September 2017 - ITP-quantumseminare

today's meeting 15:45 HIT K51
by Joe Renes 25 Sep '17

25 Sep '17

Hi everyone, today we'll meet in K51 at our new time, 15:45. We have a guest from downtown, Tobias Sutter, who will tell us something interesting about optimization problems. Best, -joe

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tomorrow's group meeting E41.1 @ 4pm
by Joe Renes 17 Sep '17

17 Sep '17

Hi all, tomorrow we'll hear from Nuriya Nurgalieva on her master's thesis. The title and abstract follow. We should also discuss whether Monday at 4pm will be a convenient meeting time for everyone this semester. Best, -joe Title: Quantum reference frames for experiments where observers can be measured Abstract: Frauchiger and Renner recently proposed an expansion of Wigner’s friend experiment to prove that single-world interpretations of quantum theory cannot be self-consistent. Experimenters are modeled as agents who use quantum theory, and additionally can themselves be measured as physical systems. However, Frauchiger and Renner’s description of the experiment implicitly assumes that all agents have access to perfect, classical reference frames. In doing so it imposes artificial classicality on a setting that tries to model only quantum evolutions, and risks missing out on subtleties that could explain the paradox. We model each lab as a system which consists of a spin, a reference frame and an agent’s memory, evolving under a unitary. Concretely, we investigate whether different agents refer to the same degrees of freedom and quantum subsystems when they talk about the outcome of a measurement. Our results show that in the setting with the finite reference frames agents are not able to make deterministic predictions.

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another 15 minute delay
by Joe Renes 13 Sep '17

13 Sep '17

Hi all, sorry for the multiple emails -- it looks like we'll start at 4:30 in H51. Best, -joe

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meeting start at 16:15
by Joe Renes 13 Sep '17

13 Sep '17

Hi all, we'll start a bit later to give those attending the Bernays lecture time to return from the downtown campus. Best, -joe

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talk tomorrow 4pm H51 by Henrik Wilming
by Joe Renes 12 Sep '17

12 Sep '17

Hi all, tomorrow we'll have yesterday's group meeting --- Henrik Wilming from FU Berlin will give a talk at 4pm in H51. Title and abstract below. Best, -joe Statistical ensembles without typicality ----------------------------------------- Maximum-entropy ensembles are key primitives in statistical mechanics from which thermodynamic properties can be derived. Over the decades, several approaches have been put forward in order to justify from minimal assumptions the use of these ensembles in statistical descriptions. I will explain a new approach to derive maximum-entropy ensembles taking a strictly operational perspective. To do that I will consider the set of possible transitions that a system can undergo together with an environment, when one only has partial information about the quantum states of both the system and its environment. The set of all these allowed transitions encodes thermodynamic laws and limitations on thermodynamic tasks as particular cases. Our main result is that the set of allowed transitions coincides with the one possible if both system and environment were assigned the maximum entropy state compatible with the partial information. This provides a new explanation for the overwhelming success of such ensembles and provides a derivation without relying on considerations of typicality or information-theoretic measures.

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Thursday at 10.15am: Composability in Quantum Cryptography
by Christopher Portmann 12 Sep '17

12 Sep '17

Dear all, I'm giving a tutorial talk at QCRYPT next week, "Composability in Quantum Cryptography". For those who won't be at QCRYPT, you can listen to same talk the day after tomorrow: Date/Time: 14 September 2017, 10.15am Duration: 80 minutes Location: CAB H53 (Zentrum) Title: Composability in Quantum Cryptography Abstract: This is (hopefully) a very accessible introduction on how to define composable security, with many examples from quantum key distribution, encryption, authentication, device-independent cryptography, and baking bread. Best, Christopher

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tomorrow's group meeting E41.1 @ 4pm
by Joe Renes 03 Sep '17

03 Sep '17

Hi all, tomorrow Vilasini will give a tutorial-style talk on quantum causality. My sending this message is purely a matter of correlation... ;) Best, -joe

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