# Past events

**October 21, 2019 at 12:15 **

**Seminar given by Arieh Ben-Naim**

The Hebrew University of Jerusalem, Israel

Title: **Entropy and the Second Law based on Information Theory**

Place: Institute of Theoretical Physics and Astrophysics (IFTiA), Faculty of Mathematics, Physics and Informatics UG, Wita Stwosza 57, Gdansk, third floor, seminar room no. 361

**October 18, 2019 at 12:15 **

**Seminar given by Borhan Ahmadi**

University of Kurdistan Hewler (UKH), Irak

Title: **Quantum thermodynamic force and flow**

Abstract:

Why do quantum evolutions occur and why do they stop at certain points? In classical thermodynamics, affinity was introduced to predict in which direction an irreversible process proceeds. In this paper, the quantum mechanical counterpart of the classical affinity is found. It is shown that the quantum version of affinity can predict in which direction a process evolves. A new version of the second law of thermodynamics is derived through quantum affinity for energy-incoherent state interconversion under thermal operations. we will also see that the quantum affinity can be a good candidate to be responsible, as a force, for driving the flow and backflow of information in Markovian and non-Markovian evolutions. Finally, we show that the rate of quantum coherence can be interpreted as the pure quantum mechanical contribution of the total thermodynamic force and flow. Thus it is seen that, from a thermodynamic point of view, any interaction from the outside with the system or any measurement on the system may be represented by a quantum affinity.

Place: Institute of Theoretical Physics and Astrophysics (IFTiA), Faculty of Mathematics, Physics and Informatics UG, Wita Stwosza 57, Gdansk, third floor, seminar room no. 361

**October 11, 2019 at 12:15 **

**Seminar given by Anubhav Chaturvedi**

National Quantum Information Centre (KCIK), University of Gdansk

Title: **Unifying quantum theory’s ontological (hidden variable) incompatibility**

Abstract:

The ontological (hidden variable) framework provides for a vital ground for notions of classicality such as Bell’s local causality, Kochen-Specker’s non-contextuality, and Spekken’s non-contextuality. These notions of classicality formulated as principles, yield operational consequences that contradict predictions of quantum theory, thereby systematically discarding substantial classes of ontological models of quantum theory. Crucially, these notions highlight the different ways in which quantum theory departs from classical theories.

In this seminar, I shall facilitate a unifying insight into these seemingly distinct, yet related notions of classicality. Subsequently, I will present a new notion of classicality as the (hopefully natural) next piece in the puzzle. We refer to this notion as “bounded ontological distinctness”, quantum violation of which implies “quantum preparations, measurements, and transformations are more distinct than they are distinguishable”. This notion not only addresses many of the shortcomings of the other well-known notions of classicality but also unifies them such that violations of the other notions imply the violation of bounded ontological distinctness.

Place: Institute of Theoretical Physics and Astrophysics (IFTiA), Faculty of Mathematics, Physics and Informatics UG, Wita Stwosza 57, Gdansk, third floor, seminar room no. 361

**October 3, 2019 at 11:30 a.m. **

**Seminar given by Tim Evans**

University of Sydney

Title: **Scalable Bayesian learning of local Hamiltonians and Lindbladians**

Abstract:

As the size of quantum devices continues to grow, the development of scalable methods to characterise and diagnose noisy devices is becoming an increasingly important problem. Recent results demonstrate how a local Hamiltonians and Lindbladians can be reconstructed from a single, arbitrary steady state with a number of measurements that scales efficiently in the size of the system. These methods, however, can only characterise the system up to scalar factor and lack sufficient robustness to noise, both of which are imperative to be of practical use. In this talk I will present a Bayesian method that addresses both of these issues by making use of any, or all, of the following: experimental control of Hamiltonian couplings, the preparation of multiple states and the availability of any prior information we may already have for the Hamiltonian couplings. Moreover we provide an adaptive measurement protocol that can be performed online, updating estimates and their corresponding uncertainties as experimental data becomes available.

