May 2011 - ITP-quantumseminare - lists.phys.ethz.ch

Group seminar: Cyril Stark
by Frédéric Dupuis 30 May '11

30 May '11

Hi everyone, It will soon be that time of the week again when we congregate in J51 to listen to glorious tales of scientific breakthrough. This week it will be the Tale of the Localization of Toric Code Defects, by Cyril Stark. --Your devoted organizer, Frédéric -------------------------------------------- Speaker: Cyril Stark Title: Localization of Toric Code Defects Date/Time/Place: Tuesday, May 31, 17:00, HIT J51 Abstract: I will try to sketch the joint project with Renato, Atac and Lode in which we explore the possibility of passive error correction in the toric code. We first show that imperfections in the toric code Hamiltonian lead to logical errors. We then argue that Anderson localization of the defects, arising from unavoidable fluctuations of the coupling constants, provides a remedy. This protection is demonstrated using general analytical arguments that are complemented with numerical results. The talk is mainly based on arXiv:1101.6028.

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Optics Colloquium, Tony F. Heinz, Columbia University, Friday, May 20, 14:00, HCI J-3
by QSIT Seminar 18 May '11

18 May '11

Dear all Please be informed about the following Optics Colloquium. With best regards, Ilona Blatter ------------------------------------------------------------ Invitation to Optics Colloquium next Friday: Date: Friday, 20.05.11 Time: 14:00 Location: ETH Zurich, Hönggerberg Campus, HCI J-3 Speaker: Tony F. Heinz, Departments of Physics and Electrical Engineering, Columbia University, New York Title: Seeing electrons in two-dimensions: Optical sprectroscopy of graphene Abstract: Optical spectroscopy provides an excellent means of understanding the distinctive properties of electrons in the two-dimensional system of graphene. Within the simplest picture, one has a (zero-gap) semiconductor with direct transitions between the well-known conical bands. This picture gives rise to a predicted frequency-dependent absorption of pa = 2.3%, where a is the fine-structure constant. We will demonstrate that this relation is indeed satisfied in an appropriate spectral range in the near infrared, but that at higher photon energies electron-hole interactions significantly modify this result through the formation of saddle-point excitons. Optical spectroscopy also permits a detailed analysis of how the linear bands of graphene, corresponding to massless Dirac Fermions, are modified to yield massive electrons through interlayer interactions in bilayer and few-layer graphene sheets. The observation of a tunable band gap in bilayer and trilayer graphene will also be discussed. We will also discuss recent measurements in which the electron and phonon dynamics are investigated by ultrafast pump-probe spectroscopy. Host: Atac Imamoglu, Quantum Photonics, IQE For a complete OPTICS COLLOQUIUM schedule and up-to-date information please go to http://www.opteth.ethz.ch/news/optics_colloquium. If you don’t want to receive this invitation, please send an email to the above address with the subject line "unsubscribe". ---------------------------------------------------- ETH Zurich Dr. Andreas Heinle Coordinator optETH Laboratory of Physical Chemistry CH-8093 Zurich, Switzerland Phone +41 44 633 6871 Fax +41 44 633 1316 www.opteth.ethz.ch ---------------------------------------------------- ------------------------------------------------------------------------------------------------------ ETH Zurich Dr. Ilona Blatter NCCR QSIT Coordinator Laboratory for Solid State Physics HPF E 17 Schafmattstrasse 16 8093 Zurich ilona.blatter(a)phys.ethz.ch www.nccr-qsit.ethz.ch Phone: +41 44 633 36 06 Home: +41 44 844 42 50

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Seminar by Klaus Reim: Tuesday May 17, 2011
by QSIT Seminar 16 May '11

16 May '11

Dear all Please be informed about the following seminar. With best regards, Ilona Blatter ------------------------------------------------- Date: Tuesday May 17, 2011 Time: 18:00 Place: ETH Science City, HPF G 6 Host: Andreas Wallraff High-speed optical quantum memories Klaus Reim University of Oxford, UK Abstract: In a globalised world with ever-increasing, intercontinental information exchange, there is growing demand for secure communication technology, such as could be provided by photonic quantum communications networks. Currently, the biggest challenge for such networks is distance. Over short distances, photons, interacting only weakly with their environment, easily and reliably carry quantum information without much decoherence, but intercontinental quantum communication will require quantum repeaters embedded in potentially isolated locations, because photon loss rises otherwise exponentially with distance. In general, these repeaters will require some sort of quantum memory, a coherent device where single photons are reversibly coupled into and out of an atomic system, to be stored, possibly processed and then redistributed. In order to be practically useful, this will need to have sufficiently large bandwidth, high efficiency and long storage time, with multimode capacity, and a low-enough noise level to enable operation at the quantum level. I am going to talk about our ensemble-based, far off-resonant Raman approach to quantum memories, describe how the interaction mechanism works and show how we store a single photon level signal in the quantum memory and retrieve it at a controlled later point in time. Furthermore, I am going to address de-phasing mechanisms for the stored spin-wave excitation that limit storage times and discuss storage and retrieval of polarization-encoded qubits. Publications: Reim, K. F. et al. Nature Photon. 4, 218-221 (2010) Reim, K. F. et al. arXiv:1010.3975v1 ------------------------------------------------- ETH Zurich Dr. Ilona Blatter NCCR QSIT Coordinator Laboratory for Solid State Physics HPF E 17 Schafmattstrasse 16 8093 Zurich ilona.blatter(a)phys.ethz.ch www.nccr-qsit.ethz.ch Phone: +41 44 633 36 06 Home: +41 44 844 42 50

