From MPG Institute for Quantum Optics [MPG Institut für Quantenoptik] (DE)
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May 16, 2022
The Kardar-Parisi-Zhang universality combines classical everyday phenomena such as coffee stains with quantum mechanical spin chains in a surprising way. Credit: MPG Institute of Quantum Optics.
The behavior of microscopic quantum magnets has long been a subject taught in lectures in theoretical physics. However, investigating the dynamics of systems that are far out of equilibrium and watching them “live” has been difficult so far. Now, researchers at the Max Planck Institute of Quantum Optics in Garching have accomplished precisely this, using a quantum gas microscope. With this tool, quantum systems can be manipulated and then imaged with such high resolution that even individual atoms are visible. The results of the experiments on linear chains of spins show that the way their orientation propagates corresponds to the so-called Kardar-Parisi-Zhang superdiffusion. This confirms a conjecture that recently emerged from theoretical considerations.
A team of physicists around Dr. Johannes Zeiher and Prof Immanuel Bloch has eyes on objects that others hardly ever get to see. The researchers at the Max Planck Institute of Quantum Optics (MPQ) in Garching use a so-called quantum gas microscope to track down processes on the tiny scale of quantum physics. Such an instrument allows—with the help of atoms and lasers—to specifically create quantum systems with desired properties and to investigate them with high resolution. In these experiments, the researchers also focus on transport phenomena—how quantum objects move under certain external conditions.
The team has now made a surprising experimental discovery. The researchers were able to show that the one-dimensional transport of spins—the term “spin” stands for a specific, magnetic quantum property of atoms and other particles—resembles macroscopic phenomena in certain areas. For the most part, processes in the quantum realm and in the everyday world differ significantly. “But our work reveals an interesting connection between quantum mechanical spin systems in cold atoms and classical systems such as growing bacterial colonies or spreading wildfires,” says Johannes Zeiher, group leader in the Quantum Many-Body Systems division at MPQ. “This discovery is completely unexpected and points to a deep connection in the field of non-equilibrium physics that is still poorly understood.”
Physicists refer to such a theoretical analogy between random motion in quantum and classical systems as “universality.” In this specific case, it is the Kardar-Parisi-Zhang universality (KPZ)—a phenomenon previously known only from classical physics.
The telling exponent
In order to observe the phenomenon microscopically, the Garching team first cooled down a cloud of atoms to temperatures close to absolute zero. That way, movements due to heat could be ruled out. Then they locked the ultracold atoms in a specially formed “box-shaped” potential, formed by an arrangement of tiny mirrors. “We used this to study the relaxation of a single magnetic domain wall in a chain of 50 linearly arranged spins,” explains David Wei, a researcher in Johannes Zeiher’s group. The domain wall separates areas with identical orientation of neighboring spins from each other. The researchers first created the domain wall for the experiment using a new trick, whereby an “effective magnetic field” was generated by projecting light. In doing so, the researchers can strongly suppress the couplings between spins, effectively “locking” them into place.
The relaxation within the spin chain occurred after the couplings between spins were switched on in a controlled manner and, as it turned out, followed a characteristic pattern. “This can be described mathematically by a power law with the exponent 3/2,” says Wei—a hint at the connection with KPZ universality. Further evidence for this relationship was provided when the researchers detected the motion of individual spins, which was revealed through the quantum gas microscope.
“This high precision was the basis for a detailed statistical evaluation,” says Zeiher. “The striking course of spin diffusion that our experiment showed corresponds in its mathematical form approximately to the spread of a coffee stain on a tablecloth, for example,” explains the Max Planck physicist. That such an astonishing connection could exist had been suspected by a team of theorists about two years ago on the basis of theoretical considerations. However, experimental confirmation of this hypothesis was still lacking.
An old model amazes physicists
For the description of quantum mechanical spin phenomena, physicists have been using the so-called Heisenberg model very successfully for a long time (but it was only recently that spin transport phenomena could be described theoretically within this model). “Our results show that surprising new insights are still possible even within an established theoretical framework,” Johannes Zeiher emphasizes. “And they are proof of how theory and experiment cross-fertilize in physics.”
The results that have now been achieved by the team in Garching are not only of academic value. They could also be useful for tangible technical applications. For example, spins also constitute the basis of certain forms of quantum computers. Knowledge of the transport properties of the information carriers could be of critical importance for the practical realization of such novel computer architectures.
The study appears in Science.
See the full article here .
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Research at the MPG Institute for Quantum Optics [Max Planck Institut für Quantenoptik ] (DE)
Light can behave as an electromagnetic wave or a shower of particles that have no mass, called photons, depending on the conditions under which it is studied or used. Matter, on the other hand, is composed of particles, but it can actually exhibit wave-like properties, giving rise to many astonishing phenomena in the microcosm.
