Sven Höfling, Wuerzburg University and University of St Andrews
Room 3.10, Mathematics Building, IST
Semiconductor diode lasers play a major role in everyday life in our information society. These lasers generate coherent light by stimulated emission of photons. In contrast, laser-like operation can be obtained also by stimulated scattering of bosonic quasiparticles called exciton-polaritons into the ground state of strongly coupled light-matter systems in microcavities. This polariton laser or dynamic and non-equilibrium polariton condensate regime can be reached with pump thresholds lower than conventional lasing. The exciton-polaritons decay by the leakage of photons from a cavity, which produces a monochromatic and coherent light output. In this talk, we discuss the electrical injection of exciton-polaritons into microcavity structures and the formation of exciton-polariton condensates in lattice structures with deep and tailorable confinement potential. More Information..
Texas A&M University, USA
Invited talk in the scope of the CodeStream Project
Tuesday, 9th of June 2015, 14h00
FEUP - DEEC, room I -105
Weakly secure codes aim to hide information about individual packets as well as small groups of packets from an eavesdropper that can intercept wireless transmissions or has access to a small number of storage nodes. Such codes are a practical alternative to traditional information-theoretic schemes that hide information about the entire set of files from the eavesdropper. The weakly secure codes do not use random keys, and as a result have better performance and lower overhead than the traditional schemes.
The talk will include two parts. First, we will present an algorithm for constructing weakly secure codes that enable clients to exchange data over a shared broadcast channel in the presence of an eavesdropper. We show that this problem has many interesting reformulations, such as designing constrained generator matrices of MDS codes. Second, we present an explicit construction of a coset coding based outer code to enhance the weak security properties of a regeneration code, i.e., a code which optimizes the repair bandwidth in a distributed storage system.
Dr. Sprintson is an Associate Professor in the Department of Electrical and Computer Engineering, Texas A&M University, College Station. From 2003 to 2005, he was a Postdoctoral Research Fellow at the California Institute of Technology, Pasadena. His research interests lie in the general area of communication networks with a focus on network coding and software defined networks. Dr. Sprintson received the Wolf Award for Distinguished Ph.D.students, the Viterbi Postdoctoral Fellowship, and the NSF CAREER award. Currently, he serves as an associate editor of the IEEE Transactions on Wireless Communications. He has been a member of the Technical Program Committee for the IEEE Infocom 2006–2016.