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Group seminar: Stavros Kousidis
by Frédéric Dupuis 10 May '11

10 May '11

Hi everyone, Our next seminar speaker will be Stavros Kousidis. Since he's Matthias's guest, I'll let Matthias introduce him: "Dear all, Next week, Stavros Kousidis will be visiting us and will give a talk in our seminar. As you can see from the abstract, he is working on rather abstract representation theory, but in fact, he is developing some quantum central limit theorems that may be of interest to us! Matthias" --Fred, your friendly organizer. --------------------------------- Speaker: Stavros Kousidis, Universität zu Köln Date/Time/Place: Tuesday, May 17, 17:00, HIT J51 Title: Statistics of graded tensor product multiplicities Abstract: Dimensions of invariant subspaces inside tensor products with respect to some group action are of actual interest. We will make the problem harder by discussing graded tensor products, which replace the dimensions in question by polynomials. Interesting symmetries appear in this graded setting, e.g. a conjectured Gaussian behaviour under some limit considerations. It sounds heavy, but the talk will start by introducing irreducible representations of SU(2). My aim is to ignore any technicality that appears along the way, and rather to deliver a feeling of what's going on.

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Fwd: QIPC 2011, September 5-9 2011, ETH Zurich, Switzerland: Registration Deadline May 15, 2011
by QSIT Seminar 09 May '11

09 May '11

Dear NCCR QSIT colleagues and students, you and your group members are cordially invited to participate in the international conference on Quantum Information Processing and Communication (QIPC) 2011 to be held at ETH Zurich from September 5-9, 2011. The program committee has selected an exciting range of speakers covering the diverse aspects of the field of quantum information science and technology. Detailed information about the conference is available at the website www.qipc2011.ethz.ch. In addition to the set program the possibility is offered to submit abstracts to be selected as hot topic talks held in the plenum or contributed talks presented in parallel sessions. Abstracts for poster presentations may be submitted too. Registration and abstract submission deadlines are May 15, 2011. Please consider registering for the conference now to secure your participation in this event which in past years has reached its capacity limits. Prior to the conference, we are hosting a QIPC 2011 School in the Swiss Alps that is aimed at introducing early stage graduate students to the main research topics of the conference. Lecturers are listed on the conference web site. Interested students are requested to apply through the conference web site. Students must register for the main conference too. We also invite you to draw the attention of students and colleagues to the QIPC 2011 conference and school which strives to bring together leading scientist and young researchers alike. We are looking forward to welcoming you to Zurich With best regards Andreas Wallraff and Atac Imamoglu, for the organizing and program committees -- Andreas Wallraff Professor for Solid State Physics ETH Zurich Department of Physics HPF D 8/9 Schafmattstr. 16 8093 Zurich Switzerland +41 44 633 75 63 (office) +41 44 633 76 17 (secretary) +41 44 633 14 16 (fax) andreas.wallraff(a)phys.ethz.ch http://www.qudev.ethz.ch/ - group's home page http://www.solid.phys.ethz.ch/ - Laboratory for Solid State Physics http://www.phys.ethz.ch/ - Department of Physics http://www.ethz.ch/ - ETH Zurich --------------------------------------------------- --------------------------------------------------- ETH Zurich Dr. Ilona Blatter NCCR QSIT Coordinator Laboratory for Solid State Physics HPF E 17 Schafmattstrasse 16 8093 Zurich ilona.blatter(a)phys.ethz.ch www.nccr-qsit.ethz.ch Phone: +41 44 633 36 06 Home: +41 44 844 42 50

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Introductory Lecture: Vanessa Wood
by QSIT Seminar 06 May '11

06 May '11

Dear all Please be informed about Vanessa Wood's introductory lecture. With best regards, Ilona --------------------------------------------------- Date: Wednesday May 11, 2011 Time: 17:15 Place: ETH main building, HG F 30 (Audi Max) Nanoelectronics - Bringing the Ultra-small to Batteries, LEDs, and other Devices Vanessa Wood Departement of Information Technology and Electrical Engineering, ETH Zurich Introductory lecture: http://www.ethz.ch/news/lectures/index_EN --------------------------------------------------- ETH Zurich Dr. Ilona Blatter NCCR QSIT Coordinator Laboratory for Solid State Physics HPF E 17 Schafmattstrasse 16 8093 Zurich ilona.blatter(a)phys.ethz.ch www.nccr-qsit.ethz.ch Phone: +41 44 633 36 06 Home: +41 44 844 42 50

