February 2019 - ITP-quantumseminare

Talk title and abstract
by Joe Renes 26 Feb '19

26 Feb '19

Hi all, Below is the title and abstract for Tamara Kohler’s talk. Best, Joe ——————- Title: Complete Toy Models of Holographic Duality Abstract: This talk will discuss recent work applying quantum information theory techniques to construct toy models of the AdS/CFT correspondence. The AdS/CFT correspondence is a conjectured duality between quantum gravity in (d+1) dimensional asymptotically AdS space, and a conformal field theory defined on its boundary. It has recently been pointed out that the emergence of bulk locality in AdS/CFT can be characterised in terms of quantum error correcting codes. This has led to the construction of holographic quantum error correcting codes (HQECC) which are toy models of the duality. However, in previous HQECC the boundary Hamiltonian which results from mapping a local bulk Hamiltonian to the boundary is a non-local Hamiltonian, with global terms that act over the entire boundary. In this work we combine previous HQECC results with the theory of Hamiltonian simulation to construct a bulk-boundary model between local Hamiltonians. This mapping of local Hamiltonians extends the toy models to encompass the relationship between bulk and boundary energy scales, and in particular the mapping between bulk and boundary time dynamics. We discuss what insight this gives into toy models of black hole formation.

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Tuesday’s meeting --- H42 @ 16:45 (!)
by Joe Renes 25 Feb '19

25 Feb '19

Hi all, This week we will have talks by two visitors, Tamara Kohler from UCL and Esteban Castro Ruiz from Vienna. Also, due to a scheduling conflict, we will have to start late, at 16:45, and in a different room, H42. I hope this is not an inconvenience. So far I have an abstract from Esteban Castro Ruiz, which you can find below. I will send more information on Tamara Kohler's talk when it becomes available. Best, -joe %%%%%%% Title: Time reference frames and gravitating quantum clocks Abstract: The standard formulation of quantum theory relies on the assumption of a fixed background notion of time, according to which events are localised and the order between them is well defined. In general relativity, physics is independent of any such background notion --spacetime points have no direct physical meaning. For this reason, the localisation of events in time is defined operationally, via the measurement of physical clocks. When the clocks are classical, the order between events is still well-defined. Here, we explore the problem of defining the localisation of events with respect to gravitating quantum clocks. I will present a quantum framework for “time reference frames,” describing quantum states, dynamics and measurements with respect to different quantum clocks, which might interact, gravitationally or otherwise, with other quantum systems. We will see that, with respect to interacting quantum clocks, the time localisability of events, as well as their order, becomes a relative concept, depending on the time reference frame. We discuss the consequences of this finding for the physical realisation of indefinite causal structures at the interplay between quantum physics and gravity.

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Talk tomorrow (Wednesday) by Fabien Clivaz, HIT J51, 3:30 pm.
by Ralph Silva 19 Feb '19

19 Feb '19

Dear all Fabien Clivaz, who is visiting us from IQOQI Vienna, will give us a whiteboard talk tomorrow on the *"Optimal creation of correlations in thermal environments"*, the abstract is below. The talk will be in J51, at 15:30. *Abstract:* In quantum thermodynamics, correlations are of paramount importance for any statement made, quantifying the interplay between information and thermodynamic tasks. Correlating different entities in a thermal background comes at an energetic cost that has to be invested, that very much depends on the details of the interaction dynamics. In this paper, we put forward a framework for studying the process of correlating (thermal) quantum systems from an energetic perspective in terms of entangled subspaces. We show how this framework can be used to prove that two identical qutrits can always be correlated at an optimal energy cost and how many sufficient conditions for the existence of quantum marginal configurations can be made in terms of convex combinations of stochastic majorisation theory with permutational symmetries. Regards Ralph

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next week's meeting Tuesday 15:30 HIT E41.1
by Joe Renes 15 Feb '19

15 Feb '19

Hi all, next week we'll start with the meeting at its new time on Tuesdays at 3:30 pm in HIT E41.1. Leo Wossnig is visiting Raban from UCL and will give a talk on "Randomized methods and quantum computation". The abstract is below. Best, -joe Title: Randomized methods and quantum computation Abstract: In this talk I will introduce some of the fundamental ideas of randomized numerical linear algebra, based on early results for matrix multiplication and low rank approximations and will then explain how these can be used in various scenarios. In particularly, I will recap our own results for randomized Hamiltonian simulation, and explain how these methods can be extended to obtain so called quantum inspired methods for machine learning, which have lately experienced high attention in the quantum computation community.

