ITP-quantumseminare

itp-quantumseminare@lists.phys.ethz.ch

1 participants
1357 discussions

Talk by Andre Ranchin
by Stefan Wolf 31 Jan '11

31 Jan '11

Hi, There will be a seminar talk by Andre Ranchin tomorrow, Feb. 1, 17:00 in HIT K 51. The title is "On multipartite entanglement: concentration, reversibility and measures of entanglement" Cheers, Stefan

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Talk by Volkher Scholz
by Stefan Wolf 31 Jan '11

31 Jan '11

Hi, Volkher Scholz from Hannover will be in Zurich and give a seminar talk on Wed., Feb. 9., 16:30 - 17:30, in HIT K 51. Best regards, Stefan __________________________________________________________________________ Disordered Quantum Walks in one lattice dimension - Andre Ahlbrecht, *Volkher B. Scholz*, Albert H. Werner - arXiv:1101.2298 We study a spin-$\frac{1}{2}$-particle moving on a one dimensional lattice subject to disorder induced by a random, space-dependent quantum coin. The discrete time evolution is given by a family of random unitary quantum walk operators, where the shift operation is assumed to be deterministic. Each coin is an independent identically distributed random variable with values in the group of two dimensional unitary matrices. We derive sufficient conditions on the probability distribution of the coins such that the system exhibits dynamical localization. Put differently, the tunneling probability between two lattice sites decays rapidly for almost all choices of random coins and after arbitrary many time steps with increasing distance. Our findings imply that this effect takes place if the coin is chosen at random from the Haar measure, or some measure continuous with respect to it, but also for a class of discrete probability measures which support consists of two coins, one of them being the Hadamard coin. __________________________________________________________________________

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QSIT Lunch Seminar: Thursday February 3rd, 2011
by Ilona Blatter 28 Jan '11

28 Jan '11

Dear QSIT members Our first QSIT Lunch Seminar within the frame of the NCCR will take place on Thursday February 3rd, 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. Strong coupling regime in parabolic semiconductor quantum wells Markus Geiser, Quantum Optoelectronics Group, ETH Zurich and Dynamical resurrection of the visibility in a Mach-Zehnder interferometer Andrey Lebedev, Institut for Theoretical Physics, ETH Zurich Abstracts: http://www.nccr-qsit.ethz.ch/news/lunchseminar/february2011 Please register for your free pizza at the following link by Tuesday February 1, 12:00 noon: http://doodle.ethz.ch/r8f7tq7gczkyb4dr 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.qsit.ethz.ch www.nccr-qsit.ethz.ch Phone: +41 44 633 36 06 Home: +41 44 844 42 50

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Fwd: Canadian Summer School on Quantum information & Student Conference
by Frédéric Dupuis 27 Jan '11

27 Jan '11

---------- Message transféré ---------- De : *David Poulin* <David.Poulin(a)usherbrooke.ca <mailto:David.Poulin@usherbrooke.ca>> Date : 27 janvier 2011 10:30 Objet : Canadian Summer School on Quantum information & Student Conference À : Dear colleague, (with apologies if you receive this message multiple times) Registration for the 11th Canadian Summer School on Quantum Information and the 8th Canadian Student Conference on Quantum Information is now open. Please advertise these events to any colleagues, students and postdocs who might be interested. Best wishes, David * * *Registration now open:* *11th Canadian Summer School on Quantum Information (June 6th-15th)* *8th Canadian Student Conference on Quantum Information (June 16th-17th)* *Jouvence, Québec, Canada* The 11th edition of the Canadian Summer School on Quantum Information and the 8th Canadian Student Conference on Quantum Information will be held from June 6th to 17th 2011 at the Centre de Villegiature de Jouvence, located in a Quebec National Park. Once again this year, many of the world's leading experts on quantum information will present series of lectures targeted at prospective and current graduate students, as well as postdocs, in the areas of physics, mathematics, computer science and engineering. The Student Conference is a unique occasion for students to present their work and exchange with their fellow students. More information about these events can be found at the web page http://www.crm.umontreal.ca/QI11/index_e.php Registration is now open. Early registration ends March 11th, 2011. *Places are limited, first come first served. Hurry up!* Deadline to submit a contribution to the Student Conference: April 20th Looking forward to see you in Jouvence. Organizers: David Poulin (Main organizer) Alexandre Blais Michel Pioro-Ladrière Bertrand Reulet

