June 2019 - ITP-quantumseminare - lists.phys.ethz.ch

next week's group meeting, E41.1
by Joe Renes 25 Jun '19

25 Jun '19

Hi all, Apologies for not sending out an email about this week's meeting, which of course didn't take place because many of us are here in Leysin. But let me already announce next week's talk, which will be on _Monday_ at 1600 in E41.1. The talk will be given by Zhengwei Liu, who is visiting from Harvard. The title and abstract are below; it may look quite a bit abstract, but from chatting with him here, I believe there are concrete applications of their formalism to things like, for example, circuit optimization. Best, -joe Title: Quon Graphs and Quantum Error Corrections Abstract: Graph theory is important in information theory. We will give a quantum analogue of graphs using the quon language and apply that to quantum information. We give a new method to construct quantum error correcting codes and exactly solvable models. We establish a further connection to the geometric group theory in mathematics.

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no meeting tomorrow
by Joe Renes 17 Jun '19

17 Jun '19

Hi all, no group meeting tomorrow, in view of the Solstice of Foundations summer school (https://foundations.ethz.ch/) Best, -joe

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Thursday 4pm: tutorial on shape dynamics by Henrique Gomes
by Lidia del Rio 11 Jun '19

11 Jun '19

Dear all, As announced, we are hosting a tutorial on shape dynamics (a relational approach to quantum gravity) on Thursday at 4pm. Best, Lídia -- Henrique Gomes, University of Oxford A brief tutorial in geometrodynamics in general and shape dynamics in particular Thursday, 13th of June, HIL E5 A recurring theme in the obstacles we face on our way to quantum gravity --- placed at the intersection between the conceptual and technical categories --- is Time, with a capital T. In quantum mechanics, an absolute evolution in time is an essential ingredient. Time flows from past to future, and with it, one instantaneous quantum state is brought to another. In general relativity, Time is a dynamical concept, with no absolute notion of past and future. One instant is given by the value of an arbitrary label, with no physical meaning. Conflict ensues when quantization is applied to space-time itself. In the words of two icons of the field, R. Wald and W. Unruh: / // "In quantum mechanics, all measurements are made at "instants of time"; only quantities referring to the instantaneous state of a system have physical meaning. In particular, "histories" are unmeasurable in quantum theory. On the other hand, in general relativity "time" is merely an arbitrary label [...]. The physically meaningful quantities must be independent of such labels [...]. In other words, only the spacetime geometry is measurable; i.e., only histories have physical meaning. Thus, it should not be surprising that when one naively combines quantum theory and general relativity, the only meaningful quantities which survive are those which are both instantaneously measurable [...] and yet depend only on the spacetime geometry [...]"./ This is certainly confusing at a conceptual level. After all, we believe quantum evolution in time amounts to a transformation between physically distinct states, whereas in gravity different instants would be associated with the same physical state. In these tutorials, I will introduce the geometrodynamical approach to general relativity, with a special emphasis on the role played by time. I will then describe the theory of shape dynamics. Shape dynamics amounts to taking many hints ---coming from the initial value formulation of general relativity and from the consideration of symmetries compatible with a quantum mechanical evolution between instantaneous physical configuration states--- seriously. It does this by considering dynamical systems whose natural configuration space is not the space of spacetime geometries, but that of conformally invariant spatial geometries: conformal superspace. Such a configuration space embodies natural tenets of relationalism (with respect to size and location). By using shape dynamics, we trade Lorentz invariance (or refoliation invariance), by spatial scale invariance and a spatially non-local Hamiltonian. Such characteristics may render shape dynamics more congenial to the Bohmian interpretation of quantum mechanics than other geometrodynamical theories.

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tomorrow's group meeting @15:30 E41.1
by Joe Renes 10 Jun '19

10 Jun '19

Hi all, Tomorrow we'll hear from Jinzhao on his research into causal diamonds. I believe this has to do with (quantum) gravity. Best, -joe

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Group seminar tomorrow: 9am HG D3.1
by Lidia del Rio 03 Jun '19

03 Jun '19

Dear all, This week Johannes Bausch <http://www.damtp.cam.ac.uk/people/jkrb2/> from Cambridge is visiting us. He'll be in the centre today and tomorrow for the Open Source Quantum Computing workshop <http://squids.ch/2019/05/open-source-quantum-computing-workshop/>, will come to Hönggerberg on Wednesday and will visit IBM on Thursday. Tomorrow's QIT group meeting will be replaced with Johannes' lecture at the workshop: *Maximum finding with quantum computers* * Motivation: finding the maximum of a list * Grover’s algorithm: extension to unknown number of elements * Toy example: finding ‘not the smallest element’ * Circuit to compare bit strings [Sena Oliveira, Melo Sousa & Viana Ramos 2006 <https://ieeexplore.ieee.org/abstract/document/4433341>] * Algorithm for maximum finding [Durr, Hoyer 1996 <http://arxiv.org/abs/quant-ph/9607014>andAhuja, Kapoor 1999 <http://arxiv.org/abs/quant-ph/9911082>] * Extensions, speed-ups and applications This will take place at 9:00 in HG D3.1. It will be followed by a coffee break and then a tutorial on how to implement this algorithm on ProjectQ by Ngyuen Damien, from Huawei. For the full programme of the workshop, see the website <http://squids.ch/2019/05/open-source-quantum-computing-workshop/>. Best wishes, Lídia

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