University of Paderborn

About: University of Paderborn is a education organization based out in Paderborn, Nordrhein-Westfalen, Germany. It is known for research contribution in the topics: Control reconfiguration & Software. The organization has 6684 authors who have published 16929 publications receiving 323154 citations.

Limits on the deterministic creation of pure single-photon states using parametric down-conversion

Abstract: Parametric down-conversion (PDC) is one of the most widely used methods to create pure single-photon states for quantum information applications. However, little attention has been paid to higher-order photon components in the PDC process, yet these ultimately limit the prospects of generating single photons of high quality. In this paper we investigate the impact of higher-order photon components and multiple frequency modes on the heralding rates and single-photon fidelities. This enables us to determine the limits of PDC sources for single-photon generation. Our results show that a perfectly single-mode PDC source in conjunction with a photon-number-resolving detector is ultimately capable of creating single-photon Fock states with unit fidelity and a maximal state creation probability of 25$%$. Hence, an array of 17 switched sources is required to build a deterministic ($g$99$%$ emission probability) pure single-photon source.

Sensor Scheduling in Variance Based Event Triggered Estimation With Packet Drops

Abstract: This paper considers a remote state estimation problem with multiple sensors observing a dynamical process, where sensors transmit local state estimates over an independent and identically distributed (i.i.d.) packet dropping channel to a remote estimator. At every discrete time instant, the remote estimator decides whether each sensor should transmit or not, with each sensor transmission incurring a fixed energy cost. The channel is shared such that collisions will occur if more than one sensor transmits at a time. Performance is quantified via an optimization problem that minimizes a convex combination of the expected estimation error covariance at the remote estimator and expected energy usage across the sensors. For transmission schedules dependent only on the estimation error covariance at the remote estimator, this work establishes structural results on the optimal scheduling which show that: 1) for unstable systems, if the error covariance is large then a sensor will always be scheduled to transmit and 2) there is a threshold-type behavior in switching from one sensor transmitting to another. Specializing to the single sensor case, these structural results demonstrate that a threshold policy (i.e., transmit if the error covariance exceeds a certain threshold and don't transmit otherwise) is optimal. We also consider the situation where sensors transmit measurements instead of state estimates, and establish structural results including the optimality of threshold policies for the single sensor, scalar case. These results provide a theoretical justification for the use of such threshold policies in variance based event triggered estimation. Numerical studies confirm the qualitative behavior predicted by our structural results.

ClassSheets: automatic generation of spreadsheet applications from object-oriented specifications

Abstract: Spreadsheets are widely used in all kinds of business applications. Numerous studies have shown that they contain many errors that sometimes have dramatic impacts. One reason for this situation is the low-level, cell-oriented development process of spreadsheets.We improve this process by introducing and formalizing a higher-level object-oriented model termed ClassSheet. While still following the tabular look-and feel of spreadsheets, ClassSheets allow the developer to express explicitly business object structures within a spreadsheet, which is achieved by integrating concepts from the UML (Unified Modeling Language). A stepwise automatic transformation process generates a spreadsheet application that is consistent with the ClassSheet model. Thus, by deploying the formal underpinning of ClassSheets, a large variety of errors can be prevented that occur in many existing spreadsheet applications today.The presented ClassSheet approach links spreadsheet applications to the object-oriented modeling world and advocates an automatic model-driven development process for spreadsheet applications of high quality.