Highlights of Max Planck Institute for the Physics of Complex Systems https://www.pks.mpg.de/ here are the highlights of Max Planck Institute for the Physics of Complex Systems en_GB Max Planck Institute for the Physics of Complex Systems Wed, 29 Nov 2023 19:57:18 +0100 Wed, 29 Nov 2023 19:57:18 +0100 TYPO3 EXT:news news-764 Fri, 17 Nov 2023 22:00:00 +0100 Using quantum computers to test Jarzynski’s equality for many interacting particles https://doi.org/10.1103/PhysRevX.13.041023 Statistical mechanics is a branch of physics that uses statistical and probabilistic methods to understand the behaviour of large numbers of microscopic particles, such as atoms and molecules, in a system. Instead of focusing on the individual motion of each particle, statistical mechanics analyses the collective properties of the system. It provides a bridge between the microscopic world of particles and the macroscopic world that we can observe, explaining phenomena like the behaviour of liquids and gases, phase transitions, and the thermodynamic properties of materials. Through the statistical distribution of particle properties, such as energy and velocity, statistical mechanics helps us make predictions about how physical systems behave on a larger scale, contributing to our understanding of fundamental principles in physics and chemistry. One of the most remarkable relations in statistical mechanics is Jarzynski's equality, connecting the irreversible work performed in an arbitrary thermodynamic process with the energy and entropy of the system in thermodynamic equilibrium. Because the system is free to leave the equilibrium state during its evolution, Jarzynski’s equality is a prime example of how equilibrium physics can constrain the outcome of nonequilibrium processes. Remarkably, the familiar Second Law of Thermodynamics – a fundamental principle of physics – follows directly from Jarzynski’s equality. The Second Law is a statement about the average properties of particles in a system undergoing a thermodynamic process, and postulates that heat always flows spontaneously from hotter to colder regions of the system. Intriguingly, Jarzynski’s equality shows that this fundamental law of Thermodynamics can be “violated” in individual realizations of a process (but never on average!). Despite its fundamental importance, experimental tests of Jarzynski’s equality for classical and quantum systems are extremely challenging, since they require complete control in manipulating and measuring the system. Even more so, a test for many quantum interacting particles was until recently completely missing. In a new joint study, an international team from the Max Planck Institute for the Physics of Complex Systems, the University of California at Berkeley, the Lawrence Berkeley National Laboratory, the German Cluster of Excellence ML4Q and the Universities of Cologne, Bonn, and Sofia identified quantum computers as a natural platform to test the validity of Jarzynski’s equality for many interacting quantum particles. (A quantum computer is a computing device that uses the principles of Quantum Mechanics to perform certain types of calculations at speeds and efficiency levels that are unattainable by classical computers. Quantum computers use quantum bits, or qubits, as the basic unit of information. Hence, any quantum computer is, at its core, a system of interacting quantum particles.) The researchers used the quantum bits of the quantum processor to simulate the behaviour of many quantum particles undergoing nonequilibrium processes, as is desired for an experimental verification of Jarzynski’s equality. They tested this fundamental principle of nature on multiple devices and using different quantum computing platforms. To their surprise, they found that the agreement between theory and quantum simulation was more accurate than originally expected due to the presence of computational errors, which are omnipresent in current quantum computers. The results demonstrate a direct link between certain types of errors that can occur in quantum computations and violations of Jarzynski’s equality, revealing a fascinating connection between quantum computing technology and this fundamental principle of physics. Dominik Hahn, Maxime Dupont, Markus Schmitt, David J. Luitz, and Marin Bukov, Physical Review X 13, 041023 (2023) Publication Highlights news-763 Fri, 10 Nov 2023 22:00:00 +0100 Investigating the impact of a defect basepair on DNA melting https://pubs.aip.org/aip/jcp/article/159/14/145102/2916016/Equilibrium-melting-probabilities-of-a-DNA As temperature is increased, the two strands of DNA separate. This DNA melting is described by a powerful model of statistical physics, the Poland–Scheraga model. It is exactly solvable for homogeneous DNA (with only one type of basepairs), and predicts a first-order phase transition. Arthur Genthon of the Max Planck Institute for the Physics of Complex Systems, Albertas Dvirnas and Tobias Ambjörnsson (Lund University, Sweden) have now derived an exact equilibrium solution of an extended Poland–Scheraga model that describes DNA with a defect site that could, for instance, result from DNA basepair mismatching, cross-linking, or the chemical modifications from attaching fluorescent labels, such as fluorescent-quencher pairs, to DNA. This defect was characterized by a change in the Watson–Crick basepair energy of the defect basepair, and in the associated two stacking (nearest-neighbour) energies for the defect compared to the remaining