Department of Mathematics and Computer Science

Speaker: Julio C. Magdalena de la Fuente (Freie Universität Berlin).Abstract: Topological quantum error correction encodes quantum information in the ground space of a topologically ordered lattice system or in the fusion space of topological defects. In this talk I will focus on the former. To use such codes for reliable quantum computation, one must design low-overhead circuits that protect and manipulate the encoded information in a fault-tolerant way.I will start with presenting simple protocols based on two-dimensional topological codes that are composed of 2D local gates. Representing these protocols as tensor networks local in a 3D spacetime lattice leads to a useful viewpoint. We identify a topological QEC circuit with an imaginary-time topological path integral of a topological gauge theory. Within this picture, both physical errors and non-trivial measurement outcomes appear as certain defects in the path integral and their combinatorial structure defines the associated classical decoding problem.I will go through the construction of logically non-trivial fault-tolerant gates using topological boundaries and domain walls between topological phases. In order to perform universal computation a non-Abelian state must be stabilized during the computation. The path-integral perspective allows to calculate the logical action and extract the resulting causality constraints on the classical decoder that is needed to make the protocols resilient to arbitrary errors. It also provides an efficient way to simulate the success of a given decoding strategy using Monte-Carlo sampling based on third-order cohomology invariants of the underlying spacetime complex. I want to introduce the necessary ingredients to construct and analyze such QEC protocols for their performance and argue about their reliable implementation in the presence of errors.

Speaker: Olga Solodovnikova (University of Southern Denmark).Abstract: In this seminar, I will introduce continuous quantum variables [1], which are used to describe systems of oscillators, that is, systems with infinite Hilbert spaces such as photonic systems or the vibrational motion of trapped ions. To build a universal and fault-tolerant quantum computer with a continuous-variable system, it is necessary to encode a qubit in an oscillator, perform gates from the universal gate set, and measure stabilisers to implement error correction.  In the second part of the introductory seminar, I will introduce the measurement-based quantum computing framework for optical systems, in which Gottesman-Kitaev-Preskill (GKP) states are injected into a cluster state, and homodyne/heterodyne detectors are used to i) apply gates via teleportation and ii) measure stabilisers [2]. Lastly, I will discuss the experimental progress on building a measurement-based quantum computer [3], where, in particular, the generation of GKP states [4] is a major bottleneck due to photon loss. [1] Braunstein and van Loock. “Quantum Information with Continuous Variables.” Rev. Mod. Phys. 77, no. 2 (2005).[2] Gottesman, et al. “Encoding a Qubit in an Oscillator.” Physical Review A 64, no. 1 (2001): 012310. [3] Aghaee Rad, H., T. Ainsworth, R. N. Alexander, et al. “Scaling and Networking a Modular Photonic Quantum Computer.” Nature 638, no. 8052 (2025): 912–19. [4] Larsen, M. V., J. E. Bourassa, S. Kocsis, et al. “Integrated Photonic Source of Gottesman–Kitaev–Preskill Qubits.” Nature 642, no. 8068 (2025): 587–91.

Speaker: Olga Solodovnikova (University of Southern Denmark).Abstract: In this research seminar, I will discuss techniques for simulating continuous-variable circuits, which typically fall into two categories: phase-space simulation (Gaussian), and Fock-space simulation. I will present the methodology behind a CV circuit simulation library, which I developed during my PhD, which extends the Gaussian representation to systems that can be written as linear combinations of Gaussians. By approximating Fock states as superpositions of coherent states, any finite-energy CV state can be represented in this formalism. Furthermore, the complexity of this algorithm scales with the stellar rank of the non-Gaussian circuit elements. In the two manuscripts, I showcase the library by simulating and optimising GKP state preparation circuits in the presence of loss. Having said that, the formalism is applicable to any continuous-variable system. [1] Solodovnikova et al. “Fast Simulations of Continuous-Variable Circuits Using the Coherent State Decomposition.” arXiv:2508.06175 [quant-ph][2] Solodovnikova et al. “The Loss Tolerance of Cat Breeding for Fault-Tolerant Grid State Generation.” arXiv:2508.06193 [quant-ph]

Want to know what is going on behind the scenes at IMADA?Come and join us for 2 x 20 min. inspiring talks while you enjoy a free “casual after-work” beer with your fellow student, colleague or teacher.This time Postdoc Serhii Petrovychi (Topic: From Classroom to Living Lab: Rethinking STEM Learning through Sustainability Projects) and Associate Professor Fabian Haiden (Topic: Counting Problems: from Billiards to Quantum States) will each spend 20 minutes each telling you about their current research.

The Cake Club is a new and cozy initiative that meets four times each semester with free coffee, cake, and great company.So whether you study AI, Applied Mathematics, Computer Science, Mathematics, or Mathematics-Economics, you are invited.Remember to bring your fellow students (lecturers are also welcome).The club meetings are held at the IMADA Forskertorv.You can read more in the Facebook group IMADA-students.

