ITP-quantumseminare

itp-quantumseminare@lists.phys.ethz.ch

1 participants
1357 discussions

tomorrow's QIT Seminar, 2pm zoom
by Joe Renes 21 Dec '20

21 Dec '20

Hi all, Tomorrow at 2pm Jan Li will tell us about his master thesis on "Device-independent Quantum Key distribution and Nonlocality Distillation", which he did with Dr. Koon Tong Goh and Prof. Dr. Charles Ci Wen Lim at CQT and NUS in Singapore. See below for the abstract. The zoom link is https://ethz.zoom.us/j/362994444. Best, Joe Abstract: In this project, we have investigated the use of local wirings as described in Short et al. [table 1 https://arxiv.org/abs/quant-ph/0508120] to revive zero keyrates of DIQKD set-ups to positive keyrates. In this project, we first considered the correlations generated by a two qubit set-up. Due to the high computational cost of considering all possible wirings, we checked for a subclass of extremal wirings if there is revival. For this model, we found that some revival was possible for some wirings and that revival could be pushed further by wiring multiple times. Next, we moved to a more realistic model, the all-photonics system as is considered in Tsujimoto et al. [ https://journals.aps.org/pra/abstract/10.1103/PhysRevA.98.063842]. For this model however, we were not able to find any improvements and further research is needed.

1 0

QIT Seminar 15 December, 2pm
by Joe Renes 14 Dec '20

14 Dec '20

Hi all, Tomorrow Amira Abbas from IBM Zürich and the University of Durban will tell us about "The power of quantum neural networks". The full abstract is below. Join us at 2pm on zoom, at https://ethz.zoom.us/j/362994444. Best, Joe Abstract: Fault-tolerant quantum computers offer the promise of dramatically improving machine learning through speed-ups in computation or improved model scalability. In the near-term, however, the benefits of quantum machine learning are not so clear. Understanding expressibility and trainability of quantum models–-and quantum neural networks in particular–-requires further investigation. In this work, we use tools from information geometry to define a notion of expressibility for quantum and classical models. The effective dimension, which depends on the Fisher information, is used to prove a novel generalisation bound and establish a robust measure of expressibility. We show that quantum neural networks are able to achieve a significantly better effective dimension than comparable classical neural networks. To then assess the trainability of quantum models, we connect the Fisher information spectrum to barren plateaus, the problem of vanishing gradients. Importantly, certain quantum neural networks can show resilience to this phenomenon and train faster than classical models due to their favourable optimisation landscapes, captured by a more evenly spread Fisher information spectrum. Our work is the first to demonstrate that well-designed quantum neural networks offer an advantage over classical neural networks through a higher effective dimension and faster training ability, which we verify on real quantum hardware.

1 0

Tuesday's QIT Seminar
by Joe Renes 07 Dec '20

07 Dec '20

Hi all, Tuesday at 2pm Alexander Miessen will present his master thesis on "Variational Quantum Algorithms for Real Space Wave Packet Dynamics", which he carried out with Ivano Tavernelli at IBM Research. See below for the abstract. The zoom link is https://ethz.zoom.us/j/362994444. Note that at 3pm Andru Gheorghiu will deliver the ITS Fellows' Seminar on "Quantum computation: hardness, verification and protocols for near-term devices". See https://eth-its.ethz.ch/activities/its-fellows--seminar/Alexandru-Gheorghiu… for more details. The zoom link is https://ethz.zoom.us/j/99922681517. Best, Joe Abstract: Variational quantum algorithms (VQAs) have become the new paradigm in applied quantum computing, enabling calculations on current-day quantum hardware that would be far out of reach otherwise. The triumph of hybrid quantum-classical schemes over purely-quantum methods has led to numerous further-developments and applications to stationary problems in recent years, yet the most widely used method for quantum dynamics simulation remains the Trotterization of the unitary time-evolution operator. However, it relies on deep quantum circuits and is therefore hampered by the strong limitations of available quantum technology which prohibits its use for practical tasks in the near future. The development of a variational time-evolution (VTE) algorithm was therefore an important and necessary s tep for quantum dynamics to gain more foothold in present-day quantum computing. Nonetheless, VTE faces the difficulty of finding an ansatz for expressing the wavefunction which is able to maintain satisfactory accuracy throughout an evolution without diverging from the true state trajectory. While heuristic ansätze enjoy popularity, findings suggest that they require exponentially many parameters to offer enough flexibility, jeopardizing any potential quantum advantage. One hypothesized way out of this dilemma is the use of a physically motivated ansatz, the quantum circuit analog of an educated guess, which samples from a reduced variational space by taking into consideration model-specific symmetries. In this work, we aim to explore this possibility by studying the dynamics of molecular vibrations as well as a spin-boson model. We analyze existing physically motivated ansätze, developed for stationary VQAs, and propose modifications thereof to make them better suited for VTE. Subsequently, they are tested in the simulation of various system's dynamics. Our results indicate that it is indeed possible to find a compact yet accurate variational ansatz by leveraging symmetries of the system under study, requiring far less than exponentially many parameters.