parts of the DNA. The exact solution yields the probability that the defect basepair and its neighbors are separated at different temperatures. In particular, the authors investigated the impact of the defect on the phase transition, and the number of base pairs away from the defect at which its impact is felt. This work has implications for studies in which fluorophore-quencher pairs are used to analyse single-basepair fluctuations of designed DNA molecules. Arthur Genthon, Albertas Dvirnas, and Tobias Ambjörnsson, J, Chem. Phys. 159, 145102 (2023) Publication Highlights news-761 Sun, 29 Oct 2023 22:00:00 +0100 A Quantum Root of Time for Interacting Systems https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.131.140202 In 1983, the two physicists Page and Wootters postulated a timeless entangled quantum state of the universe in which time emerges for a subsystem in relation to the rest of the universe. This radical perspective of one quantum system serving as the other’s temporal reference resembles our traditional use of celestial bodies’ relative motion to track time. However, a vital piece has been missing: the inevitable interaction of physical systems. Forty years later, Sebastian Gemsheim and Jan M. Rost from the Max Planck Institute for the Physics of Complex Systems have finally shown how a static global state, a solution of the time-independent Schrödinger equation, gives rise to the time-dependent Schrödinger equation for the state of the subsystem once it is separated from its environment to which it retains arbitrary static couplings. Exposing a twofold role, the environment additionally provides a time-dependent effective potential governing the system dynamics, which is intricately encoded in the entanglement of the global state. Since no approximation is required, intriguing applications beyond the question of time are within reach for heavily entangled quantum systems, which are elusive but relevant for processing quantum information. Sebastian Gemsheim and Jan M. Rost, Phys. Rev. Lett. 131, 140202 (2023) Publication Highlights news-755 Thu, 19 Oct 2023 10:00:00 +0200 New Max Planck Fellow group established at the institute https://www.pks.mpg.de/research/divisions-and-groups The Max Planck Fellows Programme promotes cooperation between universities and Max Planck institutes and enables a university professor to install a research group at an MPI. We are glad to announce that Prof. Jan Budich from TU Dresden has started a new Max Planck Fellow group "Dissipative Quantum Matter" at MPI-PKS. The research group will explore quantum many-body systems in which dissipation plays a crucial role, for example inducing novel phases of topological matter or enabling the controlled preparation of complex quantum states in the context of quantum simulators. Regarding physical platforms, the spectrum of interest ranges from quantum condensed matter to atomic and quantum-optical many-body systems. Welcome at the institute, Jan! Institute's News news-754 Wed, 18 Oct 2023 22:00:00 +0200 Unraveling the mysteries of glassy liquids https://journals.aps.org/prx/abstract/10.1103/PhysRevX.13.031034 When a liquid is cooled to form a glass, its dynamic slows down significantly, resulting in its unique properties. This process, known as “glass transition”, has puzzled scientists for decades. One of its intriguing aspects is the emergence of “dynamical heterogeneities”, when the dynamics become increasingly correlated and intermittent as the liquid cools down and approaches the glass transition temperature. In a new collaborative study, Ali Tahaei and Marko Popovic from the Max Planck Institute for the Physics of Complex Systems, with colleagues from EPFL Lausanne, ENS Paris, and Université Grenoble Alpes, propose a new theoretical framework to explain the origin of the dynamical heterogeneities in glass-forming liquids. Based on the premise that relaxation in these materials occurs occurs through local rearrangements of particles that interact via elastic interactions, the researchers formulated a scaling theory that predicts a growing length-scale of dynamical heterogeneties upon decreasing temperature. The proposed mechanism is an example of extremal dynamics that leads to self-organised critical behavior. The proposed scaling theory also accounts for the Stokes-Einstein breakdown, which is a phenomenon observed in glass-forming liquids in which the viscosity becomes uncoupled from the diffusion coefficient. To validate their theoretical predictions, the researchers conducted extensive numerical simulations that confirmed the predictions of the scaling theory. Ali Tahaei, Giulio Biroli, Misaki Ozawa, Marko Popovic, and Matthieu Wyart, Phys. Rev. X 13, 031034 (2023). Publication Highlights news-753 Mon, 16 Oct 2023 12:05:00 +0200 Marin Bukov receives John Atanasoff Award https://m.president.bg/en/cat37/5/About-award-John-Atanasov.html The John Atanasoff Award, named after the creator of the first electronic computer - the famous scholar of Bulgarian descent, John Atanasoff, was first awarded in 2003 in support of the personal achievements of young Bulgarian researchers working in the fields of informatics and information technology. Marin Bukov, group leader at MPI-PKS, is among this year's awardees ”for his outstanding contributions to the field of artificial intelligence applied to quantum technologies, and for his role in the development of efficient innovative research and education tools used worldwide”. Congratulations, Marin!  

