Time-of-flight imaging of invisibility cloaks

As invisibility cloaking has recently become experimental reality, it is interesting to explore ways to reveal remaining imperfections. In essence, the idea of most invisibility cloaks is to recover the optical path lengths without an object (to be made invisible) by a suitable arrangement around that object. Optical path length is proportional to the time of flight of a light ray or to the optical phase accumulated by a light wave. Thus, time-of-flight images provide a direct and intuitive tool for probing imperfections. Indeed, recent phase-sensitive experiments on the carpet cloak have already made early steps in this direction. In the macroscopic world, time-of-flight images could be measured directly by light detection and ranging (LIDAR). Here, we show calculated time-of-flight images of the conformal Gaussian carpet cloak, the conformal grating cloak, the cylindrical free-space cloak, and of the invisible sphere. All results are obtained by using a ray-velocity equation of motion derived from Fermat’s principle

Fractional excitations in cold atomic gases

We study the behavior of excitations in the tilted one-dimensional Bose-Hubbard model. In the phase with broken symmetry, fundamental excitations are domain walls which show fractional statistics. Using perturbation theory, we derive an analytic model for the time evolution of these fractional excitations, and demonstrate the existence of a repulsively bound state above a critical center-of-mass momentum. The validity of the perturbative analysis is confirmed by the use of time-adaptive density-matrix renormalization group simulations. These findings open the path for the experimental detection of fractional particles in cold atomic gases

Quantum Computing for High-Energy Physics: State of the Art and Challenges. Summary of the QC4HEP Working Group

Quantum computers offer an intriguing path for a paradigmatic change of computing in the natural sciences and beyond, with the potential for achieving a so-called quantum advantage, namely a significant (in some cases exponential) speed-up of numerical simulations. The rapid development of hardware devices with various realizations of qubits enables the execution of small scale but representative applications on quantum computers. In particular, the high-energy physics community plays a pivotal role in accessing the power of quantum computing, since the field is a driving source for challenging computational problems. This concerns, on the theoretical side, the exploration of models which are very hard or even impossible to address with classical techniques and, on the experimental side, the enormous data challenge of newly emerging experiments, such as the upgrade of the Large Hadron Collider. In this roadmap paper, led by CERN, DESY and IBM, we provide the status of high-energy physics quantum computations and give examples for theoretical and experimental target benchmark applications, which can be addressed in the near future. Having the IBM 100 x 100 challenge in mind, where possible, we also provide resource estimates for the examples given using error mitigated quantum computing

Evaluation and management of postpartum hemorrhage : consensus from an international expert panel

BACKGROUND: Postpartum hemorrhage (PPH) remains one of the leading causes of maternal morbidity and mortality worldwide, although the lack of a precise definition precludes accurate data of the absolute prevalence of PPH. STUDY DESIGN AND METHODS: An international expert panel in obstetrics, gynecology, hematology, transfusion, and anesthesiology undertook a comprehensive review of the literature. At a meeting in November 2011, the panel agreed on a definition of severe PPH that would identify those women who were at a high risk of adverse clinical outcomes. RESULTS: The panel agreed on the following definition for severe persistent (ongoing) PPH: "Active bleeding >1000\u2009mL within the 24 hours following birth that continues despite the use of initial measures including first-line uterotonic agents and uterine massage." A treatment algorithm for severe persistent PPH was subsequently developed. Initial evaluations include measurement of blood loss and clinical assessments of PPH severity. Coagulation screens should be performed as soon as persistent (ongoing) PPH is diagnosed, to guide subsequent therapy. If initial measures fail to stop bleeding and uterine atony persists, second- and third-line (if required) interventions should be instated. These include mechanical or surgical maneuvers, i.e., intrauterine balloon tamponade or hemostatic brace sutures with hysterectomy as the final surgical option for uncontrollable PPH. Pharmacologic options include hemostatic agents (tranexamic acid), with timely transfusion of blood and plasma products playing an important role in persistent and severe PPH. CONCLUSION: Early, aggressive, and coordinated intervention by health care professionals is critical in minimizing blood loss to ensure optimal clinical outcomes in management of women with severe, persistent PPH