ITP-quantumseminare

itp-quantumseminare@lists.phys.ethz.ch

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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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Thursday May 5: QSIT Lunch Seminar
by QSIT Seminar 29 Apr '11

29 Apr '11

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Group seminar: Normand Beaudry
by Frédéric Dupuis 27 Apr '11

27 Apr '11

Hi everyone, Do not miss the glorious return of our group seminar next Tuesday with a talk by Normand Beaudry. Your devoted organizer, --Frédéric -------------------------------------- Title: QKD Security Beyond Qubits Date/Time/Place: Tuesday, May 3, 16:00, HIT J51 Abstract: Currently, security proofs for quantum key distribution (QKD) protocols against the most general type of attack are only possible when Alice sends individual qubits to Bob. However, there exist other protocols, such as the differential phase-shift (DPS) or coherent one-way (COW), that do not use qubits to do QKD. I'll outline these protocols and a new approach that should prove their security. The security proof primarily relies on the uncertainty relation of [Tomamichel arXiv:1009.2015]. This is ongoing joint work with Lana Sheridan and Adriana Marais.

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No group seminar this week
by Frédéric Dupuis 18 Apr '11

18 Apr '11

Well, the title says it all I guess! --Frédéric

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QSIT Seminar: Robert A. Nyman, Friday April 15, 2011
by Ilona Blatter 13 Apr '11

13 Apr '11

Dear all Please be informed about the following QSIT Seminar. With best regards, Ilona Blatter --------------------------------------------------- Date: Friday April 15, 2011 Time: 11:00 Place: ETH Science City, HPF G 6 Host: Tilman Esslinger An Integrated Photonic Atom Chip and Minimally-Destructive Detection of Magnetically-Trapped Atoms Robert A. Nyman Imperial College London, UK We have constructed a new kind of atom chip using integrated optical waveguides, combined with structures for magnetic trapping. There are 12 buried, single-mode optical waveguides in doped silica, cut across by a trench. We detect low-density samples of laser-cooled rubidium atoms launched into the trench, by measuring the absorption of light[1]. Conversely, we have used the atoms to probe the intensity and polarisation of the light carried by the waveguides. We have also developed a two-frequency interferometer to measure atomic density in a magnetic trap more than 100 times on a single sample[2]. We achieve statistically-limited phase noise down to 5800 detected photons in 10 microsecond. Atomic loss rates fit a simple rate model of photon scattering, and can be combined with the phase response to form a figure of merit to optimise the detection system: the more photons used, the more sensitive the measurement, but the greater the loss. Smaller beams make for better detection with less loss, hence the interest in integrating the microfabricated photonic chip. [1] M. Kohnen et al., Nature Photonics vol.5, p35 (2011). [2] M. Kohnen et al., arXiv:1104.0236 (2011) --------------------------------------------------- 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 Daniela Frauchiger
by Stefan Wolf 08 Apr '11

08 Apr '11

Hi, Next week's seminar talk will be given by Daniela Frauchiger, who did her Semester thesis in Renato's group. Tuesday, April 12, 17:00 at HIT J 51. Cheers, Stefan Title: Entropic Uncertainty Relations with Quantum Side Information". Abstract: This semester project recites the proof of the uncertainty relation for smooth entropies outlined in the corresponding paper [Tomamichel and Renner (2011), Phys. Rev. Lett. 106, 110506]. The goal is to enable a reader with basic knowledge in quantum information theory to follow their reasoning.

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QSIT Seminar: Nigel Cooper, Monday April 11, 2011
by Ilona Blatter 08 Apr '11

08 Apr '11

Dear all Please be informed about the following QSIT Seminar. With best regards, Ilona Blatter --------------------------------------------------- Date: Monday April 11, 2011 Time: 11:00 Place: ETH Science City, HPF G 6 Host: Atac Imamoglu Neutral Fermions and Skyrmions in the Moore-Read state at ν= 5/2 Nigel Cooper University of Cambridge, U.K. The fractional quantum Hall state at filling factor ν=5/2 is the subject of a great deal of experimental and theoretical interest at present. This arises from the belief that it is likely described by the Moore-Read state -- an exotic phase of quantum matter, the charged excitations of which are predicted to exhibit non-abelian exchange statistics. I shall describe the different excitations of the Moore- Read state, making connections to its interpretation as a paired state of composite fermions. I shall present the results of our numerical studies of the excitations of the ν=5/2 state. Our results establish the properties a "neutral fermion" branch of excitations.They further predict the existence of "Skyrmions" (spin-unpolarized charged excitations). I shall explain how evidence for neutral fermions and Skyrmions can be sought in photoluminescence experiments. --------------------------------------------------- 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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Reminder: QSIT Lunch Seminar, Thursday April 7
by Ilona Blatter 04 Apr '11

04 Apr '11

Dear QSIT members The next QSIT Lunch Seminar will take place on Thursday April 7, 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. Interferometric Measurement of Local Spin-Fluctuations in a Quantum Gas by Jakob Meineke, Quantum Optics Group, ETH Zurich and Spin-Squeezing a Bose-Einstein Condensate on an Atom Chip by Roman Schmied, Quantum Atom Optics Lab, University of Basel Abstracts: http://www.nccr-qsit.ethz.ch/news/lunchseminar/april2011 Please register for your free pizza at the following link by Tuesday April 5, 12:00 noon: http://doodle.ethz.ch/q5kew3t74zzgwdqa 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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PC Colloquium by Alex Wiederkehr
by Ilona Blatter 04 Apr '11

04 Apr '11

Dear all Please be informed about the following Colloquium of the Laboratory of Physical Chemistry tomorrow. With best regards, Ilona Blatter --------------------------------------------------- Date: Tuesday April 5, 2011 Place: ETH Science City, HCI J 3 Time: 16:45 Cold atoms and molecules by multistage Zeeman deceleration Alex Wiederkehr Laboratorium für Physikalische Chemie, ETH Zürich Invitation/abstract: http://www.nccr-qsit.ethz.ch/news/talks/wiederkehrpdf --------------------------------------------------- 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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ITP-quantumseminare