1,337 research outputs found
Desert navigator: the journey of an ant/ Rüdiger Wehner
No full textIncludes bibliographical references and index"How does a small-brained ant living in the Sahara desert know where it is when searching for prey in the vast expanse of sand and gravel? In Desert Navigator Rudiger Wehner describes and illustrates, in a lively and lucid narrative, how the ants accomplish their navigational tasks by using visual cues in the sky that humans are unable to see, the Earth's magnetic field, the direction of the wind, a step counter, an optic-flow meter and path integrator as well panoramic 'snapshots' of their landmark surroundings, and how they combine all this information to optimally steer their courses. Moreover, a glimpse into the navigator's brain reveals the kind of neural circuitry mediating the observed behavior. Truly, the desert ants have now become model organisms in the study of animal navigation. In telling this discovery story, which he enriches by frequent excursions to other animals and even humans, the author lets us participate in the joys and challenges experienced on a fascinating journey to the desert navigator"--Setting the scene -- The thermophiles -- Finding directions -- Estimating distances -- Integrating paths -- Using landmarks -- Organizing the journey1 online resource (392 pages
Quantum resource-saving protocols for early quantum networks
No full textThe Internet as we know it has had an immense impact on the way we communicate. We can now do it faster and more securely than ever before. Enabling quantum communication between any two points on Earth is the next step towards even more secure communication. This is the goal of the quantum internet. Although it is hard to predict all of the applications for the quantum internet, many protocols running on a network connecting nodes able to process qubits have already been identified. Typically, these applications require many qubits to be realized, a requirement which will not likely be met in the early quantum internet.QID/Wehner Grou
SimulaQron—a simulator for developing quantum internet software
No full textWe introduce a simulator of a quantum internet with the specific goal to support software development. A quantum internet consists of local quantum processors, which are interconnected by quantum communication channels that enable the transmission of qubits between the different processors. While many simulators exist for local quantum processors, there is presently no simulator for a quantum internet tailored towards software development. Quantum internet protocols require both classical as well as quantum information to be exchanged between the network nodes, next to the execution of gates and measurements on a local quantum processor. This requires quantum internet software to integrate classical communication programming practises with novel quantum ones. SimulaQron is built to enable application development and explore software engineering practises for a quantum internet. SimulaQron can be run on one or more classical computers to simulate local quantum processors, which are transparently connected in the background to enable the transmission of qubits or the generation of entanglement between remote processors. Application software can access the simulated local quantum processors to execute local quantum instructions and measurements, but also to transmit qubits to remote nodes in the network. SimulaQron features a modular design that performs a distributed simulation based on any existing simulation of a quantum computer capable of integrating with Python. Programming libraries for Python and C are provided to facilitate application development.Accepted Author ManuscriptQID/Wehner GroupQuantum Internet DivisionQuantum Information and Softwar
Artifactual expression of maxi-K+ channels in basolateral membrane of gallbladder epithelial cells
No full text To patch clamp the basolateral cell membrane, sheets of Necturus gallbladder epithelium were stripped of the subepithelial tissue layers and affixed apical side down on cover slips coated with Cell-Tak [F. Wehner, L. Garretson, K. Dawson, Y. Segal, and L. Reuss. Am. J. Physiol. 258 (Cell Physiol. 27): C1159-C1164, 1990]. In 90% of the patches we observed K+ channels identical to the maxi-K+ channels previously demonstrated in the apical membrane (Y. Segal and L. Reuss. J. Gen. Physiol. 95: 791-818, 1990). To ascertain whether these channels were present in the native tissue, we carried out intracellular-microelectrode studies. We tested for activation of basolateral membrane K+ conductance by depolarization or by elevation of intracellular Ca2+ and for tetraethylammonium sensitivity of the basolateral membrane voltage and fractional resistance. The results were negative, indicating that maxi-K+ channels are not expressed in the basolateral membrane of the "intact" epithelium. Using the same intracellular-microelectrode protocol on the apical membrane, we demonstrated the presence of an apical K+ conductance attributable to maxi-K+ channels. Additional experiments revealed a Ba(2+)-sensitive basolateral K+ conductance in the native epithelium. We conclude that in the stripped preparation there is artifactual expression of maxi-K+ channels. In addition, the native basolateral membrane K+ channels either are not expressed in this preparation or have a low conductance and cannot be discerned from the background noise. </jats:p
"Staatistik" - Zur Vermessung politischer Beteiligung
No full textWehner J, Mämecke T. "Staatistik" - Zur Vermessung politischer Beteiligung. In: Voss K, ed. Internet und Partizipation. Bottom-up oder Top-down? Politische Beteiligungsmöglichkeiten im Internet. Wiesbaden: Springer VS; 2014: 311-322
Multiplexed entanglement generation over quantum networks using multi-qubit nodes
No full textQuantum networks distributed over distances greater than a few kilometres will be limited by the time required for information to propagate between nodes. We analyse protocols that are able to circumvent this bottleneck by employing multi-qubit nodes and multiplexing. For each protocol, we investigate the key network parameters that determine its performance. We model achievable entangling rates based on the anticipated near-term performance of nitrogen-vacancy centres and other promising network platforms. This analysis allows us to compare the potential of the proposed multiplexed protocols in different regimes. Moreover, by identifying the gains that may be achieved byimproving particular network parameters, our analysis suggests the most promising avenues for research and development of prototype quantum networks.Accepted Author ManuscriptQID/Hanson LabQID/Wehner GroupQuantum Internet DivisionQuantum Information and SoftwareQN/Hanson La
Hybrid Quantum Networks for High-Fidelity Entanglement Distribution
No full textWe present an architecture for multiplexed quantum repeaters using local connectivity to improve fidelity in entanglement distribution. Simulations indicate our scheme achieves rates comparable to competing schemes, with fidelity improvements that increase with repeater size.Virtual/online event due to COVID-19QID/Wehner GroupQuantum Internet DivisionQuantum Information and Softwar
High-fidelity Greenberger-Horne-Zeilinger state generation within nearby nodes
No full textGenerating entanglement in a distributed scenario is a fundamental task for implementing the quantum network of the future. We here report a protocol that uses only linear optics for generating Greenberger-Horne-Zeilinger states with high fidelities in a nearby node configuration. Moreover, we analytically show that the scheme is optimal for certain initial states in providing the highest success probability for sequential protocols. Finally, we give some estimates for the generation rate in a real scenario.QID/Wehner GroupQuantum Internet DivisionQuantum Information and Softwar
Visual navigation strategies in insects: lessons from desert ants
No full textWehner R, Cheng K, Cruse H. Visual navigation strategies in insects: lessons from desert ants. In: Werner JS, Chalupa LM, eds. The New Visual Neurosciences. Cambridge, MA: MIT Press; 2014: 1153-1163
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