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Talk: William Matthews
by Matthias Christandl 26 Jan '11

26 Jan '11

Dear all, Will Matthews will be visiting us next week (2.-4th Feb) and will give a talk on Wednesday. Time and Location: Wednesday, 2 February 2011, noon, HIT K 51 Speaker: William Matthews (IQC Waterloo) Title: Entanglement can increase asymptotic rates of zero-error classical communication over classical channels Abstract: It is known that the number of different classical messages which can be communicated with a single use of a classical channel with zero probability of decoding error can sometimes be increased by using entanglement shared between sender and receiver. It has been an open question to determine whether entanglement can ever increase the zero-error communication rates achievable in the limit of many channel uses. In this paper we show, by explicit examples, that entanglement can indeed increase asymptotic zero-error capacity, even to the extent that it is equal to the normal capacity of the channel. Interestingly, our examples are based on the exceptional simple root systems E7 and E8. See http://arxiv.org/abs/1009.1195 See you, Matthias. Save the date: QCRYPT 2011 - First Annual Conference on Quantum Cryptography September 12-16, 2011 ETH Zurich www.qcrypt.net Matthias Christandl Institute for Theoretical Physics ETH Zurich http://www.itp.phys.ethz.ch/people/christandl/index

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Talk by Jochen Rau
by Stefan Wolf 19 Jan '11

19 Jan '11

Good afternoon, There will be a seminar talk by our visitor Jochen Rau in February: Tuesday, Feb. 8, 17:00 in HIT K 52 on Hoenggerberg. Best regards, Stefan _______________________________________________________________ TITLE Bayesian methods in quantum-state tomography ABSTRACT Conventional tomography protocols reach their limits when sample sizes become very small, or when there is no consensus about the parametric form of the state to be inferred. Protocols must then be modified to account explicitly for a prior bias, and be supplemented by methods that allow one to infer the most plausible parametric form from the data. The necessary tools are furnished by Bayesian statistics: Bayesian interpolation, the evidence procedure, and Bayesian model selection. _______________________________________________________________

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QSIT Seminar by Emre Togan, 17. Jan 2011
by Ilona Blatter 14 Jan '11

14 Jan '11

Dear all Please be informed about the following QSIT Seminar. With best regards, Ilona Blatter -------------------------------------------- Monday January 17, 2011 Time: 14:00 Place: HPF G 6 Host: Atac Imamoglu Quantum entanglement between an optical photon and a solid-state spin qubit Emre Togan Harvard University, USA Quantum entanglement is among the most fascinating aspects of quantum theory. In this work, I will report on the realization of quantum entanglement between a solid-state spin qubit and the polarization of a single optical photon. The experimental entanglement verification demonstrates a high degree of control over the interactions between the quantum light field and the electronic spin of the nitrogen vacancy center in diamond. The entanglement source provides a key building block for the solid-state realization of quantum optical networks and may be used in studies of fundamental physical phenomena. --------------------------------------------------- ETH Zurich Dr. Ilona Blatter QSIT Coordinator Laboratory for Solid State Physics HPF E 13 Schafmattstrasse 16 8093 Zurich ilona.blatter(a)phys.ethz.ch www.qsit.ethz.ch www.nccr-qsit.ethz.ch Phone: +41 44 633 36 06 Home: +41 44 844 42 50

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** CHANGE OF DATE ** Talk by Corsin Pfister
by Stefan Wolf 04 Jan '11