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Awards and Honors
news-751 Fri, 06 Oct 2023 10:04:00 +0200 Call for Distinguished PKS Postdoctoral Fellowship 2024 open! https://www.pks.mpg.de/fileadmin/user_upload/MPIPKS/Contact/Work_with_us/PKS_Fellow24.pdf Application deadline: 10 November 2023. Distinguished PKS postdoctoral fellows appear personally along with the departments and groups on the main research page of the institute and are expected to have at least one year of postdoctoral experience at an institution other than the one at which their PhD was awarded. Applications for this fellowship directly after completion of the PhD might be considered in exceptional cases. Please click on the link- button to see the full advertisement!  

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Institute's News
news-748 Tue, 12 Sep 2023 22:00:00 +0200 Cell Lineage Statistics with Incomplete Population Trees https://journals.aps.org/prxlife/abstract/10.1103/PRXLife.1.013014 Cell lineage statistics is a powerful tool for inferring cellular parameters, such as division rate, death rate, fitness landscape and selection. Yet, in practice such an analysis suffers from a basic problem: how should we treat incomplete lineages that do not survive until the end of the experiment? Examples of such lineages are found in experiments in which cells can die (antibiotic experiments, ...) and in experiments in which cells are diluted to maintain the population constant (microchannels, cytometers, ...). Arthur Genthon of the Max Planck Institute for the Physics of Complex Systems, Takashi Nozoe (U. Tokyo, Japan), Luca Peliti (Santa Marinella Research Institute, Italy), and David Lacoste (Gulliver, Paris) have now developed a model-independent theoretical framework to address this issue. They show how to quantify fitness landscape, survivor bias, and selection for arbitrary cell traits from cell lineage statistics in the presence of death, and they test this method using an experimental data set in which a cell population is exposed to a drug that kills a large fraction of the population. This analysis reveals that failing to properly account for dead lineages can lead to misleading fitness estimations. For simple trait dynamics, they prove and illustrate numerically that the fitness landscape and the survivor bias can in addition be used for the nonparametric estimation of the division and death rates, using only lineage histories. Their framework provides universal bounds on the population growth rate, and a fluctuation-response relation that quantifies the change in population growth rate due to the variability in death rate. Further, in the context of cell size control, they obtain generalizations of Powell's relation that link the distributions of generation times with the population growth rate, and they show that the survivor bias can sometimes conceal the adder property, namely the constant increment of volume between birth and division. Arthur Genthon, Takashi Nozoe, Luca Peliti, and David Lacoste, PRX Life 1, 013014 (2023) Publication Highlights news-747 Tue, 05 Sep 2023 14:05:00 +0200 Two ERC Starting Grants awarded to group leaders at MPI-PKS https://erc.europa.eu/news-events/news/erc-2023-starting-grants-results The European Research Council (ERC) has announced early-career top researchers across Europe who will receive a starting grant. The prestigious grants enable the best young researchers in Europe to build their own teams and to conduct pioneering research across all disciplines. This year, two of these grants were awarded to research group leaders at the MPI-PKS: Marin Bukov for his proposal "Nonequilibrium Many Body Control of Quantum Simulators" and Ricard Alert for his proposal "The Spectrum of Fluctuations in Living Matter". Congratulations!!  

