Speaker: N. Asger Mortensen POLIMA – Center for Polariton-driven Light-Matter Interactions Danish Institute for Advanced Study University of Southern Denmark Abstract:Polaritons are hybrid particles – quasiparticles – that result from the strong interaction between light (photons) and matter (such as electrons, excitons or phonons). These quasiparticles exhibit mixed characteristics, combining features of both photons and elementary particles like electrons. Colloquially, they constitute half-light-half-matter excitations. The interaction between light and matter in polaritons leads to unique physical properties and behaviors that are now also being explored in sheets of atomically thin two-dimensional materials and in artificial nanostructures. The electrodynamics of matter and optical phenomena are commonly explored within the framework of classical electrodynamics and semiclassical models for the interactions of light with matter. Materials are commonly assumed homogenous, and light-matter interactions are treated in an intuitive local manner. The plasmonic response of metal nanostructures is one such example, where the understanding of mesoscopic electrodynamics at metal surfaces is, however, becoming increasingly important for both fundamental developments in quantum plasmonics and potential applications in emerging light-based quantum technologies. The seminar will discuss recent examples of quantum nonlocal effects that emerge in surface-polaritonic systems, including metal surfaces, 2D materials, and combinations thereof. Biography: Mortensen is a full professor in the Center for Polariton-driven Light-Matter Interactions (POLIMA) and a Chair of Physics in the Danish Institute for Advanced Study, both at the University of Southern Denmark. Previously, he held a full professorship (faculty since 2004) at the Technical University of Denmark (DTU). In addition to his MSc (1998) and PhD (2001) degrees from DTU, he holds higher doctoral degrees from University of Copenhagen (Dr. Scient., 2021) and DTU (Dr. Tech., 2006). He is a fellow of APS, OSA, SPIE, IOP, and European Academy of Sciences. Currently, he serves the AAAS as an associate editor for Science Advances.

Speaker: Qianyu Hao (University of Geneva) Abstract:Conformal blocks are essential objects to study in the 2d CFTs. They depend on the data of a vertex algebra $\CV$, a punctured Riemann surface $C$, and possible decorations inserted at the punctures. The Virasoro conformal blocks are very interesting since they have many connections to other areas of math and physics. I will describe a new way to construct Virasoro conformal blocks at $c=1$. This is closely related to the idea of nonabelianization in the study of $SL(N,\mathbb{C})$ connections by using $GL(1,\mathbb{C})$ connection in the work of Gaiotto-Moore-Neitzke and Hollands-Neitzke. I will talk about our work on relating the $c=1$ Virasoro conformal blocks on $C$ to the "abelian" Heisenberg conformal blocks on a branched double cover of $C$. The main new idea in our work is the use of the spectral network on the surface $C$. The nonabelianization construction enables us to study the harder to get Virasoro conformal blocks using the simpler abelian objects. This is joint work in progress with Andrew Neitzke.

The seminar is cancelled.Speaker: Astrid Eichhorn Department of Physics, Chemistry and Pharmacy University of Southern Denmark Abstract:I will present a tentative answer to this question, consisting in a theory of quantum spacetime and matter, to which I will give a pedagogical introduction. I will argue that the main challenge for such a theory is the question of how to probe it experimentally, given that we expect its effects to manifest at tiny distances below the Planck length of 10^-35 m. I will challenge this expectation and show that not all effects are untestably small. Concretely, I will show how consequences of the microscopic physics leave their imprints on macroscopic scales in particle physics and black holes.Location: D-IAS Aud. (V24-501a-0), Danish Institute for Advanced Study - DIAS. The event is open to all.

DIAS lecture by Professor Francesco Sannino, DIAS Chair of Physics, Head of the Quantum Field Theory Center, Founder of the Centre for Cosmology and Particle Physics Phenomenology (CP³-Origins) at SDU. The lecture takes place in the DIAS Auditorium and is open to all.Abstract We live in an era marked by the LIGO Laboratory discovery of gravitational waves, emitted when two black holes coalesce, and the Event Horizon Telescope imaging of black holes. While these amazing discoveries crystallise Einstein’s theory of general relativity they also beg for a fresh look at the problem of unifying gravity and quantum field theory. These two theories constitute our current understanding of Nature but are notoriously at odds with each other. I will first review basic facts about black holes and then argue in favour of a recent approach that aims at shortcutting the problem of the absence of a theory of quantum gravity. This will be achieved by introducing a quantum gravity model independent approach focussed on effective metric descriptions of quantum black holes. We believe that our findings will herald novel ways to explore quantum corrections to black hole dynamics with impact for our understanding of the fabric of space time.About Francesco SanninoFrancesco Sannino is the Head of the Quantum Field Theory Center, the Founder of the Centre for Cosmology and Particle Physics Phenomenology (CP³-Origins) at SDU. He is also one of the Founders of the Danish IAS and Professor of Theoretical Physics at the Federico II University in Italy.Professor Francesco Sannino is widely recognized for having pioneered the analytical and numerical investigations of the conformal structure of gauge theories of fundamental interactions, for the construction of minimal composite extensions of the standard model, and for the recent discovery of four-dimensional asymptotically safe theories.Recently he has also applied and developed mathematical tools stemming from theoretical physics to describe the evolution of infectious diseases at human and viral level.His work crosses several realms of particle physics and cosmology from bright and dark extensions of the standard model and inflationary cosmology to the mathematical underpinning of theories of fundamental interactions.

