ITP-quantumseminare September 2022

itp-quantumseminare@lists.phys.ethz.ch

2 participants
5 discussions

Tomorrow's QIT Seminar 2pm HIT E 41.1 & zoom
by Ladina Hausmann 26 Sep '22

26 Sep '22

Hi all, Tomorrow Esteban Castro-Ruiz will tell us about his recent work 'Quantum conformal symmetries for spacetimes in superposition’ (https://arxiv.org/abs/2207.00021). See below for the abstract. The talk will take place at 2pm in HIT E 41.1 or on Zoom: https://ethz.zoom.us/j/362994444. Best, Ladina %%%%%% Without a complete theory of quantum gravity, the question of how quantum fields and quantum particles behave in a superposition of spacetimes seems beyond the reach of theoretical and experimental investigations. Here we use an extension of the quantum reference frame formalism to address this question for the Klein-Gordon field residing on a superposition of conformally equivalent metrics. Based on the group structure of ``quantum conformal transformations'', we construct an explicit quantum operator that can map states describing a quantum field on a superposition of spacetimes to states representing a quantum field with a superposition of masses on a Minkowski background. This constitutes an extended symmetry principle, namely invariance under quantum conformal transformations. The latter allows to build an understanding of superpositions of diffeomorphically non-equivalent spacetimes by relating them to a more intuitive superposition of quantum fields on curved spacetime. Furthermore, it can be used to import the phenomenon of particle production in curved spacetime to its conformally equivalent counterpart, thus revealing new features in modified Minkowski spacetime.

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Tomorrow's QIT Seminar 2pm HIT E 41.1 & zoom
by Ladina Hausmann 19 Sep '22

19 Sep '22

Hi all, Tomorrow Anna Efimova will tell us about her semesterthesis with Ramona. See below for the abstract. The talk will take place at 2pm in HIT E 41.1 or on Zoom: https://ethz.zoom.us/j/362994444. Best, Ladina %%%% Today I'm going to tell you about Quantum Random Number Generators which can be used in different areas from physics experiments to commercial purposes. However, true randomness is not always understood correctly. We are going to consider different scenarios of device imperfections and emphasize some important details of the mathematical description of different protocols.

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Tomorrow's QIT Seminar 2pm HIT E 41.1 & zoom
by Ladina Hausmann 12 Sep '22

12 Sep '22

Hi all, Tomorrow we will have two talks. Marc Sanz Drudis will tell us about his semester project with Lidia del Rio. Florian Meier will tell us about his master thesis he conducted in Vienna, entitled 'Performance limits of decay clocks'. See below for the abstracts. The talks will take place at 2pm in E 41.1 or on Zoom: https://ethz.zoom.us/j/362994444. Best, Ladina %%%% Contextuality in quantum mechanics is one of the main features that set it aside from "classical" theories. Before making such an assumption one wants to be convinced that a non-contextual model would not be able to replicate the same results. Pre- and Post- Selection Paradoxes (PPS Paradoxes) are a good candidate to prove contextuality. In 2014 it was proven that the existence of anomalous weak values in quantum mechanics makes it incompatible with any non-contextual model. A year after that it was proven that a non-contextual model would not be able to replicate "Logical" PPS Paradoxes. We try to relax the assumption that our PPS Paradoxes need to be logical by exploring the relationship between weak values and PPS paradoxes. We show that we can relax the assumption for binary measurements and establish a methodology to generalize the result to an arbitrary number of possible outcomes. %%%% Performance limits of decay clocks Clocks are among the most precise measurement devices ever built, but like anything else, they are bound by the laws of thermodynamics. As a consequence, all clocks are inherently subject to noise and thus cannot be infinitely precise. We examine these limitations and the thermodynamic cost of running a clock. From minimal assumptions, we derive that processes driving a clock must be irreversible. In the simplest memory-less thermodynamic setting, this leads to exponential decay. Under the assumption of a fixed decay rate \Gamma Γ, we explore what types of quantum clocks can be built using an exponentially decaying process to generate the ticks of the clock, but with a clockwork that is otherwise unconstrained. Using the average number of ticks N N until a clock is off by one tick as the measure for its accuracy, and the inverse average tick time as the measure for its resolution R R, we show that any increase in accuracy ultimately comes at the cost of resolution, subject to the bound N\leq \Gamma^2/R^2 N≤Γ 2 /R 2 . With a periodic process in the clockwork to concentrate the decay event probability to specific times, we can build clocks that approach this optimal accuracy-resolution trade-off. Based on a quantum clock from Schwarzhans et al. [1], that uses as its only resource out of equilibrium heat baths, we design a clock that we conjecture to reach the scaling N\sim \text{const.}/R^2 N∼const./R 2 asymptotically. In this example, the entropy production grows linearly with the accuracy, confirming the thermodynamic limitation of the clock performance. [1] Emanuel Schwarzhans, Maximilian P. E. Lock, Paul Erker, Nicolai Friis, and Marcus Huber. Autonomous Temporal Probability Concentration: Clockworks and the Second Law of Thermodynamics. RX, 11(1):011046, 2021. doi: 10.1103/PhysRevX.11.011046. URL https://link.aps.org/doi/10.1103/PhysRevX.11.011046 <https://link.aps.org/doi/10.1103/PhysRevX.11.011046>.

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Semester project
by nexis md 11 Sep '22

11 Sep '22

Hello, My name is Marc Sanz Drudis. I have been doing my semester project with Lidia del Rio and will be presenting this week. Apparently, I needed to send you and abstract, so here it is: """ Contextuality in quantum mechanics is one of the main features that set it aside from "classical" theories. Before making such an assumption one wants to be convinced that a non-contextual model would not be able to replicate the same results. Pre- and Post- Selection Paradoxes (PPS Paradoxes) are a good candidate to prove contextuality. In 2014 it was proven that the existence of anomalous weak values in quantum mechanics makes it incompatible with any non-contextual model. A year after that it was proven that a non-contextual model would not be able to replicate "Logical" PPS Paradoxes. We try to relax the assumption that our PPS Paradoxes need to be logical by exploring the relationship between weak values and PPS paradoxes. We show that we can relax the assumption for binary measurements and establish a methodology to generalize the result to an arbitrary number of possible outcomes. """ At what time and where will the presentation be? Best Regards, Marc

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Tomorrow's QIT Seminar 13:30 HIT K 52 & zoom
by Ladina Hausmann 05 Sep '22

05 Sep '22

Hi all, Tomorrow Elie Bermot will tell us about his master thesis conducted at IBM entitled 'Quantum Generative Adversarial Networks for Anomaly Detection in High Energy Physics'. See below for the abstract. The talk will take place at 13:30 in HIT K 52 or on Zoom: https://ethz.zoom.us/j/362994444. Best, Ladina %%%%%%%% The standard model (SM) of particle physics is an accomplishment of decades of theoretical and experimental work. It describes almost all known elementary particles and their interactions: strong, weak and electromagnetic. However, some of the observed events occurring in a particle accelerator, e.g., the Large Hadron Collider, correspond to anomalous and unpredictable events, whereby the underlying physics is not governed by the SM. The detection of anomalous events and, the corresponding potential discovery of new fundamental physics, is far from trivial. In fact – until recently – most of the high energy physics data analysis relied on model-specific selection process. In this work, we consider a quantum generative adversarial network (qGAN) based scoring function that identifies anomalous events by determining whether an event is characteristic for a certain background distribution such as the SM. We implement the qGAN training and the anomaly detection scheme with Qiskit and test the method on proof-of-principle examples using numerical simulations as well as actual IBM quantum processors.

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ITP-quantumseminare September 2022