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Awards and Honors
news-746 Wed, 23 Aug 2023 22:00:00 +0200 Anderson localization of a Rydberg electron https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.5.033032 The hydrogen atom is one of the few exactly solvable quantum systems. Its well-known properties are shared by highly excited Rydberg atoms, albeit to such an exaggerated degree that their behavior is often wholly unexpected. Scientists at the Max Planck Institute for the Physics of Complex Systems have now investigated a Rydberg atom perturbed by ground state atoms, exploiting hydrogen's infinite spectrum and high degeneracy to show that the Rydberg electron localizes in the same fashion as electrons in a disordered solid. This unexpected manifestation of Anderson localization is enabled by the existence of a well-defined thermodynamic limit of the single Rydberg electron as its principle quantum number and the number of ground state atoms increase in tandem. Myriad localization regimes can be realized as a function of the geometry of the system. Matthew T. Eiles, Alexander Eisfeld, and Jan M. Rost, Phys. Rev. Research 5, 033032 (2023) Publication Highlights news-745 Thu, 10 Aug 2023 11:04:00 +0200 ELBE Postdoctoral Fellowships call is open! https://www.csbdresden.de/join-us/as-a-postdoc/ Application deadline: 25 September 2023. The ELBE postdoctoral fellows program addresses independent researchers on the postdoctoral level, who come with their own research proposal and freely choose which groups to affiliate with. The program provides an ideal springboard to an independent research career in systems biology, theoretical biophysics, computational biology, mathematics in the life sciences, computer science and machine learning with application to biological systems, and related areas. Please click on the link- button for more info and application instructions!  

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Institute's News
news-744 Wed, 26 Jul 2023 22:00:00 +0200 An artificial intelligence agent manipulates many interacting quantum bits of information https://doi.org/10.1038/s42256-023-00687-5 In recent years, quantum technologies have experienced significant growth, offering immense potential in various areas. Quantum computers are expected to revolutionise optimisation and search algorithms; quantum simulators help explore new quantum phases of matter; quantum sensors can achieve unparalleled precision in measurements, and quantum cryptography provides robust security for communication protocols. The advantage of these new technologies over their classical counterparts lies in quantum correlations (called by physicists quantum entanglement), and realises phenomena beyond the scope of classical physics. However, the successful implementation of most quantum technologies relies heavily on the ability to manipulate the underlying quantum systems. This task is already challenging in classical dynamics, but quantum physics adds an extra layer of complexity. The issue arises from the difficulty in simulating quantum systems with many interacting qubits, as the memory requirements exceed the capabilities of even the best classical supercomputers.Physicists refer to this challenge as the "curse of dimensionality", rendering it infeasible to simulate the behavior of large quantum many-body systems using classical computers and devising optimal control strategies for them. Addressing this problem, Friederike Metz (OIST and EPFL) and Marin Bukov (Max Planck Institute for the Physics of Complex Systems and Sofia University) introduced a new approach: they applied deep reinforcement learning (RL), a subfield of machine learning, to design an artificial intelligent agent capable of controlling quantum many-body systems effectively. To overcome the curse of dimensionality, they employed tensor networks–mathematical structures that allow for an approximate representation of large quantum states on classical computers. Leveraging tensor networks, Metz and Bukov developed a novel deep learning architecture that empowers RL agents to process and interpret quantum many-body states seamlessly. The trained RL agent demonstrated remarkable performance in preparing ordered ground states in the quantum Ising chain, a fundamental model for studying quantum magnetism. This new framework surpassed the limitations of standard neural-network-only architectures, enabling the control of significantly larger systems while retaining the benefits of deep learning algorithms, such as generalizability and trainable robustness to noise. Notably, the RL agent exhibited the ability to find universal controls in few-qubit systems, learn to steer previously unseen many-qubit states optimally, and adapt control protocols in real-time when faced with stochastic perturbations in quantum dynamics. Additionally, the authors propose a way to map their RL framework to a hybrid quantum-classical algorithm that can be executed on noisy intermediate-scale quantum devices. This research has profound implications, paving the way for applying deep RL to efficiently control large quantum systems–a crucial requirement for advancing modern quantum technologies. With these techniques, researchers expect to explore novel quantum phases, design complex molecules, achieve unprecedented measurement precision, and build secure networks using quantum communication, among other groundbreaking applications. An earlier version of this text was improved using ChatGPT. The image accompanying the text was created with the assistance of DALL·E 2 using the prompt "A robot manipulating atoms in a quantum computer, Surrealism". Friederike Metz and Marin Bukov, Nat. Mach. Intell. 