NEWS
23.05.2023The IOP–Humboldt Postdoctoral Fellowship in PhysicsNominations are open for postdoctoral fellowships between two cities, Berlin and Beijing, as part of a joint physics program between the Integrative Research Institute for the Sciences (IRIS Adlershof) of Humboldt-Universität zu Berlin (HU Berlin) and the Institute of Physics, Chinese Academy of Sciences, (IOP) Beijing. FELLOWSHIP PROGRAMEstablished in 2020, the prestigious two-year research fellowships are intended for exceptional early-career scientists, in preparation for an independent career in research at the frontier of condensed matter physics, quantum materials or device physics. Successful candidates will spend one year in Berlin and one in Beijing at the research groups of their choice, supported by up to 4,500 EUR/month. The selected fellows are expected to be appointed in 2023 and 2024. A first networking event is scheduled in Berlin. Fellows will work at the Campus Adlershof of HU Berlin and the IOP Zhongguancun Beijing Campus. The fellows have the possibility to visit and interact with associated Partners at the Max Born Institute, the Helmholtz-Zentrum Berlin and its Electron Storage Ring BESSY II, the Leibniz-Institut für Kristallzüchtung or the Fritz-Haber Institute of the Max Planck Society.The prestigious two-year research fellowships are intended for exceptional early-career scientists, in preparation for an independent career in research at the frontier of condensed matter physics, quantum materials or device physics. Successful candidates will spend one year in Berlin and one in Beijing at the research groups of their choice, supported by up to 4,500 EUR/month. The selected fellows will be appointed from August 2022 onwards. A first networking event is programmed in Berlin. Fellows will work at the Campus Adlershof of HU Berlin and the IOP Zhongcuancun Beijing Campus. The fellows have the possibility to visit and interact with associated Partners at the Max Born Institute, the Helmholtz-Zentrum Berlin and its Electron Storage Ring BESSY II, the Freie Universität Berlin, at the Leibniz-Institut für Kristallzüchtung or the Fritz-Haber Institute of the Max Planck Society. A full list of participating groups can be found at HU Physics and the IOP website. Exemplary fields and participating groups includeCondensed Matter Theory Prof. Claudia Draxl, Prof. Sheng Meng, Prof. Hongming Weng, Prof. Chen Fang, Prof. Xinguo Ren, Prof. Jiangping Hu, Prof. Zhong Fang, Prof. Tao Xiang, Prof. Matthias Scheffler Ultrafast Laser Spectroscopy Photoemission Spectroscopy and Surface Science Optoelectronic Devices and Quantum Transport Scanning Probe Microscopy Quantum Information Electron Microscopy
Commitment to a one-year research stay at IOP followed by a further year at HU Berlin. Special travel preferences will be considered. A PhD degree in physics, chemistry, mathematics, or materials, obtained no more than five years prior to the application deadline. Previous international experience, such as conference talks and research abroad.
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Prof. Dr. rer. nat. Dr. h.c. Joachim Sauer, who is a Senior Researcher at the Department of Chemistry at Humboldt-Universität zu Berlin, has been appointed a member of the American Academy of Arts and Sciences based on his research activities at the department, in two Collaborative Research Centres at Humboldt-Universität and in the Cluster of Excellence UNICAT. Admission to the Academy will take place in a formal ceremony on 30 September 2023 in Cambridge, Massachusetts. |
| Illustration: Defect centres in diamond nanostructures can be used as quantum bits. The quantum information can be stored in individual photons via quantumoperation and than be transmitted in optical fibres in the future quantum internet. |
Diamond material is of great importance for future technologies such as the quantum internet. Special defect centers can be used as quantum bits (qubits) and emit single light particles that are referred to as single photons. To enable data transmission with feasible communication rates over long distances in a quantum network, all photons must be collected in optical fibers and transmitted without being lost. It must also be ensured that these photons all have the same color, i.e., the same frequency. Fulfilling these requirements has been impossible until now.
Researchers in the "Integrated Quantum Photonics" group led by Prof. Dr. Tim Schröder, member of IRIS Adlershof, have succeeded for the first time worldwide in generating and detecting photons with stable photon frequencies emitted from quantum light sources, or, more precisely, from nitrogen-vacancy defect centers in diamond nanostructures. This was enabled by carefully choosing the diamond material, sophisticated nanofabrication methods carried out at the Joint Lab Diamond Nanophotonics of the Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, and specific experimental control protocols. By combining these methods, the noise of the electrons, which previously disturbed data transmission, can be significantly reduced, and the photons are emitted at a stable (communication) frequency.
In addition, the Berlin researchers show that the current communication rates between spatially separated quantum systems can prospectively be increased more than 1000-fold with the help of the developed methods—an important step closer to a future quantum internet.
The scientists have integrated individual qubits into optimized diamond nanostructures. These structures are 1000 times thinner than a human hair and make it possible to transfer emitted photons in a directed manner into glass fibers. However, during the fabrication of the nanostructures, the material surface is damaged at the atomic level, and free electrons create uncontrollable noise for the generated light particles. Noise, comparable to an unstable radio frequency, causes fluctuations in the photon frequency, preventing successful quantum operations such as entanglement.
A special feature of the diamond material used is its relatively high density of nitrogen impurity atoms in the crystal lattice. These possibly shield the quantum light source from electron noise at the surface of the nanostructure. "However, the exact physical processes need to be studied in more detail in the future," explains Laura Orphal-Kobin, representative of the junior scientist at IRIS Adlershof, who investigates quantum systems together with Prof. Dr. Tim Schröder. The conclusions drawn from the experimental observations are supported by statistical models and simulations, which Dr. Gregor Pieplow from the same research group is developing and implementing together with the experimental physicists.