Place: International Centre for Theory of Quantum Technologies, Wita Stwosza 63, Gdansk (Chemistry Department), seminar room no. F16

**September 30, 2019 at 11:30 a.m. **

**Seminar given by Marc-Olivier Renou**

University of Geneva, Switzerland

Title: **Triangle network nonlocality**

Abstract:

Network nonlocality extends standard Bell nonlocality to networks, where several independent sources are distributed to several parties according to the network structure. Here we focus one the triangle network. The existence of a genuine quantum violation of triangle network

locality was open last years.

• We present the first genuine example of quantum nonlocality without inputs in the triangle scenario, a new form of quantum nonlocality [1].

• We generalize the Finner concentration inequality to quantum resources and Box World [2].

[1] MO. Renou, E. Bäumer, S. Boreiri, N. Brunner, N. Gisin, and S. Beigi, Phys. Rev. Lett., arXiv 1905.04902 (2019)

[2] MO. Renou, Y. Wang, S. Boreiri, S. Beigi, N. Gisin, and Nicolas Brunner, Phys. Rev. Lett. 123, 070403 (2019)

Place: International Centre for Theory of Quantum Technologies, Wita Stwosza 63, Gdansk (Chemistry Department), seminar room no. F16

**5th International Conference for Young Quantum Information Scientists (YQIS)
25-27 September 2019, Sopot, Poland**

The aim of the conference series is to bring together early-stage researchers from a broad range of quantum information sciences. Apart from the oral and poster presentations of the participants and the invited speakers, the conference provides the opportunity for scientific and informal discussions in a relaxed environment.

YQIS organisers are the University of Gdansk and the National Quantum Information Centre (KCIK).

For more information, please visit https://yqis2019.ug.edu.pl/

**September 18, 2019 at 11:30 a.m.**

**Seminar given by Stanisław Szarek**

Case Western Reserve University & Sorbonne University

Title:

**When Alice and Bob met Banach**

Abstract:

As has been known for many decades, there are very close links between various flavors of functional analysis and quantum theory. We will report on one connection that became apparent in the last 10-15 years, namely on the interaction between the so-called Asymptotic Geometric Analysis and Quantum Information Theory. The former area investigates approximate symmetries and quantitative properties of high dimensional objects and includes, in particular, local theory of Banach spaces, convex geometry, and random matrices. The latter area constitutes a theoretical basis for the emerging quantum information technologies and for the quest to build a quantum computer. One of the reasons for this connection is the fact that quantum systems consisting of just several particles naturally lead to models whose dimension is from thousands to billions. We will introduce several invariants used to quantify the size or complexity of high-dimensional objects. We then indicate how these notions can be used to study entanglement and other phenomena that are of interest in quantum theory.

Place: International Centre for Theory of Quantum Technologies, Wita Stwosza 63, Gdansk (Chemistry Department), seminar room no. F16

**September 3, 2019 at 11:30 a.m.**

**Seminar given by Erik Aurell**

KTH-Royal Institute of Technology, Stockholm, Sweden

Title:

**Open quantum systems interacting with harmonic and anharmonic baths**

Abstract:

The Feynman-Vernon approach to open quantum systems is to express the evolution of the reduced density matrix of the system as a double path integral, where one path („forward path”) comes from the unitary U acting from the left, and one path („backward path”) comes from the inverse unitary U^{\dagger} acting from the right. In the open systems context the Feynman-Vernon approach is closely related to the Keldysh theory, where the forward-backward paths correspond to the positive/negative parts of the Keldysh contour.

I will first present an alternative derivation of Feynman-Vernon theory by analyzing the von-Neumann-Liouville equation as a linear evolution law in the space of Hermitian operators. Results on full counting statistics (generating functions of energy changes in one or several baths), that are somewhat complicated to obtain in the path integral language, then emerge in a much simpler way.

I will then look at systems interacting linearly with baths that are not harmonic, but instead characterized by an expansion in cumulants. Every non-zero cumulant of certain environment correlation functions then gives a kernel in a higher-order term in the Feynman-Vernon action, and I will discuss a few of these higher-order terms.