5, 780 (2023) Publication Highlights news-743 Tue, 18 Jul 2023 22:00:00 +0200 Understanding 3D Active Fluids Through Mathematical Supercomputing https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.5.L022061 Active matter physics is a cornerstone theory to understand biological phenomena across multiple scales, ranging from cellular movement to tissue morphogenesis and the flocking behavior of animals. One such fascinating class of active matter are active fluids. These are densely packed, soft substances whose component parts can flow independently and operate by dissipating energy at the microscopic scale to perform directed motion. Although this offers a general framework that can be applied to practically all of biology, active fluids are incredibly challenging to understand in three dimensions due to increased mathematical and computational complexity. Given the technical obstacles and a lack of the necessary supercomputing scientific software for 3D investigations, only two-dimensional models of active fluids were investigated in the previous decade. In a current study, Frank Jülicher, director at the Max Planck Institute of the Complex Systems, investigates, together with the research group of Ivo Sbalzarini, TU Dresden Professor in the Center for Systems Biology Dresden (CSBD), Research Group Leader at the Max Planck Institute of Molecular Cell Biology and Genetics (MPI-CBG), and Dean of the Faculty of Computer Science at the TU Dresden, how an active fluid behaves in a three-dimensional environment. Recent experiments that directly correspond to the three-dimensional world we live in, have observed that microtubules and kinesin motor protein mixtures can flow on their own in different directions, but a comprehensive theoretical model explaining these observations and how to control them was missing. Abhinav Singh, the first author of the study, explains: “Our most important discovery is that boundary conditions, which are frequently overlooked in ideal physical models, are crucial in the formation of instabilities in active matter. In simple terms, this means that the active material can latch onto and interact with the boundary or surface it is against, and then move in two ways: in the direction of alignment (in-plane) or perpendicular to the alignment of polymers (out-of-plane). Whether it is pulled or pushed by its internal motors, and the way molecules orient at the edges, dictate the movement. Interestingly, we discovered a unique 3D 'rippling' or 'wrinkling' effect that corresponds directly to the observed puzzling behavior of microtubules when they are under a stretching force created by motors called kinesins. These results were confirmed through rigorous mathematical analysis and unprecedented supercomputing codes of novel numerical techniques, marking a significant leap in our understanding of active biological processes.” “These findings expand our understanding of the behavior of active matter and move us one step closer to unraveling the beautiful complexity of morphogenesis,” concludes Ivo Sbalzarini, who supervised the study. “Our findings and software contributions in OpenFPM will be instrumental for physicists, biologists, and materials scientists who are looking into the behavior of active fluids made up of living materials. This new understanding can enhance the manipulation and control of active fluids, paving the way for a range of applications, from microfluidic devices to drug delivery systems and novel material designs. However, further research is necessary to validate our findings in various real-world scenarios.” (Highlight text by Katrin Boes, MPI-CBG) Abhinav Singh, Quentin Vagne, Frank Jülicher, and Ivo F. Sbalzarini, Phys. Rev. Research 5, L022061 (2023) Publication Highlights news-742 Wed, 12 Jul 2023 11:49:00 +0200 "Physik-Preis Dresden 2023" awarded to Professor Jörg Schmalian On July 11, 2023, Prof. Jörg Schmalian from the Karlsruhe Institute of Technology received the "Physik-Preis Dresden 2023" (Dresden Physics Prize), jointly awarded by the TU Dresden and the Max Planck Institute for the Physics of Complex Systems (MPI-PKS). The "Physik-Preis Dresden" has been established, with a generous donation by Prof. Peter Fulde, to promote cooperation between the Max Planck Institute for the Physics of Complex Systems and the Faculty of Physics of TU Dresden. It is geared towards outstanding researchers whose research is of particular interest to scientists in Dresden. This year's recipient, Prof. Jörg Schmalian, fits this condition perfectly. Jörg Schmalian studied physics in Leipzig and Merseburg and graduated from the Technische Hochschule Merseburg in 1990. The German reunification made it possible for him to obtain a doctorate in physics in 1993 from Freie Universität Berlin under the supervision of Karl Bennemann. He stayed at FU Berlin as a postdoc before joining the group of David Pines at the University of Illinois at Urbana-Champaign in 1997. In 1999, Jörg Schmalian moved back to Europe and became a fellow of St. Catherine's College at the University of Oxford. In the same year, he accepted an offer for a tenure-track faculty position at Iowa State University, in connection with a researcher position at Ames National Lab. Jörg Schmalian quickly moved up through the ranks to become full professor in 2007. In 2011, he moved to the Karlsruhe Institute of Technology as a professor. Currently, he is the Dean of the Faculty of Physics of KIT. Jörg Schmalian has been a