Online Seminars on Quantum Information in Poland. Warsaw time zone.

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Past events

Foundations of quantum thermodynamics and applications in quantum information (CANCELLED)

Date: Thursday, December 7, 2023
Time: 14:30
Host: Quantum Information and Quantum Computing Working Group

Speaker: Tiago Debarba (Universidade Tecnológica Federal do Paraná/TU Wien)

Abstract Quantum information provides a description of quantum mechanical systems based on informational assumptions, which leads to an informational characterization of the quantum world. However, it requires perfect control of microscopic systems, as described by the laws of quantum mechanics. This has proven to be one of the most critical challenges in recent technology development since quantum systems are highly sensitive to any noise. Thermodynamic effects can introduce noise, imposing limitations on the ability to control the preparation, operations, and measurement of quantum systems. Therefore, considering the laws of thermodynamics in quantum informational protocols appears natural and more realistic. In this talk, I will discuss the foundations of thermodynamics in microscopic systems and explore the limitations that thermodynamic effects impose on certain informational protocols, such as information broadcasting and Schumacher compression.

An exactly solvable relativistic quantum Otto engine

Date: Thursday, November 30, 2023
Time: 14:00
Host: ICTQT Seminar, room 319
Zoom link: https://zoom.us/j/99589495433?pwd=WVBtaGtyellMTTRMMGUwZmFEWFlvZz09
Passcode: YJ6WRg, Meeting ID 995 8949 5433

Speaker: Nikolaos Kollas (University of Patras)

Abstract We review the mathematics of exactly solvable Unruh-DeWitt detector models, interacting with massive scalar fields under instantaneous interactions, to construct a relativistic quantum Otto heat engine. By deriving the conditions under which the thermodynamic cycle is closed we present preliminary results on the dependence of the extracted work as a function of the relativistic velocities of the detector during its interaction with the hot and cold baths and compare these results for two different couplings defined in the laboratory and the detector’s frame of reference respectively.

Roman Ingarden Memorial Session 2023

Date: Wednesday, November 29, 2023
Time: 15:30
Host: KCIK
Passcode: please contact pawel.mazurek@ug.edu.pl

Details

Programme
15.30 – 15:55 Dariusz Chruściński “Roman S. Ingarden and his passion for physics”

16:00 – 16:55 2022 Ingarden Memorial Lecture

                        Artur Ekert “Bell inequalities: From Curiosity to Security”

17:00 – 17:15 Coffee break

17:15-17:45 Distinguished talk (to be announced Nov. 29th, 2023)

17:45-18:15 Awarding of Junior KCIK Award for best Bachelor Thesis in quantum Information (to be announced Nov. 29th, 2023)

18:18 The End

State-independent certification of quantum observables and minimal bipartite full nonlocality

Date: Wednesday, November 29, 2023
Time: 14:30
Host: Quantum Information and Quantum Computing Working Group
Zoom link: https://us06web.zoom.us/j/87431414089
Passcode: nisq, Meeting ID: 874 3141 4089

Speaker: Adán Cabello (Universidad de Sevilla)

Abstract We will present some recent results. First, we show that some sets of quantum observables are unique up to an isometry and have a contextuality witness that attains the same value for any initial state. These two properties enable to certify them using the statistics of experiments with sequential measurements on any initial state of full rank. Second, we show that the following statements are equivalent: (i) A quantum correlation p is in a face of the nonsignaling polytope that does not contain local points. (ii) p has local fraction zero, i.e., p has full nonlocality (FN). (iii) p provides an all-versus-nothing (AVN) or Greenberger-Horne-Zeilinger-like proof of nonlocality. (iv) p is a pseudo telepathy (PT) strategy. These equivalences imply that a long-standing question of what is the simplest example of bipartite FN/AVN/PT has fundamental relevance. We will answer this question.

Gaussian decomposition of magic states for matchgate computations

Date: Wednesday, November 29, 2023
Time: 14:00
Host: ICTQT Seminar, room 319
Zoom link: https://zoom.us/j/99589495433?pwd=WVBtaGtyellMTTRMMGUwZmFEWFlvZz09
Passcode: YJ6WRg, Meeting ID 995 8949 5433

Speaker: Josh Cudby (The University of Cambridge)

Abstract Magic states were originally introduced as a resource that enables universal quantum computation using classically simulable Clifford gates. This concept has been extended to matchgate circuits (MGCs) which are made of two-qubit nearest-neighbour quantum gates defined by a set of algebraic constraints. In our work, we study the Gaussian rank of a quantum state — defined as the minimum number of terms in any decomposition of that state into Gaussian states — and associated quantities: the Gaussian Fidelity and the Gaussian Extent. First, we will give a review of rank-based simulation methods in the stabilizer setting, and describe the operational relevance of the Rank, Fidelity & Extent. We will then give some background on MGCs and their physical relevance. Then, we will move onto the new results from our work. The primary result is a description of the algebraic structure of Gaussian states, including the independent sets of constraints upper-bounding the dimension of the manifold of Gaussian states. Using these equations, we can derive results including the form of linearly dependent triples of Gaussian states. We then discuss properties of the Gaussian Fidelity and Extent, making progress towards resolving the question of multiplicativity of the Gaussian Fidelity. Finally, we investigate the Gaussian Rank. we show that the rank of two copies of our canonical magic state is 4 for symmetry-restricted decompositions. Numerical investigation suggests that no low-rank decompositions exist of either 2 or 3 copies of the magic state. Finally, we consider approximate Gaussian rank and present approximate decompositions for selected magic states. Paper available at https://arxiv.org/abs/2307.12654.