L. Orphal-Kobin, K. Unterguggenberger, T. Pregnolato, N. Kemf, M. Matalla, R.-S. Unger, I. Ostermay, G. Pieplow, and T. Schröder
Physical Review X (2023)
Contact:
Laura Orphal-Kobin, phone: +49 30 2093 82146, mail: orphalphysik.hu-berlin.de
Prof. Dr. Tim Schröder, phone: +49 30 2093 82140, mail: tim.schroederphysik-hu-berlin.de
Humboldt-Universität zu Berlin, Department of Physics and IRIS Adlershof, Integrated Quantum Photonics Group & Joint Lab Diamond Nanophotonics, Ferdinand-Braun-Institut
30.03.2023Prof. Jan Plefka receives ERC Advanced Grant
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| Prof. Jan Plefka |
Jan Plefka receives a prestigious Advanced Grant from the European Research Council (ERC). He and his team at the Department of Physics and IRIS Adlershof of HU Berlin will receive 2.2 million euros over the next five years for the GraWFTy project (High-Precision Gravitational Wave Physics from a Worldline Quantum Field Theory) to describe gravitational waves using quantum field theory. The predictions made possible in this way are needed for the wave detectors of the next generation to go online in the 2030s.
The ERC Advanced Grant
ERC Advanced Grants are endowed with up to 2.5 million euros and support excellent and self-initiated research projects of leading top researchers. It is the most highly endowed European research grant. The awardees are exceptional leaders who distinguish themselves through the originality and significance of their approaches.
About the awardee
Professor Jan Plefka is a renowned theoretical physicist and professor at Humboldt-Universität zu Berlin. After studying physics and receiving his PhD from the University of Hannover in 1996, he was a postdoctoral researcher in New York, Amsterdam, and at the MPI Potsdam. He was a visiting professor at ETH Zurich and at CERN. His research is concerned with quantum field theory and its relation to gravity. Here, he made important contributions to questions of quantum gravity and string theory, in particular in the area of AdS/CFT correspondence and hidden symmetries in supersymmetric quantum field theories. More recently, he has developed together with his group an innovative quantum field theoretical formalism to answer questions in classical gravitational wave physics. The ERC Advanced Grant was awarded to him to fully unfold the potential of this quantum approach to classical physics. He is the spokesperson of the DFG Research Training Group 2575, "Rethinking Quantum Field Theory." Jan Plefka has received several awards, including a Feodor Lynen Fellowship from the Humboldt Foundation and the Lichtenberg Professorship from the Volkswagen Foundation.
The GraWFTy Projekt: High-Precision Gravitational Wave Physics from a Worldline Quantum Field Theory
Gravitational waves are tiny ripples of the space-time fabric that travel through our universe at the speed of light. They arise as soon as masses are accelerated. They are a direct prediction of Einstein's theory of relativity, which he established during his fruitful Berlin years as early as 1916. They were first directly detected only 100 years later in 2015 with the LIGO detector, emerging from a merger of two black holes and after a journey of billions of light years through our universe to us. There are currently three gravitational wave observatories in operation: LIGO, Virgo, and Kagra. They routinely detect gravitational waves emanating from such mergers of black holes and neutron stars. To date, about 90 such events have been detected. In the 2030s, a new generation of ground- and space-based gravitational wave detectors will come on-line that will significantly increase the sensitivities of these measurements. To match these sensitivities, theoretical physics must predict highly accurate waveforms from Einstein's theory that greatly exceed the current state of the art. The GraWFTy project will provide these predictions for the high-precision form of gravitational waves. With their help, fundamental questions in physics will be studied:
- Is Einstein's theory correct in the strong gravitational field regime?
- How are black holes formed, what is their population in the universe?
- Can we see signals for physics beyond the known natural forces and particles?
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| Visualization of gravitational bremsstrahlung from the scattering of two black holes (BSc thesis O. Babayemi) |
Jan Plefka explains his approach: "Together with my research group, we have been able to develop an innovative method since 2020 that addresses this problem of classical physics using methods from quantum field theory. Quantum field theory is the mathematical description of elementary particle physics, that is the smallest building blocks of our universe and their interactions. It is exceedingly fascinating that this language can also be applied to classical gravitational physics with high efficiency. In short, we replace the scattering of protons, as it happens in accelerators like the LHC at CERN, in our formalism by the scattering of black holes or neutron stars. There is, of course, the initial simplification that we can now neglect the quantum effects in the extensive calculations - which in the case of gravity are also still ill understood. Yet, this simplification is compensated by the complexity of Einstein's theory compared to the standard model of elementary particle physics relevant to proton scatterings.
The great advantage of our so-called "world-line" approach is that we can directly target the observable quantities in the detector, using the modern mathematical technology of quantum field theory, namely Feynman integrals. Another peculiar aspect of our approach is that the spin of black holes is described by a supersymmetry. Its existence has been speculated so far in elementary particle physics. We could show that it appears in the effective description of rotating black holes. The idea for this approach comes from string theory. For me, this project represents a crucial step in my career. So far, I have focused my research primarily on the question of quantum gravity and its relation to gauge field theories. This was primarily mathematical physics and far away from direct measurements. With GraWFTy, I am now applying these ideas priorly developed in an abstract setting to pressing, to pressing questions in gravitational wave physics. We have already been able to prove the efficiency of this approach. The ERC Advanced Grant will allow me to fully unfold the potential of our approach."
Contact
Prof. Dr. Jan Christoph Plefka
jan.plefkaphysik.hu-berlin.de
Department of Physik and IRIS Adlershof
Zum Großen Windkanal 2, 12489 Berlin