visiting professor at Royal Holloway University, University of Paris Diderot, and Stanford University. He has received multiple honors, among them a fellowship of the American Physical Society and the 2022 John Bardeen Prize for Theory of Superconductivity. Jörg Schmalian is an internationally highly visible theoretical physicist with a broad range of interests. He has published over 200 research papers with over 10.000 citations. Jörg Schmalian started to work on strongly correlated electrons and superconductivity during his doctoral studies, at that time with a focus on cuprate high-temperature superconductors. He later made significant contributions to superconductivity and other ordering phenomena in iron-based and organic compounds as well as more generally on the physics of coupled order parameters. It is characteristic for Jörg Schmalian's work that he has both established conceptual foundations and modeled and predicted specific phenomena, working close to experiments. Jörg Schmalian's papers on spin-fluctuation-mediated superconductivity and on nematic order have become standard references in these fields. Moreover, Jörg Schmalian's works on quantum criticality and transport in graphene have strongly advanced the hydrodynamics of electron liquids. They were essential for identifying graphene as a readily available system in which many aspects of hydrodynamical transport can be studied experimentally. Last but not least, Jörg Schmalian has made significant contributions to the field of disordered systems. He has worked on electronic glasses and disordered magnets as well as on novel superconducting phases in models with strong disorder. Jörg Schmalian has multiple connections to Dresden, not only to theoretical physics groups at MPI-PKS and TUD. There is also strong overlap with experimental work done at IFW Dresden, at the Helmholtz-Zentrum Dresden-Rossendorf, and by Andrew Mackenzie's group at the Max Planck Institute for Chemical Physics of Solids. This is exemplified by a new paper on strontium ruthenate with Jörg Schmalian and Andrew Mackenzie as two of the authors. The Physik-Preis Dresden for the year 2023 honors Jörg Schmalian as an outstanding theoretical condensed-matter physicist with strong connections to Dresden and will hopefully help to strengthen these connections further. On July 11, 2023, Prof. Jörg Schmalian from the Karlsruhe Institute of Technology received the "Physik-Preis Dresden 2023" (Dresden Physics Prize), jointly awarded by the TU Dresden and the Max Planck Institute for the Physics of Complex Systems (MPI-PKS).

The "Physik-Preis Dresden" has been established, with a generous donation by Prof. Peter Fulde, to promote cooperation between the Max Planck Institute for the Physics of Complex Systems and the Faculty of Physics of TU Dresden. It is geared towards outstanding researchers whose research is of particular interest to scientists in Dresden. This year's recipient, Prof. Jörg Schmalian, fits this condition perfectly.

Jörg Schmalian studied physics in Leipzig and Merseburg and graduated from the Technische Hochschule Merseburg in 1990. The German reunification made it possible for him to obtain a doctorate in physics in 1993 from Freie Universität Berlin under the supervision of Karl Bennemann. He stayed at FU Berlin as a postdoc before joining the group of David Pines at the University of Illinois at Urbana-Champaign in 1997. In 1999, Jörg Schmalian moved back to Europe and became a fellow of St. Catherine's College at the University of Oxford. In the same year, he accepted an offer for a tenure-track faculty position at Iowa State University, in connection with a researcher position at Ames National Lab. Jörg Schmalian quickly moved up through the ranks to become full professor in 2007. In 2011, he moved to the Karlsruhe Institute of Technology as a professor. Currently, he is the Dean of the Faculty of Physics of KIT. Jörg Schmalian has been a visiting professor at Royal Holloway University, University of Paris Diderot, and Stanford University. He has received multiple honors, among them a fellowship of the American Physical Society and the 2022 John Bardeen Prize for Theory of Superconductivity.

Jörg Schmalian is an internationally highly visible theoretical physicist with a broad range of interests. He has published over 200 research papers with over 10.000 citations. Jörg Schmalian started to work on strongly correlated electrons and superconductivity during his doctoral studies, at that time with a focus on cuprate high-temperature superconductors. He later made significant contributions to superconductivity and other ordering phenomena in iron-based and organic compounds as well as more generally on the physics of coupled order parameters. It is characteristic for Jörg Schmalian's work that he has both established conceptual foundations and modeled and predicted specific phenomena, working close to experiments. Jörg Schmalian's papers on spin-fluctuation-mediated superconductivity and on nematic order have become standard references in these fields. Moreover, Jörg Schmalian's works on quantum criticality and transport in graphene have strongly advanced the hydrodynamics of electron liquids. They were essential for identifying graphene as a readily available system in which many aspects of hydrodynamical transport can be studied experimentally. Last but not least, Jörg Schmalian has made significant contributions to the field of disordered systems. He has worked on electronic glasses and disordered magnets as well as on novel superconducting phases in models with strong disorder.