This talks is partly work in progress; results so far are presented in joint paper with Ryoichi Kawai and Ketan Goyal, available as arXiv:1907.02671.

Place: International Centre for Theory of Quantum Technologies, Wita Stwosza 63, Gdansk (Chemistry Department), seminar room no. F16

**August 2, 2019 at 11:30 a.m.**

**Seminar given by Jeongho Bang**

Korea Institute for Advanced Study, South Korea

Title:

**Much easing learning-with-errors (LWE) problem with small-sized quantum samples**

Abstract:

Learning-with-errors (LWE) problem has been a long-standing challenge in computation science and machine learning. In particular, the LWE problem offers many useful primitives in modern post-quantum cryptography, since it is believed as an „intractable” problem even in quantum setting. Meanwhile, very recently, Grilo et al. have proposed an efficient—i.e., exhibiting polynomial sample and running-time complexities—LWE algorithm which utilizes quantum samples and quantum Fourier transform (QFT). Nevertheless, we still have reservations about whether the Grilo et al’s algorithm truly beats the hardness of the LWE problem. The most serious issue is that a large number of data are required to be accessed in superposition during the sampling process. In general, however, such a task costs a lot of computational resources and even may offset the quantum efficiency. To circumvent this, here we propose a super-efficient and near-term implementable LWE algorithm with `small-sized’ quantum samples.

Place: International Centre for Theory of Quantum Technologies, Wita Stwosza 63, Gdansk (Chemistry Department), seminar room no. F16

**August 1, 2019 at 11:30 a.m.**

**Seminar given by Kabgyun Jeong**

Seoul National University, South Korea

Title:

**Quantum channel capacity bounds through QEPI for bosonic Gaussian-noise channels**

Abstract:

In this talk, I briefly review the entropy power inequality (EPI) from classical to quantum cases.

By using the EPI, I will introduce a method to bound quantum channel capacities on bosonc Gaussian channels.

Place: International Centre for Theory of Quantum Technologies, Wita Stwosza 63, Gdansk (Chemistry Department), seminar room no. F16

**July 18, 2019 at 11:30 a.m.**

**Seminar given by Sergii Strelchuk**

University of Cambridge, UK

Title:

**Hybrid quantum-classical computation and Clifford Magic circuits**

Abstract:

Given the difficulty of building and controlling large numbers of qubits, early applications of quantum algorithms are likely to involve both quantum and classical ingredients. One of the most active areas of quantum computing investigates the fundamental limits of computation which could be carried out in these systems by studying the trade-off possibilities between classical and quantum resources. Inspired by a Pauli-based computing model by Bravyi et al. we will introduce a computational model of unitary Clifford circuits with solely magic state inputs (‘Clifford Magic’ circuits) supplemented by classical efficient computation, as well as an extended Gottesman-Knill theorem. I will further discuss the implications of achieving quantum advantage using Clifford Magic circuits and possible extensions to other gate sets. This talk is based on https://arxiv.org/abs/1806.03200.

Place: International Centre for Theory of Quantum Technologies, Wita Stwosza 63, Gdansk (Chemistry Department), seminar room no. F16

**July 11, 2019 at 11:30 a.m.**

**Seminar given by Susane Calegari**

Federal University of Santa Catarina, Brazil

Title:

**Genuine Multipartite Correlations in Dicke Superradiance**

Abstract:

Correlations can describe global properties that are not explained by the sole knowledge of the features of the system parts. In this work, we study genuine multipartite correlations (GMC), correlations that cannot be reduced to lower partitions, in the Dicke model of superradiance. We compute GMC of order k for Dicke states with an arbitrary number of excitations and for the time-dependent superradiant state. The results display nonintuitive behaviours, i.e., there are situations in which genuine correlations between k particles are stronger than between m particles for k>m. Another feature is that the subsystems are more correlated right after the time of maximum emission of radiation. Finally, we use the weaving to classify how multipartite correlations scale by increasing the number of particles in the system and we observe that for larger N the GMC scale faster than the most correlated Dicke state, which may indicate the presence of correlations different from entanglement, such as quantum discord and classical correlations.