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Introduction to Euler, Fri 15.2.
by Lennart Baumgaertner 13 Feb '19

13 Feb '19

Dear all, As announced in the group meeting on Monday, I will be giving a short (15-20 min) interactive introduction to working with the ETHZ Euler Cluster *this Friday, February 15th, 2pm, HIT E 41.1*. Please feel welcome to attend but not obliged if you do not feel like this session is necessary for you. For anybody who is interested but can not make it this Friday, I can also quickly go over the basics with you in person. *Why use the cluster? * The ETH clusters can be very useful for anybody doing computationally intense simulations or data processing. The cluster is essentially a second, powerful computer where you can "outsource" jobs from your machine to. This means that once you started a program on the cluster, you may turn off your own computer or work on something else and check back at a later time if the job has finished. The cluster supports all sorts of programming environments (Python, Matlab, Mathematica, ...) and has a lot of packages pre-installed for direct use. *What do I need to prepare?* In order for us to run a very basic exemplary code on the cluster, I have attached a Python file to this email. Please download it and save it to a location that you will be able to find using the terminal during the tutorial, for example the Desktop. There is no need to install python and run this code on your own computer. *For Windows users:* Windows does not provide an included ssh client. In order to access the cluster, you will therefore need to download third-party software for this. ETH recommends Cygwin for this ( http://www.cygwin.com) There are other options that you might prefer, but with Cygwin the syntax should be the same as it is for Mac and Linux users, so I would go for this solution for the tutorial. Please download and install Cygwin or some alternative before the tutorial, then we can all follow along without many delays. *What do I need to bring? * If you want to follow along in this interactive session, make sure to bring your prepared Laptop with the files listed above. Other than this, we do not need anything else. *Are there alternatives to this tutorial? * Yes. Using the cluster is actually not that hard and ETH has done a very good job in documenting the first steps of using the cluster. The aim of our tutorial is more to show what working with the cluster looks like and to set it up directly for everybody who thinks might work with it in the future. You can also check out https://scicomp.ethz.ch/wiki/Getting_started_with_clusters if you prefer to have a look at it by yourself. Those who are attending the tutorial do not need to read up on anything, we will look at it together. *Will there be food or beverages?* Unfortunately I will not provide anything other than this somewhat prepared tutorial, but of course I highly encourage anybody who is motivated to bring food or drinks to lighten up this Friday afternoon. Otherwise an ITP coffee will probably do. If there is anything else that I forgot or that you would like to know, don't hesitate to write me an email. Looking forward to the Friday session, see you all then, Lennart -- Lennart Baumgärtner Gloriastrasse 58 CH- 8044 Zürich Mobil +41- 78 632 82 05

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new group meeting time: 3:30 Tuesdays
by Joe Renes 11 Feb '19

11 Feb '19

Hi all, starting next week the 19th we'll have the group meeting on Tuesdays, at 3:30 pm. For the next two weeks we'll have talks by visitors: Leo Wossnig next week and then Tamara Kohler the week after, both from University College London. More details to follow. Best, -joe

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Monday's meeting E41.1 @ 15:45
by Joe Renes 11 Feb '19

11 Feb '19

Hi all, we're still in the between-semester low, but we should meet to finalize when the group meeting will take place next semester. I've made a preliminary check with the postdocs and PhD students, and the best times are either Tuesday or Thursday afternoon, with a preference for Tuesday. We can discuss this as well as perhaps some short reports about what we've been doing lately. It would be good to have a brief idea of what topics people would like to present in the coming semester. Best, -joe

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no meeting tomorrow
by Joe Renes 03 Feb '19

03 Feb '19

Hi all, tomorrow's meeting is cancelled as it overlaps with several exams and the QSIT meeting in Arosa. Best, -joe

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