Hi Everybody, Next week we are having two visitors, namely, Rotem Arnon Friedman (ETH Zurich) and Marco Tomamichel (University of Sydney). Both are staying at the CTP from Monday (June 22) until Friday (June 26) and they are both giving a seminar. Please find details below and please fill out the doodle http://doodle.com/9wbz6sauh2ygkn4c if you want to meet Rotem, and http://doodle.com/whnrzzgxnwk4q5t3 if you want to meet Marco. I will put together a schedule on Sunday night. Thanks and best wishes, cyril =================== Date: June 23 at 1:30pm Speaker: Rotem Arnon Friedman (ETH Zurich) Title: Non-signalling parallel repetition using de Finetti reductions Abstract: We study the question of parallel repetition of multiplayer non-signalling games, i.e., the only restriction on the players is that they are not allowed to communicate during the game. For complete-support games we prove a threshold theorem, stating that for any number of players the probability that non-signalling players win more than a fraction 1 − α of the n games is exponentially small in n. For games with incomplete-support we prove a similar statement, for a slightly modified form of repetition. The most important contribution of the present work is the, arguably simpler, proof technique which exploits the permutation symmetry of the repeated game. While most parallel repetition results closely follow the proof technique introduced by Raz we give a completely different proof, based on ideas emerging from quantum information theory, such as a recent de Finetti theorem and quantum tomography. Although de Finetti theorems seem like a natural tool for parallel repetition theorems, this is the first time that a de Finetti theorem is used successfully in this context. Our proof technique allows us to avoid central technical difficulties which arise in proofs of parallel repetition theorems due to the arbitrary structure of the players’ strategies. Joint work with Renato Renner (ETH Zurich) and Thomas Vidick (Caltech) arXiv: http://arxiv.org/abs/1411.1582 =================== Date: June 26 at 1:30pm Speaker: Marco Tomamichel (University of Sydney) Title: Processing Information with Small Quantum Devices Abstract: The capacity of a memoryless channel is often used as a single figure of merit to characterize its ability to transmit or store information reliably The capacity determines the maximal rate at which we can code reliably over asymptotically many uses of the channel. I will argue that this asymptotic treatment is insufficient in the quantum setting where decoherence severely limits our ability to manipulate large quantum systems in the encoder and decoder. For all practical purposes we should instead focus on the trade-off between three parameters: the rate of the code, the number of coherent uses of the channel, and the fidelity of the transmission. The aim is then to specify the region determined by allowed combinations of these parameters. This talk will discuss several recent results in this direction. =================== Cyril Stark Center for Theoretical Physics Massachusetts Institute of Technology 77 Massachusetts Ave, 6-304 Cambridge, MA 02139, USA _______________________________________________ qip mailing list qip(a)mit.edu http://mailman.mit.edu/mailman/listinfo/qip