Quantum operations and generators of Markovian dynamics (joint working seminar)

Date: Monday, November 27, 2023
Time: 14:15
Host: Quantum Chaos and Quantum Information (Jagiellonian University)
Zoom link: https://us05web.zoom.us/j/89601291160?
Passcode: please contact albertrico23 at gmail.com

Speaker: Dariusz Chruściński, Sergey Denisov, Wojciech Tarnowski

Abstract

Bell Entanglement Witnesses and Intangible States

Date: Monday, November 20, 2023
Time: 14:15
Host: Quantum Chaos and Quantum Information (Jagiellonian University)
Zoom link: https://us05web.zoom.us/j/89601291160?
Passcode: please contact albertrico23 at gmail.com

Speaker: Stanisław Czachórski (UJ) 

Abstract

Certification of nonclassical properties via Bargmann invariants

Date: Wednesday, November 15, 2023
Time: 16:00
Host: Quantum Foundations, ICTQT, room 319
Zoom link: https://zoom.us/j/97976952027?pwd=NFNGK0Z0L0lORjE3MU40WG1ZVnp6QT09

Speaker: Rafael Wagner (University of Minho)

Abstract Certifying quantum devices and their ability to generate nonclassical data is a crucial task to calibrate and benchmark near-term quantum hardware. In this presentation I will discuss some recent efforts of using nonclassical relational information, provided by the measurement of Bargmann invariants, to witness nonclassicality. In more detail, I will discuss their potential applications for linear-optical devices

Detecting entanglement and steering without idealised measurements

Date: Wednesday, November 15, 2023
Time: 14:30
Host: Quantum Information and Quantum Computing Working Group
Zoom link: https://us06web.zoom.us/j/87431414089
Passcode: nisq, Meeting ID: 874 3141 4089

Speaker: Armin Tavakoli (Lund University)

Abstract Standard methods for witnessing entanglement and steering require that some parties are able to perfectly implement a set of quantum measurements. However, real quantum devices cannot be perfectly controlled. We propose an operational framework of imprecise measurements, tailored for devices which are trusted but not flawless. We investigate how entanglement and steering witnessing is influenced by tiny systematic imperfections in the measurement devices, finding that tiny errors have large impact. Then, we set out to construct detection criteria which explicitly take the imperfections into account.

Graph Picture for the Heralded Non-Destructive Generation of Bosonic N-partite Entanglement

Date: Wednesday, November 15, 2023
Time: 14:00
Host: ICTQT Seminar, room 319
Zoom link: https://zoom.us/j/93990135207?pwd=ZEtzeUpHMWRIS05vUTdYbGl1NXpUQT09

Speaker: Seungbeom Chin (Sungkyunkwan University & ICTQT)

Abstract Heralded entanglement generated among identical particles is a useful resource for quantum computations, as heralded schemes distinguish experimental runs producing target states without direct measurement. Nonetheless, these heralded schemes generally entail the incorporation of supplementary particles and modes, thus amplifying the design intricacy. In response to this challenge, our recent work (arXiv:2211.04042) introduced a graph approach for systematic heralded scheme design, which provided several graphical schemes (dubbed “sculpting bigraphs”) for creating multipartite boson entanglement with boson subtractions. However, an indispensable intermediate step remains essential to transmute these sculpting bigraphs into practical heralded entanglement generation circuits: the proposition of heralded subtraction operators (herein dubbed “subtractors”). Assembling the subtractors under the guidence of the sculpting bigraphs, we can seamlessly design heralded schemes for multipartite entangled states. Our study establishes a set of translation rules, enabling the mapping of sculpting bigraph elements into linear optical networks through the incorporation of heralded subtractors. Consequently, we devise heralded schemes for the N-partite GHZ state with 2N photons, N-partite W state with (2N+1) photons, and N=3 Type 5 state (the superpostion of N=3 GHZ and W states) with 9 photons. Our results demonstrate that the process of designing heralded schemes for generating entanglement is simplified into the task of searching for suitable sculpting bigraphs. References -Chin, Seungbeom, Marcin Karczewski, and Yong-Su Kim. “From graphs to circuits: Optical heralded generation of N-partite GHZ and W states”, arXiv:2310.10291 (2023). -Chin, Seungbeom, “From linear quantum system graphs to qubit graphs: Heralded generation of graph states”, arXiv preprint, arXiv:2306.15148 (2023). -Chin, Seungbeom, Yong-Su Kim, and Marcin Karczewski. “Shortcut to Multipartite Entanglement Generation: A Graph Approach to Boson Subtractions”, arXiv preprint arXiv:2211.04042 (2022). -Chin, Seungbeom, Yong-Su Kim, and Sangmin Lee.“Graph picture of linear quantum networks and entanglement.” Quantum 5 (2021): 611.
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