Danish Quantum Community invites to participate in our annual Scientific Quantum Conference 2024 This year’s conference is hosted by Centre for Quantum Mathematics (QM) with support from the Novo Nordisk Foundation. Join us for a two-day deep dive into the Danish quantum research community - across universities and across disciplines. About the event:The conference will present recent results from Danish quantum research with a special focus on younger researchers at Danish universities. Serving as a meeting point for the research community, the conference aims to strengthen the Danish quantum ecosystem and promote industry-academia collaborations.Across two days, the conference will provide a deep dive into four key research tracks: quantum hardware, quantum software/algorithms, components for quantum systems, and early quantum applications in chemistry and finance.Participation is free of charges, but requires registration.

Speaker: Ying-Hsuan Lin (Harvard University) Abstract:We numerically studied an anyon chain based on the Haagerup fusion category, and found evidence that it leads in the long-distance limit to a conformal field theory (CFT) whose central charge is ~2. Our findings were in agreement with concurrent research by Vanhove et al., who explored a closely related statistical lattice model. Subsequent analyses of the operator product expansion by Liu, Zou, Ryu, however, revealed a deeper complexity than our data had initially suggested. In this talk, I will discuss these developments and contextualize them within the broader program of classifying CFTs.

Speaker: Erik Donovan Hedegård Department of Physics, Chemistry and Pharmacy University of Southern Denmark Abstract:Transition metals in biological systems pose a formidable challenge in modern quantum chemistry. Unfortunately, these metals are close to everywhere in biological systems. For instance, about one-third of all enzymes contain a transition metal. The main issues when dealing with transition metals are (i) the metal typically demands so-called complete active space (CAS) methods with billions of electron configurations included. This quickly becomes computationally costly. (ii) Relativistic effects can be sizable. Addressing these effects also becomes computationally demanding. (iii) The relevant chemistry usually occurs in a surrounding solvent or within a protein environment that also needs to be taken into account, both in terms of the nuclear dynamics as well as the electronic interactions between the metal and the environment.In this talk, we demonstrate how challenges (i)–(iii) can be tackled efficiently and accurately. We discuss how this allows us to understand a part of the global carbon cycle, enzymes that can boost the production of biofuel, and new drugs against cancer.Location: D-IAS Aud. (V24-501a-0), Danish Institute for Advanced Study - DIAS. The event is open to all.

Speaker: Manuel Meyer Department of Physics, Chemistry and PharmacyUniversity of Southern Denmark Abstract:The nature of dark matter continues to elude us, even after almost one century after first evidence for this non-luminous substance appeared. A leading hypothesis is that dark matter, which makes up more than 80% of all matter in the universe, consists of yet undiscovered fundamental particles. Such dark matter particles might interact feebly with known particles of the Standard Model, making them potentially detectable in the laboratory. The predicted low interaction rates require extremely sensitive detectors and ultra-low background levels. In this talk, I will discuss our recent progress in characterizing and improving the performance of transition edge sensors (TESs). Such TESs are planned to be used in the Any Light Particle (ALPS) II experiment, which searches for axions and axion-like particles. I will also review how we can use our TES to search for weakly interacting massive particles. With our ongoing research, we hope to achieve a new record for background suppression employing both optical filtering inside a cryostat as well as machine learning techniques while maintaining a quantum efficiency close to unity. Location: D-IAS Aud. (V24-501a-0), Danish Institute for Advanced Study - DIAS. The event is open to all.

Speaker: Sergey I. Bozhevolnyi Center for Nano Optics University of Southern Denmark Abstract:Manipulation of single-photon emission from quantum emitters (QEs) has attracted a considerable attention in recent years due to its importance for quantum information technologies in quantum communication, computation, sensing and metrology. Here, recent progress in on-chip manipulation of the polarization, directionality and phase distribution in single-photon emission by making use of planar holographic QE-coupled metasurfaces is presented and discussed. The underlying idea is related to the concept of meta-atom, in which a QE is efficiently and non-radiatively coupled to surface modes, such as surface plasmon polaritons (SPPs), that are subsequently outcoupled into free propagating waves. An innovative metasurface design approach, vectorial scattering (computer-generated) holography, is introduced for the purpose of designing hybrid SPP-QE coupled metasurfaces suitable for generation of well-collimated beams of single photons with desirable polarization characteristics propagating along given directions. Latest results include its extension for realizing single-photon sources with radiation channels that exhibit diverse (including vectorial with spin and orbital angular momenta) wavefronts and polarization characteristics, opening thereby a way to generating quantum structured light in high dimensions.Location: D-IAS Aud. (V24-501a-0), Danish Institute for Advanced Study - DIAS. The event is open to all.