non-classical correlations, was first demonstrated 20 years ago. Meanwhile, it is considered an essential tool for the implementation of quantum repeaters since it allows for interfacing quantum memories with telecom-wavelength photons as quantum information carriers. Here we demonstrate efficient (>30%) QFC of visible single photons (711 nm) emitted by a quantum dot (QD) to a telecom wavelength (1,313 nm). Analysis of the first and second-order coherence before and after wavelength conversion clearly proves that important properties, such as the coherence time and photon antibunching, are fully conserved during the frequency translation process. Our findings underline the great potential of single photon sources on demand in combination with QFC as a promising technique for quantum repeater schemes.Comment: 11 pages, 4 figure

Inducing micromechanical motion by optical excitation of a single quantum dot

Hybrid quantum optomechanical systems1 interface a macroscopic mechanical degree of freedom with a single two-level system such as a single spin2–4, a superconducting qubit5–7 or a single optical emitter8–12. Recently, hybrid systems operating in the microwave domain have witnessed impressive progress13,14. Concurrently, only a few experimental approaches have successfully addressed hybrid systems in the optical domain, demonstrating that macroscopic motion can modulate the two-level system transition energy9,10,15. However, the reciprocal effect, corresponding to the backaction of a single quantum system on a macroscopic mechanical resonator, has remained elusive. In contrast to an optical cavity, a two-level system operates with no more than a single energy quantum. Hence, it requires a much stronger hybrid coupling rate compared to cavity optomechanical systems1,16. Here, we build on the large strain coupling between an oscillating microwire and a single embedded quantum dot9. We resonantly drive the quantum dot’s exciton using a laser modulated at the mechanical frequency. State-dependent strain then results in a time-dependent mechanical force that actuates microwire motion. This force is almost three orders of magnitude larger than the radiation pressure produced by the photon flux interacting with the quantum dot. In principle, the state-dependent force could constitute a strategy to coherently encode the quantum dot quantum state onto a mechanical degree of freedom1

Practical examination of bystanders performing Basic Life Support in Germany: a prospective manikin study

<p>Abstract</p> <p>Background</p> <p>In an out-of-hospital emergency situation bystander intervention is essential for a sufficient functioning of the chain of rescue. The basic measures of cardiopulmonary resuscitation (Basic Life Support – BLS) by lay people are therefore definitely part of an effective emergency service of a patient needing resuscitation. Relevant knowledge is provided to the public by various course conceptions. The learning success concerning a one day first aid course ("LSM" course in Germany) has not been much investigated in the past. We investigated to what extent lay people could perform BLS correctly in a standardised manikin scenario. An aim of this study was to show how course repetitions affected success in performing BLS.</p> <p>Methods</p> <p>The "LSM course" was carried out in a standardised manner. We tested prospectively 100 participants in two groups (<b>Group 1: </b>Participants with previous attendance of a BLS course; <b>Group 2: </b>Participants with no previous attendance of a BLS course) in their practical abilities in BLS after the course. Success parameter was the correct performance of BLS in accordance with the current ERC guidelines.</p> <p>Results</p> <p>Twenty-two (22%) of the 100 investigated participants obtained satisfactory results in the practical performance of BLS. Participants with repeated participation in BLS obtained significantly better results (<b>Group 1: </b>32.7% vs. <b>Group 2: </b>10.4%; p < 0.01) than course participants with no relevant previous knowledge.</p> <p>Conclusion</p> <p>Only 22% of the investigated participants at the end of a "LSM course" were able to perform BLS satisfactorily according to the ERC guidelines. Participants who had previously attended comparable courses obtained significantly better results in the practical test. Through regular repetitions it seems to be possible to achieve, at least on the manikin, an improvement of the results in bystander resuscitation and, consequently, a better patient outcome. To validate this hypothesis further investigations are recommended by specialised societies.</p

Grand Theft Auto-Based Cycling Simulator for Cognitive Enhancement Technologies in Dangerous Traffic Situations

While developing traffic-based cognitive enhancement technology (CET), such as bike accident prevention systems, it can be challenging to test and evaluate them properly. After all, the real-world scenario could endanger the subjects’ health and safety. Therefore, a simulator is needed, preferably one that is realistic yet low cost. This paper introduces a way to use the video game Grand Theft Auto V (GTA V) and its sophisticated traffic system as a base to create such a simulator, allowing for the safe and realistic testing of dangerous traffic situations involving cyclists, cars, and trucks. The open world of GTA V, which can be explored on foot and via various vehicles, serves as an immersive stand-in for the real world. Custom modification scripts of the game give the researchers control over the experiment scenario and the output data to be evaluated. An off-the-shelf bicycle equipped with three sensors serves as a realistic input device for the subject’s movement direction and speed. The simulator was used to test two early-stage CET concepts enabling cyclists to sense dangerous traffic situations, such as trucks approaching from behind the cyclist. Thus, this paper also presents the user evaluation of the cycling simulator and the CET used by the subjects to sense dangerous traffic situations. With the knowledge of the first iteration of the user-centered design (UCD) process, this paper concludes by naming improvements for the cycling simulator and discussing further research directions for CET that enable users to sense dangerous situations better

Cellular uptake of nanoparticles as determined by particle properties, experimental conditions, and cell type

The increased application of nanoparticles (NPs) is increasing the risk of their release into the environment. Although many toxicity studies have been conducted, the environmental risk is difficult to estimate, because uptake mechanisms are often not determined in toxicity studies. In the present study, the authors review dominant uptake mechanisms of NPs in cells, as well as the effect of NP properties, experimental conditions, and cell type on NP uptake. Knowledge of NP uptake is crucial for risk assessment and is essential to predict the behavior of NPs based on their physical-chemical properties. Important uptake mechanisms for eukaryotic cells are macropinocytosis, receptor-mediated endocytosis, and phagocytosis in specialized mammalian cells. The studies reviewed demonstrate that uptake into nonphagocytic cells depends strongly on NP size, with an uptake optimum at an NP diameter of approximately 50nm. Increasing surface charges, either positive or negative, have been shown to increase particle uptake in comparison with uncharged NPs. Another important factor is the degree of (homo-) aggregation. Results regarding shape have been ambiguous. Difficulties in the production of NPs, with 1 property changed at a time, call for a full characterization of NP properties. Only then will it be possible to draw conclusions as to which property affected the uptake. Environ Toxicol Chem 2014;33:481-492. © 2013 SETAC