Speaker: Ben Brown (IBM).Abstract: In order to scale a quantum computer to solve difficult problems, not only do we need to produce a quantum memory that protect quantum information from noise, but we also need to perform logical operations (logic gates) to manipulate the protected states. Like the memory, these logic gates must also protect their encoded quantum information as gates are performed. A number of the major breakthroughs in the field of error-corrected logic gates have been made through building connections between quantum error-correcting codes and topological phases of matter. Indeed, the surface code is central to this connection, and this model has captured the imagination of the entire error-correction community. In this talk I will explain how error-corrected logic is performed with the surface code by introducing lattice dislocations with behaviour that is analogous to anyonic quasiparticle excitations known as Majorana fermions. I will also explain how we can use transformations between different topological phases of matter via gauging operations to create magic states; an essential component in a logic gate set. I will mention experimental progress towards the realisations of these gates, and I will look ahead to describe how these ideas are being adapted for quantum computing architectures with long-range interactions, that can potentially minimise the high resource cost of building a practical quantum computer.

Poster Session and presentation by Prajakt Pande, Associate Professor, Aarhus University

Speaker: Steffen Schmidt (University of Southern Denmark).Abstract: Symmetry serves as a guiding principle in mathematics and physics. The language of symmetry groups and their actionsorganizes a wide range of phenomena. In this setting, Dirac operators form a natural bridge between quantum mechanics, geometry, and representation theory. In representation theory, Dirac operators provide conceptual and computational tools for addressing basic problems concerning a (semisimple) Lie group: they furnish explicit constructions, give effective criteria for unitarity, contribute to classification results, and relate the topology of locally symmetric spaces to representation-theoretic data. A foundational instance is Parthasarathy's use of a representation-theoretic Dirac operator in the study of discrete series representations. Interest in this circle of ideas intensified in the late 1990s, following Kostant's introduction of the cubic Dirac operator and the subsequent development of \emph{Dirac cohomology}, including Huang–Pandžić’s proofof Vogan's conjecture. In this talk, I present a modern construction of (algebraic) Dirac operators and discuss applications of Dirac operators and Dirac cohomology to representations of Lie superalgebras, including localization principles, relations with Duflo–Serganova cohomology, and character formulas.

The Cake Club is a new and cozy initiative that meets four times each semester with free coffee, cake, and great company.So if you study Data Science, you are invited.Remember to bring your fellow students (lecturers are also welcome).The club meetings are held at the IMADA Forskertorv.You can read more in the Facebook group IMADA-students.

Abdullah Akgül defends her PhD thesis at a public lecture: “Probabilistic Reinforcement Learning for Sample-Efficient Control”.The chairman of the assessment committee, Professor Arthur Zimek, will act as chairman at the defence.The PhD defence takes place in U181 (Ø22-601b-2).All are welcome.

Speaker: Thomas Klein Kvorning (​KTH Royal Institute of Technology). Abstract: Simulating quantum many-body systems is fundamentally challenging because quantum states encode correlations that cannot be decomposed into local parts, leading to an exponential growth of required resources with system size. Yet physical observables are typically local: they are fully determined by density matrices of small subsystems. This raises a central question: can local density matrices be time-evolved without explicitly tracking long-range correlations? In this talk, I address this question using the framework of the information lattice, a scale-resolved decomposition of the information content of a quantum state. This construction provides a precise notion of where information resides in a quantum system, both in space and across length scales, and thereby offers a diagnostic of how correlations build up dynamically. I will show how this perspective reveals regimes in which local degrees of freedom are exactly decoupled from long-range entanglement, as well as how it can guide the development of approximate numerical methods for ab initio simulation of condensed matter systems.

How are SDU students using AI chatbots as personalized learning tools — and how can science teachers guide students towards fruitful and academically appropriate uses?

This year's theme: FROM COGNITION TO CAPACITY Foundations of Empowering KnowledgeThe conference focuses on how empowerment arises through knowledge, and how it is strengthened and supported through interdisciplinary and cross-sectoral collaboration.

This year's theme: FROM COGNITION TO CAPACITY Foundations of Empowering KnowledgeThe conference focuses on how empowerment arises through knowledge, and how it is strengthened and supported through interdisciplinary and cross-sectoral collaboration.

Adelina conducted a teaching experiment using figure construction to make student reasoning explicit and support integrative understanding of metabolic pathways.

SDU and NAFA invite you to a webinar where PhD Sizwe Nxasana presents his research on how to support teachers in unlearning old habits and adopting new, more student-centered teaching methods – and on identifying which forms of professional development actually work to make this happen. This presentation offers a unique insight into how project-based learning (PBL) is being adopted and developed in a South African context.At NiSE webinars, Danish science education researchers meet to further develop the science education knowledge ecology.It is about ensuring that everyone both receives knowledge and contributes knowledge and experiences within the pedagogical and scientific work of science education.The NiSE webinars are organized by the STEM Education Research Center – FNUG and the Center of Excellence in Science Education/Naturfagsakademiet (CESE/NAFA). NiSE is the name of the network: Network in STEM Education.This webinar is the second in a series of three during the autumn semester of 2025.Everyone is welcome.

We end the academic year at IMADA with strawberry cake, wine, water, beer, snacks and lots of summer mood 😃!All IMADA students and all staff are invited.No registration needed – just turn up!

CSC2026 is a student-organised symposium that explores the exciting and promising field of computational systems chemistry and cheminformatics - and their applications in research areas such as chemical reaction networks, metabolic pathways, generative models, and analytical chemistry.This free-to-register two day symposium is open to young researchers, ranging from Masters to post-docs, and even industry R&D specialists in the field of computational chemistry wishing to showcase, share, and discuss their work with like-minded researchers in the field. The deadline for registration is: May 15th, 2026Please note: attendees will need to pay for accommodation (if they require it) at a rate of 550 DKK per night - hotel rooms are organised by the team for you!