November 2008 - ITP-quantumseminare

Talk next week
by Ligong Wang 21 Nov '08

21 Nov '08

Hi all, Next week I'll be talking on the topic "One-shot Classical-Quantum Channels". It will be on Tuesday at 5pm, in HIT J 52. I will explain the problem of transmitting classical information through a quantum channel, and the differences between the usual channel capacity and the "one-shot capacity". I will also show some simple concepts and techniques used in our approach to upper- and lower-bound the "one-shot capacity". Comments and suggestions that may help me prepare this talk are welcome, until Monday afternoon. Cheers, Ligong

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additional talk tomorrow
by Roger Colbeck 20 Nov '08

20 Nov '08

Hi all, Lawrence Ioannou from Cambridge will be giving an additional talk tomorrow 5pm in HIT J51 (sorry, I don't know why they gave us J floor instead of K). Title and abstract below. Cheers, Roger Universal quantum computation in a hidden basis Suppose we are given several copies of a state |psi> that is promised to be orthogonal to |0>, but is otherwise unknown. We consider the quantum-information-theoretic tasks of state preparation and universal quantum computation with respect to the "hidden basis" {|0>,e^{i \theta}|psi>\}^{\otimes l}, of an l-logical-qubit system, for a random \theta. We give an exact algorithm for state preparation, and give an efficient approximation algorithm for universal computation. We apply our results to quantum-public-key authentication protocols, by showing that a class of digital signature schemes is insecure.

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abstract of talk, research day, 19.11.2008
by Forster Manuel 17 Nov '08

17 Nov '08

Hi, The next talk will take place 5 pm at IFW E42. The talk will be held by Severin and Manuel about non-locality distillation, following a recent paper: http://arxiv.org/abs/0809.3173 Abstract: "Quantum non-locality -- the fact that the behavior under measurements of (spatially separated) parts of a system can have a correlation unexplainable by shared classical information -- has proven to be a helpful resource in cryptography and communication complexity. Since non-locality is more useful if it is stronger, it is a natural question whether it can be distilled, i.e., whether strong non-local correlations can be obtained from weaker ones. We answer this question with *yes* by giving the first known examples of distillable non-locality." The talk will give a very basic introduction into non-signaling systems and non-locality distillation and explain a recently found result. Best regards. Manuel

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speaker list
by Roger Colbeck 13 Nov '08

13 Nov '08

Hi all, For future reference, the speaker list and instructions can be found on the following weblink: www.itp.phys.ethz.ch/research/qinfo/onsite/seminars (thanks Oscar) Roger

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[QI] QI Seminar
by Dejan D. Dukaric 13 Nov '08

13 Nov '08

Dear all, Here is what we decided at yesterday's meeting: Talks will continue at the same time (5pm Tuesday) as before. We will try to stick to Tuesday except in exceptional circumstances. We will roughly alternate between Hoenggerberg and IFW. Speakers are requested to write abstracts which make clear the level of the talk, and the topic. Please try to make the talk as simple as possible, baring in mind the audience. The main ideas are more useful to a broad audience than details of a proof. Also, a broad introduction to the problem and where it fits into the field is useful. It is also suitable to give tutorials on some area if you feel not many people know about the topic. The list of speakers is below. We decided to continue adding visitors etc. when they come (unless at short notice), so your talk may be moved back. If you can't make the slot then please find somebody to swap with. We start next Wednesday at IFW, D44 at 5:00 pm (because of the evaluation on Tuesday). We have reserved room IFW E42 for those who want to work here during the day. Any problems, please let us know. Roger and Dejan --- Severin Winkler Ligong Wang Manuel Forster Roger Colbeck Esther Hänggi Oscar Dahlsten Dejan Dukaric Marco Tomamichel Viktor Galliard Johan Aaberg Patrick Kuppinger Renato Renner Stefan Wolf Cyril Stark Matthias Fitzi Stefan Hengl

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research day next week
by Roger Colbeck 06 Nov '08

06 Nov '08

Hi all, Next week's research day will be at Honggerberg on Wednesday to coincide with Seth Lloyd's talk at the physics colloquium. Details of the talk are at http://www.colloquium.phys.ethz.ch/ Cheers, Roger

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[QI] QI Seminar
by Dejan D. Dukaric 03 Nov '08

03 Nov '08

Dear All, This weeks research day on Tuesday will be at the Computer Science Building IFW. There wont be a talk. But there is a talk by the guy who writes the PhD comics: Dear fellow Ph.D. students it is a pleasure for us to invite you to a lecture and book signing by Jorge Cham, the creator of the famous PhD Comics (http://www.phdcomics.com) The talk will take place on Tuesday, November 4th, at 5.15pm in HG F 7. After the talk, you are cordially invited to an aperitif. This event is supported by AVETH, VSETH and the ETH Zurich Rectorate and hence the talk is free of charge for everybody. We hope that many of you will attend the talk! Kind regards and see you there AVETH Board Cheers, Dejan

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Talks this week
by Roger Colbeck 02 Nov '08

02 Nov '08

Dear all, There are two talks that may be of interest this week: Nicolas Gisin will speak on "Towards Understanding Quantum Correlations: New Bell tests and simulating Entanglement with Nonlocal Boxes" on Monday at 16:45 in HCI J 7. and Wednesday, November 5, 2008 Moty Heiblum Weizmann Institute, Rehovot, Israel Entangled Electrons in the Solid State: Quantum Interference and Dephasing I will describe two experiments, where pairs of electrons were entangled in a solid state Mach-Zehnder interferometer, leading to entirely different outcomes. In one experiment a 'which path' detector was entangled with an interferometer, leading to total dephasing of the interference. The lost interference was recovered by doing a 'post selection' type measurement; proving that phase information stayed in the system. In another experiment two remote, indistinguishable electrons were entangled without ever interacting with each other. Since they propagated along different paths, interference took place only due to the electrons' exchange statistics.

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