Place: International Centre for Theory of Quantum Technologies, Wita Stwosza 63, Gdansk (Chemistry Department), seminar room no. F16

**X Jubilee Symposium KCIK I Symposium ICTQT-KCIK**

QUANTUM RESOURCES AND THEIR APPLICATION

23-25 May 2019, Sopot, Poland

QUANTUM RESOURCES AND THEIR APPLICATION

23-25 May 2019, Sopot, Poland

The Symposium is jointly organized by National Quantum Information Centre (KCIK) and the International Centre for Theory of Quantum Technologies (ICTQT), University of Gdansk. Details are available on the web page: https://symposium-ictqt-kcik-2019-quantum-resources.ug.edu.pl/

Place: Quantum Information Center (KCIK) of the University of Gdansk, Gen. Wł. Andersa 27, 81-824 Sopot, lecture room

**May 7, 2019 at 11 a.m.**

**Seminar given by Sebastian Szybka**

Astronomical Observatory of the Jagiellonian University, Poland

Title:

**Standing gravitational waves in general relativity**

Abstract:

We propose a covariant definition of standing gravitational waves in general relativity.

Place: Quantum Information Center (KCIK) of the University of Gdansk, Gen. Wł. Andersa 27, 81-824 Sopot, lecture room

**April 10, 2019 at 4 p.m.**

**Seminar given by Łukasz Rudnicki**

Max Planck Institute for the Science of Light, Germany

Title:

**Quantum correlations and complementarity of vectorial light fields**

Abstract:

We explore quantum correlations of general vector-light fields in multislit interference, connecting the nth-order field correlations with the reduced n-photon states. The connection is utilized to examine photon wave-particle duality in the double-slit configuration, revealing that there is a hidden information-theoretic contribution that complements the standard inequality associated with such duality by transforming it into strict equality, a triality identity. We also establish a general quantum complementarity relation among the field correlations and the particle correlations which holds for any number of slits, correlation orders, and vector-light states. The framework that we advance hence uncovers fundamental physics about quantum interference.

Place: Faculty of Mathematics, Physics and Informatics UG, seminar room no. 361

**February 26, 2019 at 11:30 a.m.**

**Seminar given by Peter Wittek**

Perimeter Institute for Theoretical Physics, Canada

Title:

**Quantum-Enhanced Machine Learning: A Sanity Check**

Abstract:

Machine learning is one of the fields that could benefit from near-term quantum computers: just the same way massively parallel digital computers enabled deep learning to scale up, quantum processing units (QPUs) are great at doing certain workloads. The problem is that the emergent field of quantum machine learning has been plagued with expectations that are unrealistic on contemporary quantum computers and relevance to the machine learning and AI communities have largely been overlooked. In this talk, we give a survey on what early quantum devices can contribute to machine learning. The primary algorithmic primitives are sampling, optimization, calculating kernel functions, and some variational problems efficiently which map to hybrid classical-quantum protocols. The main application areas in machine learning are probabilistic graphical models, in particular, Boltzmann machines and deep variants thereof, quantum neural networks, and searches over discrete parameter spaces. These models have different strengths than the ones trained on digital computers, hence quantum machine learning plays a complementary role to classical techniques, rather than acting as a replacement. We will also highlight possible pathways forward that would make upcoming quantum architectures more relevant to AI research.

Place: Faculty of Mathematics, Physics and Informatics UG, seminar room no. 361

**February 6, 2019 at 12:15**

**Seminar given by Piotr Biskupski**

IBM Polska Sp. z o.o., Poland

Title:

**The future is quantum – IBM Q experience**

Abstract:

The rate of progress has been remarkable. Only a two years ago, we put the IBM Q experience prototype 5-qubit machine in the cloud, and made it available for the world to use, explore, and learn from. A year later, we added a second device with 50 qubits. Today, more than 100,000 users from more than 2000 universities, 600 high schools, and 400 private institutions have registered for accounts on the IBM Q experience, and collectively run 2 million experiments. The members of the research community have also published more than 170 research papers using our platform as a testbed for ideas. This is only the beginning.