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Physics Colloquium by Amir Yacobi, May 11, 2011
by QSIT Seminar 05 May '11

05 May '11

Dear all Please be informed about the Physics Colloquium next week. Amir Yacobi will be in Zurich on Tuesday and on Wednesday. With best regards, Ilona Blatter --------------------------------------------------- Date: Wed May 11, 2011 Time: 16:45 (coffee and tea at 16:15) Place: ETH Science City, HPV G 4 Host: Thomas Ihn Quantum Information Processing and Metrology Using Few Electron Spins in Solids Amir Yacobi Department of Physics, Harvard University, USA abstract: http://www.colloquium.phys.ethz.ch/program/Yacobi_pdf --------------------------------------------------- ETH Zurich Dr. Ilona Blatter NCCR QSIT Coordinator Laboratory for Solid State Physics HPF E 17 Schafmattstrasse 16 8093 Zurich ilona.blatter(a)phys.ethz.ch www.nccr-qsit.ethz.ch Phone: +41 44 633 36 06 Home: +41 44 844 42 50

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Talk by Sebastian Diehl, today Thursday May 5,2011
by QSIT Seminar 05 May '11

05 May '11

Dear all Please be informed about the following informal seminar. With best regards, Ilona Blatter --------------------------------------------------- Date: May 5, 2011 Time: 10:00 Place: HPT G 18 Host: Atac Imamoglu Majorana fermions via dissipation Sebastian Diehl University of Innsbruck --------------------------------------------------- ETH Zurich Dr. Ilona Blatter NCCR QSIT Coordinator Laboratory for Solid State Physics HPF E 17 Schafmattstrasse 16 8093 Zurich ilona.blatter(a)phys.ethz.ch www.nccr-qsit.ethz.ch Phone: +41 44 633 36 06 Home: +41 44 844 42 50

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Group seminar: Christopher Portmann
by Frédéric Dupuis 04 May '11

04 May '11

Hi everyone, The next episode of our group seminars next Tuesday will feature a talk by Christopher Portmann. Do not miss it! --Frédéric --------------------------------------- Title: Information-theoretic non-malleable encryption. Date/Time/Place: Tuesday, May 10, 17:00, HIT J51 Speaker: Christopher Portmann Abstract: An encryption scheme is said to be non-malleable, if no adversary can modify a ciphertext so that the resulting message is meaningfully related to the original message. In the first part of the talk, I'll give the same presentation as at the upcoming ICITS on the classical case (eprint.iacr.org/2011/092) In the second part of the talk I'll review the work by Ambainis, Bouda and Winter (arXiv:0808.0353) on quantum non-malleability. We compare information-theoretic non-malleability for classical schemes to secrecy and authenticity, and provide a complete characterization of their relative strengths. In particular, we show that information-theoretic perfect non-malleability is equivalent to perfect secrecy of two different messages. This implies that for $n$-bit messages a shared secret key of length roughly $2n$ is necessary to achieve non-malleability, which meets the previously known upper bound. We define approximate non-malleability by relaxing the security conditions and only requiring non-malleability to hold with high probability (over the choice of secret key), and show that any authentication scheme implies approximate non-malleability. Since authentication is possible with a shared secret key of length roughly $\log n$, the same applies to approximate non-malleability. Ambainis et al. study non-malleable encryption for quantum messages, but restrict their considerations to encryption operations consisting in unitary transformations. They show that such a scheme is equivalent to a "unitary 2-design", as opposed to normal encryption which is a unitary 1-design.

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Reminder: Thursday May 5: QSIT Lunch Seminar
by QSIT Seminar 02 May '11

02 May '11

Dear QSIT members The next QSIT Lunch Seminar will take place on Thursday May 5, at 12:00 noon in the room HPF G6, ETH Hönggerberg, Zurich. There will be two talks of 30 minutes duration jointly presented by two collaborators from different research groups. At 13:00 pm free pizza is offered to the participants. Symmetry breaking and fluctuations at the Dicke quantum phase transition by Rafael Mottl, Quantum Optics Group, ETH Zurich Quantum storage of photonic entanglement in a crystal by Félix Bussières, Group of Applied Physics - Optique, Université de Genève Abstracts: http://www.nccr-qsit.ethz.ch/news/lunchseminar/may2011 Please register for your free pizza at the following link by Tuesday April 3, 12:00 noon: https://ethz.doodle.com/nnp2zz3u6sd52534 If you have suggestions on topics or speakers, or would like to present recent results of your research, please send your information to Andreas Wallraff or Ilona Blatter. With best regards, Andreas Wallraff Ilona Blatter Professor for Solid State Physics QSIT Coordinator --------------------------------------------------- ETH Zurich Dr. Ilona Blatter QSIT Coordinator Laboratory for Solid State Physics HPF E 17 Schafmattstrasse 16 8093 Zurich ilona.blatter(a)phys.ethz.ch www.nccr-qsit.ethz.ch Phone: +41 44 633 36 06 Home: +41 44 844 42 50

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