A wavelength-tunable fiber-coupled source of narrowband entangled photons

We demonstrate a wavelength-tunable, fiber-coupled source of polarization-entangled photons with extremely high spectral brightness and quality of entanglement. Using a 25 mm PPKTP crystal inside a polarization Sagnac interferometer we detect a spectral brightness of 273000 pairs/(s mW nm), a factor of 28 better than comparable previous sources while state tomography showed the two-photon state to have a tangle of T=0.987. This improvement was achieved by use of a long crystal, careful selection of focusing parameters and single-mode fiber coupling. We demonstrate that, due to the particular geometry of the setup, the signal and idler wavelengths can be tuned over a wide range without loss of entanglement.Comment: 10 pages, 5 figures. Article rewritten, added Fig.(1a-1b). Published in Optics Express, comments welcom

Experimental quantum teleportation over a high-loss free-space channel

We present a high-fidelity quantum teleportation experiment over a high-loss free-space channel between two laboratories. We teleported six states of three mutually unbiased bases and obtained an average state fidelity of 0.82(1), well beyond the classical limit of 2/3. With the obtained data, we tomographically reconstructed the process matrices of quantum teleportation. The free-space channel attenuation of 31 dB corresponds to the estimated attenuation regime for a down-link from a low-earth-orbit satellite to a ground station. We also discussed various important technical issues for future experiments, including the dark counts of single-photon detectors, coincidence-window width etc. Our experiment tested the limit of performing quantum teleportation with state-of-the-art resources. It is an important step towards future satellite-based quantum teleportation and paves the way for establishing a worldwide quantum communication network

Pilot study: rapidly cycling hypobaric pressure improves pain after 5 days in adiposis dolorosa

Adiposis dolorosa (AD) is a rare disorder of painful nodular subcutaneous fat accompanied by fatigue, difficulty with weight loss, inflammation, increased fluid in adipose tissue (lipedema and lymphedema), and hyperalgesia. Sequential compression relieves lymphedema pain; we therefore hypothesized that whole body cyclic pneumatic hypobaric compression may relieve pain in AD. To avoid exacerbating hyperalgesia, we utilized a touch-free method, which is delivered via a high-performance altitude simulator, the Cyclic Variations in Altitude Conditioning™ (CVAC™) process. As a pilot study, 10 participants with AD completed pain and quality of life questionnaires before and after 20–40 minutes of CVAC process daily for 5 days. Participants lost weight (195.5 ± 17.6–193.8 ± 17.3 lb; P = 0.03), and bioimpedance significantly decreased (510 ± 36–490 ± 38 ohm; P = 0.01). There was a significant decrease in scores on the Pain Catastrophizing Scale (P = 0.039), in average (P = 0.002), highest (P = 0.029), lowest (P = 0.04), and current pain severity (P = 0.02) on the Visual Analogue Scale, but there was no change in pain quality by the McGill Pain Questionnaire. There were no significant changes in total and physical SF-36 scores, but the mental score improved significantly (P = 0.049). There were no changes in the Pain Disability Index or Pittsburgh Sleep Quality Index. These data present a potential, new, noninvasive means of treating pain in AD by whole body pneumatic compression as part of the CVAC process. Although randomized, controlled trials are needed to confirm these data, the CVAC process could potentially help in treating AD pain and other chronic pain disorders

Determining the Quality of Product Data Integration

To meet customer demands, companies must manage numerous variants and versions of their products. Since product-related data (e.g., requirements' specifications, geometric models, and source code, or test cases) are usually scattered over a large number of heterogeneous, autonomous information systems, their integration becomes crucial when developing complex products on one hand and aiming at reduced development costs on the other. In general, product data are created in different stages of the product development process. Furthermore, they should be integrated in a complete and consistent way at certain milestones during process development (e.g., prototype construction). Usually, this data integration process is accomplished manually, which is both costly and error prone. Instead semi-automated product data integration is required meeting the data quality requirements of the various stages during product development. In turn, this necessitates a close monitoring of the progress of the data integration process based on proper metrics. Contemporary approaches solely focus on metrics assessing schema integration, while not measuring the quality and progress of data integration. This paper elicits fundamental requirements relevant in this context. Based on them, we develop appropriate metrics for measuring product data quality and apply them in a case study we conducted at an automotive original equipment manufacturer

Quantum erasure with causally disconnected choice

The counterintuitive features of quantum physics challenge many common-sense assumptions. In an interferometric quantum eraser experiment, one can actively choose whether or not to erase which-path information, a particle feature, of one quantum system and thus observe its wave feature via interference or not by performing a suitable measurement on a distant quantum system entangled with it. In all experiments performed to date, this choice took place either in the past or, in some delayed-choice arrangements, in the future of the interference. Thus in principle, physical communications between choice and interference were not excluded. Here we report a quantum eraser experiment, in which by enforcing Einstein locality no such communication is possible. This is achieved by independent active choices, which are space-like separated from the interference. Our setup employs hybrid path-polarization entangled photon pairs which are distributed over an optical fiber link of 55 m in one experiment, or over a free-space link of 144 km in another. No naive realistic picture is compatible with our results because whether a quantum could be seen as showing particle- or wave-like behavior would depend on a causally disconnected choice. It is therefore suggestive to abandon such pictures altogether

Unterstützung informellen Lernens Studierender. Möglichkeiten studentischen Arbeitens mit Social Software

Innerhalb des Projektes „Learner Communities of Practice“ (LCP) wurde mit Förderung durch das Sächsische Staatsministerium für Wissenschaft und Kunst ein Schulungskonzept entwickelt, welches das informelle Lernen Studierender in der Studieneingangsphase mittels Social-Software-Tools unterstützt. Der Beitrag beschreibt die didaktische und technische Umsetzung des Schulungskonzeptes, stellt die Ergebnisse einer testweisen Durchführung dar und skizziert generelle Herausforderungen beim Einsatz von Social Software in der akademischen Aus- und Weiterbildung. (DIPF/Orig.