Place: Faculty of Mathematics, Physics and Informatics UG, seminar room no. 361

**December 18, 2018 at 1:00 p.m.**

**Seminar given by Aleksander Kubica**

Perimeter Institute for Theoretical Physics, Canada

Title:

**Cellular-automaton decoders with provable thresholds for topological codes**

Abstract:

I will propose a new cellular automaton, the Sweep Rule, which generalizes Toom’s rule to any locally Euclidean lattice. The Sweep Rule can be used to design a local decoder for the toric code in d≥3 dimensions, the Sweep Decoder, and to rigorously establish a lower bound on its performance. I will present numerical estimates of the Sweep Decoder threshold for the three-dimensional toric code on the cubic and body-centered cubic lattices for phenomenological phase-flip noise. Our results lead to new cellular-automaton decoders with provable error-correction thresholds for other topological quantum codes including the color code. If time permits, I will discuss recent progress in color code decoding in d≥2 dimensions. Based on joint work with J. Preskill, http://arXiv:1809.10145.

Place: Faculty of Mathematics, Physics and Informatics UG, seminar room no. 361

**ICTQT Kick-Off Meeting**

16 November 2018, Gdansk, Poland

16 November 2018, Gdansk, Poland

We invite you cordially to participate in the opening ceremony of the International Centre for Theory of Quantum Technologies (ICTQT), which is a new joint research unit of the University of Gdansk and the Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences.

The first part of this event will be of an official nature and during it will be presented the research program of the Centre and possible directions of cooperation with other scientific institutions. The second part of the event will take a form of a mini scientific symposium, with talks by invited speakers. Programme-ICTQT.

This is an extremely important day for ICTQT, but it is also a natural opportunity for quantum science community in Poland to meet and exchange opinions about possible cooperation within the field.

Place: Faculty of Social Sciences, Jana Bazynskiego 4, Gdansk

**November 14, 2018 at 5.30 p.m.**

**Seminar given by Gerhard Leuchs**

Max Planck Institute for the Science of Light (Erlangen), Germany

Title:

**The quantum vacuum – from an optics point of view**

Place: Quantum Information Center (KCIK) of the University of Gdansk, Gen. Wł. Andersa 27, 81-824 Sopot, lecture room

**November 14, 2018 at 4 p.m.**

**Seminar given by Bob Coecke**

Oxford University, UK

Title:

**Quantum compilation and natural language processing in one picture**

Abstract:

For well over a decade, we developed an entirely pictorial (and of course, formally rigorous) presentation of quantum theory [1], and it was recently shown that graphical reasoning can reproduce all equational reasoning in Hilbert space [2a, 2b].

In practical terms, it is currently for example being used as the core of quantum compilation [3], as it allows for easy translation between different computational models, allows for automation, and has outperformed any other method for circuit reduction.

At present, experiments are also being setup aimed at establishing the age at which children could effectively learn quantum theory in this manner.

Meanwhile, the pictorial language has also been successful in the study of natural language [4] which induces new quantum algorithms [5], and we have started to apply it to model cognition, where we employ GPT-alike models [6].

We present the key ingredients of the pictorial language as well as their interpretation across disciplines, and the applications mentioned above.

References:

[1] BC & A. Kissinger (2017) Picturing Quantum Processes. A first course on quantum theory and diagrammatic reasoning. Cambridge University Press.

[2a] E. Jeandel, S. Perdrix & R. Vilmart (2017) A Complete Axiomatisation of the ZX-Calculus for Clifford+T Quantum Mechanics. arXiv:1705.11151

[2b] K. F. Ng & Q. Wang (2017) A universal completion of the ZX-calculus. arXiv:1706.09877

[3] https://cambridgequantum.com/2017/10/20/collaboration-with-university-of-oxford-computer-science-department/

Place: Quantum Information Center (KCIK) of the University of Gdansk, Gen. Wł. Andersa 27, 81-824 Sopot, lecture room