Attacking quantum key distribution with single-photon two-qubit quantum logic

The Fuchs-Peres-Brandt (FPB) probe realizes the most powerful individual attack on Bennett-Brassard 1984 quantum key distribution (BB84 QKD) by means of a single controlled-NOT (CNOT) gate. This paper describes a complete physical simulation of the FPB-probe attack on polarization-based BB84 QKD using a deterministic CNOT constructed from single-photon two-qubit quantum logic. Adding polarization-preserving quantum nondemolition measurements of photon number to this configuration converts the physical simulation into a true deterministic realization of the FPB attack.Comment: 8 pages, 9 figures; references added, 1 new figure, appendix expanded; accepted for publication in Phys. Rev.

Simulations of Surfactant Spreading

Thin liquid films driven by surface tension gradients are studied in diverse applications, including the spreading of a droplet and fluid flow in the lung. The nonlinear partial differential equations that govern thin films are difficult to solve analytically, and must be approached through numerical simulations. We describe the development of a numerical solver designed to solve a variety of thin film problems in two dimensions. Validation of the solver includes grid refinement studies and comparison to previous results for thin film problems. In addition, we apply the solver to a model of surfactant spreading and make comparisons with theoretical and experimental results

Revisiting working memory: Are domain, process and global models mutually exclusive, nested or orthogonal?

Working memory (WM) is a cognitive function whereby task-relevant information is actively maintained and manipulated in mind for goal-directed behaviour. Three competing models, here dubbed the global, domain and process models, have attempted to explain its neural underpinnings. Despite extensive research however, no consensus has been reached. Here, we use two new WM paradigms to demonstrate that all three models are partially correct. In the first experiment, our results show that selected frontoparietal regions (MD), from the global model, are largely stimulus-independent. However, more posterior and caudal frontoparietal regions show stimulus-dependent activations as described by the domain model. In the second experiment, our results reveal that a dorsal MD sub-network is more active when information is manipulated, as described by the process model. Thus, WM is best represented by all three models, with the process model nested within the global, and the domain model partially independent from the others