Jörg Schmalian has multiple connections to Dresden, not only to theoretical physics groups at MPI-PKS and TUD. There is also strong overlap with experimental work done at IFW Dresden, at the Helmholtz-Zentrum Dresden-Rossendorf, and by Andrew Mackenzie's group at the Max Planck Institute for Chemical Physics of Solids. This is exemplified by a new paper on strontium ruthenate with Jörg Schmalian and Andrew Mackenzie as two of the authors.

The Physik-Preis Dresden for the year 2023 honors Jörg Schmalian as an outstanding theoretical condensed-matter physicist with strong connections to Dresden and will hopefully help to strengthen these connections further.

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Awards and Honors
news-740 Sun, 21 May 2023 22:00:00 +0200 Towards the realisation of chiral spin liquids and non-Abelian anyons in quantum simulators https://journals.aps.org/prxquantum/abstract/10.1103/PRXQuantum.4.020329 Chiral spin liquids are one of the most fascinating phases of matter ever imagined by physicists. These exotic liquids exhibit quasi-particles known as non-Abelian anyons that are neither bosons nor fermions, the manipulation of which could allow for the realisation of a universal quantum computer. Despite intense efforts in condensed matter physics, discovering such a phase in Nature remains an outstanding challenge at the forefront of modern research. From a theoretical point of view, chiral spin liquids emerge in a simple model that was imagined by Kitaev in 2006, and which allows revealing their properties using analytical tools. Remarkably, recent advances in the design of quantum simulators open a possible path for the first experimental realisation of the original Kitaev model, hence suggesting that chiral spin liquids (including their exotic quasi-particles) can be studied and manipulated in a highly-controlled experimental environment. Recent work by an international collaboration involving BoYe Sun and Nathan Goldman (ULB, Brussels), Monika Aidelsburger (LMU, Munich), and Marin Bukov (Max Planck Institute for the Physics of Complex Systems and Sofia University) proposes a realistic implementation of the Kitaev model in quantum simulators. Based on a precise pulse sequence, their system is shown to host a chiral spin liquid with non-Abelian anyons. The authors describe practical methods to probe the striking properties of these exotic states. In particular, their methods unambiguously reveal the topological heat current that flows on the edge of the system: a hallmark signature of the non-Abelian anyons that emerge on the edge of chiral spin liquids. This work paves the way for the quantum simulation of chiral spin liquids, offering an appealing alternative to their experimental investigation in quantum materials. Bo-Ye Sun, Nathan Goldman, Monika Aidelsburger, and Marin Bukov, Phys. Rev. X Quantum 4, 020329 (2023). Publication Highlights news-739 Tue, 02 May 2023 22:00:00 +0200 The tissue collider https://www.nature.com/articles/s41467-022-31459-1 Physics has a long tradition of learning about fundamental interactions by making particles collide against each other. Could a similar approach be applied to biological systems? Work by Ricard Alert of the Max Planck Institute for the Physics of Complex Systems and collaborators shows what can be learnt about the mechanics of living tissues by making them collide against each other. In experiments, the researchers placed cell monolayers on a substrate and allowed them to expand and collide. The work first characterised how two tissues change shape upon collision. The researchers discovered that denser tissues, with more cells per unit area, can mechanically displace less dense tissues. Based on their calculations, the team proposes that this displacement arises because denser tissues have a higher pressure, which allows them to push on other tissues. This theory enables measurements of the elastic properties of the tissues just from their displacements upon collision. The researchers then analyzed collisions between three tissues. Surprisingly, they found that these three-tissue events are not simply a superposition of two-tissue collisions. Instead, some cells speed up as if trying to squeeze between the two other tissues. Finally, they used all these collision principles to design and assemble specific tissue patterns, similar to tile patterns, like the diamond pattern in the image. Ultimately, these results might help engineering tissue composites for implants, as well as understanding and controlling tissue interactions during embryonic development or wound healing. In all these situations, tissues grow and collide, either merging into a single tissue or establishing clear boundaries between different tissues and organs. Matthew A. Heinrich*, Ricard Alert*, Abraham E. Wolf*, Andrej Košmrlj, and Daniel J. Cohen, Nat. Commun. 