September 2016 - ITP-quantumseminare

no meeting today
by Joe Renes 26 Sep '16

26 Sep '16

Hi all, no meeting today, due to scheduling conflicts. We'll pick up next week and if no one else wants to volunteer, I'll tell you about a new fault-tolerant decoding scheme Alvaro and I stumbled upon. Best, -joe

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Fwd: Talk: "Structural Information" by Prof. Wojciech Szpankowski, Purdue University, on Tuesday, September 27th 2016, 4.15 pm, HG D 3.2
by Joe Renes 20 Sep '16

20 Sep '16

Hi all, some or all of you might be interested in the talk below. Best, -joe From: Michael Tschannen <michaelt(a)nari.ee.ethz.ch> Subject: Talk: "Structural Information" by Prof. Wojciech Szpankowski, Purdue University, on Tuesday, September 27th 2016, 4.15 pm, HG D 3.2 Date: 20 September 2016 at 10:14:57 GMT+2 To: wiss-mitarb(a)ee.ethz.ch Dear colleagues, you are cordially invited to attend the following talk by Professor Wojciech Szpankowski, Purdue University: Title: "Structural Information" Time and place: Tuesday, September 27th 2016, 4.15 pm in HG D 3.2 Abstract: F. Brooks argued in his 2003 JACM paper on the challenges of computer sciences that there is "no theory that gives us a metric for the information embodied in structure''. C. Shannon himself noticed this fifty years earlier in his 1953 paper. More generally, we lack an information theory of data structures (e.g., graphs, sets, social networks, chemical structures, biological networks). In this talk, we present some recent research results on structural information. We first propose some fundamental limits of information content for a wide range of data structures with correlated labels and then propose asymptotically optimal lossless compression algorithms achieving these limits for unlabeled graphs and binary (plane and non-plane) trees. Then we shall discuss a different structural information by considering a channel that maps binary sequences to self-avoiding walks in the two-dimensional grid, inspired by a model of protein statistics. This channel, which we also call the Boltzmann sequence-structure channel, is characterized by a Boltzmann/Gibbs distribution with a free parameter corresponding to temperature. The capacity of this channel appears to exhibit a phase transition for small temperature and decays to zero for high temperature. If time allows we also discuss structural properties of large systems with local mutual dependencies and interaction, focusing on enumerating Markov fields and universal types. We tackle most of these problems by complex analysis methods, thus within the realm of analytic information theory. Bio: Wojciech Szpankowski is Saul Rosen Distinguished Professor of Computer Science at Purdue University where he teaches and conducts research in analysis of algorithms, information theory, bioinformatics, analytic combinatorics, random structures, and stability problems of distributed systems. He received his M.S. and Ph.D. degrees in Electrical and Computer Engineering from Gdansk University of Technology. He held several Visiting Professor/Scholar positions, including McGill University, INRIA, France, Stanford, Hewlett-Packard Labs, Universite de Versailles, University of Canterbury, New Zealand, Ecole Polytechnique, France, the Newton Institute, Cambridge, UK, ETH, Zurich, Gdansk University of Technology, and Jagiellonian University, Poland. He is a Fellow of IEEE, and the Erskine Fellow. In 2010 he received the Humboldt Research Award and in 2015 the inaugural Arden L. Bement Jr. Award. He published two books: "Average Case Analysis of Algorithms on Sequences", John Wiley & Sons, 2001, and "Analytic Pattern Matching: >From DNA to Twitter", Cambridge, 2015. He has been a guest editor and an editor of technical journals, including Theoretical Computer Science, the ACM Transaction on Algorithms, the IEEE Transactions on Information Theory, Foundation and Trends in Communications and Information Theory, Combinatorics, Probability, and Computing, and Algorithmica. In 2008 he launched the interdisciplinary Institute for Science of Information, and in 2010 he became the Director of the newly established NSF Science and Technology Center for Science of Information. We very much look forward to seeing you there. Best wishes, Michael Tschannen -- Michael Tschannen ETH Zurich, Communication Technology Laboratory Sternwartstrasse 7 CH-8092 Zürich Tel: +41 44 63 27638 E-Mail: michaelt(a)nari.ee.ethz.ch Web: http://www.nari.ee.ethz.ch/commth/people/show/michaelt

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today's talk by Henrik Wilming: 4pm in E41.1
by Joe Renes 20 Sep '16

20 Sep '16

Hi all, indeed the talk will be at the same time and same place as yesterday's group meeting. Best, -joe

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group meeting tomorrow E41.1 4pm // Henrik Wilming talk on Tuesday 4pm
by Joe Renes 18 Sep '16

18 Sep '16

Hi all, tomorrow Axel Dahlberg will present the results of his master's thesis, titled \ket{classical codes}: Quantum code construction using classical codes. We will also hear from our visitor Henrik Wilming on Tuesday at 4pm, I predict also in E41.1, but this is not completely certain. He'll talk about algorithmic cooling and the third law of thermodynamics. Best, -joe

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talk by Mischa Woods Wednesday 2pm E41.1
by Joe Renes 12 Sep '16

12 Sep '16

Here's a title and abstract of the talk. It's http://arxiv.org/abs/1607.04591 in case you want a preview. -joe Autonomous quantum machines and finite sized clocks in collaboration with Ralph Silva and Jonathan Oppenheim. Abstract: Processes such as quantum computation, or the evolution of quantum cellular automata are typically described by a unitary operation implemented by an external observer. In particular, an interaction is generally turned on for a precise amount of time, using a classical clock. A fully quantum mechanical description of such a device would include a quantum description of the clock whose state is generally disturbed because of the back-reaction on it. Such a description is needed if we wish to consider finite sized autonomous quantum machines requiring no external control. The extent of the back-reaction has implications on how small the device can be, on the length of time the device can run, and is required if we want to understand what a fully quantum mechanical treatment of an observer would look like. Here, we consider the implementation of a unitary by a finite sized device, and show that the back-reaction on it can be made exponentially small in the device's dimension. As a result, an autonomous quantum machine need only be of modest size. We are also able to solve a long-standing open problem by using a finite sized quantum clock to approximate the continuous evolution of an idealised clock. The result has implications on the equivalence of different paradigms of quantum thermodynamics, some which allow external control and some which only allow autonomous thermal machines.

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Meeting moved to Wednesday
by Joe Renes 12 Sep '16

12 Sep '16

Hi all, No meeting today due to the holiday. On Wednesday Mischa Woods from UCL/Delft will tell us about quantum clocks and autonomous quantum systems at 2pm. Joe

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today's meeting
by Joe Renes 05 Sep '16

05 Sep '16

Hi all, today Rotem will give us a preview of her Qcrypt talk(s). 4pm in E41.1! -joe

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