At our institute we explore the interaction of light and quantum systems, exploiting the two extreme regimes of the wave-particle duality of light and matter. On the one hand we handle light at the single photon level where wave-interference phenomena differ from those of intense light beams. On the other hand, when cooling ensembles of massive particles down to extremely low temperatures we suddenly observe phenomena that go back to their wave-like nature. Furthermore, when dealing with ultrashort and highly intense light pulses comprising trillions of photons we can completely neglect the particle properties of light. We take advantage of the large force that the rapidly oscillating electromagnetic field exerts on electrons to steer their motion within molecules or accelerate them to relativistic energies.
MPG Society for the Advancement of Science [MPG Gesellschaft zur Förderung der Wissenschaften e. V.] is a formally independent non-governmental and non-profit association of German research institutes founded in 1911 as the Kaiser Wilhelm Society and renamed the Max Planck Society in 1948 in honor of its former president, theoretical physicist Max Planck. The society is funded by the federal and state governments of Germany as well as other sources.
According to its primary goal, the MPG Society supports fundamental research in the natural, life and social sciences, the arts and humanities in its 83 (as of January 2014) MPG Institutes. The society has a total staff of approximately 17,000 permanent employees, including 5,470 scientists, plus around 4,600 non-tenured scientists and guests. Society budget for 2015 was about €1.7 billion.
The MPG Institutes focus on excellence in research. The MPG Society has a world-leading reputation as a science and technology research organization, with 33 Nobel Prizes awarded to their scientists, and is generally regarded as the foremost basic research organization in Europe and the world. In 2013, the Nature Publishing Index placed the MPG institutes fifth worldwide in terms of research published in Nature journals (after Harvard University, The Massachusetts Institute of Technology, Stanford University and The National Institutes of Health). In terms of total research volume (unweighted by citations or impact), the Max Planck Society is only outranked by The Chinese Academy of Sciences [中国科学院](CN), The Russian Academy of Sciences [Росси́йская акаде́мия нау́к](RU) and Harvard University. The Thomson Reuters-Science Watch website placed the MPG Society as the second leading research organization worldwide following Harvard University, in terms of the impact of the produced research over science fields.
The MPG Society and its predecessor Kaiser Wilhelm Society hosted several renowned scientists in their fields, including Otto Hahn, Werner Heisenberg, and Albert Einstein.
History
The organization was established in 1911 as the Kaiser Wilhelm Society, or Kaiser-Wilhelm-Gesellschaft (KWG), a non-governmental research organization named for the then German emperor. The KWG was one of the world’s leading research organizations; its board of directors included scientists like Walther Bothe, Peter Debye, Albert Einstein, and Fritz Haber. In 1946, Otto Hahn assumed the position of President of KWG, and in 1948, the society was renamed the Max Planck Society (MPG) after its former President (1930–37) Max Planck, who died in 1947.
The MPG Society has a world-leading reputation as a science and technology research organization. In 2006, the Times Higher Education Supplement rankings of non-university research institutions (based on international peer review by academics) placed the MPG Society as No.1 in the world for science research, and No.3 in technology research (behind AT&T Corporation and The DOE’s Argonne National Laboratory.
The domain mpg.de attracted at least 1.7 million visitors annually by 2008 according to a Compete.com study.
MPG Institutes and research groups
The MPG Society consists of over 80 research institutes. In addition, the society funds a number of Max Planck Research Groups (MPRG) and International Max Planck Research Schools (IMPRS). The purpose of establishing independent research groups at various universities is to strengthen the required networking between universities and institutes of the Max Planck Society.
The research units are primarily located across Europe with a few in South Korea and the U.S. In 2007, the Society established its first non-European centre, with an institute on the Jupiter campus of Florida Atlantic University (US) focusing on neuroscience.
The MPG Institutes operate independently from, though in close cooperation with, the universities, and focus on innovative research which does not fit into the university structure due to their interdisciplinary or transdisciplinary nature or which require resources that cannot be met by the state universities.
Internally, MPG Institutes are organized into research departments headed by directors such that each MPI has several directors, a position roughly comparable to anything from full professor to department head at a university. Other core members include Junior and Senior Research Fellows.