13, 4026 (2022). Publication Highlights news-736 Tue, 04 Apr 2023 22:00:00 +0200 From Dual Unitarity to Generic Quantum Operator Spreading https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.130.130402 Chaotic quantum many-body systems hide information non-locally in many degrees of freedom via a dynamical process called scrambling. Understanding the capacity of quantum systems to scramble information is a crucial requirement for the design and control of quantum computing platforms as well as being intimately related to questions of thermalisation and quantum chaos. In recent years, dual-unitary circuits have emerged as minimal models for quantum many-body dynamics in which the dynamics are chaotic yet analytically tractable. However, despite their chaoticity these circuits display behaviour that is in many respects non-generic. Michael Rampp, Roderich Moessner, and Pieter Claeys from the Max Planck Institute for the Physics of Complex Systems have investigated the effect of weakly broken dual-unitarity on the spreading of local operators, a particular probe of information scrambling. They recover two universal features of ergodic quantum spin chains absent in dual-unitary circuit dynamics: a butterfly velocity smaller than the light-cone velocity and a diffusively broadening operator front. They present a physical picture for these effects through a discrete path-integral formalism, allowing for a quantitative connection between the microscopic properties of these gates and the macroscopic butterfly velocity and diffusion constant. M. A. Rampp, R. Moessner, P. W. Claeys, Phys. Rev. Lett. 130, 130402 (2023). Publication Highlights news-735 Wed, 29 Mar 2023 12:05:00 +0200 IUPAP Medal for Frank Jülicher https://iupap.org/who-we-are/internal-organization/commissions/biological-physics/c6-news/ Frank Jülicher shares the inaugural 2023 IUPAP Medal for the Physics of Life The International Union of Pure and Applied Physics (IUPAP) has awarded the 2023 IUPAP Medal for the Physics of Life jointly to John J. Hopfield and to Frank Jülicher, director at the Max Planck Institute for the Physics of Complex Systems. The citation reads “For his key contributions to biological active matter physics, shedding light on the physical mechanisms that underlie cellular processes, including cooperative molecular motors; hearing; flagellar beat; active gels, fluids, and droplets; the active cell cortex; tissue growth and patterning; protein phase separation in cells; and self-organization of active surfaces.” The IUPAP Medal for the Physics of Life is a new award of the International Union for Pure and Applied Physics (IUPAP), presented by its C6 Commission on Biological Physics every three years, at the IUPAP International Conference on Biological Physics (ICBP). The Award, consisting of a gilded medal and a certificate, recognizes outstanding achievements in Biological Physics, regardless of the country where the research has been done, the age, or the employment status of the nominee. Congratulations, Frank!  

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Awards and Honors
news-734 Fri, 24 Mar 2023 22:00:00 +0100 Cancer cells move to stiff environments as living droplets https://www.nature.com/articles/s41567-022-01835-1 Recent work by Ricard Alert of the Max Planck Institute for the Physics of Complex Systems and his collaborators uncovered a similarity between liquid droplets and cell groups, revealing that surface tension helps cells to migrate towards stiffer environments. The new work proposes that this process, called durotaxis and which was defined in the field of cell biology, can be accounted for quite precisely with the physics of wetting. This new insight could help us to understand how cancer cells disseminate across tissues with different rigidity in our body. M. E. Pallarès*, I. Pi-Jaumà*, I. C. Fortunato, V. Grazu, M. Gómez-González, P. Roca-Cusachs, J. M. de la Fuente, R. Alert, R. Sunyer, J. Casademunt, and X. Trepat. Nat. Phys. 19, 279 (2023). Publication Highlights news-733 Fri, 24 Mar 2023 12:05:00 +0100 IUPAP Early Career Prize for Ricard Alert https://iupap.org/who-we-are/internal-organization/commissions/biological-physics/c6-news/ Ricard Alert receives the IUPAP Early Career Scientist Prize in Biological Physics (C6) 2023 The International Union of Pure and Applied Physics (IUPAP) has awarded the 2023 Early Career Prize 2023 in Biological Physics to Ricard Alert, research group leader at the Max Planck Institute for the Physics of Complex Systems and the Center for Systems Biology Dresden for "revealing how new phenomena in active matter underlie a wide range of biological processes, from the spreading of epithelial tissues, to turbulent-like flows in cytoskeletal networks, to the formation of fruiting bodies in bacterial colonies". The IUPAP C6 Early Career Scientist Prize recognizes exceptional achievements of scientists in the field of Biological Physics at a relatively early stage of their career. The recipients must be no more than eight years past the award of their PhDs (excluding career interruptions), and they are expected to have demonstrated significant scientific achievements and display exceptional promise for future achievements in Biological Physics. Congratulations, Ricard!  

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Awards and Honors