1 0

Bitcoin auf dem Weg zum Rekord ↑
by Bitcoin System 02 Dec '20

02 Dec '20

Bitcoin System Erfahrungen – Funktioniert Bitcoin System wirklich? Laufend gibt es neue Plattformen, welche sich auf den Handel mit Kryptowährung aller Art spezialisiert haben. Doch wie sollen Kunden und Anleger noch herausfinden, welche wirklich seriös sind und bei welchen sich die Anmeldung überhaupt lohnt? Derzeit gibt es Tausende verschiedene Währungen – auch hier ist es schwierig, als unerfahrener Anleger den Überblick zu wahren. Umso wichtiger ist ein Anbieter, der das Trading durch eine übersichtliche Benutzeroberfläche und eine leichte Bedienung einfacher macht. Generell fragen sich sehr viele Menschen gerade an Anfang, ob die Nutzung eines Bots in ihrem individuellen Fall überhaupt Sinn ergibt. Viele entscheiden sich schlussendlich dafür, weil es sich um eine Möglichkeit handelt, welche auch Laien direkt effektiv nutzen können. Bei Bitcoin System handelt es sich nur um einen von vielen Bots, doch dieser gilt als zuverlässig und einsteigerfreundlich. Unser Fazit vorab: Bitcoin System hat uns Überzeugt und ist kein Betrug! JETZT KOSTENLOSES BITCOIN SYSTEM DEMOKONTO ERÖFFNEN >>>

1 0

continuation of Philipp Höhn's talk, today at 15:30
by Joe Renes 30 Nov '20

30 Nov '20

Hi all, Sorry for the terribly late notice --- today Philipp Höhn will continue his talk on reference frames. Here's the link: https://ethz.zoom.us/j/362994444. We will also record and post the talk. Best, Joe

1 0

Tomorrow's QIT Seminar, 2pm zoom
by Joe Renes 30 Nov '20

30 Nov '20

Hi all, Tomorrow Oliver Knapp will present his semester project, entitled "Relativity from relational quantum mechanics: the emergence of Lorentz transformations in rotational invariant qubit systems." See the abstract below. The zoom link is https://ethz.zoom.us/j/362994444. Best Joe Abstract: We show how Lorentz transformations emerge as a natural consequence of rotational symmetry in qubit systems. To this end, we first review relational quantum mechanics and subsequently propose a framework to integrate the relational principle in multi- qubit systems. This principle inevitably requires every multi-qubit system to be SU(2) symmetric, that is one may rotate the qubits without changing the dynamics. We then examine the properties of such SU(2) symmetric qubit systems and prove that time evolution must consist only of permutations of the qubits, similar to the SWAP gate. As a direct consequence, SU(2) symmetric systems are then necessarily GL(2, C) symmetric. To deal with such non-unitary symmetry transformations, we first consider a thought experiment exhibiting GL(2,C) symmetry and then propose to generalize the postulates of quantum mechanics. By regarding states as rays in a projective space the relevant symmetry group reduces to PGL(2, C), which as a group is isomorphic to the proper orthochronous Lorentz transformations SO+(1, 3). At last we show that the action of PGL(2,C) on the Bloch sphere yields exactly the group of all orientation- preserving conformal maps of the sphere S2, also known as Möbius transformations.

1 0

tomorrow's QIT Seminar, 2pm
by Joe Renes 23 Nov '20

23 Nov '20

Hi all, Tomorrow Thomas Hahn will present his master's thesis project, carried out with Ernest, on "Fidelity Bounds for Device-Independent Advantage Distillation". See below for the abstract. The zoom link is https://ethz.zoom.us/j/362994444. Best Joe Abstract: Low noise tolerances for current device-independent quantum key distribution protocols and the existence of fidelity-related security conditions in device-independent advantage distillation motivate the need for strong lower bounds on the fidelity. This thesis shows that a reduction to qubits does not deliver optimal bounds. An algorithm is derived that can in principle bound the fidelity for our device-independent setup to an arbitrary precision. This algorithm is computable with a semi-definite program and a constraint optimization. We conclude with a conjecture for a necessary security condition against collective attacks, where a repetition-code protocol that applies advantage distillation is considered.

1 0

PhD and postdoc positions in Singapore
by Lidia del Rio 19 Nov '20

19 Nov '20

Dear all, Marco Tomamichel is hiring PhD students and postdocs in Singapore. This is an open call. He works mostly on single-shot quantum information theory. https://marcotom.info Best, Lídia

1 0

Tomorrow's QIT Seminar
by Joe Renes 16 Nov '20

16 Nov '20

Hi all, Tomorrow Philipp Höhn from the Okinawa Institute of Science and Technology will tell us about "A Perspective-neutral approach to quantum frame covariance". See below for the abstract. The talk starts, as usual, at 2pm on zoom: https://ethz.zoom.us/j/362994444. Best, -joe Title: Perspective-neutral approach to quantum frame covariance Abstract: General covariance posits that “all the laws of physics are the same in every reference frame.” While this is an established pillar of general relativity, its fate in the quantum realm remains an open question, both in quantum gravity and the foundations of quantum theory. I will summarize a perspective-neutral approach to quantum reference frames aimed at addressing this question. This approach permits one to switch from the description of physics relative to one quantum frame (a perspective) to that relative to another. Such perspective changes work in analogy to coordinate changes on a manifold, except that these “quantum coordinate changes” proceed between different Hilbert spaces. In particular, they lead to a "quantum relativity" of physical notions such as entanglement, superposition, temporal locality or comparing clock readings. I will explain how this approach resolves a puzzle known as the 'paradox of the third particle' and how it has revealed a previously unknown equivalence between three different approaches to the problem of time (relational observables, Page-Wootters formalism and deparametrizations).

1 0

tomorrow's QIT Seminar
by Joe Renes 09 Nov '20

09 Nov '20

Hi all, Tomorrow Timon Knigge will tell us about his semester project, which was supervised by Niels Gleinig in the CS group of Prof. Torsten Hoefler. The talk will start at 2pm on zoom: https://ethz.zoom.us/j/362994444 Title: Approximation of Classical Functions using Quantum Circuits Abstract: We discuss the problem of approximating classical boolean functions using quantum circuits. We specifically focus on bounding the circuit length for general classes of boolean functions and discuss some proof techniques for providing lower bounds on the length. Best, -joe

1 0

Jump to page:

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

2012

2011

2010

2009

2008

2007

ITP-quantumseminare