04 Jan '11

Hi, The talk as announced before will take place one week later, on ** Jan. 25 **. Everything else remains unchanged. Please apologize for the spamming. Cheers, Stefan -------- Original-Nachricht -------- Betreff: Talk by Corsin Pfister Datum: Tue, 4 Jan 2011 14:36:59 +0100 Von: Stefan Wolf <wolf(a)inf.ethz.ch> An: <itp-quantumseminare(a)phys.ethz.ch>, Corsin Pfister <pfisterc(a)student.ethz.ch> Good afternoon, First of all, happy new year to all of you, I wish you joy and luck and success! This year's first seminar talk will be given by Corsin Pfister: Tuesday, Jan. 18, 17:00 in HIT J 52 (or maybe one of the K rooms, if available) on Hoenggerberg. Best regards, Stefan _______________________________________________________________ Title: Tsirelson's bound in time Abstract: The mathematical descriptions of joint probability distributions of measure- ment outcomes occurring in quantum mechanics are very diﬀerent. Two local measurements on diﬀerent subsystems are described by observables of tensor product form on a common tensor Hilbert space (two-systems correlations). Two measurements on the same system with an intermediate dynamical evolu- tion are described by a state update rule, trace-preserving completely positive maps and observables without a tensor product form (two-times correlations). Two-systems correlations are restricted by Tsirelson’s bound. One might ask if Tsirelson’s bound can also be used to ﬁnd restrictions on two-times correlations. This thesis partially answers this question. Tsirelson’s bound is combined with an extended version of the Choi-Jamiolkowski Isomorphism, the Leifer Isomorphism, which shows an equivalence between two-systems and two-times correlations. It is shown that Tsirelson’s bound, together with the Leifer Iso- morphism, implies a tight bound on the average success probability of a special type of (2, 1,p)-Random Access Codings (RACs). RACs can be realised using two-systems correlations as well as two-times correlations, which allows a com- parison of the two cases. An attempt to interpret the analogue of the locality condition in the case of two-times correlations is made. It is found that two- times correlations used to realise this special type of (2, 1,p)-RAC cannot be used to communicate, as is the case for two-systems correlations. _______________________________________________________________

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Talk by Corsin Pfister
by Stefan Wolf 04 Jan '11

04 Jan '11

Good afternoon, First of all, happy new year to all of you, I wish you joy and luck and success! This year's first seminar talk will be given by Corsin Pfister: Tuesday, Jan. 18, 17:00 in HIT J 52 (or maybe one of the K rooms, if available) on Hoenggerberg. Best regards, Stefan _______________________________________________________________ Title: Tsirelson's bound in time Abstract: The mathematical descriptions of joint probability distributions of measure- ment outcomes occurring in quantum mechanics are very diﬀerent. Two local measurements on diﬀerent subsystems are described by observables of tensor product form on a common tensor Hilbert space (two-systems correlations). Two measurements on the same system with an intermediate dynamical evolu- tion are described by a state update rule, trace-preserving completely positive maps and observables without a tensor product form (two-times correlations). Two-systems correlations are restricted by Tsirelson’s bound. One might ask if Tsirelson’s bound can also be used to ﬁnd restrictions on two-times correlations. This thesis partially answers this question. Tsirelson’s bound is combined with an extended version of the Choi-Jamiolkowski Isomorphism, the Leifer Isomorphism, which shows an equivalence between two-systems and two-times correlations. It is shown that Tsirelson’s bound, together with the Leifer Iso- morphism, implies a tight bound on the average success probability of a special type of (2, 1,p)-Random Access Codings (RACs). RACs can be realised using two-systems correlations as well as two-times correlations, which allows a com- parison of the two cases. An attempt to interpret the analogue of the locality condition in the case of two-times correlations is made. It is found that two- times correlations used to realise this special type of (2, 1,p)-RAC cannot be used to communicate, as is the case for two-systems correlations. _______________________________________________________________

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Talk by Stephanie Wehner
by Stefan Wolf 20 Dec '10

20 Dec '10

Good morning, This year's final seminar talk will be given by Stephanie Wehner from CQT in Singapore: Tuesday, Dec. 21, 16.30, in HIT J 52 on Hoenggerberg. Best regards, Stefan ______________________________________________________________________ The uncertainty principle determines the non-locality of quantum mechanics Two central concepts of quantum mechanics are Heisenberg's uncertainty principle, and a subtle form of non-locality that Einstein famously called "spooky action at a distance". These two fundamental features have thus far been distinct concepts. Here we show that they are inextricably and quantitatively linked. Quantum mechanics cannot be more non-local with measurements that respect the uncertainty principle. In fact, the link between uncertainty and non-locality holds for all physical theories. More specifically, the degree of non-locality of any theory is determined by two factors the strength of the uncertainty principle, and the strength of a property called "steering," which determines which states can be prepared at one location given a measurement at another. Joint work with Jonathan Oppenheim. arXiv:1004.2507 ______________________________________________________________________

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