In addition, there are several associated institutes:
International Max Planck Research Schools
International Max Planck Research Schools
Together with the Association of Universities and other Education Institutions in Germany, the Max Planck Society established numerous International Max Planck Research Schools (IMPRS) to promote junior scientists:
• Cologne Graduate School of Ageing Research, Cologne
• International Max Planck Research School for Intelligent Systems, at the Max Planck Institute for Intelligent Systems located in Tübingen and Stuttgart
• International Max Planck Research School on Adapting Behavior in a Fundamentally Uncertain World (Uncertainty School), at the Max Planck Institutes for Economics, for Human Development, and/or Research on Collective Goods
• International Max Planck Research School for Analysis, Design and Optimization in Chemical and Biochemical Process Engineering, Magdeburg
• International Max Planck Research School for Astronomy and Cosmic Physics, Heidelberg at the MPI for Astronomy
• International Max Planck Research School for Astrophysics, Garching at the MPI for Astrophysics
• International Max Planck Research School for Complex Surfaces in Material Sciences, Berlin
• International Max Planck Research School for Computer Science, Saarbrücken
• International Max Planck Research School for Earth System Modeling, Hamburg
• International Max Planck Research School for Elementary Particle Physics, Munich, at the MPI for Physics
• International Max Planck Research School for Environmental, Cellular and Molecular Microbiology, Marburg at the Max Planck Institute for Terrestrial Microbiology
• International Max Planck Research School for Evolutionary Biology, Plön at the Max Planck Institute for Evolutionary Biology
• International Max Planck Research School “From Molecules to Organisms”, Tübingen at the Max Planck Institute for Developmental Biology
• International Max Planck Research School for Global Biogeochemical Cycles, Jena at the Max Planck Institute for Biogeochemistry
• International Max Planck Research School on Gravitational Wave Astronomy, Hannover and Potsdam MPI for Gravitational Physics
• International Max Planck Research School for Heart and Lung Research, Bad Nauheim at the Max Planck Institute for Heart and Lung Research
• International Max Planck Research School for Infectious Diseases and Immunity, Berlin at the Max Planck Institute for Infection Biology
• International Max Planck Research School for Language Sciences, Nijmegen
• International Max Planck Research School for Neurosciences, Göttingen
• International Max Planck Research School for Cognitive and Systems Neuroscience, Tübingen
• International Max Planck Research School for Marine Microbiology (MarMic), joint program of the Max Planck Institute for Marine Microbiology in Bremen, the University of Bremen, the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, and the Jacobs University Bremen
• International Max Planck Research School for Maritime Affairs, Hamburg
• International Max Planck Research School for Molecular and Cellular Biology, Freiburg
• International Max Planck Research School for Molecular and Cellular Life Sciences, Munich
• International Max Planck Research School for Molecular Biology, Göttingen
• International Max Planck Research School for Molecular Cell Biology and Bioengineering, Dresden
• International Max Planck Research School Molecular Biomedicine, program combined with the ‘Graduate Programm Cell Dynamics And Disease’ at the University of Münster and the Max Planck Institute for Molecular Biomedicine
• International Max Planck Research School on Multiscale Bio-Systems, Potsdam
• International Max Planck Research School for Organismal Biology, at the University of Konstanz and the Max Planck Institute for Ornithology
• International Max Planck Research School on Reactive Structure Analysis for Chemical Reactions (IMPRS RECHARGE), Mülheim an der Ruhr, at the Max Planck Institute for Chemical Energy Conversion
• International Max Planck Research School for Science and Technology of Nano-Systems, Halle at Max Planck Institute of Microstructure Physics
• International Max Planck Research School for Solar System Science at the University of Göttingen hosted by MPI for Solar System Research
• International Max Planck Research School for Astronomy and Astrophysics, Bonn, at the MPI for Radio Astronomy (formerly the International Max Planck Research School for Radio and Infrared Astronomy)
• International Max Planck Research School for the Social and Political Constitution of the Economy, Cologne
• International Max Planck Research School for Surface and Interface Engineering in Advanced Materials, Düsseldorf at Max Planck Institute for Iron Research GmbH
• International Max Planck Research School for Ultrafast Imaging and Structural Dynamics, Hamburg
Max Planck Schools
• Max Planck School of Cognition
• Max Planck School Matter to Life
• Max Planck School of Photonics
Max Planck Center
• The Max Planck Centre for Attosecond Science (MPC-AS), POSTECH Pohang
• The Max Planck POSTECH Center for Complex Phase Materials, POSTECH Pohang
Max Planck Institutes
Among others:
• Max Planck Institute for Neurobiology of Behavior – caesar, Bonn
• Max Planck Institute for Aeronomics in Katlenburg-Lindau was renamed to Max Planck Institute for Solar System Research in 2004;
• Max Planck Institute for Biology in Tübingen was closed in 2005;
• Max Planck Institute for Cell Biology in Ladenburg b. Heidelberg was closed in 2003;
• Max Planck Institute for Economics in Jena was renamed to the Max Planck Institute for the Science of Human History in 2014;
• Max Planck Institute for Ionospheric Research in Katlenburg-Lindau was renamed to Max Planck Institute for Aeronomics in 1958;
• Max Planck Institute for Metals Research, Stuttgart
• Max Planck Institute of Oceanic Biology in Wilhelmshaven was renamed to Max Planck Institute of Cell Biology in 1968 and moved to Ladenburg 1977;
• Max Planck Institute for Psychological Research in Munich merged into the Max Planck Institute for Human Cognitive and Brain Sciences in 2004;
• Max Planck Institute for Protein and Leather Research in Regensburg moved to Munich 1957 and was united with the Max Planck Institute for Biochemistry in 1977;
• Max Planck Institute for Virus Research in Tübingen was renamed as Max Planck Institute for Developmental Biology in 1985;
• Max Planck Institute for the Study of the Scientific-Technical World in Starnberg (from 1970 until 1981 (closed)) directed by Carl Friedrich von Weizsäcker and Jürgen Habermas.
• Max Planck Institute for Behavioral Physiology
• Max Planck Institute of Experimental Endocrinology
• Max Planck Institute for Foreign and International Social Law
• Max Planck Institute for Physics and Astrophysics
• Max Planck Research Unit for Enzymology of Protein Folding
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