University of Vienna

About: University of Vienna is a education organization based out in Vienna, Austria. It is known for research contribution in the topics: Population & Context (language use). The organization has 44686 authors who have published 95840 publications receiving 2907492 citations.

Remote quantum entanglement between two micromechanical oscillators

Abstract: Entanglement, an essential feature of quantum theory that allows for inseparable quantum correlations to be shared between distant parties, is a crucial resource for quantum networks1. Of particular importance is the ability to distribute entanglement between remote objects that can also serve as quantum memories. This has been previously realized using systems such as warm2,3 and cold atomic vapours4,5, individual atoms6 and ions7,8, and defects in solid-state systems9–11. Practical communication applications require a combination of several advantageous features, such as a particular operating wavelength, high bandwidth and long memory lifetimes. Here we introduce a purely micromachined solid-state platform in the form of chip-based optomechanical resonators made of nanostructured silicon beams. We create and demonstrate entanglement between two micromechanical oscillators across two chips that are separated by 20 centimetres . The entangled quantum state is distributed by an optical field at a designed wavelength near 1,550 nanometres. Therefore, our system can be directly incorporated in a realistic fibre-optic quantum network operating in the conventional optical telecommunication band. Our results are an important step towards the development of large-area quantum networks based on silicon photonics. Remote quantum entanglement is demonstrated in a micromachined solid-state system comprising two optomechanical oscillators across two chips physically separated by 20 cm and with an optical separation of around 70 m.

The anomalous magnetic moment of the muon in the Standard Model

Abstract: We review the present status of the Standard Model calculation of the anomalous magnetic moment of the muon. This is performed in a perturbative expansion in the fine-structure constant $\alpha$ and is broken down into pure QED, electroweak, and hadronic contributions. The pure QED contribution is by far the largest and has been evaluated up to and including $\mathcal{O}(\alpha^5)$ with negligible numerical uncertainty. The electroweak contribution is suppressed by $(m_\mu/M_W)^2$ and only shows up at the level of the seventh significant digit. It has been evaluated up to two loops and is known to better than one percent. Hadronic contributions are the most difficult to calculate and are responsible for almost all of the theoretical uncertainty. The leading hadronic contribution appears at $\mathcal{O}(\alpha^2)$ and is due to hadronic vacuum polarization, whereas at $\mathcal{O}(\alpha^3)$ the hadronic light-by-light scattering contribution appears. Given the low characteristic scale of this observable, these contributions have to be calculated with nonperturbative methods, in particular, dispersion relations and the lattice approach to QCD. The largest part of this review is dedicated to a detailed account of recent efforts to improve the calculation of these two contributions with either a data-driven, dispersive approach, or a first-principle, lattice-QCD approach. The final result reads $a_\mu^\text{SM}=116\,591\,810(43)\times 10^{-11}$ and is smaller than the Brookhaven measurement by 3.7$\sigma$. The experimental uncertainty will soon be reduced by up to a factor four by the new experiment currently running at Fermilab, and also by the future J-PARC experiment. This and the prospects to further reduce the theoretical uncertainty in the near future-which are also discussed here-make this quantity one of the most promising places to look for evidence of new physics.

On the global convergence of stochastic fictitious play

Abstract: We establish global convergence results for stochastic fictitious play for four classes of games: games with an interior ESS, zero sum games, potential games, and supermodular games. We do so by appealing to techniques from stochastic approximation theory, which relate the limit behavior of a stochastic process to the limit behavior of a differential equation defined by the expected motion of the process. The key result in our analysis of supermodular games is that the relevant differential equation defines a strongly monotone dynamical system. Our analyses of the other cases combine Lyapunov function arguments with a discrete choice theory result: that the choice probabilities generated by any additive random utility model can be derived from a deterministic model based on payoff perturbations that depend nonlinearly on the vector of choice probabilities.

Ultrasonographic Guidance Improves Sensory Block and Onset Time of Three-in-One Blocks

Abstract: The use of ultrasound reduces the onset time, improves the quality of sensory block, and minimizes the risks associated with the supraclavicular approach for brachial plexus and stellate ganglion blockade. The present study was designed to evaluate whether ultrasound also facilitates the approach for 3-in-1 blocks. Forty patients (ASA physical status II or III) undergoing hip surgery after trauma were randomly assigned to two groups. In the ultrasound (US) group, 20 mL bupivaCaine 0.5% was administered under US guidance, whereas in the control group, the same amount and concentration of local anesthetic was administered with the assistance of a nerve stimulator (NS). After US- or NS-based identification of the femoral nerve, the local anesthetic solution was administered, and the distribution of the local anesthetic solution was visualized and recorded on videotape in the US group. The quality and the onset of the sensory block was assessed by using the pinprick test in the central sensory region of each of the three nerves and compared with the same stimulation on the contralateral leg every 10 min for 60 min. The rating was performed using a scale from 100% (uncompromised sensibility) to 0% (no sensory sensation). Heart rate, noninvasive blood pressure, and oxygen saturation were measured at short intervals for 60 min. The onset of sensory blockade was significantly shorter in Group US compared with Group NS (US 16 ? 14 min, NS 27 -C 16 min, P < 0.05). The quality of the sensory block after injection of the local anesthetic was also significantly better in Group US compared with Group NS (US 15% -C 10% of initial value, NS 27% + 14% of initial value, P < 0.05). A good analgesic effect was achieved in 95% of the patients in the US group and in 85% of the patients in the NS group. In the US group, visualization of the cannula tip, the femoral nerve, the major vessels, and the local anesthetic spread was possible in 85% of patients. Incidental arterial puncture (n = 3) was observed only in the NS group. We conclude that an USguided approach for 3-in-1 block reduces the onset time, improves the quality of the sensory block and minimizes the risks associated with this regional anesthetic technique. Implications: The onset time and the quality of a regional anesthetic technique for the lower extremity is improved by ultrasonographic nerve identification compared with older techniques. (Anesth Analg 1997;85:854-7) he 3-in-1 block, including the femoral nerve, the obturator nerve, and the lateral cutaneous femoral nerve, is a widely used regional anesthetic technique for many operations and for pain management of the lower extremity. Indications for the 3-in-1 block include operations and wound care of the thigh, muscle biopsy of the thigh, obturator paralysis for transurethral resection of the prostate and urinary bladder, and, in combination with the sciatic nerve block, all operations for one lower limb. For analgesic therapy, the 3-in-1 block can be used for hip fractures, stump pain after amputation of lower limb, and mobilization therapy of the knee and hip joint.

Bond-Forming and -Breaking Reactions at Sulfur(IV): Sulfoxides, Sulfonium Salts, Sulfur Ylides, and Sulfinate Salts.

Abstract: Organosulfur compounds have long played a vital role in organic chemistry and in the development of novel chemical structures and architectures. Prominent among these organosulfur compounds are those involving a sulfur(IV) center, which have been the subject of countless investigations over more than a hundred years. In addition to a long list of textbook sulfur-based reactions, there has been a sustained interest in the chemistry of organosulfur(IV) compounds in recent years. Of particular interest within organosulfur chemistry is the ease with which the synthetic chemist can effect a wide range of transformations through either bond formation or bond cleavage at sulfur. This review aims to cover the developments of the past decade in the chemistry of organic sulfur(IV) molecules and provide insight into both the wide range of reactions which critically rely on this versatile element and the diverse scaffolds that can thereby be synthesized.